2021-07-06T16:27:48Z
Republic of Ethiopia EPA (2003) Ambient Environment Standards for Ethiopia.pdf
Republic of Ethiopia EPA (2003) Ambient Environment Standards for Ethiopia
GUIDLINE
AMBIENT
ENVIRONMENT
STANDARDS
FOR
ETHIOPIA
Prepared By:
The Environmental Protection
Authority
And
The United Nations Industrial
Development Organization
Prepared Under the
Ecologically Sustainable
Industrial Development (ESID)
Project
US/ETH/99/068/ETHIOPIA
August 2003
ADDIS ABABA
Parts of this publication may be reproduced without further permission provided the source is
acknowledged.
ISBN
Unique No.
Price V 1.1
GUIDELINE AMBIENT ENVIRONMENT STANDARDS FOR ETHIOPIA
Acknowledgements
The Environmental Protection Authority would like to acknowledge the United Nations Industrial
Development Organisation for their assistance under the Ecologically Sustainable Industrial Development
(ESID) Project US/ETH/99/068/ETHIOPIA in the preparation of these standards.
The Environmental Protection Authority would also like to take this opportunity to thank the following
bodies who were consulted during the drafting of these standards:
The Ministry of Water Resources
The Ministry of Health
The Ministry of Agriculture
The National Metrology Service Agency
Addis Ababa Administration Environmental Protection Authority
And
All participants of the workshop held for review of this document in Addis Ababa July 24 th 2003
GUIDELINE AMBIENT ENVIRONMENT STANDARDS FOR ETHIOPIA
PREFACE
The Federal Government of Ethiopia, through Proclamation 9/1995, established the Federal
Environmental Protection Authority. The Authority is mandated to protect and preserve ecosystems
of the Ethiopian environment.
It is in fulfilment of this mandate that these provisional standards for industrial pollution control are
hereby presented. These are guideline standards, which will be periodically reviewed and updated
in the light of additional information and knowledge.
It is now globally accepted that where there are threats of serious irreversible environmental
damages, lack of scientific certainty should not be used as a reason for postponing measures to
prevent environmental degradation.
The survival of man, and of any nation for that matter, depends on the ability to manage wastes in
an environmentally sound manner. This can only be achieved through establishment and
enforcement of appropriate standards and guidelines set to ensure that we do not destroy our
environment and indeed the very basis of our existence.
Dr. Telwode Brehan Gebre Egziabieher
General manager
Environmental Protection Authority
GUIDELINE AMBIENT ENVIRONMENT STANDARDS FOR ETHIOPIA
Contents
1 INTRODUCTION.....................................................................................................................1
2 GUIDELINE AMBIENT ENVIRONMENTAL STANDARDS FOR ETHIOPIA........................................3
APPENDIX 1 GUIDLINE AIR QUALITY STANDARDS................................................................12
APPENDIX 2 WATER QUALITY STANDARDS (SURFACE WATERS).........................................35
APPENDIX 3 SOIL AND GROUNDWATER QUALITY STANDARDS..............................................92
APPENDIX 4 NOISE STANDARDS.........................................................................................102
GUIDELINE AMBIENT ENVIRONMENT STANDARDS FOR ETHIOPIA
1 INTRODUCTION
Ambient environmental quality standards are set with a goal of safeguarding public health and
protecting the environment. Both objectives have very high quality requirements which
complement each other to a great extent. For example, in general terms, if a river or lake water
meets the most stringent fishery requirements it will meet all or virtually all other environmental
quality objectives.
It is appropriate then for the government of Ethiopia to set standards which will ensure that the
ambient environment of the country is protected and ensure environmental quality is not degraded
while also ensuring a healthy environment within people must live.
The government of Ethiopia has mandated the Environmental Protection Authority to set such
standards and this document represent the Authorities guideline standards with respect to the
ambient environment..
In practice, standards can be set from either first principles or based on existing national or
international guidelines.
Deriving such standards from first principles requires classification, and prioritisation of pollutants,
derivation of pollutant exposure processes and their ecological effects, determine. predicted
environmental concentrations and predicted no effect concentration for the receiving environment.
Given the resources required to derive country specific standards from first principles, standards
are generally derived based on existing published guidelines as is the case in this instance. The
information upon which international guidelines are based are derived predominantly from
extensive epidemiological and toxicological studies to determine the observed health and
environmental effects of the compound in question. As such, there are a limited number of
international sources who collate and interprets this data in order to prepare guideline for such
parameters. The principle international and national guidelines used in the preparation of these
guideline standards for Ethiopia are referenced throughout the document.
Where sufficient national baseline information is available, the guideline values prepared by
international bodies may be further modified at to take account of particular national criteria prior
to their implementation as a national standard. Additional baseline data collection is then
undertaken to improve or adapt the initial standards to own country situation. Baseline data is
important for the implementation of environmental quality standards particularly with regard to the
following:
• forming a basis for zoning; where general or special standards should apply;
• assessing the assimilative capacity of the receiving environment;
• identifying the areas which require stringent or less stringent application of standards; and,
• formulating rehabilitation and/or conservation measures.
There is currently insufficient baseline data available within Ethiopia to allow modification of
international guidelines for ambient environmental quality. As such many of the guideline
standards have been adopted directly as recommended for developing countries.
These guideline standards are being introduced to be used all throughout the country subjected to
amendment, as more information on the state or pollution is made available through the
Ecologically Sustainable Industrial Development (ESID) project. The regional states can establish
more stringent standards taking into consideration particular ecological conditions in their localities
provided EPA’s standards are used as the minimum. .
PAGE 1
GUIDELINE AMBIENT ENVIRONMENT STANDARDS FOR ETHIOPIA
These guideline standards are primarily aimed at protection of ambient environmental quality
within all components of the Ethiopian Environment. The guideline standards provided within this
document with regard to water quality are not based on use related criteria e.g water for abstraction
as a source of drinking water, or for example irrigation purposes. It is anticipated that such
standards will be prepared by the Ministry of Water resources at a later date.
1.1 STRUCTURE OF THE DOCUMENT
The Guideline Standards are presented in summary form in the following section. Additional
appendices are included which provides detailed information and background for the guideline
standards in each area as follows.
Appendix 1: Air Quality Standards
Appendix 2: Water Quality Standards
Appendix 3: Soil and Groundwater Quality Standards
Appendix 4: Noise Standards
PAGE 2
GUIDELINE AMBIENT ENVIRONMENT STANDARDS FOR ETHIOPIA
2 GUIDELINE AMBIENT ENVIRONMENTAL STANDARDS FOR ETHIOPIA
The guideline environmental standards for Ethiopia are presented below in summary form.
Additional information is given on each parameter in a set of Appendixes attached to this
document.
2.1 GUIDELINE AIR QUALITY STANDARDS
Guideline standards for priority ambient atmospheric pollutants are given below. Information on
additional parameters is provided in Appendix 1.
Compound Guideline Value [µg/m3] Averaging time
Sulphur dioxide 500
125
50
10 minutes
24 hours
1 year
Nitrogen dioxide 200
40
1 hour
1 year
Carbon monoxide 100 000
60 000
30 000
10 000
15 minutes
30 minutes
1 hour
8 hours
Ozone 120 8 hours
Suspended Particulate Matter
PM10 50 1 year
150 24 hours
PM2.5 15 1 year
65 24 hours
Lead 0.5 1 year
2.2
PAGE 3
GUIDELINE AMBIENT ENVIRONMENT STANDARDS FOR ETHIOPIA
GUIDELINE SURFACE WATER QUALITY STANDARDS
Guideline standards for priority surface water pollutants with regard to protection of aquatic
species are given below. Detailed information on each parameter is provided in Appendix 2
Compound Limit
Aluminium 200 µg/l Al;
Ammonium 20 µg/l NH
3
un-ionised
25 µg/l NH
3
un-ionised
Antimony 20 µg/l Sb
Arsenic 50 µg/l As
Barium 100 µg/l Ba
Benzene 10.0 µg/l
Benzo(A)Pyrene 0.01 µg/l
BOD
5
[Biochemical oxygen demand] < 5 mg/l O
2
Cadmium 5.0 µg/l Cd [Total];
Chloride 250 mg/l Cl
Chlorine, Residual 5 µg/l as HOCl
Chromium 50 µg/l Cr
Conductivity 1000 µS/Cm (@ 20 °C)
Copper 5-112 µg/l dissolved Cu for hardness
range 10-500 mg/l CaCO
3
Cyanide 50 µg/l CN
Dissolved oxygen Game Fish - 50% samples > 9 mg/l
O
2
[minimum 6 mg/l O
2
]
Course Fish - 50% samples > 7 mg/l
O2[minimum 4 mg/l O2]
Fluoride 1.0 mg/l F
Iron 1.0 mg/l dissolved Fe
Lead 50 µg/l Pb
Manganese 300 µg/l Mn
Mercury 1 µg/l Hg
Methylene Blue Active
Substances[(Anionic) Detergents]
200 µg/l lauryl-SO
4
Nickel 100 µg/l Ni AM
Nitrate 50 mg/l NO
3
Nitrite Game Fish - 200 µg/l NO
2
Course Fish - 400 µg/l NO
2
PAGE 4
GUIDELINE AMBIENT ENVIRONMENT STANDARDS FOR ETHIOPIA
Compound Limit
Nitrogen, Kjeldahl 2 mg/l N
PCBs and PCTs 1 µg/l AM
Pesticides
Aldrin 0.01 µg/l
Dieldrin 0.01 µg/l
Endrin 0.005 µg/l
Isodrin 0.005 µg/l
Atrazine 1.0 µg/l
Chloridazon 0.1 µg/l
2,4-D 0.005 µg/l
DDT (y-isomer) 10 µg/l
DDT (all isomers) 25 µg/l
Diazinon 5 µg/l
Dichlorbenil 10µg/l
Dichlorvos 0.001 µg/l
Diuron 25 µg/l
Endosulphan 0.001 µg/l
Fenitrothion 0.01 µg/l
Isoproturon 0.5 µg/l
Lindane 0.1 µg/l
Linuron 1.0 µg/l
Malathion 0.01 µg/l
MCPA 10 µg/l
Mecoprop 10 µg/l
Parathionethyl 0.01 µg/l
Pentachlorophenol 2.0 µg/l
Simazine 1.0 µg/l
Tributyltin oxide 0,001 µg/l
Trifuralin 0.1 µg/l
Triphenyltin acetate 0.01 µg/l
Triphenyltin hydroxide 0.01 µg/l
pH 6 to 9, but no change more than 0.2 units
from natural level in 95% of samples
Phenols [non specific/total] 0.5 µg/l C
6
H
5
OH AM
PAGE 5
GUIDELINE AMBIENT ENVIRONMENT STANDARDS FOR ETHIOPIA
Compound Limit
Polycyclic aromatic hydrocarbons [PAH] 2 µg/l [Total for 6 specified
compounds**] AM
Selenium 10 µg/l Se
Silver 10 µg/l Ag
Total Suspended Solids, < 25 mg/l [annual mean]
50 mg/l [maximum value]
Sulphate 200 mg/l SO
4
Temperature Game Fish - Discharge must not result in
variation of more than 1.5
o
C; temperature
down stream of thermal discharge
Course Fish - Discharge must not result in
variation of more than 3
o
C; temperature
down stream of thermal discharge
Thallium 5 µg/l Tl AM
Toluene 10.0 µg/l AM
1,1,1-Trichloroethane 500 µg/l AM
Tetrachloroethylene 10 µg/l AM
Trichloroethylene 10 µg/l AM
Uranium 20 µg/l U AM
Vinyl chloride 10 µg/l AM
Zinc 30 µg/l to 500 µg/l Zn @ hardness 10 to
500 mg/l
2.3
PAGE 6
GUIDELINE AMBIENT ENVIRONMENT STANDARDS FOR ETHIOPIA
GUIDELINE SOIL AND GROUNDWATER STANDARDS
Guideline standards for soil quality are provided below. These standards represent “clean-up”
values for soils and groundwater’s which have been contaminated as a result of anthropogenic
activity. These values are based on a generic “risk assessment” and as such should be regarded as
guideline values. A detailed risk assessment should be undertaken to obtain site specific values for
the parameters in question. Additional information on this approach and the guideline standards is
presented in Appendix 3.
2.3.1 Guideline Soil Quality Standards.
Substance Guideline Standard
(mg/kg dry weight)
Acetone 8
Arsenic 201(2)
Benzene 1.52
BTEX, total 102
Cadmium 0.52
Chloroform 502
Chlorophenols, total 32
Pentachlorophenol 0.15
Chromium, total 500
Chromium (VI) 20
Copper 5001
Cyanide, total 500
Cyanide, acid volatile 102
DDT 1
Detergents, anionic 1,5002
1,2-dibromomethane 0.022
1,2-dichloroethane 1.42
1,1-dichloroethylene 52
1,2-dichloroethylene 852
Dichloromethane 82
Fluorides, inorganic 201
Gas oil (Total hydrocarbons (C5–C35)
5) 100
Lead 402
Mercury 1
Molybdenum 5
MTBE 5002
Nickel 301
PAGE 7
GUIDELINE AMBIENT ENVIRONMENT STANDARDS FOR ETHIOPIA
Substance Guideline Standard
(mg/kg dry weight)
Nickel 301
Nitrophenols
Mono- 1252
Di- 102
Tri- 302
PAH, total 1.52,3
Benzo(a)pyrene 0.12
Dibenzo(a,h) anthracene 0.12
Petrol (C5-C10) 25
Petrol (C9-C16) 25
Phenols, total 701
Phthalates, total 2502
DEHP 252
Styrene 402
Turpentine, mineral (C7 – C12) 25
Tetrachloroethylene 52
Tetrachloromethane 52
1,1,1-trichloroethane 2002
Trichloroethylene 52
Vinyl chloride 0.42
Zinc 500
1: Based on acute harmful effects
2: Based on chronic harmful effects
3PAH, total defined as the sum of individual components: fluoranthene, benzyl(b+j+k)fluoranthene, benzyl(a)pyrene,
dibenzyl(a,h)anthracene, and ideno(1,2,3-cd)pyrene.
2.3.2 Guideline Standards for Groundwater Beneath Contaminated Sites
Substance Groundwater Quality Standard µg/l
Acetone 10
Arsenic 8
Benzene 1
Boron 300
Butylacetates 10
Cadmium 0.5
PAGE 8
GUIDELINE AMBIENT ENVIRONMENT STANDARDS FOR ETHIOPIA
Chlorinated solvents (not vinyl chloride) 1
Chloroform As low as possible
Chromium, total 25
Chromium VI 1
Copper 100
Cyanide, total 50
DEHP 1
Detergents, anionic 100
1,2-dibromomethane 0.01
Diethylether 10
Isopropyl alcohol 10
PAH 1 0.2
Lead 1
Methylisobutylketone 10
Methyl-tert-butylether (MTBE) 30
Mineral oil, total 9
Molybdenum 20
Naphthalene 1
Nickel 10
Nitrophenols 0.5
Pentachlorophenol 0.01
Pesticides, total
Pesticides
Pesticides, persistent chlorinated
0.5
0.1
0.03
Phenols 0.5
Phthalates (not DEHP) 10
Styrene 1
Toluene 5
Vinyl chloride 0.2
Xylenes 5
Zinc 100
1 Sum of fluoranthene, benzo(b)fluoranthene, benzo(k)fluoranthene, benzo(a)pyrene,
benzo(g,h,i)perylene, indeno(1,2,3-cd)pyrene.
2.3.3 Guideline Standards for Cations and Anions*
* It is not possible to assign a universal set of standards for groundwater due to the natural
variation in hydrochemistry. Therefore, indicators can be used to assess groundwater
status, which takes account of natural variation in quality. It should be noted that a
PAGE 9
GUIDELINE AMBIENT ENVIRONMENT STANDARDS FOR ETHIOPIA
guideline value may not be applicable in some cases due to the widely variable nature of
groundwater bodies.
Parameter Groundwater Guideline Value (mg/l)
Alkalinity No abnormal change to background
Aluminium 0.2
Ammonia (as NH4) 0.15
Barium 0.1
Bicarbonate/Carbonate No abnormal change to background
Calcium 200
Chloride 30
Dissolved Oxygen No abnormal change to background
Fluoride 1
Iron 0.2
Magnesium 50
Manganese 0.05
Mercury 0.001
Nitrate (as NO3) 25
Nitrite (as NO2) 0.1
Orthophosphate 0.03
Potassium 5
Silica No abnormal change to background
Sodium 150
Sulphate 200
2.4 GUIDELINE STANDARDS FOR NOISE
The objective of these guidelines is to minimise the amount of noise to which people, living or
working in sensitive locations, are exposed. Examples of such areas include domestic dwellings,
hospitals, schools, places of worship, or areas of high amenity.
The sensitivity to noise is usually greater at night-time than it is during the day, by about
10dB(A). Ideally, if the total noise level from all sources is taken into account, the noise level at
sensitive locations should be kept within the following values:
Limits in dB (A) Leq
Area Code Category of area Day timeNote 1 Night timeNote 2
A Industrial area 75 70
B Commercial area 65 55
C Residential area 55 45
PAGE 10
GUIDELINE AMBIENT ENVIRONMENT STANDARDS FOR ETHIOPIA
Note-1: Day time reckoned in between 6.00 am to 9.00p.m
Note 2: Night time reckoned in between 9.00p.m. to 6.00am
Additional information on noise and vibration standards is provided in Appendix 4.
PAGE 11
GUIDELINE AMBIENT ENVIRONMENT STANDARDS FOR ETHIOPIA
APPENDIX 1
GUIDLINE AIR QUALITY STANDARDS
PAGE 12
GUIDELINE AMBIENT ENVIRONMENT STANDARDS FOR ETHIOPIA
1 SULPHUR DIOXIDE
Chemical Symbol or Formula: SO2
Standard*: Averaging Time
500 µg/m3 10 minutes
125 µg/m3 24 hours
50 µg/m3 1 year
* The volume must be standardised at a temperature of 293 °K and a pressure of 101,3 kPa.
1.1 HEALTH EFFECTS1
1.1.1 Short-period exposures (less than 24 hours)
Most information on the acute effects of SO2 comes from controlled chamber experiments on
volunteers exposed to SO 2 for periods ranging from a few minutes up to one hour (WHO 1999a).
Acute responses occur within the first few minutes after commencement of inhalation. Further
exposure does not increase effects. Effects include reductions in the mean forced expiratory volume
over one second (FEV1), increases in specific airway resistance (sRAW), and symptoms such as
wheezing or shortness of breath. These effects are enhanced by exercise that increases the volume
of air inspired, as it allows SO2 to penetrate further into the respiratory tract.
A wide range of sensitivity has been demonstrated, both among normal subjects and among those
with asthma. People with asthma are the most sensitive group in the community. Continuous
exposure-response relationships, without any clearly defined threshold, are evident. To develop a
guideline value, the minimum concentrations associated with adverse effects in asthmatic patients
exercising in chambers have been considered.
1.1.2 Exposure over a 24-hour period
Information on the effects of exposure averaged over a 24-hour period is derived mainly from
epidemiological studies in which the effects of SO2, SPM and other associated pollutants are
considered. Exacerbation of symptoms among panels of selected sensitive patients seems to arise in
a consistent manner when the concentration of SO 2 exceeds 250 µg/m
3 in the presence of SPM.
Several more recent studies in Europe have involved mixed industrial and vehicular emissions now
common in ambient air. At low levels of exposure (mean annual levels below 50 µg/m3; daily
levels usually not exceeding 125 µg/m3 ) effects on mortality (total, cardiovascular and respiratory)
and on hospital emergency admissions for total respiratory causes and chronic obstructive
pulmonary disease (COPD), have been consistently demonstrated. These results have been shown,
in some instances, to persist when black smoke and SPM levels were controlled for, while in others
no attempts have been made to separate the pollutant effects. In these studies no obvious threshold
levels for SO2 has been identified.
1 For further information on health effects see Guidelines for Air Quality, WHO, Geneva, 2000
PAGE 13
GUIDELINE AMBIENT ENVIRONMENT STANDARDS FOR ETHIOPIA
1.1.3 Long-term exposure
Earlier assessments examined findings on the prevalence of respiratory symptoms, respiratory
illness frequencies, or differences in lung function values in localities with contrasting
concentrations of SO2 and SPM, using data from the coal-burning era in Europe. The lowest-
observed- adverse-effect level of SO 2 was judged to be at an annual average of 100 µg/m
3, when
present with SPM. More recent studies related to industrial sources of SO2, or to the changed urban
mixture of air pollutants, have shown adverse effects below this level. But a major difficulty in
interpretation is that long-term effects are liable to be affected not only by current conditions, but
also by the qualitatively and quantitatively different pollution of earlier years. However, cohort
studies on differences in mortality between areas with contrasting pollution levels indicate that
mortality is more closely associated with SPM, than with SO2.
1.2 MONITORING
As the main source of this pollutant is the combustion of fossil fuels containing sulphur, either in
power stations or domestic/commercial space heating, the major local source types strongly
influences monitoring and assessment strategies. Automatic analyzers need to be used if
compliance against a short-term guideline is to be determined; a variety of active samplers are
suitable for comparison with daily or annual guidelines. Passive samplers may be used to provide
data for comparison with the long-term annual guideline.
1.2.1 Passive samplers
There are currently no national or international standards governing the application of SO2
diffusion tubes to ambient air monitoring, nor for their laboratory preparation and analysis.
Protocols for sample preparation and analysis by spectrophotometry and ion exchange
chromatography have, however, been published in scientific literature (Bennett et al. 1992;
Downing et al. 1994; Hargreaves and Atkins 1988).
A variety of passive sampling techniques are available (UNEP/WHO 1994b). The most widely
used include:
• The triethanolamine (TEA)/glycol/spectrophotometry method (Hangartner et al. 1989).
• The potassium hydroxyde (KOH)/glycerol/spectrophotometry method (Hargreaves and
Atkins 1988).
• The sodium carbonate (Na2CO3)/glycerine/ion-exchange chromatography method (Ferm
1991).
Hybridization of these techniques is widespread. In the UK, for instance, KOH or NaOH is used as
absorbent, but with the tube membrane proposed by Ferm (1991) and using ion-exchange
chromatography as the analysis method. In practice, the ion-exchange chromatographic technique
has been informally accepted as the standard method for SO2 diffusion tube analysis. The typical
sensitivity of this hybrid technique is ±8.5 mg/m 3 : some under-reading against automatic
analysers has been observed (about 30%), although agreement with active samplers is better
(Downing et al. 1994).
1.2.2 Active samplers
The equipment required for sampling gaseous sulphur compounds in ambient air is described in full
in International Standard ISO 4219 (ISO 1979). This standard gives details of the equipment
necessary to sample gaseous pollutants by absorption in a liquid bubbler. The standard also
includes guidance for siting and installation of the apparatus. The principle of active-sampling
PAGE 14
GUIDELINE AMBIENT ENVIRONMENT STANDARDS FOR ETHIOPIA
methodologies is to draw ambient air through a collecting medium (typically a liquid bubbler), for
a specified time, typically 24 hours. The volume of air is metered. The collecting medium is
subsequently analysed and the concentration of pollutant in the sampled air determined. This
proven method is well established, and has been used in many monitoring networks worldwide for
a number of years. In consequence, there is a long history of active sampler SO2 measurements
available for trend assessment.
There are several methods of SO2 monitoring based on this principle, which can be carried out
using the apparatus specified in ISO 4219. They differ with respect to the solutions used in the
bubblers for SO2 absorption and the method of analysis. The four most widely used methods are
described below.
Acidimetric (total acidity) method.
This method, given in ISO 4220 (ISO 1983), is used to determine a gaseous acid air pollution
index. Although this method measures total acidity, and is not specific for SO2, it is adequate for
general use. The simplicity of the method, and the fact that the reagents are relatively safe, makes it
a popular choice for routine monitoring (AEA 1997). An accuracy of ±10% has been estimated for
SO2 measurements using the total acidity method, taking account of all contributory factors. A
precision of ±4 mg/m 3 is achievable for this widely-used method (AEA 1997).
Ion-exchange chromatography.
A variation on the above technique. The exposed peroxide solutions are analysed for sulphate ions
by means of ion-exchange chromatography, rather than titration. This has the advantage of being
sulphate-specific, but requires the use of an expensive ion-exchange chromatograph.
Tetrachloromercurate (TCM) method.
This is also known as the Pararosaniline method ISO 6767 (ISO 1990). This is the reference
method specified in the EC Directive on SO2 and suspended particulate matter(EC 1980).
However, the reagents used are very toxic, and for this reason the method is not widely used.
Thorin method.
This method is given in ISO 4221 (ISO 1980). The reagents used include perchloric acid, barium
perchlorate, dioxane and thorin. These are hazardous and must be handled and disposed of with
care. Accordingly, this method is not commonly used world-wide.
1.2.3 Automatic analysers
The measurement of SO2 in ambient air using automatic analysers is covered by ISO/DIS 10498
(ISO/DIS 1999). Well-established automatic monitoring techniques are available. The most widely
used method for automatic SO2 measurement is ultraviolet fluorescence (UVF). SO2 molecules in
the sample airstream are excited to higher, unstable energy states by UV radiation at 212 nm. These
energy states decay, causing an emission of secondary fluorescent radiation with an intensity
proportional to the concentration of SO2 in the sample.
The accuracy of data from automatic SO2 analysers depends on a range of factors encompassing
the entire measurement chain. These include accuracy of calibration standards, analyser stability
and sample losses in the measurement system. An accuracy of ±10% has been estimated for SO2
measurements in UK national automatic networks, taking account of all contributory factors. The
precision of SO2 measurements, determined from long-term variations in baseline response of in-
service analysers, is estimated to be ±3 mg/m3 (AEA 1996).
1.2.4 Remote sensors
Remote optical sensor systems, such as the Differential Optical Absorption System (DOAS), use a
long-path spectroscopic technique to make real-time measurements of the pollutant concentration
by integrating readings along a path between a light source and a detector. Long-path monitoring
PAGE 15
GUIDELINE AMBIENT ENVIRONMENT STANDARDS FOR ETHIOPIA
systems can be used to measure SO2, but the methodology is less well established than that for
automatic point monitors. The accuracy and precision of the data from these instruments are,
therefore, much more difficult to determine. The method does not conform to ISO 7996 (ISO
1985b). Particularly careful attention needs to be paid to instrument calibration and quality
assurance to obtain meaningful data from remote sensing instruments.
PAGE 16
GUIDELINE AMBIENT ENVIRONMENT STANDARDS FOR ETHIOPIA
2 NITROGEN DIOXIDE
Chemical Symbol or Formula: NO2
Standard*: Averaging Time
200 µg/m3 24 hours
40 µg/m3 1 year
* The volume must be standardised at a temperature of 293 °K and a pressure of 101,3 kPa.
2.1 HEALTH EFFECTS2
2.1.1 Short-term exposure effect
Available data from animal toxicology experiments indicate that acute exposure to NO2
concentrations of less than 1880 µg/m 3 (1 ppm) rarely produce observable effects. Normal healthy
humans, exposed at rest or with light exercise for less than two hours to concentrations above 4700
µg/m3 (2.5 ppm), experience pronounced decreases in pulmonary function; generally, normal
subjects are not affected by concentrations less than 1880 µg/m 3 (1.0 ppm). One study showed that
the lung function of subjects with chronic obstructive pulmonary disease is slightly affected by a
3.75-hour exposure to 560 µg/m3 (0.3 ppm).
A wide range of findings in asthmatics has been reported. Asthmatics are likely to be the most
sensitive subjects, although uncertainties exist in the health database. The lowest concentration
causing effects on pulmonary function was reported from two laboratories that exposed mild
asthmatics for 30-110 minutes to 565 µg/m 3 (0.3ppm) NO2 during intermittent exercise. However,
neither of these laboratories was able to replicate these responses with a larger group of asthmatic
subjects. One of these studies indicated that NO2 can increase airway reactivity to cold air in
asthmatic subjects. At lower concentrations, the pulmonary function of asthmatics was not changed
significantly.
NO2 increases bronchial reactivity, as measured by the response of normal and asthmatic subjects
following exposure to pharmacological bronchoconstrictor agents, even at levels that do not affect
pulmonary function directly in the absence of a bronchoconstrictor. Some, but not all, studies show
increased responsiveness to bronchoconstrictors at NO 2 levels as low as 376-565 µg/m
3
(0.2 to 0.3
ppm); in other studies, higher levels had no such effect. Because the actual mechanisms of effect
are not fully defined and NO2 studies with allergen challenges showed no effects at the lowest
concentration tested (188 µg/m3; 0.1 ppm), full evaluation of the health consequences of the
increased responsiveness to bronchoconstrictors is not yet possible. Recent studies have shown an
increased reactivity to natural allergens in the same concentration range. The results of repetitive
exposures of such individuals, or the impact of single exposures on more severe asthmatics, are not
known.
2.1.2 Long-term exposure effects
Studies with animals have clearly shown that several weeks to months of exposure to N O2
concentrations of less than 1880 µg/m 3 (1ppm) causes a range of effects, primarily in the lung, but
also in other organs such as the spleen and liver, and in blood. Both reversible and irreversible lung
2 For further information on health effects see Guidelines for Air Quality, WHO, Geneva, 2000.
PAGE 17
GUIDELINE AMBIENT ENVIRONMENT STANDARDS FOR ETHIOPIA
effects have been observed. Structural changes range from a change in cell type in the
tracheobronchial and pulmonary regions (at a lowest reported level of 640 µg/m 3), to emphysema-
like effects. Biochemical changes often reflect cellular alterations, with the lowest effective NO 2
concentrations in several studies ranging from 380-750 µg/m3.
NO2 levels of about 940 µg/m
3
(0.5ppm) also increase susceptibility to bacterial and viral infection
of the lung. There are no epidemiological studies that can be confidently used to quantify a long-
term NO2 exposure or concentration likely to be associated with the induction of unacceptable
health risks in children or adults. Homes with gas cooking appliances have peak levels of NO2 in the
same range as levels causing effects in some animal and human clinical studies. Epidemiological
studies evaluating the effects of NO2 exposures in such homes have been conducted. In general,
epidemiological studies of adults and infants (less than 2years old) show no significant effect of the
use of gas cooking appliances on respiratory illness; nor do the few available studies of infants and
adults show any associations between pulmonary function changes and gas stove use. However,
children 5-12 years old are estimated to have a 20% increased risk for respiratory symptoms and
disease for each increase of 28 µg/m3 NO2 (2-week average), where the weekly average
concentrations are in the range of 15-128 µg/m 3 or possibly higher. However, the observed effects
cannot clearly be attributed to either the repeated short-term high level peak, or to long-term
exposures in the range of the stated weekly averages (or possibly both).
The results of outdoor studies consistently indicate that children with long-term ambient NO2
exposures exhibit increased respiratory symptoms that are of longer duration, and show a decrease
in lung function. However, outdoor NO 2 epidemiological studies, as with indoor studies, provide
little evidence that long-term ambient NO 2 exposures are associated with health effects in adults.
None of the available studies yields confident estimates of long-term exposure-effect levels, but
available results most clearly suggest respiratory effects in children at annual average NO2
concentrations in the range of 50-75 µg/m3 or higher.
2.2 MONITORING
Automatic analysers must be used for the direct determination of compliance against the hourly
guideline, although much useful information can be inferred using passive samplers (see section
4.5). Either technique is applicable for comparing ambient levels against the annual guideline.
2.2.1 Passive samplers
Monitoring ambient NO2 concentrations using passive diffusion tube samplers is now well
established. This method provides an integrated, average concentration for the pollutant over the
exposure period (typically 2-4 weeks) and is particularly well suited to baseline and screening
studies for assessing the spatial distribution of NO2 concentrations in an urban environment. The
most widely used techniques are variants on the Palmes-type sampler, originally developed for the
assessment of occupational exposure. This uses a tube sampler, employing TEA as absorbent.
Sample analysis, after thermal desorption, is by spectrophotometry or ion-exchange
chromatography (Palmes et al. 1976). Very large scale mapping surveys are possible using
diffusion tubes, but careful attention both to the harmonization of analytical procedures and to the
outputs from different analytical laboratories is essential for the success of large-scale passive
sampler surveys.
Although extensively used throughout the UK and Europe there are, at present, no national or
international standards governing the application of diffusion tubes for ambient air quality
monitoring, nor for the laboratory preparation and analysis of diffusion tubes. Protocols for sampler
preparation and analysis by spectrophotometry have, however, been published in the scientific
literature (Palmes et al. 1976; Atkins et al. 1986); these have been informally accepted as standard
procedures for NO2 diffusion tube preparation and analysis.
PAGE 18
GUIDELINE AMBIENT ENVIRONMENT STANDARDS FOR ETHIOPIA
Recent comparisons of NO2 diffusion tube measurements with co-located chemiluminescent NOx
analysers show good agreement (Smith et al. 1997; Gerboles and Amantini 1993). Over the range
of concentrations generally encountered in urban areas (20-80 mg/m 3 ), it was found that on
average NO2 diffusion tubes, exposed for one month, tended to overestimate ambient NO2 by
approximately 10% compared with a chemiluminescent NOx analyser. Precision estimates of the
diffusion tube technique have been quoted as 5-8% in similar studies.
2.2.2 Active samplers
A variety of active sampler technologies are available (UNEP/WHO 1994b). The best known of
these is the Griess-Saltzman method, covered by ISO 6768 (ISO 1985a). Although this method is
sensitive and requires a relatively simple, inexpensive sampling apparatus, there are a number of
disadvantages. It is a relatively skilled and labour-intensive technique, uses corrosive chemicals
and is not readily applicable to sampling periods longer than 1-2 hours. There also remain doubts
about calibration methods, collection efficiency and possible side-reactions. In consequence, this
method cannot be recommended for general baseline monitoring applications.
2.2.3 Automatic analysers
The reference method for automatic measurement of nitrogen oxide concentrations, as defined for
compliance with EC Directive 85/203/EEC (EC 1985), is the automatic chemiluminescence
method described in ISO standard 7996 (ISO 1985b). This method is widely used world wide. The
method is based on the chemiluminescence energy emitted when NO in the sample airstream reacts
with O3 in an evacuated chamber to form an excited energy state of NO2. The chemiluminescent
reaction is:
NO + O3 = NO2* + O2
Emitted light from the excited NO 2* is converted to an output voltage by a photomultiplier tube
and amplifier.
Automatic NO2 analysers based on liquid-phase chemiluminescence, produced by reacting NO2
with a chemical solution, are also available. These highly sensitive but relatively fragile
instruments are mostly employed for research applications and are not generally regarded as being
suitable for routine baseline monitoring purposes.
The accuracy of data from automatic NO2 analysers depends on a range of factors encompassing
the entire measurement chain. These include the accuracy of calibration standards, analyser
stability and sample losses in the measurement system. Final accuracy can therefore vary from
network to network. An accuracy of ± 8% has been estimated for NO2 measurements in well-run
automatic networks, taking account of all contributory factors (AEA 1996). The precision of NO2
measurements is estimated to be ±6.5 mg/m 3 , determined from long-term variations in the
baseline responses of in-service analysers.
2.2.4 Remote sensors
Long-path monitoring systems are available for the measurement of NO2, but the methodology is
less well established than that for automatic point monitors. The accuracy and precision of the data
from these instruments are, therefore, much more difficult to determine. The method does not
conform to ISO 7996 (ISO 1995b) and, as noted previously, careful attention needs to be given to
instrument calibration and quality assurance to obtain meaningful data.
PAGE 19
GUIDELINE AMBIENT ENVIRONMENT STANDARDS FOR ETHIOPIA
3 CARBON MONOXIDE
Chemical Symbol or Formula: CO
Standard*: Averaging Time
100,000 µg/m3 15 minutes
60,000 µg/m3 15 minutes
30,000 µg/m3 1 hour
10,000 µg/m3 8 hours
* The volume must be standardised at a temperature of 293 °K and a pressure of 101,3 kPa.
3.1 HEALTH EFFECTS3
CO diffuses rapidly across alveolar, capillary and placental membranes. Approximately 80-90 % of
the absorbed CO binds with hemoglobin to form carboxyhemoglobin (COHb), which is a specific
biomarker of exposure in blood. The affinity of hemoglobin for CO is 200-250 times that for
oxygen. During exposure to a fixed concentration of CO, the COHb concentration increases rapidly
at the onset of exposure, starts to level off after 3 hours, and reaches a steady-state after 6-8 hours
of exposure. It is noted that the elimination half-life in the fetus is much longer than in the pregnant
mother. The binding of CO with hemoglobin to form COHb reduces the oxygen-carrying capacity
of the blood and impairs the release of oxygen from hemoglobin. These are the main causes of
tissue hypoxia produced by CO at low exposure levels. At higher concentrations, the rest of the
absorbed CO binds with other heme proteins such as myoglobin and with cytochrome oxidase and
cytochrome P-450. The toxic effects of CO first become evident in organs and tissues with high
oxygen consumption, such as the brain, heart, exercising skeletal muscle and the developing fetus.
Severe hypoxia due to acute CO poisoning may cause both reversible, short-lasting, neurological
deficits and severe, often delayed, neurological damage. The neurobehavioural effects include
impaired coordination, tracking, driving ability, vigilance and cognitive performance at COHb
levels as low as 5.1-8.2%. In apparently healthy subjects, the maximal exercise performance
decreases at COHb levels as low as 5%. The regression between the percentage decrease in
maximal oxygen consumption and the percentage increase in COHb concentration appears to be
linear, with a fall in oxygen consumption of approximately 1% for each 1% rise in COHb level
above 4%.
In controlled studies involving patients with documented coronary artery disease, mean pre-
exposure COHb levels of 2.9-5.9% (corresponding to post-exercise COHb levels of 2.0-5.2%) have
been associated with a significant shortening in the time to onset of angina, with increased
electrocardiographic changes and with impaired left ventricular function during exercise. In
addition, ventricular arhythmias may be increased significantly at the higher range of mean post-
exercise COHb levels. Epidemiological and clinical data indicate that CO from smoking and
environmental or occupational exposures may contribute to cardiovascular mortality and to the
early course of myocardial infarction. Current data from epidemiological studies and experimental
animal studies indicate that common environmental exposures to CO in the developed world would
not have atherogenic effects on humans (WHO 1999a).
During pregnancy, endogenous production of CO is increased so that maternal COHb levels are
usually about 20% higher than the non-pregnant values. At steady-state, the fetal COHb levels are
3 For further information on health effects see Guidelines for Air Quality, WHO, Geneva, 2000.
PAGE 20
GUIDELINE AMBIENT ENVIRONMENT STANDARDS FOR ETHIOPIA
as much as 10-15% higher than the maternal COHb levels. There is a well-established and probably
causal relationship between maternal smoking and low birth weight at fetal COHb levels of 2-10%.
In addition, maternal smoking seems to be associated with a dose-dependent increase in perinatal
deaths and with behavioural effects in infants and young children.
3.2 MONITORING
CO in urban areas results almost entirely (typically ~90%) from road traffic emissions. Since CO is
a primary pollutant, its ambient concentrations closely follow emissions. In urban areas,
concentrations are therefore highest at the kerbside and decrease rapidly with increasing distance
from the road. Mostly automatic analysers are being used for the direct assessment of ambient
levels against guidelines.
3.2.1 Passive samplers
A passive sampler has been developed for CO, utilizing a zeolite absorber and a narrow filamental
diffusion passage to optimize uptake, and involving GC/FID analysis after thermal desorption (Lee
et al. 1992). This technique may be useful for screening, mapping and ‘hot-spot’ identification. Its
use does not, however, appear to be widespread at the present time. Active samplers
Grab samples may be collected for subsequent laboratory analysis. However, this technique is not
known to be widely used.
3.2.2 Automatic analysers
The measurement of CO in ambient air is covered by international standards ISO/FDIS 4224
(ISO/FDIS 1999a) and ISO 8186. (ISO 1989) .
Baseline ambient CO monitoring is normally carried out using IR analysers. A number of
electrochemical CO analysers are available, but these are generally of low sensitivity and not
suitable for routine ambient monitoring. However, they may have application in areas of high
concentrations. A version of this sensor is incorporated in a commercially available roadside
pollution monitoring system.
CO analysis is based on the absorption of IR radiation at wavelengths of 4.5-4.9 micrometres.
Since other gases and particles can also absorb IR, the analyser must distinguish between
absorption by CO and absorption by interferences. In the most common analyser type, this is done
using a gas filter correlation wheel containing a cell of pure nitrogen and a cell of nitrogen plus
CO. The cell containing CO removes the CO-sensitive wavelengths before the IR signal enters the
absorption chamber, whilst all wavelengths are transmitted by the other cell. The difference in the
intensity of the two absorption signals, divided by the intensity of the IR source, provides a
measure of the ambient CO concentration.
The accuracy of data from automatic CO analysers depends on a range of factors encompassing the
entire measurement chain. These include accuracy of calibration standards, analyser stability and
sample losses in the measurement system. An accuracy of ± 8% and a precision of ±0.5 mg/m 3
may be achieved using this technique in well-managed and quality-assured programmes.
PAGE 21
GUIDELINE AMBIENT ENVIRONMENT STANDARDS FOR ETHIOPIA
4 OZONE AND OTHER PHOTOCHEMICAL OXIDANTS
Chemical Symbol or Formula: O3
Standard*: Averaging Time
120 µg/m3 8 hours
* The volume must be standardised at a temperature of 293 °K and a pressure of 101,3 kPa.
4.1 HEALTH EFFECTS4
O3 toxicity occurs in a continuum in which higher concentrations, longer exposure duration, and
greater activity levels during exposure cause greater effects. Short-term acute effects include
pulmonary function changes, increased airway responsiveness and airway inflammation, and other
symptoms. These health effects are statistically significant at 160 µg/m 3 (0.08 ppm) for 6.6 hour
exposures in a group of healthy exercising adults, with the most sensitive subjects experiencing a
more than 10% functional decrease within 4-5 hours. Controlled exposure of heavily exercising
adults, or children to an O3 concentration of 240 µg/m
3
(0.l2 ppm) for 2 hours, also produced
decreases in pulmonary function. There is no question that substantial acute adverse effects occur
during exercise with one hour exposure to concentrations of 500 µg/m 3 or higher, particularly in
susceptible individuals or subgroups.
Field studies in children, adolescents, and young adults have indicated that pulmonary function
decrease can occur as a result of short term exposure to O3 concentrations in the range 120-240
µg/m3 and higher. Mobile laboratory studies have observed changes in pulmonary function in
children or asthmatics exposed to O3 concentrations of 280-340 µg/m 3 (0.14-0.17 ppm) for several
hours. Respiratory symptoms, especially coughing, have been associated with O3 concentrations as
low as 300 µg/m 3 (0.15 ppm). O3 exposure has also been reported to be associated with increased
respiratory hospital admissions and exacerbation of asthma. The effects are observed with
exposures to ambient O3 (and co-pollutants) and with controlled exposures to O3 alone. This
demonstrates that the functional and symptomatic responses can be attributed primarily to O3.
A number of studies evaluating animals (rats and monkeys) exposed to O 3 for a few hours or days
have shown alterations in the respiratory tract, in which the lowest-observed-effect levels were in
the range of 160-400 µg/m3 (0.08-0.2 ppm). These included the potentiation of bacterial lung
infections, inflammation, morphological alterations in the lung, increases in the function of lung
enzymes active in oxidant defenses, and increases in collagen content. Long-term exposure to O3 in
the range of 240-500 µg/m3 (0.12 to 0.25 ppm) causes morphological changes in the epithelium and
interstitium of the centri-acinar region of the lung, including fibrotic changes.
4.2 MONITORING
O3 is not emitted directly from man-made sources in any significant quantities, but is formed in the
atmosphere by sunlight-driven chemical reactions involving NOx and VOC (see Section 2.1.2).
These reactions are not immediate, but may take from hours to days to complete. O3 is chemically
scavenged by primary NOx emissions from traffic, and is also removed from the atmosphere by
deposition to the ground.
4 For further information on health effects see Guidelines for Air Quality, WHO, Geneva, 2000
PAGE 22
GUIDELINE AMBIENT ENVIRONMENT STANDARDS FOR ETHIOPIA
Both spatial and temporal distributions of O3 differ markedly from those of other pollutants. In
particular, significant impacts may occur in areas up to hundreds of kilometres downwind of the
original precursor emissions, as a result of long-range as a result of long-range transport. Ambient
concentrations and population exposure may often be maximized in suburban and rural areas. This
has important implications for monitoring system design.
4.2.1 Passive samplers
A variety of techniques are available (UNEP/WHO 1994b). These include:
1,2,di-(4-pyridyl) ethylene absorbent- spectrophotometry (Monn and Hangartner 1990).
KI –spectrophotometry (Grosjean and Hisham 1992).
NaNO2/Na2CO3/glycerine -ion chromatography (Koutrakis et al. 1990).
Indigo carmine-reflectance (Alexander et al. 1991).
These methods are not as widely used or validated as corresponding samplers for NO2 and no clear
consensus as to a standard technique has yet emerged.
4.2.2 Active samplers
The most widely used active sampler technique was the Neutral Buffered Potassium Iodide (NKBI)
method. Although relatively simple and inexpensive, there are practical problems with
deterioration of the iodine complex and interference (most notably from NO2 and SO2). These
issues have reduced its use to the extent that the technique may now be regarded as obsolete.
4.2.3 Automatic analysers
ISO 10313 (ISO 1993a) is not of real relevance, as the chemiluminescence detection technique it
describes is no longer widely used. The most commonly used technology is now that of UV
absorption; this is specified as the reference method for the purposes of EC Directive 92/72/EEC
(EC 1992). An ISO standard is being developed for the UV method.
UV absorption is a robust, well-developed technique. Ambient O3 concentrations are calculated
from the absorption of UV light at 254 nm wavelength. The sample passes through a detection cell
of known length (l). An O3-removing scrubber is used to provide a zero reference light intensity,
I0. The analyser alternately measures the absorption of air in the cell with no O3 present and the
absorption in the experimental sample cell, Is. The ambient O3 concentration, c, may be simply
calculated using the Beer-Lambert equation:
Is = I0e
-alc
where a is the relevant absorption coefficient at 254 nm.
Given appropriate attention to system design, calibration and equipment support a typical
measurement accuracy of ±11% and a precision of ±4 mg/m 3 should be readily achievable in well-
run automatic networks.
4.2.4 Remote sensors
Open-path optical remote sensing techniques such as DOAS are available for O3, although the
associated practical issues noted in previous sections are applicable.
PAGE 23
GUIDELINE AMBIENT ENVIRONMENT STANDARDS FOR ETHIOPIA
5 SUSPENDED PARTICULATE MATTER
Chemical Symbol or Formula: Not Applicable
Standard: Averaging Time
PM10 50 µg/m3 1 Year
150 µg/m3 24 hours
PM2.5 15 µg/m3 1 Year
65 µg/m3 24 hours
5.1 HEALTH EFFECTS5
Health effects of SPM in humans depend on particle size and concentration, and can fluctuate with
daily fluctuations in PM10 or PM2.5 levels. They include acute effects such as increased daily
mortality, increased rates of hospital admissions for exacerbation of respiratory disease,
fluctuations in the prevalence of bronchodilator use and cough and peak flow reductions. Long-
term effects of SPM refer also to mortality and respiratory morbidity, but only few studies on the
long-term effects of SPM exist. Air pollution by particulate matter has been considered to be
primarily an urban phenomenon, but it is now clear that in many areas of developed countries,
urban-rural differences in PM10 are small or even absent, indicating that PM exposure is widespread.
This is not to imply that exposure to primary, combustion-related PM may not be higher in urban
areas.
A variety of methods exist to measure different fractions of particulate matter in air, with different
health significance. This evaluation has tended to focus on studies in which PM exposure was
expressed as PM10 and PM2.5. Health effect studies conducted with various TSP and BS as exposure
indicators have provided valuable additional information. However, they are less suitable for
deriving exposure-response relationships for PM because TSP includes particles that are too large
to be inhaled, or because the health significance of particle opacity as measured by the Black
Smoke method is uncertain.
The current time-series epidemiological studies are unable to define a threshold below which no
effects occur. Recent studies suggest that even at low levels of PM (less than 100 µg/m 3), short-
term exposure is associated with health effects. At low levels of PM 10 (0 - 100 µg/m
3), the short-
term exposure-response curve fits a straight line reasonably well. However, there are indications
from several studies that at higher levels of exposure (several hundreds of µg/m3 of PM10), at least
for effects on mortality, the curve is flatter than at low levels of exposure. This is discussed later in
this section.
Although many studies have obtained acute effect estimates for PM10 that are reasonably
consistent, this does not imply that particle composition or size distribution within the PM10
fraction is unimportant. Limited evidence from studies on dust storms indicates that such PM10
particles are much less toxic than those associated with combustion sources. Recent studies in
which PM10 size fractions and/or constituents have been measured suggest that the observed effects
of PM10 are largely associated with fine particles and not with the coarse fraction (PM10 minus
PM2.5). In some areas strong aerosol acidity or sulphate may be the cause of the effects associated
with PM2.5.
5 For further information on health effects see Guidelines for Air Quality, WHO, Geneva, 2000
PAGE 24
GUIDELINE AMBIENT ENVIRONMENT STANDARDS FOR ETHIOPIA
Evidence is also emerging that long-term exposure to low concentrations of PM in air is associated
with mortality and other chronic effects, such as increased rates of bronchitis and reduced lung
function. Two cohort studies conducted in the U.S.A. suggest that life expectancy may be 2-3 years
shorter in communities with high PM than in communities with low PM. This is consistent with
earlier cross-sectional studies, which compared age-adjusted mortality rates across a range of long-
term average PM concentrations. The results showed that long-term average exposures to low PM
levels, starting at about 10 µg/m3 of fine particulate matter, were associated with a reduction in life
expectancy. Whilst such observations require further corroboration, preferably also from other
areas in the world, these new studies suggest that the public health implications of PM exposure
may be large.
5.2 MONITORING
SPM is a generic term embracing all airborne particulate matter. This therefore encompasses a
wide range of size fractions, morphologies and chemical compositions, as discussed in Chapter 2.
Although coarse particle size ranges may cause significant local nuisance or soiling, it is the finer
fractions, such as PM2.5, that are capable of deep lung/airway penetration. Concern about the
potential health impacts of fine particulate matter has increased rapidly over recent years.
SPM monitoring is fundamentally different from the measurement of gaseous pollutants, and the
methods are generally less precise. A wide variety of different sampling and detection
methodologies is available, including the Tapered Element Oscillating Microbalance (TEOM), b-
ray analysis, gravimetric sampling (low or high-volume) and a number of indirect optical, particle
counting and light-scattering methods. The sampling system strongly affects the measurement
process and appropriate aerodynamically designed inlets are essential for proper sample-
fractionated determinations (UNEP/WHO 1994c).
5.2.1 Active samplers
Gravimetric samplers collect particulate matter onto a filter using high-volume (about 100 m 3
/hour) or low-volume (about 1 m 3 /hour) pumped sample flows. The weight of particulate matter
deposited on the filter is used to calculate a 24-hour average mass concentration. No ISO or CEN
standards have yet been promulgated for ambient measurement of PM10 particulate matter using
gravimetric samplers, although these are under development at the present time. An ISO standard
for evaluating PM10 inlet heads is, however, available (EN 1999). A United States Environmental
Protection Agency procedure for PM10 using the high-volume sampler is given in Federal Register
40 CFR Part 50 (CFR 1993). However, compliance with this procedure does not ensure consistency
with the anticipated CEN standards.
The various SPM monitoring techniques may not necessarily produce comparable measurements.
Different sampling systems, operating temperature, filter media and filter history may also
potentially affect measurement equivalence. The accuracy and precision of any measured mass
concentration is, therefore, liable to a wide margin of error. A target accuracy of <10 µg/m 3 and a
precision of <5 µg/m 3 (for daily average concentrations <100 µg/m 3 ) are given for PM10
measurements by EN 12341 (EN 1999).
Medium- or low-volume gravimetric samplers are more portable and less noisy than high-volume
samplers, making them more suitable for use in urban areas. However, the mass of particles
collected is far less than with high-volume samplers, giving a greater potential for errors due to
filter weighing. According to a recent large-scale instrument comparison, a number of
commercially available high- and medium-volume samplers are equivalent to a reference Wide
Ranging Aerosol Collector (WRAC) (EN 1999).
Correct filter handling, documentation and analysis is fundamental for obtaining valid data. The
filters must be conditioned in a temperature- and humidity-controlled environment, typically 20 o C
PAGE 25
GUIDELINE AMBIENT ENVIRONMENT STANDARDS FOR ETHIOPIA
and 50% relative humidity, for at least 24 hours before and after exposure. The filters must be
accurately weighed using a suitable balance, that has been calibrated using an accredited method.
5.2.2 Automatic analysers
Instruments are commercially available using the following techniques:
Tapered Element Oscillating Microbalance (TEOM).
Beta-ray absorption analysers (ISO/FDIS 1999b).
Light scattering systems.
Of the automatic instrument types available, the TEOM and b-ray systems have been operated
widely for many years and are well tested in the field. The light scattering type of instrument has
been developed more recently, and is therefore less well proven in service. Operating experience
and co-located measurement campaigns indicate that measurements from the different instruments
are not always equivalent or comparable
For traceable and robust measurements, samplers must be fitted with a tested PM10 inlet head and
an accurate flow control system. The PM10 sampling inlet should be tested to ISO Standard 7708
(ISO 1995) to ensure accurate size fractionation at the point of sampling. A target accuracy figure
of <10µg/m 3 and precision of <5µg/m 3 (for daily average concentrations <100 µg/m 3 ) are given
in EN 12341 (EN 1999). Tests on in-service TEOM analysers deployed in UK networks
demonstrate these figures to be realistic and achievable.
PAGE 26
GUIDELINE AMBIENT ENVIRONMENT STANDARDS FOR ETHIOPIA
6 LEAD
Chemical Symbol or Formula: Pb.
Standard: Averaging Time
0.5 µg/m3 1 Year
6.1 HEALTH EFFECTS6
The level of lead in blood is the best available indicator of current and recent past environmental
exposure and, with stable exposures, may also be a reasonably good indicator of lead body-burden.
The biological effects of lead can therefore be related to blood lead levels as an indicator of internal
exposure. The relationship between blood lead concentrations and exposure to lead in air exhibits
downward curvilinearity where the range of exposures is sufficiently large. At low levels of
exposure the deviation from linearity is negligible and linear models of the relationship between
intake and blood lead levels are satisfactory approximations.
The LOAEL for hematological and neurological effects of lead in adults and children can be
summarized as follows. Frank anemia is exhibited in adults at blood lead levels above 800 µg/l,
and in children above about 700 µg/l. Hemoglobin production is reduced in adults at blood lead
levels above 500 µg/l and in children above 250-300 µg/l. The presence of lead in the blood also
inhibits delta-aminolaevulinic acid dehydrase (ALAD), an enzyme involved in heme biosynthesis,
resulting in an accumulation of its substrate, ALA, in blood, plasma and urine (WHO 1987).
Urinary ALA and coproporyphyrin are elevated in both adults and children above blood lead levels
of about 400 µg/l. Erythrocyte protoporphyrin is found to increase in male adults at blood lead
levels above 200-300µg/l, and in female adults and children above 150-200 µg/l. A reduction in
vitamin D3 occurs in children at blood lead levels above 100-150 µg/l. Consequently, inhibition of
ALAD in adults and children is likely to occur at blood lead levels of about 100 µg/l. However,
because of its uncertain biological significance for the functional reserve capacity of the heme
biosynthetic system, ALAD inhibition is not treated as an adverse effect here. Encephalopathic
signs and symptoms appear not to occur in adults at lead concentrations in blood below 1000-1200
µg/l, and in children below 800-1000 µg/l.
Cognitive effects in lead workers have not been observed at blood lead levels below 500 µg/l,
although reductions in nerve conduction velocity were found at concentrations as low as 300 µg/l.
Elevation of free erythrocyte protoporphyrin has been observed at blood lead levels of 200- 300
µg/l. Central nervous system effects, as assessed by neurobehavioural endpoints, appear to occur in
children at levels below 200 µg/l. Consistent effects have been reported for global measures of
cognitive functioning, such as the psychometric intelligence quotient, at blood lead levels between
100-150 µg/l. Some epidemiological studies have indicated effects such as hearing impairment at
blood lead levels below 100 µg/l. Animal studies provide qualitative support for the claim that lead
is a causative agent for hearing impairment.
6.2 MONITORING
The main sources of lead in air are the combustion of petrol containing lead-based additives and
industrial emissions.
6 For further information on health effects see Guidelines for Air Quality, WHO, Geneva, 2000
PAGE 27
GUIDELINE AMBIENT ENVIRONMENT STANDARDS FOR ETHIOPIA
6.2.1 Active samplers
These are based on pumped sampling of large quantities of ambient air, capturing fine ambient
particulate matter on a filter for subsequent analysis. Analysis of filters for lead is covered by ISO
9855 (E), which specifies atomic absorption spectroscopy as the standard analytical method (ISO
1993b). There is no standard sampling method, although the EC Directive does specify some
relevant sampling and filter criteria (EC 1982).
A variety of sampling methods are used, including high-, medium-, and low-volume samplers.
There is no standard or reference sampling method. The UK method is broadly typical: this utilises
an “M Type” sampler designed specifically for this purpose. Its flow rate is controlled to 5.4-7.1 m
3 /day, and Millipore Aerosol Field Monitor filters are exposed and changed weekly. Passive
sampling methods are not applicable.
PAGE 28
GUIDELINE AMBIENT ENVIRONMENT STANDARDS FOR ETHIOPIA
7 GUIDELINES FOR AIR QUALITY: COMPOUNDS WITH NON-
CARCINOGENIC HEALTH ENDPOINTS
Compound Guideline Value (GV) or Tolerance
Concentration (TC)
µg/m3
Averaging Time
Acetaldehyde 2 000 (TC) 24 hours
50 (TC) 1 year
Acrolein 50 (GV) 30 min
Acrylic acid 54 (GV) 1 year
2-Butoxyethanol 13100 (TC) 1 week
Cadmium 5 x 10-3(GV) 1 year
Carbon disulphide 100 (GV) 24 hours
20 (GV) odour annoyance 30 min
Carbon Tetrachloride 6.1 (TC) 1 year
1,4 Dichlorobenzene 1000 (TC) 1 year
Dichloromethane 3000 (GV) 24 hours
Diesel exhaust 5.6 (GV) 1 year
Ethylbenzene 22 000 (GV) 1 year
Fluorides 1 (GV) 1 year
Formaldehyde 100 (GV) 30 min
Hydrogen sulphide 150 (GV) 24 hrs
7 (GV) Odour annoyance 30 min
Manganese 0.15 (GV) 1 year
Mercury, inorganic 1 (GV) 1 year
Methyl Methacrylate 200 (TC) 1 year
Monochlorobenzene 500 (TC) 1 year
Styrene 260 (GV) 1 week
7 (GV) Odour annoyance 30 minutes
Tetrachloroethylene 250 (GV) 24 hours
8000 (GV) Odour annoyance 30 minutes
Toluene 260 (GV) 1 week
1000 (GV) Odour annoyance 30 minutes
1,3,5 Trichlorobenzene 200 (TC) 1 year
1,2,4 Trichlorobenzene 50 (TC) 1 year
Vanadium 1 (GV) 24 hours
Xylenes 4800 (GV) 24 hours
870 (GV) 1 year
PAGE 29
GUIDELINE AMBIENT ENVIRONMENT STANDARDS FOR ETHIOPIA
Compound Tolerable Daily Intake (TDI or
ADI)
µg/kg bw d
Averaging Time (Over lifetime)
Chloroform 15 (TDI) 24 hours
Cresol 170 (ADI) 24 hours
Di-n-butyl Phthalate 66 (ADI) 24 hours
Dioxin-like compounds 1-4 (TDI) [TEQ/kg bw d] 24 hours
8 GUIDELINES FOR AIR POLLUTANTS WITH CARCINOGENIC HEALTH
ENDPOINTS
See Table 8.1
PAGE 30
GUIDELINE
Table 8.1 8 Guidelines For Air Pollutants With Carcinogenic Health Endpoints
Compound Average ambient air
concentration
µg/m3
Health endpoint
Acetaldehyde 5 Nasal tumours in rats
Acrylonitrile 0.01-10 Lung cancer in workers
Arsenic (1-30) x 10-3 Lung cancer in exposed humans
Benzene 5.0-20.0 Leukaemia in exposed workers
Benzo[a]pyrene Lung cancer in humans
Bis(chloromethyl)ether No data Epitheliomas in rats
Chloroform 0.3-10 Kidney tumours in rats
Chromium VI (5-200) x 10-3 Lung cancer in exposed workers
1,2-Dichloroethane 0.07-4 Tumour formation in rodents
Diesel exhaust 1.0-10.0 Lung cancer in rats
ETS 1-10 Lung cancer in exposed humans
Nickel 1-180 Lung cancer in exposed humans
PAH (BaP) (1-10) x 10-3 Lung cancer in exposed humans
1,1,2,2-Tetrachloroethane 0.1-0.7 Hepatocellular carcinomas in mice
Trichloroethylene 1-10 Cell tumours in testes of rats
Vinychloride 0.1-10 Hemangiosarkoma in exposed workers. Liver cancer in
exposed workers
GUIDELINE AMBIENT ENVIRONMENT STANDARDS FOR ETHIOPIA
9 INFORMATION SOURCES
The following information sources were utilised in the preparation of these standards:
• Guidelines for Air Quality, WHO, Geneva, 2000
• DEAT Guideline Values for Ambient Air Quality in South Africa
• The United Kingdom National Air Quality Strategy (March 1997 - Command no. 3587)
• USEPA National Ambient Air Quality Standards
• European Union, Directive 1999/30/EC relating to limit values for sulphur dioxide,
nitrogen dioxide, and oxides of nitrogen, particulate matter and lead in ambient air.
10 REFERENCES
AEA 1996 Site Operator’s Manual Automatic Urban Monitoring Network. AEA Technology plc,
National Environmental Technology Centre, Culham, Abingdon OX14 3ED, UK and
.http://www.aeat.co.uk/netcen/airqual/reports/lsoman/lsoman.html.
AEA 1997 Instruction Manual: UK Smoke and Sulphur Dioxide Networks. Report AEAT-1806,
AEA Technology plc, National Environmental Technology Centre, Culham, Abingdon OX14 3ED
UK and http://www.aeat.co.uk/netcen/airqual/reports/smkman/shead.html.
Alexander J, Drueke M, Traem R and Rumpel K-J. 1991 Ozon-Messungen mit SAM- kein Einfluss
Meteorologischer Groessen. Staub-Reinhaltung der Luft 51: 307-308.
Atkins CHF, Sandalls J, Law DV, Hough A, Stevenson K 1986 The measurement of nitrogen
dioxide in the outdoor environment using passive diffusion samplers. Environment & Medical
Sciences Division Report, Harwell Laboratory, N o AERE-R 12133, February 1986. AEA
Technology plc, National Environmental Technology Centre, Culham Abingdon OX14 3ED, UK.
Bennett SL, Lee DS, Sandalls FJ, Nason P, Atkins DHF 1992 The measurement of sulphur dioxide
in the outdoor environment using passive diffusion tube samplers: A second report. Environmental
Physics Department, AEA Environment and Energy. Report N o AEA-EE-0323, May 1992. AEA
Technology plc, National Environmental Technology Centre, Culham Abingdon OX14 3ED, UK.
CFR 1993 Code of Federal Regulations, Protection of Environment, National Primary and
Secondary Ambient Air Quality Standards, CFR Title 40 Part 50, Appendix J. Reference Method
for the Determination of Particulate Matter as PM10 in the Atmosphere. Office of the Federal
Register, National Archives and Records Administration, Washington DC, USA.
Downing CEH, Campbell GW, Bailey JC 1994 A survey of sulphur dioxide, ammonia and
hydrocarbon concentrations in the United Kingdom using diffusion tubes: July to December 1992.
Warren Spring Laboratory Report, Report N o LR 964, AEA Technology plc, National
Environmental Technology Centre, Culham Abingdon OX14 3ED, UK. EA 1997: Environment
Agency, Air Quality Bureau. Report of a continuous survey of the health effects of nitrogen oxides
in 1992-1995, Government of Japan.
EC 1982 Council Directive of 3 December 1982 on a Limit Value for Lead in Air 82/884/EEC.
Council of the European Communities, Brussels.
EC 1985 Council Directive 85/203/EEC of 7 March 1985 on air quality standards for nitrogen
dioxide. Official Journal of the European Communities, No. L372, p. 36.
PAGE 32
GUIDELINE AMBIENT ENVIRONMENT STANDARDS FOR ETHIOPIA
EC 1992 Council Directive 92/72/EEC of 12 September 1992 on air pollution by ozone. Official
Journal of the European Communities, No. L297, Vol. 34.
EN 1999 Air quality. Determination of the PM10 fraction of suspended particulate matter.
Reference method and field test procedure to demonstrate reference equivalence of measurement
methods – EN 12341. Available as BS EN 12341 from BSI 389 Chiswick High Road, London, W4
4AL or as a national standard from any CEN member country.
Ferm M 1991 A Sensitive Diffusional Sampler. Report No. IVL B-1020, Swedish Environmental
Research Institute, IVL Biblioteket, Stockholm, Sweden.
Grosjean, D, Hisham, MWM 1992 A passive sampler for atmospheric ozone. Journal of the Air
and Waste Management Association 42: 169-173
Hangartner M, Burri P, Monn C 1989 Passive Sampling of Nitrogen Dioxide, Sulphur Dioxide and
Ozone in Ambient Air. Proceedings of the 4th World Clean Air Congress, Hague, the Netherlands,
September 1989, Vol. 3, pp. 661-666.
Hargreaves, KJ, Atkins DHF 1988 The measurement of sulphur dioxide in the outdoor
environment using passive diffusion tube samplers: A first report. Environmental and Medical
Sciences Division, Harwell Laboratory. Report N o AERE-R-12569, July 1988. AEA Technology
plc, National Environmental Technology Centre, Culham Abingdon OX14 3ED, UK.
ISO 1979 Air Quality - Determination of gaseous sulphur compounds in ambient air- Sampling
equipment. International Standard ISO 4219. International Organization for Standardization,
Geneva
ISO 1980 Ambient Air - Determination of the mass concentration of sulfur dioxide in ambient air -
Thorin spectrophotometric method. International Standard ISO 4221. International Organization
for Standardization, Geneva
ISO 1983 Ambient Air - Determination of a gaseous acid air pollution index - Titrimetric method
with indicator or potentiometric end-point detection. International Standard ISO 4220. International
Organization for Standardization, Geneva
ISO 1985a Ambient Air - Determination of mass concentration of nitrogen dioxide – Modified
Griess-Saltzman Method. International Standard ISO 6768. International Organization for
Standardization, Geneva
ISO 1985b Ambient Air - Determination of mass concentration of nitrogen oxides –
Chemiluminescence method. International Standard ISO 7996. International Organization for
Standardization, Geneva
ISO 1989 Ambient Air - Determination of the mass concentration of carbon monoxide: Gas
chromatographic method, 8186. International Organization for Standardization, Geneva
ISO 1990 Ambient Air - Determination of the mass concentration of sulfur dioxide –
Tetrachloromercurate TCM / pararosaniline method. International Standard ISO 6767. International
Organization for Standardization, Geneva
ISO 1993a Ambient Air - Determination of the Mass Concentration of Ozone-Chemiluminescence
Method. International Standard ISO 10313. International Organization for Standardization, Geneva
ISO 1993b Ambient Air - Determination of the particulate lead content of aerosols collected in
filters. Atomic absorption spectroscopy method. International Standard ISO 9855 E . International
Organization for Standardization, Geneva
ISO 1995 Air Quality - Particle size fraction definitions for health-related sampling. International
Standard ISO 7708. International Organization for Standardization, Geneva
ISO/DIS 1999 Ambient Air - Determination of sulfur dioxide Ultraviolet fluorescence method.
International Standard ISO/DIS 10498. International Organization for Standardization, Geneva
PAGE 33
GUIDELINE AMBIENT ENVIRONMENT STANDARDS FOR ETHIOPIA
ISO/FDIS 1999a Ambient Air - Determination of carbon monoxide - Non-dispersive infrared
spectrometric method. International Standard ISO/FDIS 4224. International Organization for
Standardization, Geneva
ISO/FDIS 1999b Ambient Air - Measurement of particulate matter on a filter medium - Beta-ray
absorption method. International Standard ISO/FDIS 10473. International Organization for
Standardization, Geneva
Junker A, Schwela D 1998 Air quality guidelines and standards based on risk considerations. In:
Papers of the 11 th World Clean Air and Environment Congress, Vol. 6, paper 17D1, National
Association for Clean Air, South Africa.
Koutrakis P, Wolfson JM, Slater JL, Mulik JD, Kronmiller KJ and Williams DD 1990
Measurements of Ozone Exposure. Proceedings of the 1990 EPA-AWMA International
symposium on Measurement of Toxic and related Air Pollutants. Pittsburgh, pp. 468-474.
Monn C, Hangartner M 1990: Passive Sampling for Ozone, Journal of the Air and Waste
Management Association 40: 357-358.
Palmes ED, Gunnison AF, DiMattio J, Tomczyk C 1976 Personal sampler for nitrogen dioxide.
American Industrial Hygiene Association Journal 37: 570-577.
UNEP/WHO 1994a GEMS/Air Methodology Review Handbook Series, Vol.1- Quality Assurance
in Air Quality Measurements. WHO/EOS/94.1, UNEP /GEMS /94.A.2, United Nations
Environment Programme, Nairobi, Kenya, World Health Organization, Geneva.
UNEP/WHO 1994b: GEMS/Air Methodology Reviews Vol. 4: Passive and Active Sampling
Methodologies for Measurement of Air Quality. WHO/EOS 94.4, UNEP /GEMS/94.A.5, United
Nations Environment Programme, Nairobi, Kenya, World Health Organization, Geneva.
UNEP/WHO 1994c: GEMS/Air Methodology Reviews Vol. 3. Measurement of Suspended
Particulate matter in Ambient Air. WHO/EOS 94.3, UNEP/GEMS/94.A.4, United Nations
Environment Programme, Nairobi, Kenya, World Health Organization, Geneva.
WHO 1987 Air Quality Guidelines for Europe. WHO Regional Publications, European Series No.
23. Regional Office for Europe, World Health Organization, Copenhagen.
WHO 1999a. Air Quality Guidelines for Europe. WHO Regional Publications, European Series.
World Health Organization, Regional Office for Europe, Copenhagen, in press. Internet address:
http://www.who.dk
PAGE 34
GUIDELINE AMBIENT ENVIRONMENT STANDARDS FOR ETHIOPIA
APPENDIX 2
WATER QUALITY STANDARDS
(Surface Waters)
PAGE 35
GUIDELINE AMBIENT ENVIRONMENT STANDARDS FOR ETHIOPIA
PRESENTATION OF THE DATA
For convenience in reference each parameter included in this volume is covered in a standard
format consisting of a template in which important explanatory and background information is
summarised. The parameters are dealt with in one alphabetical. The elements of the template are
as follows, in the order in which they appear:
Chemical Symbol or Formula: These are in the conventional chemical notation, e.g. Antimony is
Sb, Silver is Ag, Zinc is Zn, and so on. In many cases the entry is "Not Applicable" as there is
either no chemical formula at all, as for microbiological parameters, or else the parameter, although
chemical, is a bulk one, e.g. Pesticides, so that the use of formulae is precluded on practical
grounds.
Units used for Analytical Results: For several key parameters the results of analysis may be
reported in terms other than those of the chemical formulae of the entities being determined.
Examples are nitrate, NO3
–, reported often as N, and phosphate, PO4
– – commonly reported as P.
Reference Methods of Analysis: Reference methods are specified for the parameter in question.
The references given relate to Standard Methods for the Examination of Water and Wastewater,
1998, (prepared and published jointly by A.P.H.A., A.W.W.A & W.E.F) 20th Ed., American Public
Health Association, 1015 Fifteenth Street, N.W., Washington DC 20005, USA, a standard text used
in most water laboratories.
As a guide, to the complexity of the method specified the following letters [A], [B], [C] and [D]
have been used throughout to indicate, respectively, an increasing degree of sophistication of the
technique and/or of the equipment used. Thus, [A] indicates a method suitable for use in a more
basic water laboratory, [B] implies a method more demanding of staff expertise or equipment, [C]
implies an elaborate laboratory set-up, with advanced instrumentation, and [D] denotes a specialist
laboratory with state-of-the-art equipment. A dual designation, e.g. [B/C], is used for those
methods which may be practicable at different levels of instrumentation or expertise. It may be
noted that these designations are quite in for mat and are offered for guidance only. In reality, there
may often be no clear gradations between the capabilities of different laboratories.
With regard to sampling, a sample should be collected such that the sample is representative of the
condition being investigated and in a manner consistent with the collection, handling and
preservation principles enunciated in the above publication section 1060.
Introduction: This section contains adequate detail to set the significance of each parameter in
perspective. In some important cases, notably " Biochemical Oxygen Demand," "Hardness" and "
Dissolved Oxygen," the entries are fairly lengthy, but this is in line with one of the primary aims of
this volume, namely to act as a "free-standing" reference for the engineer, environmentalist or
scientist.
Occurrence: A brief indication is given as to whether substances covered by the parameter occur
in rock, are constituents of sewage or industrial wastes, or are synthetic materials. It is assumed
throughout that substances attributed to industrial wastes could equally well arise from tiphead
leachates, this is not always specified.
Effect: Brief reference is made to known toxic or physiological effects - or the lack of them - of
each parameter. It must be stressed that such references are not in any way exhaustive, but are
merely indicative. This volume does not purport in any way to deal with medical matters or with
any material connection between a given parameter and the health of the user/consumer of a water
containing it.
PAGE 36
GUIDELINE AMBIENT ENVIRONMENT STANDARDS FOR ETHIOPIA
1 ALUMINIUM
Chemical Symbol or Formula: Al.
Standard: 0.2 mg/l
Percentage Compliance Required: 95% of all monitoring data must comply with the
standard.
Units Used for Analytical Results: mg/l Al.
Reference Method(s) of Analysis:
Method Type Complexity APHA Reference
Colorimetry B 3500-Al-D
Atomic Absorption Spectrometry Method B/C. 3500-Al-B
Inductively Coupled Plasma Method D 3500-Al-C
Introduction Aluminium is the third most abundant element in the earth's crust. It occurs
primarily as aluminosilicate minerals which are too insoluble to participate
readily in bio-geochemical reactions. Aluminium is a strongly hydrolysing
metal and is relatively insoluble in the neutral pH range. Under acidic (pH <
6.0) or alkaline (pH > 8.0) conditions, or in the presence of complexing ligands,
elevated concentrations may be mobilised to the aquatic environment.
The solubility of aluminium in water is strongly pH dependent. Under acid
conditions, it occurs as soluble, available and toxic hexahydrate (aquo) species.
At intermediate pH values, it is partially soluble and probably occurs as
hydroxy- and polyhydroxo- complexes. At alkaline pH values, aluminium is
present as soluble but biologically unavailable hydroxide complexes or as
colloids and flocculants.
Aluminium is described as a non-critical element, though there is growing
concern over the effects of elevated concentrations of aluminium in the
environment, primarily that mobilized as a result of acid mine drainage and acid
precipitation. Studies of the environmental chemistry and toxicity of aluminium
provide a limited understanding of the processes regulating the aqueous
concentration, speciation and bio-availability of this element. Clearly, the
toxicity of aluminium depends on the chemical species involved.
Occurrence Aluminium can be mobilised from soils and sediments by both natural
weathering and accelerated acidification processes, resulting in detectable
concentrations in surface waters. Although aluminium is found in waters made
naturally acidic by humic and fulvic acids, it usually adsorbs onto these and is
therefore not available in soluble form in such waters, even at low pH.
Aluminium is found in soluble forms mainly in acid mine drainage waters and
is also of concern in natural waters affected by acid rain. Aluminium is one of
the principal particulates emitted from the combustion of coal, and aluminium
fluoride is emitted from aluminium smelters. Industries using aluminium in
their processes or in their products include the following:
• the paper industry,
• the metal construction industry,
• the leather industry, and
PAGE 37
GUIDELINE AMBIENT ENVIRONMENT STANDARDS FOR ETHIOPIA
• the textile industry.
In addition to liquid effluents that may be generated from the above industries,
alum or aluminium sulphate is used in most water treatment processes as a
flocculating agent for suspended solids, including colloidal materials, micro-
organisms and "humic rich" dissolved organics.
Effects Elevated concentrations of bio-available aluminium in water are toxic to a wide
variety of organisms. There is, however, uncertainty as to the form(s) of bio-
available aluminium as well as to the mechanism(s) of toxicity. The toxic
effects are dependent on the species and life stage of the organism, the
concentration of calcium in the water, and pH. The pH may not only affect the
chemistry of aluminium but may also determine how the organism responds to
dissolved aluminium. In acidic waters, aluminium is generally more toxic over
the pH range of 4.4 - 5.4, with maximum toxicity occurring about pH 5.0 - 5.2.
The mechanism of toxicity in fish seems to be related to interference with ionic
and osmotic balance and with respiratory problems resulting from coagulation
of mucus on the gills. It has also been suggested that aluminium interferes with
calcium metabolism, thereby altering the functioning of the calcium regulating
protein, calmodulin. Aluminium has been shown to interfere with ion exchange
sites, in particular those involved in sodium homeostasis. This in turn may lead
to neuromuscular dysfunction.
2 AMMONIA
Chemical Symbol or Formula: NH3
Standard: Game Fishing: 0.02 mg/l NH3 (Non-ionised Ammonia)
Game Fishing: 0.04 mg/l NH4 (Total Ammonia)
Coarse Fishing: 0.025 mg/l NH3 (Non-ionised Ammonia)
Coarse Fishing: 0.2 mg/l NH4 (Total Ammonia)
Percentage Compliance Required: 95% of all monitoring data must comply with the
standard.
Units Used for Analytical Results: mg/l N.
Reference Method(s) of Analysis:
Method Type Complexity APHA Reference
Preliminary Distillation Step B 4500 NH3 B
Titrimetric Method B 4500 NH3 C
Ammonia – Selective Electrode Method B 4500 NH3 D
Colorimetric Method (Phenate) B 4500 NH3 F
Introduction Un-ionized ammonia (NH3) is a colourless, acrid-smelling gas at ambient
temperature and pressure. It is produced naturally by the biological degradation
of nitrogenous matter and provides an essential link in the nitrogen cycle.
Ammonia may be present in the free, un-ionized form (NH 3) or in the ionized
form as the ammonium ion (NH4
+). Both are reduced forms of inorganic
PAGE 38
GUIDELINE AMBIENT ENVIRONMENT STANDARDS FOR ETHIOPIA
nitrogen derived mostly from aerobic and anaerobic decomposition of organic
material. They exist either as ions, or can be adsorbed onto suspended organic
and inorganic material.
The toxicity of ammonia is directly related to the concentration of the un-
ionized form (NH3), the ammonium ion (NH4
+) having little or no toxicity to
aquatic biota. The ammonium ion does, however, contribute to eutrophication.
Modifying factors may alter the acute toxicity by altering the concentration of
un-ionized ammonia in the water through changes in the ammonia-ammonium
ion equilibrium, or may increase the toxicity of the un-ionized ammonia to
organisms.
Occurrence Ammonia is present in small amounts in air, soil and water, and in large
amounts in decomposing organic matter. Natural sources of ammonia include
gas exchange with the atmosphere; the chemical and biochemical
transformation of nitrogenous organic and inorganic matter in the soil and
water; the excretion of ammonia by living organisms; the nitrogen fixation
processes whereby dissolved nitrogen gas enters the water and ground water.
Ammonia, associated with clay minerals enters the aquatic environment through
soil erosion. Bacteria in root nodules of legumes fix large amounts of nitrogen
in the soil and this may be leached into surrounding waters.
Ammonia is a common pollutant and is one of the nutrients contributing to
eutrophication. Commercial fertilizers contain highly soluble ammonia and
ammonium salts. Following application of fertilizer, if the concentration of such
compounds exceeds the immediate requirements of the plant, transport via the
atmosphere or irrigation waters can carry these nitrogen compounds into aquatic
systems. Other sources of ammonia include:
• fish-farm effluent (un-ionized ammonia);
• sewage discharge;
• discharge from industries that use ammonia or ammonium salts in their
cleaning operations;
• manufacture of explosives and use of explosives in mining and
construction; and
• atmospheric deposition of ammonia from distillation and combustion of
coal, and the biological degradation of manure.
Effects The most significant factors that affect the proportion and toxicity of un-ionized
ammonia in aquatic ecosystems are water temperature and pH. An increase in
either results in an increase in the relative proportion of un-ionized ammonia in
solution, and hence an increase in toxicity to aquatic organisms, as given in
Table 1.
PAGE 39
GUIDELINE AMBIENT ENVIRONMENT STANDARDS FOR ETHIOPIA
Contribution of Un-ionised Ammonia to Total Ammonia (expressed as
percentage) as function of pH Value and Water Temperature
Water Temperature °C
pH 0 5 10 15 20 25 30 35
6.0 0.0083 0.012 0.019 0.027 0.039 0.056 0.079 0.11
6.5 0.026 0.039 0.059 0.086 0.12 0.18 0.25 0.35
7.0 0.083 0.12 0.18 0.27 0.39 0.56 0.79 1.1
7.5 0.26 0.39 0.58 0.85 1.2 1.7 2.4 3.4
8.0 0.82 1.2 1.8 2.6 3.8 5.3 7.3 9.9
8.5 2.6 3.8 5.5 7.9 11 15 20 26
9.0 7.6 11 16 21 28 36 44 52
9.5 21 28 37 46 55 64 71 78
Ammonia toxicity is also affected by the concentrations of dissolved oxygen,
carbon dioxide and total dissolved solids, and the presence of other toxicants,
such as metal ions. The acute toxicity of ammonia to fish increases as dissolved
oxygen decreases. Ammonia is oxidized to nitrate in well oxygenated waters.
Ammonia may also be adsorbed onto suspended and bed sediments and to
colloidal particles.
Un-ionized ammonia affects the respiratory systems of many animals, either by
inhibiting cellular metabolism or by decreasing oxygen permeability of cell
membranes. Acute toxicity to fish may cause a loss of equilibrium, hyper-
excitability, an increased breathing rate, an increased cardiac output and oxygen
intake, and in extreme cases convulsions, coma and death.
Chronic effects include a reduction in hatching success, reduction in growth rate
and morphological development, and pathological changes in tissue of gills,
liver and kidneys. An increased ventilation of the gills following exposure to
ammonia indicating a respiratory effect has been observed in mayfly larvae
Ecdyonurus dispar.
PAGE 40
GUIDELINE AMBIENT ENVIRONMENT STANDARDS FOR ETHIOPIA
3 ANTIMONY
Chemical Symbol or Formula: Sb
Standard: 20 µg/l.
Percentage Compliance Required: 95% of all monitoring data must comply with the
standard.
Units Used for Analytical Results: µg/l Sb.
Reference Method(s) of Analysis:
Method Type Complexity APHA Reference
Atomic Absorption Spectrometry Method B/C 3500-Sb-B
Inductively Coupled Plasma Method D 3500-Sb-C
Occurrence Naturally occurring trace element used in metal industry and in flame retardant
materials. Antimony can occur naturally in water from weathering of rocks but
is more likely to arise from effluents.
Effects Significance: Although the health effects of antimony have not been established
definitively, there is evidence of actual or potential carcinogenicity of some
antimony compounds. Accordingly, concentrations are limited in drinking
water.
4 ARSENIC
Chemical Symbol or Formula: As.
Standard: 0.05 mg/l
Percentage Compliance Required: All monitoring data must comply with the standard.
Units Used for Analytical Results: mg/l As.
Reference Method(s) of Analysis:
Method Type Complexity APHA Reference
Atomic Absorption Spectrometry Method C/D. 3500-As-B
Inductively Coupled Plasma Method D 3500-As-D
Introduction Arsenic is a metalloid element which is toxic to marine and freshwater aquatic
life and is a known carcinogen. Elemental arsenic is insoluble in water, but
many of its compounds are highly soluble. Arsenic occurs in several oxidation
states, namely, III, IV, V and III, -depending on the pH and redox potential of
the water. The two most common forms are arsenic (III) and arsenic (V), both
of which form stable compounds with carbon, resulting in numerous organo-
arsenical compounds. Elemental arsenic also combines readily with many
metals to form arsenide salts, which are toxic to organisms.
PAGE 41
GUIDELINE AMBIENT ENVIRONMENT STANDARDS FOR ETHIOPIA
Most forms of arsenic, including the arsenical gases arsine (AsH3) and trimethyl
arsine, are very toxic. The USEPA has classified arsenic as "very toxic and
relatively accessible" to aquatic organisms.
Occurrence Elemental arsenic is found to a limited extent in nature, mostly as a result of
weathering of arsenic-containing rocks and of volcanic activity. Arsenic most
commonly occurs as arsenides of metals or as arsenopyrite. Inorganic arsenic
occurs in aquatic ecosystems primarily as arsenic (III) and as arsenic (V),
depending on pH and redox potential. Arsenic readily adsorbs onto sediments
and suspended solids, and is lipid-soluble.
Arsenic may occur at high concentrations in water bodies subject to industrial
pollution, or in the vicinity of industrial activities utilising or discharging
arsenic or arsenal compounds.
Manufacturers that use arsenic in their processes, or in their products, include:
• the mining industry,
• the metal processing industry,
• producers of pesticides and fertilizers,
• producers of glass and ceramics,
• tanneries,
• dye manufacturers,
• producers of wood preservation products,
• the chemical industry,
• producers of detergents.
Effects Arsenic has been reported to have a variety of adverse effects on both vertebrate
and invertebrate aquatic organisms; the type and severity of adverse effects
being dependent on the life stages of the organisms concerned. Exposure to
arsenic results in reduced growth and reproduction in both fish and invertebrate
populations. Arsenic also causes behavioural changes such as reduced migration
in fish.
Organic arsenal compounds have been shown to be less toxic than inorganic
forms of arsenic to fish. In fresh water, there is little evidence to suggest that
different inorganic forms of arsenic vary significantly in their toxicity to aquatic
biota. Arsenic (V) is more toxic to plants than arsenic (III). Arsenates, although
not particularly toxic, interfere with energy metabolism, whereas arsenites
inhibit the activity of a variety of essential enzymes.
Increased duration of exposure to arsenic at a given concentration leads to a
reduction in adverse effects experienced by aquatic organisms, and they have
been shown to develop tolerance. The response of organisms to arsenic is
reduced by pre-exposure, and organisms may become gradually acclimated to
high concentrations of arsenic in aquatic ecosystems.
Although inorganic arsenic does not accumulate in aquatic organisms, various
forms of arsenic are lipid-soluble and therefore accumulate, in fatty tissue.
Arsenic accumulation is usually higher in algae and invertebrates than in fish,
though bottom-feeding fish are most likely to accumulate arsenic. Humans are
more sensitive to arsenic than are aquatic organisms; therefore, consumption of
contaminated products can pose a health risk to humans. Arsenic can be bio-
concentrated in aquatic organisms because it has a high affinity for organic
substances.
PAGE 42
GUIDELINE AMBIENT ENVIRONMENT STANDARDS FOR ETHIOPIA
Many of the toxic effects of arsenic on aquatic organisms can be reversed if
arsenic concentrations are reduced and maintained at very low levels.
5 BARIUM
Chemical Symbol or Formula: Ba.
Standard: 0.1 mg/l
Percentage Compliance Required: All monitoring data must comply with the standard.
Units Used for Analytical Results: mg/l Ba.
Reference Method(s) of Analysis:
Method Type Complexity APHA Reference
Atomic Absorption Spectrometry Method B/C 3500-Ba-B
Inductively Coupled Plasma Method D 3500-Ba-C
Occurrence Naturally occurring mineral (e.g. in barytes. According to the WHO
Guidelines, while food is the main source of barium intake by humans, where
barium occurs in drinking water supplies the latter can contribute a significant
proportion of total intake.
In normal surface waters levels are likely to be low as traces of barium will
react with sulphate present to form the highly insoluble barium sulphate.
Effects Significance: Excessive amounts of barium can cause muscular, cardiovascular
and renal damage. Although not markedly toxic, barium in excess quantities is
clearly undesirable.
6 BENZENE
Chemical Symbol or Formula: C6H6
Standard: 10 µg/l
Percentage Compliance Required: All monitoring data must comply with the standard.
Units Used for Analytical Results: µg/l compound.
Reference Method(s) of Analysis:
Method Type Complexity APHA Reference
Purge and Trap Gas Chromatographic Method I C 6220-B
Purge and Trap Gas Chromatographic Method II C 6220-C
Purge and Trap Gas Chromatographic/Mass Spectrometric
Method
D 6220-D
PAGE 43
GUIDELINE AMBIENT ENVIRONMENT STANDARDS FOR ETHIOPIA
Background: Emissions from motor vehicles account for most of the benzene in the air,
which can in due course reach the aquatic environment. Pollution from
industrial sources can also introduce benzene to water.
Benzene is not a naturally-occurring constituent of water.
Occurrence Constituent of some petroleum products; industrial raw material; solvent.
Effects Carcinogenic substance which also affects the central nervous system adversely.
7 BENZO(A)PYRENE
Chemical Symbol or Formula: C20H12
Standard: 0.01 µg/l
Percentage Compliance Required: All monitoring data must comply with the standard.
Units Used for Analytical Results: µg/l compound.
Reference Method(s) of Analysis:
Method Type Complexity APHA Reference
Liquid-Liquid Extraction Gas Chromatographic/Mass
Spectrometric Method
D 6410-B
Liquid-Liquid Extraction Gas Chromatographic Method C 6431-B
Occurrence Synthetic complex aromatic organic compound formed by pyrolysis or
combustion of organic materials.
Effects Benzo(a)pyrene is a carcinogenic and mutagenic substance which is considered
to be highly undesirable in drinking water, even though the WHO Guidelines
indicate that food is the main source of human exposure to this type of
substance.
8 BENZENE
Chemical Symbol or Formula: C6H6
Standard: 10 µg/l
Percentage Compliance Required: All monitoring data must comply with the standard.
Units Used for Analytical Results: µg/l compound.
Reference Method(s) of Analysis:
Method Type Complexity APHA Reference
Purge and Trap Gas Chromatographic Method I C 6220-B
Purge and Trap Gas Chromatographic Method II C 6220-C
Purge and Trap Gas Chromatographic/Mass Spectrometric
Method
D 6220-D
PAGE 44
GUIDELINE AMBIENT ENVIRONMENT STANDARDS FOR ETHIOPIA
Background: Emissions from motor vehicles account for most of the benzene in the air,
which can in due course reach the aquatic environment. Pollution from
industrial sources can also introduce benzene to water.
Benzene is not a naturally-occurring constituent of water.
Occurrence Constituent of some petroleum products; industrial raw material; solvent.
Effects Carcinogenic substance which also affects the central nervous system adversely.
9 BIOCHEMICAL OXYGEN DEMAND (BOD5)
Chemical Symbol or Formula: Not applicable [Bulk parameter]
Standard: ≤ 5 mg/l
Percentage Compliance Required: 95% of all monitoring data must comply with the
standard.
Units Used for Analytical Results: mg/l O2.
Reference Method(s) of Analysis:
Method Type Complexity APHA Reference
5-Day BOD Test B 5210-B
Background When organic matter is discharged into a watercourse it serves as a food source
for the bacteria present there. These will sooner or later commence the
breakdown of this matter to less complex organic substances and ultimately to
simple compounds such as carbon dioxide and water. If previously unpolluted,
the receiving water will be saturated with dissolved oxygen (DO), or nearly so,
and the bacteria present in the water will be aerobic types. Thus the bacterial
breakdown of the organic matter added will be an aerobic process - the bacteria
will multiply, degrading the waste and utilising the DO as they do so. If the
quantity of waste present is sufficiently large, the rate of bacterial uptake of
oxygen will outstrip that at which the DO is replenished from the atmosphere
and from photosynthesis, and ultimately the receiving water will become
anaerobic.
Bacterial degradation of the waste will continue but now the products will be
offensive in nature -for example, hydrogen sulphide. Even if the uptake of
oxygen is not sufficient to result in anaerobic conditions there will be other
undesirable effects as the DO level falls, notably damage to fisheries and,
ultimately, fish deaths. Where levels are around 50 per cent saturation for
significant periods there may be adverse, though non-lethal, effects on game
fish. Coarse fish will be likewise affected if levels are regularly around 30 per
cent saturation.
Because of the potential danger to the oxygen levels in receiving waters from
waste discharges considerable emphasis is placed in the laboratory on the
estimation of the oxygen demand of wastes: i.e. the amount of oxygen which
will be required in their breakdown. This is done chemically and biologically,
by a variety of tests which are also employed to assess the actual effects of
waste discharges on receiving water, as discussed below. As in most cases the
oxygen demand of a waste on the DO level of a receiving water results from
biological action, it follows that the most important analytical method should
PAGE 45
GUIDELINE AMBIENT ENVIRONMENT STANDARDS FOR ETHIOPIA
also depend on a biological process, to measure the biochemical oxygen
demand or BOD. The principle of this test, which was devised some 85 years
ago, is straightforward. The (five-day) BOD of a water is the amount of
dissolved oxygen taken up by bacteria in degrading oxidisable matter in the
sample, measured after 5 days incubation in the dark at 20°C. The BOD is
simply the amount by which the DO level has dropped during the incubation
period. This technique is the basis of BOD analyses for all types of sample even
though considerable extensions of procedure are necessary in dealing with
wastewaters and polluted surface waters.
Current scientific opinion is that waters with a BOD failing within the range of
0 - 4 mg/l O 2 are of satisfactory quality for sensitive species such as salmonid
fish and thus for other beneficial uses. If an upper limit for BOD of 4 mg/l O2 is
adopted as a criterion of satisfactory quality then it is possible to assess the
degree to which waters are polluted by reference to this datum. It is most
important to remember, however.. that a BOD figure for a receiving water
indicates the maximum extent to which the oxygen level may be depleted by the
organic matter present. In reality, no appreciable deoxygenation may occur
because of factors such as low temperatures, reaeration at weirs or shallows,
dilution by tributaries and so on. Conversely, in some waters which do not have
high BOD levels, but which are eutrophic, there may be severe night-time DO
depletions caused by algal respiration. Notwithstanding the many often
contradictory considerations which govern the interpretation of BOD data the
analysis is one of the most important elements in river quality surveillance and
it seems unlikely to be superseded for a long time yet.
Somewhat different considerations apply to the BOD analysis of effluents. BOD
data are normally required for one of two purposes. Firstly, it is necessary to
know the strength of a waste which is to be treated by biological means, as in an
oxidation ditch or percolating filter. This is essential so that adequate treatment
capacity may be provided for in the design of the plant. Secondly.. where wastes
are being discharged to receiving waters a knowledge of their strength and the
magnitude of the river discharge will permit the dilution to be calculated and
hence the maximum potential change in the river BOD at the boundary of the
mixing zone. A factor which must be borne in mind in obtaining and in
assessing BOD results is nitrification. This is the oxidation of ammonia to
nitrate by suitable micro-organisms and if the process is occurring under test
conditions high oxygen uptake values will be recorded. For normal river waters
the onset of nitrification under BOD test conditions does not occur within the 5-
day period of the analysis but in the case of waters or wastewaters containing
nitrifying organisms this phenomenon will take place much more promptly.
Unless suitable precautions are taken the result is an apparently very high BOD
level which, if the analysis is being used to check the performance of a waste
treatment works (with respect to the removal of organic matter), for example,
may lead to serious errors in the interpretation and use of the data.
Occurrence Natural or introduced organic matter in water.
Effects An indicator of overall water quality.
PAGE 46
GUIDELINE AMBIENT ENVIRONMENT STANDARDS FOR ETHIOPIA
10 CADMIUM
Chemical Symbol or Formula: Cd.
Standard: 5 µg/l
Percentage Compliance Required: 95% of all monitoring data must comply with the
standard.
Units Used for Analytical Results: µg/l Cd.
Reference Method(s) of Analysis:
Method Type Complexity APHA Reference
Atomic Absorption Spectrometric Method B/C 3500-Cd-B
Inductively Coupled Plasma Method D 3500-Cd-C
Dithizone Method B 3500-Cd-D
Introduction Cadmium is a metal element which is highly toxic to marine and fresh water
aquatic life. Elemental cadmium is insoluble in water though many of its
organic and inorganic salts are highly soluble. Cadmium occurs primarily in
fresh waters as divalent forms including free cadmium (II) ion, cadmium
chloride and cadmium carbonate, as well as a variety of other inorganic and
organic compounds.
Cadmium is defined by the United States Environmental Protection Agency as
potentially hazardous to most forms of life, and is considered to be toxic and
relatively accessible to aquatic organisms.
Occurrence Cadmium is present in the earth's crust at an average concentration of 0.2
mg/kg, usually in association with zinc, lead and copper sulphide ore bodies.
Due to its abundance, large quantities of cadmium enter the global environment
annually as a result of natural weathering processes. Cadmium is found at trace
concentrations in fresh waters and mostly a result of industrial activity.
The main sources of cadmium in the environment are due to:
• emissions to air and water from mining, metal (zinc, lead and copper)
smelters, and industries involved in manufacturing alloys, paints, batteries
and plastics;
• agricultural use of sludges, fertilizers and pesticides containing cadmium;
• burning of fossil fuels (very limited effect); and
• the deterioration of galvanized materials and cadmium-plated containers.
Effects Cadmium is easily absorbed by mammals, where it is concentrated by binding
with the protein metallothionein. Many plant and animal tissues contain
cadmium, but there is no evidence that cadmium is biologically essential or
beneficial. Cadmium is chemically similar to zinc, and its physiological effects
are often due to its replacement of zinc in some enzymes, thereby impairing
enzyme activity. Cadmium is known to inhibit bone repair mechanisms, and is
teratogenic, mutagenic and carcinogenic.
Bioavailable cadmium may be accumulated by macrophytes, phytoplankton,
zooplankton, invertebrates and fish. Bioavailability is dependent on cadmium
speciation; for example, the free ion, Cd , is readily taken up by aquatic plants,
PAGE 47
GUIDELINE AMBIENT ENVIRONMENT STANDARDS FOR ETHIOPIA
whereas organo-cadmium complexes are 2+ not absorbed. Lethal concentrations
of cadmium also vary depending on the test animal, water hardness and
temperature, and time of exposure. The level of bio-accumulation is dependent
on the species and age of the organism. Cadmium bio-accumulates in the food
chain due to its tendency to bind strongly to sulphydryl groups.
Bio-concentration factors range from 10 to 10 for both invertebrates and fish.
However, 2 5 there is no evidence for cadmium bio-magnification through the
aquatic food web.
11 CHLORIDE
Chemical Symbol or Formula: Cl−.
Standard: 250 mg/l
Percentage Compliance Required: 95% of all monitoring data must comply with the
standard.
Units Used for Analytical Results: mg/l Cl.
Normal Method(s) of Analysis: Titration (Mohr Method: Silver Nitrate) [A]
Reference Method(s) of Analysis:
Method Type Complexity APHA Reference
Mercuric Nitrate Method B 4500-Cl--C
Potentiometric Method B 4500-Cl--D
Ion Chromatographic Method B/C 4500-Cl--F
Introduction At levels above 250 mg/l Cl water will begin to taste salty and will become
increasingly objectionable as the concentration rises further. However, external
circumstances govern acceptability and in some arid areas waters containing up
to 2,000 mg/l Cl are consumed, though not by people unfamiliar with such
concentrations. High chloride levels may similarly render freshwater unsuitable
for agricultural irrigation.
Because sewage is such a rich source of chloride, a high result may indicate
pollution of a water by a sewage effluent. Natural levels in rivers and other
fresh waters are usually in the range 15-35 mg/l Cl - much below drinking water
standards. What is normally important to note in a series of results from a river,
for example, is not the absolute level, but rather the relative levels from one
sampling point to another.
An increase of even 5 mg/l at one station may give rise to suspicions of a
sewage discharge, especially if the free ammonia levels (q.v.) are also elevated.
Normal raw water treatment processes do not remove chloride.
Occurrence Chloride exists in all natural waters, the concentrations varying very widely and
reaching a maximum in sea water (up to 35,000 mg/l Cl). In fresh waters the
sources include soil and rock formations, sea spray and waste discharges.
Sewage contains large amounts of chloride, as do some industrial effluents.
Effect Chloride does not pose a health hazard to humans and the principal
consideration is in relation to palatability
PAGE 48
GUIDELINE AMBIENT ENVIRONMENT STANDARDS FOR ETHIOPIA
12 CHLORINE
Chemical Symbol or Formula: Cl2.
Standard: 5 µg/l
Percentage Compliance Required: 95% of all monitoring data must comply with the
standard.
Units Used for Analytical Results: µg/l Cl.
Reference Method(s) of Analysis:
Method Type Complexity APHA Reference
Iodometric Method I B 4500-Cl-B
Amperometric Titration Method B/C 4500-Cl-D
DPD Colorimetric Method A 4500-Cl-G
Introduction Elemental chlorine (Cl2) is a greenish-yellow gas that dissolves readily in water.
It is not normally a constituent of natural waters since chlorine is too reactive to
persist in the aquatic environment..
Occurrence Free forms of chlorine such as HOCl and OCl -, or combined available chlorine
(chloramines), occurs in aquatic ecosystems as a result of:
• chlorination of drinking water (to remove unwanted tastes and odours, and
for the purposes of disinfection);
• the textile industry (bleaching, slimicide);
• the pulp and paper industry (bleaching, slimicide);
• sewage treatment (reduce odour, algicide, bactericide);
• cooling waters (slimicide); and
• swimming pools (disinfection).
Effluents containing ammonia, organic matter or cyanides convert chlorine into
substances such as chloramines, which may be less toxic but more persistent
than chlorine, thereby posing a long-term threat to aquatic life..
Effects The toxic effects of chlorine are usually irreversible. Free chlorine is more toxic
but less persistent than combined chlorine. Diatoms are more sensitive to
chlorine than are green algae, which, in turn, are more sensitive than blue-green
algae. Newly hatched fish larvae are more sensitive to chlorine than are fish
eggs.
Avoidance behaviour, adverse changes in the blood chemistry, damage to gills,
decreased growth rate, restlessness preceding loss of equilibrium and death have
been observed for fish exposed to chlorine. Invertebrates become immobile, and
exhibit reduced reproduction and reduced survival on exposure to chlorine.
Aquatic plants may become chlorotic, whilst reduced rates of photosynthesis
and respiration are observed for phytoplankton.
Acclimation to sublethal chlorine concentrations leads to increased resistance.
Chlorine itself does not accumulate, but chlorinated organic substances may
bio-concentrate in aquatic organisms.
PAGE 49
GUIDELINE AMBIENT ENVIRONMENT STANDARDS FOR ETHIOPIA
13 CHROMIUM
Chemical Symbol or Formula: Cr.
Standard: 50 µg/l
Percentage Compliance Required: 95% of all monitoring data must comply with the
standard.
Units Used for Analytical Results: µg/l Cr.
Reference Method(s) of Analysis:
Method Type Complexity APHA Reference
Atomic Absorption Spectrometric Method B/C 3500-Cr-B
Inductively Coupled Plasma Method D 3500-Cr-C
Colorimetric Method B 3500-Cr-D
Ion Chromatographic Method B 3500-Cr-E
Introduction Chromium is a relatively scarce metal, and the occurrence and amounts thereof
in aquatic ecosystems are usually very low. Chromium ions occur in a variety of
forms:
• chromium (II) - chromous ion (Cr2+),
• chromium (III) - chromic ion (Cr3+, trivalent),
• chromium (III) - chromite ion (CrO3
3-, trivalent),
• chromium (VI) - chromate ion (CrO4
2- , hexavalent),
• chromium (VI) - dichromate ion (Cr2O7
2- , hexavalent)
Chromium(VI) is a highly oxidized state and occurs as the yellow dichromate
salt in neutral or alkaline media, and as the orange chromate salt in acid
medium. Both of these chromium(VI) salts are highly soluble at all pH values.
The reduced forms, chromium(II) and chromium(III) are reported as being less
toxic and therefore less hazardous than chromium(VI)..
Occurrence The most common ore of the metal chromium is chromite, in which chromium
occurs in the trivalent state. Other minerals containing chromium do occur, but
are not common. Most elevated levels of chromium in aquatic ecosystems are a
consequence of industrial activity.
In the aquatic environment chromous compounds tend to be oxidized to
chromic forms, whilst the chromium(VI) form can be reduced to chromium(III)
by heat, in the presence of organic matter and by reducing agents.
Of the trivalent chromium salts, the chloride, nitrate and sulphate salts are
readily soluble, whereas the hydroxide and carbonate salts are relatively
insoluble. Of the hexavalent chromate salts only the sodium, potassium, and
ammonium chromates and dichromates are soluble.
Hexavalent chromium salts are used extensively:
• in metal pickling and plating;
• in the leather industry as tanning agents; and
• in the manufacture of paints, dyes, explosives, ceramics and paper.
PAGE 50
GUIDELINE AMBIENT ENVIRONMENT STANDARDS FOR ETHIOPIA
Trivalent chromium salts are used much less frequently, but are important as:
• fixatives in textile dye manufacture;
• in the ceramic and glass industry; and
• in photography.
Chromium compounds may also be discharged in chromium-treated cooling
waters where chromium has been used as a corrosion inhibitor.
Effects Chromium exerts a toxic effect at different concentrations in different groups of
aquatic organisms. Fish are the most resistant, and in some cases the toxicity of
chromium(VI) is no greater than for chromium(III). A temporarily reduced
growth phase has been reported for young fish at low chromium concentrations.
Invertebrates are usually at least an order of magnitude more sensitive, with
daphniids showing the greatest sensitivity to chromium. Green algae are also
more sensitive than fish, whilst bacterial responses to chromium are variable.
14 CONDUCTIVITY
Chemical Symbol or Formula: Not Applicable [Physical parameter].
Standard: 1000 µS/Cm (@ 20°C)
Percentage Compliance Required: 95% of all monitoring data must comply with the
standard.
Units Used for Analytical Results: µS/cm
Reference Method(s) of Analysis:
Method Type Complexity APHA Reference
Field Method (Electrometric) A -
Laboratory Method B 2510
Introduction Also referred to as electrical conductivity and, not wholly accurately, as specific
conductance, the conductivity of a water is an expression of its ability to
conduct an electric current. As this property is related to the ionic content of the
sample which is in turn a function of the dissolved (ionisable) solids
concentration, the relevance of easily performed conductivity measurements is
apparent. In itself conductivity is a property of little interest to a water analyst
but it is an invaluable indicator of the range into which hardness and alkalinity
values are likely to fall, and also of the order of the dissolved solids content of
the water. While a certain proportion of the dissolved solids (for example, those
which are of vegetable origin) will not be ionised (and hence will not be
reflected in the conductivity figures) for many surface waters the following
approximation will apply: Conductivity (µS/cm) x 2/3 = Total Dissolved
Solids (mg/l).
In samples from a source which is regularly tested a rapid conductivity analysis
may be an adequate replacement for other, longer determinations.
It is important to note that there is an interrelationship between conductivity and
temperature, the former increasing with temperature at a rate of some 2 per cent
per degree C rise. There is a regrettable lack of uniformity in the terms in which
PAGE 51
GUIDELINE AMBIENT ENVIRONMENT STANDARDS FOR ETHIOPIA
conductivity is reported. Some UK methods manuals report the results at 20°C
while the standard US reference manual uses 25°C. A difference of 10 percent
can therefore arise depending on how the results are quoted. An error of this
magnitude could not be tolerated, especially where conductivity readings are
being used to estimate salinity.
Occurrence Reflects mineral salt content of water.
Effect No direct significance.
15 COPPER
Chemical Symbol or Formula: Cu.
Standard: Copper (µg/l) Hardness (mg/l CaCO3)
5 10
22 50
40 100
112 500
Percentage Compliance Required: 95% of all monitoring data must comply with the
standard.
Units Used for Analytical Results: µg/l Cu.
Reference Method(s) of Analysis:
Method Type Complexity APHA Reference
Atomic Absorption Spectrometric Method B/C 3500-Cu-B
Inductively Coupled Plasma Method D 3500-Cu-C
Neocuproine Method B 3500-Cu-D
Introduction Copper is one of the world's most widely used metals. Although copper occurs
naturally in most waters, it is regarded as potentially hazardous by the USEPA.
Copper occurs in four oxidation states, namely, 0, I, II and III. The two most
common forms are cuprous copper(I) and cupric copper(II). Cuprous copper is
unstable in aerated aqueous solutions and will normally be oxidized to cupric
copper..
Occurrence Copper is a common metallic element in the rocks and minerals of the earth's
crust, and is commonly found as an impurity in mineral ores. Chalcopyrite
(CuFeS2) is the most abundant of the copper minerals. Crustal (igneous) rocks
contain more copper (23 - 55 mg/kg) than sedimentary rocks (4 - 45 mg/kg).
The occurrence of natural sources of copper in the aquatic environment is due to
weathering processes or from the dissolution of copper minerals and native
copper. Metallic copper is insoluble in water, but many copper salts are highly
soluble as cupric or cuprous ions. Anthropogenic sources account for 33 - 60 %
of the total annual global input of copper to the aquatic environment.
The main anthropogenic sources of copper in the aquatic environment are:
• corrosion of brass and copper pipes by acidic waters;
PAGE 52
GUIDELINE AMBIENT ENVIRONMENT STANDARDS FOR ETHIOPIA
• sewage treatment plant effluents;
• copper compounds used as aquatic algicides;
• runoff and ground water contamination from the use of copper as fungicides
and pesticides in the treatment of soils; and
• liquid effluents and atmospheric fallout from industrial sources such as
mining, smelting and refining industries, coal-burning, and iron- and steel-
producing industries.
Effects Copper is a micronutrient and an essential component of enzymes involved in
redox reactions and is rapidly accumulated by plants and animals. It is toxic at
low concentrations in water and is known to cause brain damage in mammals.
Copper exerts its effect by forming stable co-ordinate bonds in proteins, where
it functions as a catalyst in redox reactions. Metabolically, copper interacts with
zinc, molybdenum, arsenic and selenium.
The effect of elevated copper concentrations on aquatic organisms is also
related to factors such as the duration of exposure and life stage of the
organism. Studies have shown that species richness and species composition of
invertebrate communities and changed as copper concentrations increased.
Early life stages of organisms appear to be more sensitive than adults to copper
pollution.
Nitrogen fixation by blue-green algae is reduced by the addition of trace
amounts of copper. Although bio-concentration factors range from 100 - 26
000, there is no evidence to suggest that copper is bio-magnified.
16 CYANIDE
Chemical Symbol or Formula: CN−.
Standard: 50 µg/l
Percentage Compliance Required: 95% of all monitoring data must comply with the
standard.
Units Used for Analytical Results: µg/l CN
Normal Method(s) of Analysis: Colorimetric (after distillation) [B];
Specific Ion Electrode (after distillation) [B].
Reference Method(s) of Analysis:
Method Type Complexity APHA Reference
Preliminary Treatment of Samples B 4500-CN--B
Total Cyanide after Distillation B 4500-CN--C
Titrimetric Method B 4500-CN--D
Colorimetric Method B 4500-CN--E
Cyanide Selective Electrode Method B 4500-CN--F
Introduction Hydrocyanic acid (HCN) which is the most toxic form of cyanide reacts with
water to release cyanide ions (CN-).
PAGE 53
GUIDELINE AMBIENT ENVIRONMENT STANDARDS FOR ETHIOPIA
Occurrence Most of the cyanide in water is in the hydrocyanic acid form which is largely
undissociated at pH values of 8 or less. Cyanide in the environment is usually
found complexed with metals. Cyanides are present in effluents from gas works
and coke ovens, scrubbing of gases at steel plants, metal cleaning, electroplating
and chemical industries. Cyanide is a common reagent in gold extraction
processes and large quantities of cyanide are found in gold mine tailing dams.
Cyanide is sometimes present in phenolic wastes..
Effects Cyanide interferes with aerobic respiration and is therefore toxic only to aerobic
organisms. Cyanide is thus not as toxic to "lower" organisms (invertebrates) as
it is to fish and other vertebrates. There is a greater variability in sensitivities of
invertebrates than there is in fish species. Embryos, sac larvae and warm-water-
adapted species of fish are more resistant to cyanide than are other life stages or
species of fish. The gills of fish suffering from cyanide poisoning are bright red
in colour.
17 DISOLVED OXYGEN
Chemical Symbol or Formula: O2.
Standard: Game Fish 50% Samples ≥ 9 mg/l
Minimum 6 mg/l
Course Fish 50% Samples ≥ 7 mg/l
Minimum 4 mg/l
Units Used for Analytical Results: mg/l O2
Reference Method(s) of Analysis:
Method Type Complexity APHA Reference
Iodometric (Winkler) Method B 4500-O-B
Azide Modification B 4500-O-C
Permanganate Modification B 4500-O-D
Membrane Electrode (may be modified for filed work) A 4500-O-G
Introduction Gaseous oxygen (O2) from the atmosphere dissolves in water and is also
generated during photosynthesis by aquatic plants and phytoplankton. Oxygen
is moderately soluble in water. Equilibrium solubility, termed the saturation
solubility, varies non-linearly with temperature, salinity and atmospheric
pressure, and with other site-specific chemical and physical factors.
The maintenance of adequate dissolved oxygen (DO) concentrations is critical
for the survival and functioning of the aquatic biota because it is required for the
respiration of all aerobic organisms. Therefore, the DO concentration provides a
useful measure of the health of an aquatic ecosystem. Measurement of the
biochemical oxygen demand (BOD) or the chemical oxygen demand (COD) are
inappropriate for aquatic ecosystems, but are useful for determining water
quality requirements of effluents discharged into aquatic systems, in order to
limit their impact.
PAGE 54
GUIDELINE AMBIENT ENVIRONMENT STANDARDS FOR ETHIOPIA
Occurrence In unpolluted surface waters, dissolved oxygen concentrations are usually close
to saturation. Typical saturation concentrations at sea level, and at TDS values
below 3 000 mg/l, are: 12.77 mg/l at 5 °C; 10.08 mg/R at 15 °C; 9.09 mg/l at 20
°C.
There is a natural diel variation (24 hour cycle) in dissolved oxygen associated
with the 24-hour cycle of photosynthesis and respiration by aquatic biota.
Concentrations decline through the night to a minimum near dawn, then rise to
a maximum by mid afternoon. Seasonal variations arise from changes in
temperature and biological productivity.
Reduction in the concentration of dissolved oxygen can be caused by several
factors:
• Resuspension of anoxic sediments, as a result of river floods or dredging
activities.
• Turnover or release of anoxic bottom water from a deep lake or reservoir.
• The presence of oxidizable organic matter, either of natural origin (detritus)
or originating in waste discharges, can lead to reduction in the concentration
of dissolved oxygen in surface waters. The potential for organic wastes to
deplete oxygen is commonly measured as biochemical oxygen demand
(BOD) and chemical oxygen demand (COD). The COD is used as a routine
measurement for effluents, and is measure of the amount of oxygen likely to
be used in the degration of organic waste. However, in aquatic ecosystems
it is unlikely that all organic matter will be fully oxidised.
• The amount of suspended material in the water affects the saturation
concentration of dissolved oxygen, either chemically, through the oxygen-
scavenging attributes of the suspended particles, or physically through
reduction of the volume of water available for solution.
Dissolved oxygen concentrations can be increased by natural diffusion of
gaseous oxygen from the atmosphere into water. Diffusion continues until the
saturation concentration is reached. The rate of increase of dissolution of
oxygen can be accelerated if turbulence of the water increases, causing
entrainment of air from the atmosphere.
Effects Aerobic organisms are dependent for respiration on the presence of dissolved
oxygen in water. Anoxic or hypoxic conditions may be lethal within short time
scales (minutes to hours).
The sensitivity of many species, especially fish and invertebrates, to changes in
dissolved oxygen concentrations depends on the species and the life stages
(eggs, larvae or adult) and behavioural changes (feeding and reproduction)
Juveniles of many aquatic organisms are more sensitive to physiological stress
arising from oxygen depletion, and in particular to secondary effects such as
increased vulnerability to predation and disease. Where possible, many species
will avoid anoxic or oxygen-depleted zones.
Cold-water-adapted species such as salmonids (e.g., trout) are especially
sensitive to depletion of dissolved oxygen. Reproduction and growth in these
species is reduced under continuous exposure to oxygen concentrations less
than 100 % saturation.
Oxygen concentrations above saturation may cause gas bubble disease in fish.
Super-saturated conditions also tend to inhibit photosynthesis in green algae,
favouring instead blue-green algae, which are more tolerant of super-saturation,
but which may become a nuisance to other water users.
PAGE 55
GUIDELINE AMBIENT ENVIRONMENT STANDARDS FOR ETHIOPIA
The reversibility of toxic effects on organisms depends on the duration,
frequency and timing of the occurrence of oxygen depletion. Physiological
stress effects in adult or less sensitive life stages may be rapidly reversed if
oxygen depletion is short-lived. Prolonged exposure of aquatic communities to
dissolved oxygen concentrations less than 50 % of saturation can cause
significant changes in community composition, as more tolerant species are
favoured.
18 FLORIDE
Chemical Symbol or Formula: F−.
Standard: 1 mg/l
Percentage Compliance Required: 95% of all monitoring data must comply with the
standard.
Units Used for Analytical Results: mg/l F.
Normal Method(s) of Analysis: Colorimetric (after distillation) [B];
Specific Ion Electrode [B].
Reference Method(s) of Analysis:
Method Type Complexity APHA Reference
Preliminary Distillation Step B 4500-F--B
Ion Selective Electrode Method B/C 4500-F--C
SPADNS Method B 4500-F--D
Introduction Fluoride is a halogen gas which is highly reactive with a variety of substances.
It is seldom found as free fluorine gas in nature, but occurs either as the fluoride
ion or in combination with calcium, potassium and phosphates.
Occurrence Fluoride occurs in the earth's crust at an average concentration of 0.3 g/kg, most
often as a constituent of fluorite (CaF2), often known as fluorspar or calcium
fluoride, in sedimentary rocks. Other important occurrences of fluoride are
cryolite and fluorapatite in igneous rocks. Traces of fluoride (< 1 mg/l) occur in
many aquatic ecosystems, whilst higher concentrations (often > 10 mg/l) can be
found in ground waters derived from igneous rocks.
Fluoride is used in:
• the manufacture and use of insecticides;
• disinfecting brewery apparatus;
• fluxes used in the manufacture of steel;
• wood preservatives;
• glass and enamel manufacture;
• chemical industries;
• water treatment, where fluoride may be added for dental purposes; and
• other minor uses.
PAGE 56
GUIDELINE AMBIENT ENVIRONMENT STANDARDS FOR ETHIOPIA
Effects Low concentrations of fluoride (< 1 000 µg/l) strengthen tooth enamel and
bones in mammals. Skeletal fluorosis may occur if exposure to intermediate
fluoride concentrations occurs over long periods.
19 HYDROCARBONS, DISSOLVED & EMULSIFIED
Chemical Symbol or Formula: Not Applicable [Bulk parameter].
Standard: 10 µg/l
Percentage Compliance Required: 95% of all monitoring data must comply with the
standard.
Units Used for Analytical Results: µg/l material.
Reference Method(s) of Analysis:
Method Type Complexity APHA Reference
Hydrocarbons (followed by Gas chromatography) C 5520-F
Introduction This heading includes petroleum, oil, grease and related materials. Problems
caused by these substances include interference with such vital processes as the
mass transfer of oxygen from air to water (essential in river reaeration, for
example), blockage of pipes, fouling of plant and animal life, odour and taste
problems, and the like
It is worth reiterating that this parameter as herein defined is an overall
aggregate (or bulk) parameter which is nonetheless limited in its scope by the
generalised nature of the relevant analytical methods. A large number of
specific (and potentially undesirable) hydrocarbon compounds are thus
excluded from its coverage
Occurrence Effluent discharges, oil spillages etc.
Effect The main implications are organoleptic in the context of this parameter, but
many complex hydrocarbon materials are carcinogenic (e.g. polycyclic aromatic
hydrocarbons, q.v.).
PAGE 57
GUIDELINE AMBIENT ENVIRONMENT STANDARDS FOR ETHIOPIA
20 IRON
Chemical Symbol or Formula: Fe.
Standard: 1 mg/l
Percentage Compliance Required: 95% of all monitoring data must comply with the
standard.
Units Used for Analytical Results: mg/l Fe Dissolved.
Reference Method(s) of Analysis:
Method Type Complexity APHA Reference
Atomic Absorption Spectrometric Method B/C 3500-Fe-B
Inductively Coupled Plasma Method D 3500-Fe-C
Phenanthroline Method B 3500-Fe-D
Introduction Iron is the fourth most abundant element in the earth's crust and may be present
in natural waters in varying quantities depending on the geology of the area and
other chemical properties of the water body. The two common states of iron in
water are the reduced (ferrous, Fe 2+) and the oxidised (ferric, Fe 3+) states. Most
iron in oxygenated waters occurs as ferric hydroxide in particulate and colloidal
form and as complexes with organic, especially humic, compounds. Ferric salts
are insoluble in oxygenated waters, and hence iron concentrations are usually
low in the water column. In reducing waters, the ferrous form, which is more
soluble, may persist and, in the absence of sulphide and carbonate anions, high
concentrations of ferrous iron may be found.
The toxicity of iron depends on whether it is in the ferrous or ferric state, and in
suspension or solution. Although iron has toxic properties at high
concentrations, inhibiting various enzymes, it is not easily absorbed through the
gastro-intestinal tract of vertebrates. On the basis of iron's limited toxicity and
bio-availability, it is classified as a non-critical element.
Iron is an essential micronutrient for all organisms, and is required in the
enzymatic pathways of chlorophyll and protein synthesis, and in the respiratory
enzymes of all organisms. It also forms a basic component of haeme-containing
respiratory pigments (for example, haemoglobin), catalyses, cytochromes and
peroxidases. Under certain conditions of restricted availability of iron,
photosynthetic productivity may be limited.
Occurrence Iron is naturally released into the environment from weathering of sulphide ores
(pyrite, FeS2) and igneous, sedimentary and metamorphic rocks. Leaching from
sandstones releases iron oxides and iron hydroxides to the environment. Iron is
also released into the environment by human activities, mainly from the burning
of coke and coal, acid mine drainage, mineral processing, sewage, landfill
leachates and the corrosion of iron and steel. Various industries that also use
iron in their processes, or in their products, include:
• the chlor-alkali industry,
• the household chemical industry,
• the fungicide industry,
• the petro-chemical industry.
PAGE 58
GUIDELINE AMBIENT ENVIRONMENT STANDARDS FOR ETHIOPIA
Streams may be negatively impacted by high levels of iron in acid mine
drainage. Pyrite, iron sulphide, is often found in close association with coal
deposits. Upon exposure to moisture and atmospheric oxygen, the ferrous iron
is oxidised to the ferric state, a reaction which is frequently accelerated by
bacteria of the Thiobacillus-Ferrobacillus group. If the mine drainage results in
acid conditions in the stream, the rate of oxidation will be slow. If, however, the
acid is neutralized (the rate of neutralization depends on the surface geology)
and pH rises to between 7 and 8, the rate of oxidation will increase and ferric
hydroxide will precipitate. A layer of ferric hydroxide precipitate, so-called
"yellowboy", on stream bottoms and structures is a common sight in areas
affected by acid mine drainage. The receiving water is often also oxygen
deficient.
Effects Data on the acute and chronic toxicity of iron to both invertebrates and
vertebrates are rather limited.
21 LEAD
Chemical Symbol or Formula: Pb.
Standard: 0.05 mg/l
Percentage Compliance Required: 95% of all monitoring data must comply with the
standard.
Units Used for Analytical Results: mg/l Pb.
Reference Method(s) of Analysis:
Method Type Complexity APHA Reference
Atomic Absorption Spectrometric Method B/C 3500-Pb-B
Inductively Coupled Plasma Method D 3500-Pb-C
Dithiozone Method B 3500-Pb-D
Introduction Lead exists in several oxidation states, that is, 0, I, II and IV, all of which are of
environmental importance. Lead occurs as metallic lead, inorganic compounds,
and organometallic compounds. The divalent form, lead (II), is the stable ionic
species present in the environment and is thought to be the form in which most
lead is bio-accumulated by aquatic organisms. In fresh waters lead is generally
present as PbCO3 and as lead-organic complexes, with a small proportion in the
form of free lead ions. Lead may also be complexed with organic ligands,
yielding soluble, colloidal and particulate compounds. Lead is defined by the
USEPA as potentially hazardous to most forms of life, and is considered toxic
and relatively accessible to aquatic organisms.
Occurrence Lead is principally released into the aquatic environment through the
weathering of sulphide ores, especially galena. Since metallic lead and common
lead minerals such as sulphides, sulphates, oxides, carbonates and hydroxides
are almost insoluble, levels of dissolved lead (acetate and chloride salts) in
aquatic ecosystems are generally low. Most of the lead entering aquatic
ecosystems is associated with suspended sediments, while lead in the dissolved
phase is usually complexed by organic ligands.
PAGE 59
GUIDELINE AMBIENT ENVIRONMENT STANDARDS FOR ETHIOPIA
The photolysis of lead compounds is an important process in the removal of
lead from the atmosphere. The products of this photo-degradation are lead
oxides and halides, which enter the aquatic ecosystems via direct deposition or
surface runoff.
The major sources of lead in the aquatic environment are anthropogenic, these
include:
• precipitation, fallout of lead dust and street runoff (associated with lead
emissions from gasoline-powered motor vehicles);
• industrial and municipal wastewater discharge;
• mining, milling and smelting of lead and metals associated with lead, e.g.
zinc, copper, silver, arsenic and antimony; and
• combustion of fossil fuels.
Effects Lead is a common and toxic trace metal which readily accumulates in living
tissue. Metabolically, lead interacts with iron and therefore interferes with
haemoglobin synthesis. It also affects membrane permeability by displacing
calcium at functional sites, and inhibits some of the enzymes involved in energy
metabolism. Lead that has been absorbed by vertebrate organisms is largely
deposited in the bony skeleton, where it does not usually exhibit toxic effects. If
stress results in decalcification or deossification, lead deposits may result in
toxic effects. It has been shown that rainbow trout develop spinal deformities
after exposure to lead in soft water, while no deformities were evident in hard
water.
Low concentrations of lead affect fish by causing the formation of a film of
coagulated mucous over the gills and subsequently over the entire body. This
has been attributed to a reaction between lead and an organic constituent of the
mucous. Death of fish is due to suffocation brought about by the mucous layer
since insoluble lead is apparently not toxic to fish.
Lead is bio-accumulated by benthic bacteria, freshwater plants, invertebrates
and fish. Bio-concentration factors for four species of invertebrates and two
species of fish ranged from 42 - 1 700, though lead does not appear to bio-
magnify through the aquatic food web.
PAGE 60
GUIDELINE AMBIENT ENVIRONMENT STANDARDS FOR ETHIOPIA
22 MANGANESE
Chemical Symbol or Formula: Mn.
Standard: 0.3 mg/l
Percentage Compliance Required: 95% of all monitoring data must comply with the
standard.
Units Used for Analytical Results: mg/l Mn.
Reference Method(s) of Analysis:
Method Type Complexity APHA Reference
Atomic Absorption Spectrometric Method B/C 3500-Mn-B
Inductively Coupled Plasma Method D 3500-Mn-C
Persulphate Method B 3500-Mn-D
Introduction Manganese is an essential micronutrient for plants and animals. It is a functional
component of nitrate assimilation and an essential catalyst of numerous enzyme
systems in animals, plants and bacteria. When manganese is not present in
sufficient quantities, photosynthetic productivity may be limited and plants may
exhibit chlorosis (a yellowing of the leaves) or failure of leaves to develop
properly. A deficiency in manganese in vertebrates leads to skeletal deformities
and reduced reproductive capabilities.
High concentrations of manganese are toxic, and may lead to disturbances in
various metabolic pathways, in particular disturbances of the central nervous
system caused by the inhibition of the formation of dopamine (a
neurotransmitter).
Occurrence Manganese is the eighth most abundant metal in nature, and occurs in a number
of ores. In aquatic ecosystems, manganese does not occur naturally as a metal
but is found in various salts and minerals, frequently in association with iron
compounds. It may exist in the soluble manganous (Mn 2+) form, but is readily
oxidised to the insoluble manganic (Mn4+) form. The Mn2+ ion occurs at low
redox potentials and low pH. Permanganates (Mn 7+) do not persist in the
environment. They rapidly oxidise organic materials and are therefore reduced.
Nitrate, sulphate and chloride salts of manganese are fairly soluble in water,
whereas oxides, carbonates, phosphates, sulphides and hydroxides are less
soluble.
Soils, sediments and metamorphic and sedimentary rocks are significant natural
sources of manganese. Industrial discharges also account for elevated
concentrations of manganese in receiving waters. Various industries use
manganese, its alloys and manganese compounds in their processes, or in their
products, examples of which are given below:
• the steel industry, in the manufacture of dry cell batteries;
• the fertilizer industry (manganese is used as a micro-nutrient fertilizer
additive); and
• the chemical industry in paints, dyes, glass, ceramics, matches and
fireworks.
PAGE 61
GUIDELINE AMBIENT ENVIRONMENT STANDARDS FOR ETHIOPIA
Acid mine drainage also releases a large amount of the manganese. Iron and
steel foundries release manganese into the atmosphere, where it is then
redistributed through atmospheric deposition.
Effects Information on the acute and chronic toxicity effects of manganese to algae,
invertebrates and vertebrates are very limited..
23 MERCURY
Chemical Symbol or Formula: Hg.
Standard: 1 µg/l
Percentage Compliance Required: 95% of all monitoring data must comply with the
standard.
Units Used for Analytical Results: µg/l Hg.
Reference Method(s) of Analysis:
Method Type Complexity APHA Reference
Cold-Vapor Atomic Absorption Spectrometric Method C 3500-Hg-B
Inductively Coupled Plasma Method D 3500-Hg-C
Dithizone Method B 3500-Hg-D
Introduction Mercury is a heavy metal that is of quite rare geological occurrence, and its
concentration in the environment is normally very low. Mercury occurs in three
oxidation states in the natural aquatic environment, namely: as the metal, as
mercury(I), and as mercury(II). The dissolved forms of mercury and those
adsorbed onto particulate material are included in the guideline since they are
both available for uptake by aquatic organisms. Mercury is also found as
organo-mercurial salts, the most important of which is methyl mercury.
Mercury and mercury-organic complexes are of concern in the natural aquatic
environment because of their extreme toxicity to aquatic organisms and the
potential to bio-accumulate in the food chain. Intake of mercury can occur via
air, food and water.
Occurrence Mercury may occur at high concentrations in water bodies subject to industrial
pollution, or in the vicinity of industrial activities utilising or discharging
mercury or compounds thereof. Important industries that use mercury in their
processes, or in their products, include:
• the chlor-alkali industry,
• the paint industry,
• the fungicide industry,
• the paper and pulp industry,
• medical and dental industries, and
• the electrical equipment industry.
Mercury has a strong affinity for sediments and suspended solids. Under
anaerobic conditions, bacteria readily transform inorganic mercury into methyl
PAGE 62
GUIDELINE AMBIENT ENVIRONMENT STANDARDS FOR ETHIOPIA
mercury. Dissolved mercury salts are also easily absorbed by aquatic organisms
and can be bio-accumulated.
Methyl mercury, the most common form of mercury found in aquatic
organisms, is lipid soluble (readily passes through plant and animal membranes)
and is stored within the bodies of organisms. In aquatic animals, bio-
accumulated mercury is stored in fatty tissues, whilst in aquatic plants, mercury
is usually stored in roots and stems.
Effects Because of its neuro- and renal toxicity, mercury is severely poisonous to
mammals. Poisoning by mercury takes the form of neurological disturbances,
particularly in the case of organo-mercurial salts such as methyl mercury, and of
renal dysfunction in the case of inorganic mercury. The kidneys are the main
route of excretion of inorganic mercury. De-methylation is a slow process, and
methyl mercury is only excreted over a long period.
Methyl mercury accumulated in fatty tissue or storage organs can be mobilized
rapidly into the nervous and reproductive systems. This bio-accumulated
mercury increases the risk of mercury toxicity to aquatic and terrestrial
organisms in the food chain.
Organic forms of mercury are approximately ten times more toxic than
inorganic forms because they pass rapidly through biological membranes. Solid
inorganic forms of mercury have relatively low toxicity to vertebrates since
solids are not easily absorbed by the gastrointestinal tract. In contrast, dissolved
mercury salts are easily absorbed by aquatic organisms and can be bio-
accumulated.
The toxic effects of mercury on aquatic organisms cannot be reversed.
24 METHYLENE BLUE – ACTIVE SUBSTANCES
Chemical Symbol or Formula: Not applicable [Bulk parameter].
Standard: 0.2 mg/l
Percentage Compliance Required: 95% of all monitoring data must comply with the
standard.
Units Used for Analytical Results: mg/l reference material (Lauryl sulphate).
Normal Method(s) of Analysis: Methylene Blue/Solvent Extraction [B]
Reference Method(s) of Analysis:
Method Type Complexity APHA Reference
Anionic Surfactants as MBAS B 5540-C
Introduction Often abbreviated to MBAS, the designation of this parameter is the chemically
correct term for the group of compounds commonly known as anionic
detergents. To cloud the issue further, the non-specific terms surf octants
(surface active agents) and syndets (synthetic detergents) are also used on
occasion, the former more frequently. Synthetic detergents fall into three
groups - anionic, cationic and non-ionic. The last-mentioned are all substituted
polymers of ethylene oxide which do not ionise in water. They are more
expensive than the anionic type but are coming into greater use. The cationic
PAGE 63
GUIDELINE AMBIENT ENVIRONMENT STANDARDS FOR ETHIOPIA
types are salts of quaternary ammonium hydroxide and are known for their
properties of disinfection. The major group comprises the anionic detergents
which are all sodium salts of organic sulphates or sulphonates. Such entities
form ion pairs with the reagent methylene blue, a property which forms the
basis of their estimation. The results are quoted as mg/l standard reference
material. Some authorities specify lauryl sulphate which is used increasingly as
a standard.
It is worth noting that other terms have been used in connection with synthetic
detergents. "Hard" and "soft" detergents are those which are biodegraded with
difficulty and with ease, respectively. The designations have nothing to do with
the hardness of the waters in which they are used. Some of the original anionic
detergents were very hard; structurally they were of the "ABS"
(alkylbenzenesulphonate) type. Later, there was a move towards the much more
biodegradable ("soft") linear alkylate sulphate/sulphonate ("LAS") detergents.
This was to help eliminate the major problem of foaming. In the US very
severe foaming problems were encountered in the days of first use of synthetic
detergents. Other disadvantages associated with them include interference with
the reaeration of water which is low in dissolved oxygen, and the synergistic
foaming effects which can arise when waters containing sub-foaming
concentrations of different types of detergents are mixed. Most detergent
preparations contain around 20 per cent surface active agent (which is all that is
determined in this test): the rest of the formulation consists of so-called
"builders" which enhance the properties of the active constituent. Chief among
these are phosphates which are of major environmental significance (see
below).
It should be noted that, as there may be some extraneous matter which will also
react with methylene blue, the analysis is more correctly designated as
"methylene blue active substances" than as anionic detergents, even though the
latter may in fact represent 100 per cent of levels found
Occurrence Synthetic materials in domestic and industrial wastes.
Effect No immediate implications as other problems will prevent consumption of
waters with these materials present.
25 NICKEL
Chemical Symbol or Formula: Ni.
Standard: 0.1 mg/l
Percentage Compliance Required: 95% of all monitoring data must comply with the
standard.
Units Used for Analytical Results: mg/l Ni.
Normal Method(s) of Analysis: Atomic Absorption Spectrometry [B/C]
Reference Method(s) of Analysis:
Method Type Complexity APHA Reference
Atomic Absorption Spectrometric Method B/C 3500-Ni-B
Inductively Coupled Plasma Method D 3500-Ni-C
PAGE 64
GUIDELINE AMBIENT ENVIRONMENT STANDARDS FOR ETHIOPIA
Introduction This is another metallic element which is of moderate concern because of
possible carcinogenicity as far as humans are concerned; it also has variable
harmful effects on aquatic life. It is toxic to plant life, too, and is a hazard to fish
(generally in the mg/l concentration range).
Occurrence Principal sources are minerals and industrial wastes.
Effect Very limited.
26 NITRATE
Chemical Symbol or Formula: NO3
–
Standard: 50 mg/l
Percentage Compliance Required: 95% of all monitoring data must comply with the
standard.
Units Used for Analytical Results: mg/l NO3
–.
Reference Method(s) of Analysis:
Method Type Complexity APHA Reference
Ultraviolet Spectrophotometric Screening Method B 4500-NO3
--B
Ion Chromatographic Method B/C 4500-NO3
--C
Nitrate Electrode Method B/C 4500-NO3
--D
Titanous Chloride Reduction Method B 4500-NO3
--G
Introduction Relatively little of the nitrate found in natural waters is of mineral origin, most
coming from organic and inorganic sources, the former including waste
discharges and the latter comprising chiefly artificial fertilisers. However,
bacterial oxidation and fixing of nitrogen by plants can both produce nitrate.
Interest is centred on nitrate concentrations for various reasons. Most
importantly, high nitrate levels in waters to be used for drinking will render
them hazardous to infants as they induce the "blue baby" syndrome
(methaemoglobinaemia). The nitrate itself is not a direct toxicant but is a health
hazard because of its conversion to nitrite [see also below] which reacts with
blood haemoglobin to cause methaemoglobinaemia.
Of increasing importance is the degree to which fertiliser run-off can contribute
to eutrophication problems in lakes. Sewage is rich in nitrogenous matter which
through bacterial action may ultimately appear in the aquatic environment as
nitrate. Hence, the presence of nitrate in ground waters, for example, is cause
for suspicion of past sewage pollution or of excess levels of fertilisers or
manure slurries spread on land. (High nitrite levels would indicate more recent
pollution as nitrite is an intermediate stage in the ammonia-to-nitrate oxidation).
In rivers high levels of nitrate are more likely to indicate significant run-off
from agricultural land than anything else and the parameter is not of primary
importance per se. However, it should be noted that there is a general tendency
for nitrate concentrations in rivers to increase as a result of enhanced nutrient
run-off; this may ultimately lessen their utility as potential sources of public
water supply. Nitrite concentrations in rivers are rarely more than 1 - 2 per cent
of the nitrate level so that it may therefore be acceptable to carry out the
PAGE 65
GUIDELINE AMBIENT ENVIRONMENT STANDARDS FOR ETHIOPIA
analytically convenient determination of nitrate + nitrite at the same time. This
determination is correctly referred to as total oxidised nitrogen
Occurrence Oxidation of ammonia: agricultural fertiliser run-off.
Effect Hazard to infants above 50 mg/l NO3.
27 NITRITE
Chemical Symbol or Formula: NO2
–
Standard: 0.1 mg/l
Percentage Compliance Required: 95% of all monitoring data must comply with the
standard.
Units Used for Analytical Results: mg/l NO2
–.
Normal Method(s) of Analysis: Manual or Automated Colorimetry [A/B]
Reference Method(s) of Analysis:
Method Type Complexity APHA Reference
Colorimetric Method B 4500-NO2
--B
Ion Chromatographic Method B/C 4500-NO2
--C
Introduction Nitrite exists normally in very low concentrations and even in waste treatment
plant effluents levels are relatively low, principally because the nitrogen will
tend to exist in the more reduced (ammonia; NH3) or more oxidised (nitrate;
NO3 ) forms
Because nitrite is an intermediate in the oxidisation of ammonia to nitrate,
because such oxidation can proceed in soil, and because sewage is a rich source
of ammonia nitrogen, waters which show any appreciable amounts of nitrite are
regarded as being of highly questionable quality. Levels in unpolluted waters
are normally low, below 0.03 mg/l NO 2. Values greater than this may indicate
sewage pollution.
The significance of nitrite (at the low levels often found in surface waters) is
mainly as an indicator of possible sewage pollution rather than as a hazard itself
although, as mentioned above under "Nitrate" (q.v.), it is nitrite rather than
nitrate which is the direct toxicant. There is, accordingly, a stricter limit for
nitrite in drinking waters. In addition, nitrites can give rise to the presence of
nitrosamines by reaction with organic compounds and there may be
carcinogenic effects.
Occurrence Generally from untreated or partially treated wastes.
Effect Methaemoglobinaemia-causing agent [cf. Nitrate]..
PAGE 66
GUIDELINE AMBIENT ENVIRONMENT STANDARDS FOR ETHIOPIA
28 NITROGEN (KJELDAHL)
Chemical Symbol or Formula: Not Applicable [Bulk parameter]
Standard: 1 mg/l
Percentage Compliance Required: 95% of all monitoring data must comply with the
standard.
Units Used for Analytical Results: mg/l N.
Reference Method(s) of Analysis:
Method Type Complexity APHA Reference
Macro-Kjeldahl Method B 4500-Norg-B
Semi-Micro- Kjeldahl Method B 4500-Norg-C
Introduction This determination is for organically-bound nitrogen and, under the normal test
conditions (without ammonia removal), it includes ammonia. However, the
results do not include oxidised nitrogen. The sum of the organically-bound
nitrogen and ammonia figures is the "Kjeldahl nitrogen" value; if the ammonia
has been excluded the result is "organic nitrogen." The term "total nitrogen"
refers to the sum of the Kjeldahl and total oxidised nitrogen figures.
In past years much reliance was placed on the so-called albuminoid nitrogen
determination which was frequently carried out in conjunction with the manual
distillation technique for measuring ammonia. In this test the ammonia-free
residue from the initial distillation is treated with alkaline potassium
permanganate and then distilled again to give a further quantity of ammonia
which is derived from proteinaceous matter and is a reflection of the organic
content. Although alternative procedures have superseded the albuminoid
nitrogen determination, it may still be found useful especially in assessing water
with possible sewage contamination. While high values are themselves
indicative of pollution, the albuminoid nitrogen results are most often
considered in conjunction with the figures for ammonia. This is because in
natural waters the ratio of free/saline ammonia nitrogen to albuminoid nitrogen
is normally significantly less than unity (frequently of the order of 0.2-0.4),
being a reflection of the fact that albuminoid nitrogen sources (principally
vegetable) occur with a natural frequency. When the ratio approaches or
exceeds unity an extraneous source of free ammonia is indicated and in many
cases this is a sewage discharge. Thus, by scrutinising this nitrogen ratio the
analyst can get an early indication of possible sewage contamination of a water,
an indication which may be reinforced by elevated chloride values (q.v.).
In the Kjeldahl nitrogen determination the sample is subjected to quite severe
digestion conditions which break down proteins and other organic matter and
convert the nitrogen to ammonia, in which form it is actually measured.
Occurrence Principally from organic matter naturally present (e.g. falling leaves etc.) or
added in discharges.
Effects Site-specific conditions, especially the availability of phosphorus, are critically
important in modifying the influence of inorganic nitrogen on eutrophication.
Inorganic nitrogen toxicity is not considered to be important for setting
inorganic nitrogen water quality guidelines for protection of aquatic ecosystems.
PAGE 67
GUIDELINE AMBIENT ENVIRONMENT STANDARDS FOR ETHIOPIA
Total nitrogen concentrations below 0.5 mg N/l are considered to be sufficiently
low that they can limit eutrophication and reduce the likelihood of nuisance
growths of blue-green algae and other plants. However, in the presence of
sufficient available phosphorus, nitrogen-fixing organisms will be able to fix
atmospheric nitrogen, thereby compensating for any deficit caused by low total
nitrogen concentrations.
The information given in the table below illustrates typical symptoms
associated with selected ranges of total nitrogen concentrations, if all other
nutrients and environmental conditions are within favourable ranges for the
organisms concerned.
Average Summer
Inorganic Nitrogen
Concentration(mg/l)
Effects
<0.5 Oligotrophic conditions; usually moderate levels of species
diversity; usually low productivity systems with rapid nutrient
cycling; no nuisance growth of aquatic plants or the presence of
blue-green algal blooms.
0.5 – 2.5 Mesotrophic conditions; usually high levels of species
diversity; usually productive systems; nuisance growth of
aquatic plants and blooms of blue-green algae; algal blooms
seldom toxic.
2.5 – 10 Eutrophic conditions; usually low levels of species diversity;
usually highly productive systems, nuisance growth of aquatic
plants and blooms of blue-green algae; algal blooms may
include species which are toxic to man, livestock and wildlife.
>10 Hypertrophic conditions; usually very low levels of species
diversity; usually very highly productive systems; nuisance
growth of aquatic plants and blooms of blue-green algae, often
including species which are toxic to man, livestock and
wildlife.
PAGE 68
GUIDELINE AMBIENT ENVIRONMENT STANDARDS FOR ETHIOPIA
29 PESTICIDES
Chemical Symbol or Formula: Not applicable [Bulk parameter].
Standard:
Aldrin 0.01 µg/l Fenitrothion 0.01 µg/l
Dieldrin 0.01 µg/l Isoproturon 0.5 µg/l
Endrin 0.005 µg/l Lindane 0.1 µg/l
Isodrin 0.005 µg/l Linuron 1.0 µg/l
Atrazine 1.0 µg/l Malathion 0.01 µg/l
Chloridazon 0.1 µg/l MCPA 10 µg/l
2,4-D 0.005 µg/l Mecoprop 10 µg/l
DDT (y-isomer) 10 µg/l Parathionethyl 0.01 µg/l
DDT (all isomers) 25 µg/l Pentachlorophenol 2.0 µg/l
Diazinon 5 µg/l Simazine 1.0 µg/l
Dichlorbenil 10µg/l Tributyltin oxide 0,001 µg/l
Dichlorvos 0.001 µg/l Trifuralin 0.1 µg/l
Diuron 25 µg/l Triphenyltin acetate 0.01 µg/l
Endosulphan 0.001 µg/l Triphenyltin hydroxide 0.01 µg/l
Percentage Compliance Required: 100% of all monitoring data must comply with the
standard.
Units Used for Analytical Results: µg/l specified compound
Normal Method(s) of Analysis: Chromatographic techniques (GLC/HPLC) [C]
Reference Method(s) of Analysis:
Method Type Complexity APHA Reference
Carbamate Pesticides
High Performance Liquid Chromatographic Method C/D 6610-B
Organochlorine Pesticides
Liquid-Liquid Extraction Gas Chromatographic Method C/D 6630-B
Liquid-Liquid Extraction Gas Chromatographic Method II C/D 6630-C
Liquid-Liquid Extraction Gas Chromatographic/Mass
Spectrometric Method
D 6630-D
Acidic Herbicide Compounds
Micro Liquid-Liquid Extraction Gas Chromatographic
Method
C/D 6640-B
Glyphosate Herbicides
Liquid Chromatographic Post-Column Florescence Method D 6651-B
PAGE 69
GUIDELINE AMBIENT ENVIRONMENT STANDARDS FOR ETHIOPIA
Introduction This broad designation encompasses a large group of compounds with either
related uses or similar chemical composition. The substances covered comprise
insecticides (organo-chlorine and organo-phosphorus), herbicides, fungicides,
PCBs (polychlorinated biphenyls) and PCTs (polychlorinated terphenyls).
Compounds such as pesticides are among those which cause mortality or severe
reproductive or genetic problems in fauna and which also qualify for inclusion
under the broad heading of substances which possess carcinogenic, mutagenic
or teratogenic properties. As such, they are highly undesirable in waters of
virtually any type. Even if levels in, say, a river water are very low there is the
probability of bioaccumulation in fish or other living tissue and, to compound
the matter, of retention on the in-situ sediments..
Occurrence Synthetic compounds - agricultural discharges, spillages or runoff, industrial
waste discharges
Effect Compounds of great acute or chronic toxicity.
30 PH (ACIDITY AND ALKALINITY)
Chemical Symbol or Formula: Not applicable [Physical parameter].
Standard: 6-9 (but no change of more than 0.2 units from natural
level)
Percentage Compliance Required: 95% of all monitoring data must comply with the
standard.
Units Used for Analytical Results: pH units.
Normal Method(s) of Analysis: Electrometry [pH electrode] [A/B]
Reference Method(s) of Analysis:
Method Type Complexity APHA Reference
Electrometric Method B 4500-H+-B
Introduction The pH value is a measure of the hydrogen ion activity in a water sample. It is
mathematically related to hydrogen ion activity according to the expression:
pH = -log10 [H
+], where [H+] is the hydrogen ion activity. The pH of pure water
(that is, water containing no solutes) at a temperature of 24 °C is 7.0, the
number of H+ and OH− ions are equal and the water is therefore
electrochemically neutral. As the concentration of hydrogen ions [H+] increases,
pH decreases and the solution becomes more acid. As [H+] decreases, pH
increases and the solution becomes more basic.
The equilibrium between H+ and OH− ions is influenced by reactions with acids
and bases introduced into the aqueous system. In general, acidity is the number
of OH− ions that have reacted over a given pH range during a base titration, that
is, a measure of the water's ability to neutralise base. Similarly, alkalinity is a
measure of the number of H+ ions that have reacted over a given pH range
during an acid titration, that is, a measure of the water's ability to neutralise
acid.
Alkalinity is primarily controlled by carbonate species and is therefore usually
expressed in terms of equivalence to calcium carbonate (CaCO 3). Briefly,
PAGE 70
GUIDELINE AMBIENT ENVIRONMENT STANDARDS FOR ETHIOPIA
carbon dioxide dissolves in water to form carbonic acid (H 2CO3) which,
depending on pH, dissociates to form carbonate, bicarbonate and hydrogen ions:
CO2 + H2O ' H2CO3 ' HCO3
− + H+ ' CO3
2− + 2H+
At a pH value of less than 4.0, carbonate species are mostly in the form of
H2CO3 , whilst between pH values of 6.4 and 8.6 they are in the form HCO 3
−.
As the pH increases to greater than 8.6, so the proportion of CO 3
2− increases,
and above pH 10.3 CO3
2− predominates.
The rate of change of pH, on addition of a given quantity of an acid or base,
depends on the buffering capacity of the water. The most important buffering
system in fresh waters is the carbonate-bicarbonate one, and between pH values
of 6.4 - 10.3 the hydrogen carbonate ion predominates. In naturally acid waters,
complex polyphenolic organics and their salts may form the major buffering
system, while aluminium and its salts become effective buffering agents in
waters subject to acid precipitation.
Occurrence For surface water, pH values typically range between 4 and 11. The relative
proportions of the major ions, and in consequence the pH, of natural waters, are
determined by geological and atmospheric influences. Most fresh waters, are
relatively well buffered and more or less neutral, with pH ranges between 6 and
8. Very dilute sodium-chloride-dominated waters are poorly buffered because
they contain virtually no bicarbonate or carbonate. If they drain catchments
containing certain types of vegetation (for example, fynbos), the pH may drop
as low as 3.9 owing to the influence of organic acids (for example, humic and
fulvic acids).
The pH may also vary both diurnally and seasonally. Diurnal fluctuations occur
in productive systems where the relative rates of photosynthesis and respiration
vary over a 24- hour period, because photosynthesis alters the
carbonate/bicarbonate equilibrium by removing CO from the water. Seasonal
variability is largely related to the hydrological 2 cycle, particularly in rivers
draining catchments with vegetation such as fynbos, where the concentration of
organic acids is consistently lower during the rainy season.
Industrial activities generally cause acidification rather than alkalinization of
rivers. Acidification is normally the result of three different types of pollution,
namely:
• low-pH point-source effluents from industries, such as pulp and paper and
tanning and leather industries;
• mine drainage, which is nearly always acid, leading to the pH of receiving
streams dropping to below 2; and
• acid precipitation resulting largely from atmospheric pollution caused by
the burning of coal (and subsequent production of sulphur dioxide (SO2))
and the exhausts of combustion engines (nitrogen oxides). Both sulphur
oxides (SOx) and nitrogen oxides (NOx) form strong mineral acids when
dissolved in water. When acid rain falls on a catchment, the strong acids
leach calcium and magnesium from the soil and also interfere with nutrient
availability.
Elevated pH values can be caused by increased biological activity in eutrophic
systems. The pH values may fluctuate widely from below 6 - above 10 over a
24-hour period as a result of changing rates of photosynthesis and respiration.
Effects A change in pH from that normally encountered in unimpacted streams may
have severe effects upon the biota. The extent of acidification or alkalinization
PAGE 71
GUIDELINE AMBIENT ENVIRONMENT STANDARDS FOR ETHIOPIA
is important in determining the severity of the effects, which do not vary
linearly either with pH or over time. When assessing the potential effect of a
change in pH, it is important to note that some streams are naturally more acidic
than others and their biotas are often adapted to these conditions.
Direct effects of pH changes consist of alterations in the ionic and osmotic
balance of individual organisms, in particular changes in the rate and type of ion
exchange across body surfaces. This requires greater energy expenditure, with
subsequent effects such as slow growth and reduced fecundity becoming
apparent. Aquatic organisms, however, generally have well developed
mechanisms for maintaining ionic and osmotic balance. Impacts of indirect pH
changes include changes in the availability of toxic substances such as
aluminium and ammonia.
Acidic pH
Gradual reductions in pH may result in a change in community structure, with
acid-tolerant organisms replacing less tolerant organisms.
Streams with acidic pH values have different periphyton (micro flora and fauna
living on solid surfaces) communities and lower overall production compared
with less acidic streams.
The discharge of acid wastes into water containing bicarbonate alkalinity results
in the formation of free carbon dioxide. If the water is alkaline, free CO2 may be
liberated and be toxic to fish even though the pH does not drop to a level
normally considered toxic.
Alkaline pH
Limited information is available on the effects of elevated pH.
31 PHENOLS
Chemical Symbol or Formula: Not applicable [Physical parameter].
Standard: 0.5 µg/l.
Percentage Compliance Required: 95% of all monitoring data must comply with the
standard.
Units Used for Analytical Results: mg/l C6H5OH [Phenol].
Reference Method(s) of Analysis:
Method Type Complexity APHA Reference
Liquid-Liquid Extraction Gas Chromatographic Method B 6420-B
Liquid-Liquid Extraction Gas Chromatographic/Mass
Spectrometric Method
B 6420-C
Introduction Phenol itself is an organic compound consisting of a hydroxyl group attached to
a benzene ring.
Occurrence In unimpacted water systems phenols are only found in very low
concentrations, usually in the µg/l range or less. Phenols are produced as by-
products in many industrial processes where organic chemicals are used.
Phenols are also used as a disinfectant, and as a starting material for a wide
PAGE 72
GUIDELINE AMBIENT ENVIRONMENT STANDARDS FOR ETHIOPIA
variety of synthetic organic processes. Phenolic wastes arise from the
distillation of wood and coal, from oil refineries, chemical plants, pulp and
paper industries, livestock dips and human and animal wastes. Phenol is often
present in sewage at levels between 0.07 - 0.1 mg/l. Phenols are generally
biodegraded in water.
Effects Phenols are thought to be a nerve poison which gives rise to an increased blood
supply to the gills and heart cavities. Fish exposed to phenol become excited,
swim more rapidly, become more sensitive to stimuli and show increased
respiratory rates, colour changes and increased secretion of mucus. Death may
occur quickly or follow a period of depressed activity and loss of equilibrium,
with occasional convulsions. Fish surviving long-term exposure to low phenol
concentrations show general inflammation and necrosis of tissues. This is
possibly due to irreversible changes in protein structure. Histopathological
changes in the blood, liver, heart, skin and spleen may also occur. Reduction in
growth and sexual activity and a loss of balance and co-ordination have been
observed in some fish species. Phenol affects some aquatic organisms directly
by increasing their demand for oxygen.
Reduction in oxygen consumption occurs in some invertebrates. Avoidance
behaviour has been observed in leeches. Phenols have also been shown to
reduce rates of photosynthesis in aquatic plants.
32 PHOSPHATES
Chemical Symbol or Formula: PO4–
Standard The inorganic phosphorus concentration for a specific
system must be based on the existing trophic status of the
system. It is undesirable to allow inorganic phosphorus
concentrations to rise to a level which will change the
trophic status of the system. A standard for each water
body should be derived only after case- or site-specific
studies.
• Inorganic phosphorus concentrations should not be
changed by > 15 % from that of the water body under
local, unimpacted conditions at any time of the year;
and
• The trophic status of the water body should not
increase above its present level, though a decrease in
trophic status is permissible (see Effects); and
• The amplitude and frequency of natural cycles in
inorganic phosphorus concentrations should not be
changed.
PAGE 73
GUIDELINE AMBIENT ENVIRONMENT STANDARDS FOR ETHIOPIA
Percentage Compliance Required: 95% of all monitoring data must comply with the
standard.
Units Used for Analytical Results: mg/l P.
Normal Method(s) of Analysis: Manual or Automated Colorimetry [B/C].
Reference Method(s) of Analysis:
Method Type Complexity APHA Reference
Sample Preparation B 4500-P-B
Vanadomolybdophosphoric Acid Colorimetric Method B 4500-P-C
Stannous Chloride Method B 4500-P-D
Ascorbic Method B 4500-P-E
Introduction Phosphorus can occur in numerous organic and inorganic forms, and may be
present in waters as dissolved and particulate species. Elemental phosphorus
does not occur in the natural environment. Orthophosphates, polyphosphates,
metaphosphates, pyrophosphates and organically bound phosphates are found in
natural waters. Of these, orthophosphate species H2PO4 and HPO4
2− are the only
forms of soluble inorganic phosphorus directly utilizable by aquatic biota.
Soluble Reactive Phosphate (SRP), or orthophosphate, is that phosphorus which
is immediately available to aquatic biota which can be transformed into an
available form by naturally occurring processes.
The forms of phosphorus in water are continually changing because of
processes of decomposition and synthesis between organically bound forms and
oxidised inorganic forms. The phosphorus cycle is influenced by the exchange
of phosphorus between sedimentary and aqueous compartments. In turn this is
affected by various physical, chemical and biological modifying factors such as
mineral-water equilibria, water pH values, sorption processes, oxygen-
dependent redox interactions, and the activities of living organisms.
Phosphorus is an essential macronutrient, and is accumulated by a variety of
living organisms. It has a major role in the building of nucleic acids and in the
storage and use of energy in cells. In unimpacted waters it is readily utilized by
plants and converted into cell structures by photosynthetic action. Phosphorus is
considered to be the principle nutrient controlling the degree of eutrophication
in aquatic ecosystems.
Occurrence Natural sources of phosphorus include the weathering of rocks and the
subsequent leaching of phosphate salts into surface waters, in addition to the
decomposition of organic matter. Spatial variation is high and is related to the
characteristics of regional geology. Phosphorus levels are generally lowest in
mountainous regions of crystalline rocks and levels increase in lowland waters
derived from sedimentary deposits.
Phosphorus is seldom present in high concentrations in unimpacted surface
waters because it is actively taken up by plants. Concentrations between 10 and
50 µg/l are commonly found, although concentrations as low as 1 µg/l of
soluble inorganic phosphorus may be found in "pristine" waters and as high as
200 mg/l of total phosphorus in some enclosed saline waters.
Elevated levels of phosphorus may result from point-source discharges such as
domestic and industrial effluents, and from diffuse sources (non-point sources)
in which the phosphorus load is generated by surface and subsurface drainage.
PAGE 74
GUIDELINE AMBIENT ENVIRONMENT STANDARDS FOR ETHIOPIA
Non-point sources include atmospheric precipitation, urban runoff, and drainage
from agricultural land, in particular from land on which fertilizers have been
applied.
Effects The most significant effect of elevated phosphorus concentrations is its
stimulation of the growth of aquatic plants. Both phosphorus and nitrogen limit
plant growth, and of these, phosphorus is likely to be more limiting in fresh
water. The effect is dependent on the form of phosphorus present in the water,
since not all forms are available for uptake by plants. Other factors, such as
water temperature, light and the availability of other nutrients, also play an
important role in limiting plant growth.
Inorganic phosphorus concentrations of less than 5 µg P/l are considered to be
sufficiently low to reduce the likelihood of algal and other plant growth.
The information given in the table below illustrates typical symptoms
associated with selected ranges of inorganic phosphorus concentrations, if all
other nutrients and environmental conditions are within favourable ranges for
the organisms concerned.
Average Summer
Inorganic
Phosphorous
Concentration
(µg/l)
Effects
<5 Oligotrophic conditions; usually moderate levels of species
diversity; usually low productivity systems with rapid nutrient
cycling; no nuisance growth of aquatic plants or blue-green
algae.
5-25 Mesotrophic conditions; usually high levels of species
diversity; usually productive systems; nuisance growth of
aquatic plants and blooms of blue-green algae; algal blooms
seldom toxic.
25-250 Eutrophic conditions; usually low levels of species diversity;
usually highly productive systems, nuisance growth of aquatic
plants and blooms of blue-green algae; algal blooms may
include species which are toxic to man, livestock and wildlife.
>250 Hypertrophic conditions; usually very low levels of species
diversity; usually very highly productive systems; nuisance
growth of aquatic plants and blooms of blue-green algae,
often including species which are toxic to man, livestock and
wildlife.
PAGE 75
GUIDELINE AMBIENT ENVIRONMENT STANDARDS FOR ETHIOPIA
33 POLYCHLORINATED BIPHENYLS & TERPHENYLS
Chemical Symbol or Formula: Not applicable [Physical parameter].
Standard: 1 µg/l.
Percentage Compliance Required: 100% of all monitoring data must comply with the
standard.
Units Used for Analytical Results: µg/l reference PCB/PCT (mixture) used.
Reference Method(s) of Analysis:
Method Type Complexity APHA Reference
Liquid-Liquid Extraction Gas Chromatographic Method C/D 6431-B
Liquid-Liquid Extraction Gas Chromatographic/Mass
Spectrometric Method
D 6431-C
Introduction Commonly termed PCBs/PCTs, this parameter covers those chlorinated
compounds which have been used as mixtures in transformer coolant oils. The
mixtures are normally designated by a proprietary name, for example "Aroclor,"
to which is suffixed a number, e.g. 1254 or 1260. The first two digits represent
the number of carbon atoms in the molecule and the second two the percentage
by weight of chlorine. The basic molecules present are biphenyl, which is
C12H10 and comprises two benzene rings joined together, or terphenyl (C 18H14,
consisting of three fused benzene rings).
When these are chlorinated a whole range of polychlorinated compounds is
produced and the mixtures are of such complexity that no effort is made to
identify the individual components. The mixtures are dense and extremely
stable, resisting biodegradation and conventional incineration procedures.
The best process currently available for their destruction is very high
temperature "flash" incineration. It is not without significance that, according
to current estimates, about 90% of the total world production of these materials
since the 1940s, when they were introduced, is still extant.
Occurrence Synthetic components of transformer coolant oils which gain access to water by
spillages or industrial discharges.
Effect Compounds of marked chronic toxicity; they are actual or potential carcinogens.
PCBs/PCTs are toxic, causing genetic effects and mortality to fauna. They are
accumulated to a very great extent by fauna and there are many literature
references to concentration factors of over 100,000 - in other words, an
infinitesimal concentration in a water may be matched by 100,000 times that
amount in the tissue of fish or animals normally resident in that water. When
these toxicants enter the food chain, through consumption of fish for example,
there is a health risk to man.
PAGE 76
GUIDELINE AMBIENT ENVIRONMENT STANDARDS FOR ETHIOPIA
34 POLYCYCLIC AROMATIC HYDROCARBONS
Chemical Symbol or Formula: Not applicable [Physical parameter].
Standard: 2 µg/l (Total of 6 specified).
Percentage Compliance Required: 100% of all monitoring data must comply with the
standard.
Units Used for Analytical Results: mg/l PAH [or specific PAH compound(s)].
Reference Method(s) of Analysis:
Method Type Complexity APHA Reference
Liquid-Liquid Extraction Chromatographic Method D 6440-B
Liquid-Liquid Extraction Gas Chromatographic/Mass
Spectrometric Method
D 6440-C
Introduction This term, while strictly applicable to very many substances, has been defined
as applying to six specific compounds:
• Fluoranthene
• 3,4-benzofluoranthene [benzo(b)fluoranthene]
• 11,12-benzofluoranthene [benzo(k)fluoranthene]
• 3,4-benzopyrene [benzo(a)pyrene]
• 1,12-benzoperylene [benzo(ghi)perylene]
• indeno(l,2,3-cd)pyrene
The compounds covered are the six originally identified by the WHO.
It may be useful to comment on the nomenclature of these compounds and
related materials. They are so-called aromatic compounds, the term being used
for those substances containing the "aromatic ring" (i.e. the cyclic molecular
structure of benzene) a basic element of their composition. As the substances
contain more than one such ring, they are termed polycyclic (or sometimes,
poly- aromatic compounds). The compounds are hydrocarbons - i.e. they consist
of the elements carbon and hydrogen only.
The alternative often-used designation - "polynuclear aromatic hydrocarbons" •
arises from the (inaccurate) use by organic chemists of the word "nucleus" to
refer to the benzene ring structure. As there is more than one such ring in these
compounds they are termed "polynuclear."
All of these materials are complex organic molecules which originate typically
in the combustion of organic compounds. Their analysis, like that of many other
so-called micropollutants, is difficult, but the procedures are justified because of
the potential health hazards posed by the PAH. The listed compounds can be
determined relatively easily, albeit with advanced instrumental techniques, and
their presence is also taken as indicative of the possible occurrence of other
undesirable aromatic compounds. While all have been regarded previously as
carcinogens, the six listed compounds comprising the most widely found such
group in the environment, by far the most hazardous compound among them is
benzo(a)pyrene [3,4-benzopyrene].
PAGE 77
GUIDELINE AMBIENT ENVIRONMENT STANDARDS FOR ETHIOPIA
Occurrence Synthetic compounds occurring in soot, tar, vehicle exhausts, combustion
products of hydrocarbon fuels
Effect Carcinogens of greater or lesser potency.
35 SELENIUM
Chemical Symbol or Formula: Se.
Standard: 10 µg/l (Total of 6 specified).
Percentage Compliance Required: 100% of all monitoring data must comply with the
standard.
Units Used for Analytical Results: µg/l Se.
Reference Method(s) of Analysis:
Method Type Complexity APHA Reference
Sample Preparation B 3500-Se-B
Atomic Absorption Spectrometric Method C 3500-Se-C
Inductively Coupled Plasma Method D 3500-Se-I
Colorimetric Method B 3500-Se-D
Introduction Selenium is a non-metallic element similar to sulphur. Selenium occurs in five
oxidation states, namely, -II, 0, II, IV and VI, of which the tetravalent state is
the most common. Small quantities of selenium are essential to animals and
bacteria, where it is important in certain enzyme systems, but selenium is
apparently not essential for plants.
Occurrence Selenium occurs naturally as ferric selenite, calcium selenate, as elemental
selenium and in organic compounds derived from decayed plant tissue.
Although selenium occurs in some natural waters, it is usually in nanogram
quantities.
Selenium may occur at increased concentrations in water bodies subject to
industrial pollution, or in the vicinity of industrial activities utilising or
discharging selenium or selenium compounds. Industries that use selenium in
their processes, or in their products, include:
• the paint industry;
• the food processing industry;
• the steel industry;
• vehicle and aircraft plating industries;
• the pesticide industry;
• the glass and ceramics industries;
• the dye manufacturing industry;
• the rubber industry; and
• the metal alloy and electrical apparatus industries.
PAGE 78
GUIDELINE AMBIENT ENVIRONMENT STANDARDS FOR ETHIOPIA
Effects Because these are chemical similarities between selenium and sulphur, selenium
can replace sulphur in some biologically important substances and thereby
cause toxic effects. The toxic effects are similar in cold- and warm-water
adapted fish.
Selenium toxicity effects observed in fish include changes in feeding behaviour
and equilibrium, pathological changes, deformities, haematological (blood)
changes and death. Fish are generally less sensitive to selenium than are
invertebrates. Toxic effects of selenium that have been recorded in invertebrates
include immobilisation, reduced survival and reduced reproduction.
Selenium is passed up through the aquatic food chain and accumulates in the
liver of mammals and fish; it may therefore pose a threat to predators. Selenium
undergoes biological methylation in sediments, a process similar to mercury
methylation. Selenomethionine is ten times more toxic than inorganic selenium.
36 SILVER
Chemical Symbol or Formula: Ag.
Standard: 10 µg/l.
Percentage Compliance Required: 100% of all monitoring data must comply with the
standard.
Units Used for Analytical Results: µg/l Ag..
Reference Method(s) of Analysis:
Method Type Complexity APHA Reference
Atomic Absorption Spectrometric Method B/C 3500-Ag-B
Inductively Coupled Plasma Method D 3500-Ag-C
Dithizone Method B 3500-Ag-D
Introduction This metal is toxic, especially to micro-organisms, and its soluble salts are
excellent disinfectants. It is not considered particularly toxic to humans and, as
it is likely to be found only in very low levels (such that it would be practically
impossible to reach hazardous levels through consumption of water and food),
few limits have been set. However, it has been reported that restrictions on its
use were introduced to discourage the use of silver as a disinfectant because of
possible health effects if used unduly liberally. Nowadays, economic
considerations are likely to restrict the discharge of silver.
Occurrence Ores, industrial wastes (e.g. photographic effluents).
Effect Metal of varying toxicity.
PAGE 79
GUIDELINE AMBIENT ENVIRONMENT STANDARDS FOR ETHIOPIA
37 SULPHATE
Chemical Symbol or Formula: SO4
– –.
Standard: 200 mg/l.
Percentage Compliance Required: 100% of all monitoring data must comply with the
standard.
Units Used for Analytical Results: mg/l SO4
Reference Method(s) of Analysis:
Method Type Complexity APHA Reference
Ion Chromatographic Method C 4500-SO4
---B
Turbidimetric Method B/C 4500-SO4
---E
Introduction Sulphates exist in nearly all natural waters, the concentrations varying
according to the nature of the terrain through which they flow. They are often
derived from the sulphides of heavy metals (iron, nickel, copper and lead). Iron
sulphides are present in sedimentary rocks from which they can be oxidised to
sulphate in humid climates; the latter may then leach into watercourses so that
ground waters are often excessively high in sulphates. As magnesium and
sodium are present in many waters their combination with sulphate will have an
enhanced laxative effect of greater or lesser magnitude depending on
concentration. The utility of a water for domestic purposes will therefore be
severely limited by high sulphate concentrations, hence the limit of 250 mg/l
SO4.
Occurrence Rocks, geological formations, discharges and so on .
Effect In polluted waters in which the dissolved oxygen i.e. zero, sulphate is very
readily reduced to sulphide causing noxious odours.
38 TEMPERATURE
Chemical Symbol or Formula: Not applicable [Physical parameter]
Standard: Game fish Discharge must not result in
variation of more than 1.5 °C
temperature down stream of
the thermal discharge
Coarse fish Discharge must not result in
variation of more than 3 °C
temperature down stream of
the thermal discharge
PAGE 80
GUIDELINE AMBIENT ENVIRONMENT STANDARDS FOR ETHIOPIA
Percentage Compliance Required: 100% of all monitoring data must comply with the
standard.
Units Used for Analytical Results: Degrees Celsius [°C].
Reference Method(s) of Analysis:
Method Type Complexity APHA Reference
Laboratory and Field Method A 2550-B
Introduction Temperature may be defined as the condition of a body that determines the
transfer of heat to, or from, other bodies. As temperature increases viscosity,
surface tension, compressibility, specific heat, the ionization constant and the
latent heat of vaporization decrease, whereas thermal conductivity and vapour
pressure increase. The solubilities of the following gasses, H 2, N2, CO2 and O 2
decrease with increasing temperature.
Temperature plays an important role in water by affecting the rates of chemical
reactions and therefore also the metabolic rates of organisms. Temperature is
therefore one of the major factors controlling the distribution of aquatic
organisms. Natural variations in water temperature occur in response to
seasonal and diel cycles and organisms use these changes as cues for activities
such as migration, emergence and spawning. Artificially-induced changes in
water temperature can thus impact on individual organisms and on entire
aquatic communities.
Occurrence The temperatures of inland waters generally range from 5 - 30 °C. Thermal
characteristics of running waters are dependent on various features of the region
and catchment area, including:
• the latitude and altitude of the river;
• hydrological factors such as the source of water, the relative contribution of
ground water, and the rate of flow or discharge;
• climatic factors such as air temperature, cloud cover, wind speed, vapour
pressure and precipitation events; and
• structural characteristics of the river and catchment area, including
topographic features, vegetation cover, channel form, water volume, depth
and turbidity.
Surface waters exhibit daily and annual periodicity patterns, in addition to
longitudinal changes along a river course, and vertical stratification in deeper
waters. The minimum and maximum temperatures, and temperature ranges vary
depending on the factors mentioned above.
Anthropogenic sources which result in changes in water temperature include:
• discharge of heated industrial effluents;
• discharge of heated effluents below power stations;
• heated return-flows of irrigation water;
• removal of riparian vegetation cover, and thereby an increase in the amount
of solar radiation reaching the water;
• inter-basin water transfers; and
• discharge of water from impoundments.
PAGE 81
GUIDELINE AMBIENT ENVIRONMENT STANDARDS FOR ETHIOPIA
Effects The effects of temperature on aquatic organisms have been the subject of a
number of literature reviews, predominantly conducted in the northern
hemisphere. There is however, little information on the thermal tolerances of
the African aquatic organisms, or their responses to temperature change.
Aquatic organisms have upper and lower thermal tolerance limits, optimal
temperatures for growth, a preferred temperature range in thermal gradients, and
temperature limitations for migration, spawning and egg incubation. All
organisms associated with freshwater, excluding birds and mammals, are
poikilothermic. In other words, they are unable to control their body
temperatures and are therefore highly dependent on ambient water temperature
and very susceptible to changes in water temperature. Consequently, rapid
changes in temperature may severely affect aquatic organisms and lead to mass
mortality. Causes of thermal mortality in fish from acute exposure to elevated
temperatures are basically the result of metabolic malfunctions (including fluid-
electrolyte imbalance, alterations in gaseous exchange and osmoregulation,
hypoxia of the central nervous system and inactivation of enzyme systems).
Less severe temperature changes in water bodies may have sub-lethal effects or
lead to an alteration in the existing aquatic community. The qualitative and
quantitative composition of the biota can change as a result of population shifts
caused by the disappearance of stenothermal species (organisms adapted to a
very narrow range of temperatures) from heated waters, and replacement by
heat-tolerant species which increase in number and supplant the original species
in the ecosystem.
Many organisms have life cycles in which temperature acts as a cue for the
timing of migration, spawning or emergence. Artificial changes in temperature
can interfere with temperature cues, thereby altering normal development.
39 TOTAL DISSOLVED SALTS/SOLIDS
Chemical Symbol or Formula: Not applicable [Bulk parameter].
Standard: TDS concentrations should not be changed by > 15 %
from the normal cycles of the water body under
unimpacted conditions at any time of the year; and
The amplitude and frequency of natural cycles in TDS
concentrations should not be changed.
Percentage Compliance Required: 100% of all monitoring data must comply with the
standard.
Units Used for Analytical Results: mg/l solids (Dried at stated temperature).
Reference Method(s) of Analysis:
Method Type Complexity APHA Reference
Total Dissolved Solids Dried at 180 °C A 2540-C
Introduction The total dissolved solids concentration , is a measure of the quantity of all
compounds dissolved in water. The total dissolved salts concentration is a
measure of the quantity of all dissolved compounds in water that carry an
electrical charge. Since most dissolved substances in water carry an electrical
PAGE 82
GUIDELINE AMBIENT ENVIRONMENT STANDARDS FOR ETHIOPIA
charge, the TDSalts concentration is usually, used as an estimate of the
concentration of total dissolved solids in the water.
The TDSalts concentration is directly proportional to the electrical conductivity
(EC) of water. Because EC is much easier to measure than TDSalts, it is
routinely used as an estimate of the TDSalts concentration. Therefore, it has
become common practise to use the total dissolved salts concentration, as a
measure for the total dissolved solids.
Electrical conductivity (EC) is a measure of the ability of water to conduct an
electrical current. This ability is a result of the presence in water of ions such as
carbonate, bicarbonate, chloride, sulphate, nitrate, sodium, potassium, calcium
and magnesium, all of which carry an electrical charge. Many organic
compounds dissolved in water do not dissociate into ions (ionise), and
consequently they do not affect the EC.
Occurrence Natural waters contain varying quantities of TDS as a consequence of the
dissolution of minerals in rocks, soils and decomposing plant material, the TDS
concentrations of natural waters therefore being dependent at least in part on the
characteristics of the geological formations which the water has been in contact
with. The TDS concentration also depends on physical processes such as
evaporation and rainfall.
The TDS concentrations are generally
• Low in rainwater, less than 1 mg/l;
• Low in water in contact with granite, siliceous sand and well-leached soils,
less than 30 mg/l;
• Greater than 65 mg/l in water in contact with precambrian shield areas; and
• In the range of 200 - 1100 mg/l in water in contact with palaeozoic and
mesozoic sedimentary rock formations.
• High as a result of evapoconcentration, usually greater than 1100 mg/ml.
Salts accumulate as water moves downstream because salts are continuously
being added through natural and anthropogenic sources whilst very little is
removed by precipitation or natural processes. Domestic and industrial effluent
discharges and surface runoff from urban, industrial and cultivated areas are
examples of the types of sources that may contribute to increased TDS
concentrations. Evaporation also leads to an increase in the total salts.
Effects Plants and animals possess a wide range of physiological mechanisms and
adaptations to maintain the necessary balance of water and dissolved ions in
cells and tissues. This ability is extremely important in any consideration of the
effects of changes in total dissolved solids on aquatic organisms.
The individual ions making up the TDS also exert physiological effects on
aquatic organisms.
Changes in the concentration of the total dissolved solids can affect aquatic
organisms at three levels, namely:
• effects on, and adaptations of, individual species;
• effects on community structure; and
• effects on microbial and ecological processes such as rates of metabolism
and nutrient cycling.
PAGE 83
GUIDELINE AMBIENT ENVIRONMENT STANDARDS FOR ETHIOPIA
The rate of change of the TDS concentration, and the duration of change,
appears to be more important than absolute changes in the TDS concentration,
particularly in systems where the organisms may not be adapted to fluctuating
levels of TDS. Seasonal timing of the change in TDS concentration may also
have important synergistic effects with water temperature on the total
community composition and functioning. Organisms adapted to low-salinity
habitats are generally sensitive to changes in the TDS concentration.
40 TOTAL SUSPENDED SOLIDS
Chemical Symbol or Formula: Not applicable [Physical parameter].
Standard: ≤ 25 mg/l (annual mean)
50 mg/l (maximum value)
Units Used for Analytical Results: mg/l solids (Dried at stated temperature).
Reference Method(s) of Analysis:
Method Type Complexity APHA Reference
Total Suspended Solids Dried at 103-105 °C A 2540-D
Introduction The total suspended solids (TSS) concentration is a measure of the amount of
material suspended in water. This definition includes a wide range of sizes of
material, from colloids (0.1 µm) through to large organic and inorganic
particulates.
The concentration of suspended solids increases with the discharge of sediment
washed into rivers due to rainfall and resuspension of deposited sediment. As
flow decreases the suspended solids settle out, the rate of which is dependent on
particle size and the hydrodynamics of the water body.
Water turbidity in the southern hemisphere is generally considered to be
equivalent to some measure of the concentration of suspended solids. Turbidity
is an expression of the optical property that causes light to be scattered and
absorbed rather than transmitted in straight lines through a water sample. The
scattering of light is caused by suspended matter such as clay, silt and finely
divided organic material, while the absorption of light is caused by inorganic
matter, plankton and other microscopic organisms and soluble coloured organic
compounds, such as fulvic, humic and tannic acids.
Correlation of turbidity with the concentration of suspended solids (mass/unit
volume) is difficult because the size, shape and refractive index of particulates
affects the light scattering properties of the suspension. The relationship
between turbidity and suspended solids may however, be determined on a site-
specific basis. A turbidimeter, calibrated with consideration of the site-specific
characteristics, may then potentially be used to monitor suspended solids.
Occurrence Natural variations in rivers often result in changes in the TSS, the extent of
which is governed by the hydrology and geomorphology of a particular region.
In general, all rivers become highly turbid and laden with suspended solids
during the rainy season. The major part of suspended material found in most
natural waters is made up of soil particles derived from land surfaces. Erosion
of land surfaces by wind and rain is a continuous and natural process. However,
PAGE 84
GUIDELINE AMBIENT ENVIRONMENT STANDARDS FOR ETHIOPIA
land use practices such as overgrazing, non-contour ploughing, removal of
riparian vegetation and forestry operations accelerate erosion and result in
increased loads of suspended solids in rivers.
Increases in total suspended solids may also result from anthropogenic sources,
including:
• discharge of domestic sewage,
• discharge of industrial effluents (such as the pulp/papermill, china-clay, and
brick and pottery industries),
• discharge from mining operations,
• fish-farm effluents (mostly organic suspended solids) and
• physical perturbations from road, bridge and dam construction.
Effects In turbid waters light penetration is reduced, leading to a decrease in
photosynthesis. The resultant decrease in primary production reduces food
availability for aquatic organisms higher up the food chain. Suspended solids
may interfere with the feeding mechanisms of filter-feeding organisms such as
certain macroinvertebrates, and the gill functioning, foraging efficiency (due to
visual disturbances) and growth of fish.
Suspended solids that settle out may smother or abrade benthic plants and
animals, and may result in changes to the nature of the substratum. This may
then lead to changes in the structure of the biotic community by the decline of
these organisms, through the replacement with organisms which burrow in soft
sediments. Sensitive species may be permanently eliminated if the source of the
suspended solids is not removed.
The recovery of a stream from sediment deposition is dependent on the
elimination of the sediment source and the potential for the deposited material
to be flushed out by stream flow.
PAGE 85
GUIDELINE AMBIENT ENVIRONMENT STANDARDS FOR ETHIOPIA
41 TETRACHLOROETHYLENE
Chemical Symbol or Formula: C2Cl4.
Standard: 10 µg/l.
Percentage Compliance Required: 100% of all monitoring data must comply with the
standard.
Units Used for Analytical Results: µg/l C2Cl4.
Normal Method(s) of Analysis: Gas Chromatography [B/C].
Reference Method(s) of Analysis:
Method Type Complexity APHA Reference
Purge and Trap Packed-Column Gas Chromatographic/Mass
Spectrometric Method I
C 6210-B
Purge and Trap Packed-Column Gas Chromatographic/Mass
Spectrometric Method II
C 6210-C
Purge and Trap Capillary Column Gas
Chromatographic/Mass Spectrometric Method
C 6210-D
Purge and Trap Packed-Column Gas Chromatographic
Method I
C 6230-B
Purge and Trap Packed-Column Gas Chromatographic
Method II
C 6230-C
Purge and Trap Capillary Column Gas Chromatographic
Method
C 6230-D
Introduction Information: Synonyms for tetrachloroethylene are tetrachloroethene and
perchloroethylene. It is the most commonly used dry-cleaning solvent. As with
all chlorinated solvents, this substance should be handled with care, and in well-
ventilated areas.
Occurrence Synthetic solvent used extensively in dry-cleaning industry; also used to a
significant extent for degreasing metals.
Effect Toxic solvent which can cause narcosis, dermatitis and ultimately fatal
intoxication. However, when handled according to proper procedures and with
adequate ventilation, tetrachloroethylene may be used without problems.
PAGE 86
GUIDELINE AMBIENT ENVIRONMENT STANDARDS FOR ETHIOPIA
42 THALLIUM
Chemical Symbol or Formula: Tl.
Standard: 5 µg/l.
Percentage Compliance Required: 100% of all monitoring data must comply with the
standard.
Units Used for Analytical Results: µg/l Tl.
Reference Method(s) of Analysis:
Method Type Complexity APHA Reference
Atomic Absorption Spectrometric Method B/C 3500-Tl-B
Inductively Coupled Plasma Method D 3500-Tl-C
Introduction The metal is used at 2-3% concentration in rodent poisons, and is also used in
the electrical components industry.
Occurrence Minerals, but more often from discharges.
Effect Causes a wide variety of effects including nausea, vomiting, pain and,
ultimately, death.
43 TRICHLOROETHYLENE
Chemical Symbol or Formula: C2HCl3.
Standard: 5 µg/l.
Percentage Compliance Required: 100% of all monitoring data must comply with the
standard.
Units Used for Analytical Results: µg/l C2HCl3.
Reference Method(s) of Analysis:
Method Type Complexity APHA Reference
Purge and Trap Packed-Column Gas Chromatographic/Mass
Spectrometric Method I
C 6210-B
Purge and Trap Packed-Column Gas Chromatographic/Mass
Spectrometric Method II
C 6210-C
Purge and Trap Capillary Column Gas
Chromatographic/Mass Spectrometric Method
C 6210-D
Purge and Trap Packed-Column Gas Chromatographic
Method I
C 6230-B
Purge and Trap Packed-Column Gas Chromatographic
Method II
C 6230-C
Purge and Trap Capillary Column Gas Chromatographic
Method
C 6230-D
PAGE 87
GUIDELINE AMBIENT ENVIRONMENT STANDARDS FOR ETHIOPIA
Introduction Trichloroethylene is used in the manufacture of organic chemicals and
pharmaceuticals, and it also has some medical uses.
Occurrence Synthetic solvent used in various industrial and manufacturing processes (e.g.
solvent for paints, varnishes, resins etc); used in dry-cleaning and in metals
degreasing.
Effect Potential carcinogen. Causes narcosis and effects similar to alcohol inebriation.
See also "Tetrachloroethylene," which is a very similar compound.
44 URANIUM
Chemical Symbol or Formula: U.
Standard: 5 µg/l.
Percentage Compliance Required: 100% of all monitoring data must comply with the
standard.
Units Used for Analytical Results: mg/l U.
Normal Method(s) of Analysis: Radiometric or Fluorometric techniques [D]
There are atomic absorption spectrometric procedures for
uranium analysis but (ICP analysis excepted) their
sensitivity is generally inadequate for very low levels.
Reference Method(s) of Analysis:
Method Type Complexity APHA Reference
Radiochemical Method D 7500-U-B
Introduction This radioactive element is used in the nuclear industry and is thus far from
being universally encountered.
Occurrence Rare natural occurrence; equally rare in effluents
Effect Highly toxic, with a variety of effects leading ultimately to death.
PAGE 88
GUIDELINE AMBIENT ENVIRONMENT STANDARDS FOR ETHIOPIA
45 VINYL CHLORIDE
Chemical Symbol or Formula: C2H3Cl.
Standard: 5 µg/l.
Percentage Compliance Required: 100% of all monitoring data must comply with the
standard.
Units Used for Analytical Results: µg/l C2H3Cl.
Reference Method(s) of Analysis:
Method Type Complexity APHA Reference
Purge and Trap Packed-Column Gas Chromatographic/Mass
Spectrometric Method I
C 6210-B
Purge and Trap Packed-Column Gas Chromatographic/Mass
Spectrometric Method II
C 6210-C
Purge and Trap Capillary Column Gas
Chromatographic/Mass Spectrometric Method
C 6210-D
Purge and Trap Packed-Column Gas Chromatographic
Method I
C 6230-B
Purge and Trap Packed-Column Gas Chromatographic
Method II
C 6230-C
Purge and Trap Capillary Column Gas Chromatographic
Method
C 6230-D
Introduction Although a very reactive monomer which forms plastic polymers very easily, it
is almost inevitable that in some cases the resultant polymer - the most common
of which is polyvinyl chloride or PVC - will contain vestigial amounts of vinyl
chloride itself. Thus, in the first use, in particular, of vessels made of PVC there
is the possibility of residual monomer gaining access to water..
Occurrence Synthetic gaseous compound which polymerises very readily and is an
important raw material in the manufacture of plastics. It is also used as a
refrigerant.
Effect It is a suspected causative agent of liver cancer.
46 ZINC
Chemical Symbol or Formula: Zn.
Standard: Zinc (µg/l) Hardness (mg/l CaCO3)
30 10
200 50
300 100
500 500
PAGE 89
GUIDELINE AMBIENT ENVIRONMENT STANDARDS FOR ETHIOPIA
Percentage Compliance Required: 100% of all monitoring data must comply with the
standard.
Units Used for Analytical Results: µg/l Zn
Reference Method(s) of Analysis:
Method Type Complexity APHA Reference
Atomic Absorption Spectrometric Method B/C 3500-Zn-B
Inductively Coupled Plasma Method D 3500-Zn-C
Dithizone Method II B 3500-Zn-E
Zincon Method B 3500-Zn-F
Introduction Zinc, a metallic element, is an essential micronutrient for all organisms as it
forms the active site in various metalloenzymes. Zinc occurs in two oxidation
states in aquatic ecosystems, namely as the metal, and as zinc(II).
In aquatic ecosystems the zinc(II) ion is toxic to fish and aquatic organisms at
relatively low concentrations.
Occurrence Zinc occurs in rocks and ores and is readily refined into a pure stable metal. It
can enter aquatic ecosystems through both natural processes such as weathering
and erosion, and through industrial activity.
In aqueous solutions zinc is amphoteric, that is, it dissolves in acids to form the
hydrated cations Zn 2+ and in strong bases it forms zincate anions (probably of
the form Zn(OH2−)4 ). Organozinc complexes and compounds can also be
formed. In most natural waters zinc exists mainly as the divalent cation, which
is the potentially toxic form. The proportion of other forms such as inorganic
compounds like ZnCO3 ; stable organic complexes like Zn-cysteinate; or
colloids like Zn2+ -clay or Zn2+ -humic acid, depends on the chemistry of the
water. The greatest dissolved zinc concentrations will occur in water with low
pH, low alkalinity and high ionic strength. Chemical speciation of zinc is
affected primarily by pH and alkalinity.
Soluble zinc salts (for example, zinc chloride and zinc sulphate) or insoluble
precipitates of zinc salts (for example, zinc carbonate, zinc oxide and zinc
sulphide) occur readily in industrial wastes. The carbonate, hydroxide and oxide
forms of zinc are relatively resistant to corrosion and are used extensively in the
following industries:
• metal galvanising;
• dye manufacture and processing;
• pigments (paints and cosmetics);
• pharmaceuticals; and
• fertilizer and insecticide.
Effects Zinc is a trace metal which is also an essential micronutrient in all organisms.
The requirement for trace elements frequently varies substantially between
species, but the optimal concentration range is generally narrow. Severe
imbalances can cause death, whereas marginal imbalances contribute to reduced
fitness.
The lethal effect of zinc on fish is thought to be from the formation of insoluble
compounds in the mucus covering the gills. Sub-lethal concentrations at which
PAGE 90
GUIDELINE AMBIENT ENVIRONMENT STANDARDS FOR ETHIOPIA
toxic effects are evident depend on the concentration ratio of zinc to copper,
since zinc interferes with copper absorption. Observed symptoms include
depressed white blood cell-thrombocyte counts. Observed effects of prolonged
exposure to sublethal concentrations of zinc in fish fry include oedema and liver
necrosis.
Although invertebrate responses to zinc toxicity vary, molluscs are generally
more resilient than are other organisms. Sub-lethal effects include reduced rates
of shell growth, oxygen uptake and larval development. Algal photosynthesis
can be inhibited by zinc.
47 INFORMATION SOURCES
The following information sources were utilised in the preparation of these standards:
• The Setting of Water Quality Objectives for Chemicals Dangerous to the Aquatic
Environment – List 1 Chemicals –In accordance with European Directive 76/464/EEC.
CSTE, The Scientific Advisory Committee On Toxicity and Ecotoxicity of Chemicals,
October 1993.
• South African Water Quality Guidelines, Department of Water Affairs and Forestry, 1996.
• Canadian Water Quality Guidelines. Prepared by the Task Force on Water Quality of the
Canadian Council of Resources and Environmental Ministers. 1987.
• Quality Criteria for Water. United States Environmental Protection Agency Office of
Water Regulations and Standards, Washington DC 20460. 1986.
• Australian Water Quality Guidelines. Australian and New Zealand Environmental and
Conservation Council. ANZECC 1992.
• Water Quality Assessment, A Guide to the use of Biota, Sediment and Water in
Environmental Monitoring. UNESCO/WHO/UNEP, 1996.
• Parameters of Water Quality, Interpretation and Standards, Irish Environmental Protection
Agency, 2001.
• Dangerous Substances in Water, A Practical Guide. Environmental Data Services Ltd
(ENDS). 1992.
• Environmental Quality Objectives and Environmental Quality Standards for the Aquatic
Environment. Irish Environmental Protection Agency, 1997.
• Standard Methods for the Examination of Water and Wastewater, 1998, (prepared and
published jointly by A.P.H.A., A.W.W.A & W.E.F) 20th Ed., American Public Health
Association, 1015 Fifteenth Street, N.W., Washington DC 20005, USA.
PAGE 91
GUIDELINE AMBIENT ENVIRONMENT STANDARDS FOR ETHIOPIA
APPENDIX 3
SOIL AND GROUNDWATER QUALITY
STANDARDS
.
PAGE 92
GUIDELINE AMBIENT ENVIRONMENT STANDARDS FOR ETHIOPIA
1 RISK ASSESSMENT
A risk assessment is an evaluation of environmental and health-related effects of contamination.
The purpose is to assess the need for remediation or protective measures. If contamination is found
to pose a significant risk to human health or the environment, remedial work or other protective
measures should be put in place.
Risk assessments appraise the specific circumstances of the contaminants in question, transport and
exposure pathways and potential receptors at risk in each given situation. This is the source-
pathway-receptor model. The risk assessment must be based on:
• The results of the investigations, including the nature and extent of contamination as well
as prevailing geological, hydrogeological and hydrological conditions.
• A hazard assessment pertaining to the contaminants of interest.
• A survey of possible ways of transport and exposure pathways
• Knowledge of the potential receptors exposed.
• Conceptual Model of the site.
A conceptual model of the site is an essential component of a risk assessment and gives a
representation of the environmental processes at a contaminated site including details of the source
of contamination and the potential pathways and receptors at risk. A specific risk assessment will
highlight interconnected ways and effects that may constitute a hazard to the receptor. It may also
be necessary to take ecotoxicological aspects into consideration.
A hazard assessment is a review of the inherent characteristics of a potential contaminant.
Qualitatively, a hazard may be described as carcinogenic, corrosive, toxic, etc. and effects may be
characterised as acute and more long term (chronic effects). Whenever possible, the hazard is
quantified by determining the concentration level at which harmful effects arise. Determining the
inherent hazard of a given contamination incident entails a comprehensive assessment of toxicity,
biodegradability, bioavailability, and mobility.
Risk is also assessed by considering the possible transport and exposure pathways. Three of the
most important considerations include; health considerations in connection with land use,
groundwater protection considerations and considerations regarding surface-water recipients and
soil.
It is important that the risk assessment is planned as an integral part of the site investigation work.
Soil contamination cannot be clearly distinguished from soil gas or groundwater contamination. In
the saturated zone, the space between soil particles is filled with groundwater. The contaminants
are in a state of dynamic equilibrium between soil particles and groundwater. Similarly, there is air
and water between the soil particles in the unsaturated zone and the volatile substances will reach a
dynamic equilibrium between soil, soil gas, and water. Thus, while distinction between the
contamination of soil, groundwater and soil gas may be difficult in a purely physical sense, it may
still be useful to carry out separate risk assessments in connection with land use, groundwater and
evaporation.
Criteria for soil quality have been established to be used in risk assessments in relation to land use.
Sites where the soil fully lives up to these criteria can be used without restriction for all purposes
including those that are highly sensitive to contamination. Furthermore, cut-off criteria have been
established for several contaminants. These criteria state the level at which it is necessary to
prevent all contact with the soil. It should be noted that compliance with soil quality criteria does
not necessarily ensure compliance with evaporation and groundwater criteria.
PAGE 93
GUIDELINE AMBIENT ENVIRONMENT STANDARDS FOR ETHIOPIA
At contaminated sites, indoor air in buildings as well as outdoor air may be unacceptably affected
by underlying contamination of soil or groundwater. The effect on the indoor and outdoor air
should be assessed in stages by various methods that have been constructed. In several stages,
theoretical calculation models are included. Risk assessment should be based on evaporation to the
overlying air and must not exceed the acceptable contamination contribution.
The risk of methane gas explosions in buildings on or in the immediate proximity of landfill sites
can also be assessed in stages.
Risk assessment of groundwater should be used to assess whether contamination of either soil or
groundwater contributes unacceptably to the contamination of groundwater resources. Groundwater
quality criteria have been established for use in risk assessments. Risk assessments should be based
on the aquifer complying with groundwater criteria at all points. Risk assessment can be carried out
in stages, starting with a simple assessment. If this assessment does not provide enough evidence of
the lack of risk, a more detailed risk assessment should be carried out taking sorption, dispersion
and degradation of the contaminants into account. Furthermore, the assessment of the effect on the
groundwater should be used to perform a risk assessment for surface water receptors where
groundwater discharges to or is hydraulically connected to surface waters.
It should be emphasised that the soil and groundwater criteria do not represent a risk analysis. A
specific risk analysis should take account of the local geological conditions and the sensitivity of
land use (site and adjacent land).
If the risk assessment establishes a risk to human health or the environment, residents on or in the
proximity of the site should be advised as to how to act until remediation can be implemented.
2 SOIL QUALITY STANDARDS
Standards for soil have been identified for a range of contaminants. In addition, cut-off criteria
have been identified for ten contaminants (metals, total PAH and Benxzo(a)pyrene). The Soil
Quality Standard (SQS) values and cut-off values are largely based on human toxicological data.
Most values have been determined by means of a risk assessment process which assumes a two
year old child,consuming 0.2g of soil a day as a target. Ecotoxicologial data has been taken into
consideration for 16 of the compounds assessed. Soil quality standard (SQS), cut-off values and
background values (based on total soil concentrations) are listed in Table 1 and 2.
Remediation is required if the concentration of contaminants exceeds the cut-off value. If the
concentration is between the SQS and the cut-off values, remediation is not required however
measures to reduce exposure may have to be implemented. Cut-off values have been identified for
ten compounds due to their low mobility, making it relatively easy to implement measures to
reduce exposure. They are also the contaminants most frequently encountered in topsoil from both
point sources and non-point sources.
When interpreting analytical data against the SQS values, data from distinguishable soil horizons
should be assessed separately to prevent data from contaminated soil horizons becoming diluted.
Similarly data from hot spots should also be considered separately to data from other parts of the
site.
For compounds that can lead to adverse chronic health effects average concentrations need to meet
the SQS in order to avoid risk of contamination. In the case of compounds with acute health
effects such as arsenic, the average concentration should not exceed the SQS and no more than
10% of the samples analysed should exceed the SQS by more than 50%. If these criteria are not
met the area represented by the samples could pose an unacceptable risk and further investigation is
required to determine if remedial work or other isolation or protective measures are required.
PAGE 94
GUIDELINE AMBIENT ENVIRONMENT STANDARDS FOR ETHIOPIA
2.1 APPLICATION IN RELATION TO LAND USE .
Three categories of land use are identified:
• Very sensitive e.g. home with gardens, playgrounds, allotments
• Sensitive e.g. parks
• Non sensitive e.g. industrial areas
In the case of the very sensitive land uses there is considered to be no risk from exposure to
contamination provided that SQS are not exceeded up to 3m below ground level (bgl). If the SQS
are only met to a depth of 1m bgl there is considered to be no risk to site users under ordinary
conditions. If SQS are exceeded beyond 1m, any activities such as construction work should be
controlled to take the contaminated soil into account. Sensitive land uses can take place even if the
SQS are only met within the top 0.3m of soil provided the underlying soil in which the criteria are
exceeded is isolated. For sensitive and non-sensitive land uses SQS must be met in the depth of
utilisation, which is determined on a site by site basis. For parkland and other areas of open space
the depth of utilisation is generally considered to be 0.5m. For grassed and built up areas it is set at
0.25m.
Table 1 Soil Quality Standards. All units are in mg/kg dry weight (DW).
Substance Soil quality
criteria
Substance Soil quality
criteria
Acetone 8 Molybdenum 5
Arsenic 201(2) MTBE 5002
Benzene 1.52 Nickel 301
BTEX, total 102 Nickel 301
Cadmium 0.52 Nitrophenols
Chloroform 502 Mono- 1252
Chlorophenols, total 32 Di- 102
Pentachlorophenol 0.15 Tri- 302
Chromium, total 500 PAH, total 1.52,3
Chromium (VI) 20 Benzo(a)pyrene 0.12
Copper 5001 Dibenzo(a,h) anthracene 0.12
Cyanide, total 500 Petrol (C5-C10) 25
Cyanide, acid volatile 102 Petrol (C9-C16) 25
DDT 1 Phenols, total 701
Detergents, anionic 1,5002 Phthalates, total 2502
1,2-dibromomethane 0.022 DEHP 252
1,2-dichloroethane 1.42 Styrene 402
1,1-dichloroethylene 52 Turpentine, mineral (C7 – C12) 25
1,2-dichloroethylene 852 Tetrachloroethylene 52
Dichloromethane 82 Tetrachloromethane 52
Fluorides, inorganic 201 1,1,1-trichloroethane 2002
Gas oil (Total hydrocarbons (C5–C35)
5) 100 Trichloroethylene 52
Lead 402 Vinyl chloride 0.42
Mercury 1 Zinc 500
1: Based on acute harmful effects
2: Based on chronic harmful effects
3PAH, total defined as the sum of individual components: fluoranthene, benzyl(b+j+k)fluoranthene, benzyl(a)pyrene,
dibenzyl(a,h)anthracene, and ideno(1,2,3-cd)pyrene.
PAGE 95
GUIDELINE AMBIENT ENVIRONMENT STANDARDS FOR ETHIOPIA
Table 2 Criteria for necessary contamination cut-off, mg/kg, dry weight (DW)
Substance Level where
contamination cut off is
necessary
Arsenic 201
Cadmium 52
Chromium 1,000
Copper 5001
Lead 4002
Mercury 3
Nickel 301
Zinc 1,000
PAHs 152
Benzo(a)pyrene 12
Dibenzo(a,h)anthracene 12
1: Based on acute harmful effects
2: Based on chronic harmful effects
3 GROUNDWATER QUALITY STANDARDS
Groundwater Quality Standards (GQS) have been set with the objective of protecting groundwater
for the purposes of abstraction. They should be applied irrespective of whether there are any
abstractions in the area under consideration. Values have been set for a range of substances and are
listed in Table 3. Effectively the GQS values are concentrations of contaminants which can be
reduced to those of drinking water quality by means of standard water treatment processes
(oxidation and filtration).
The interpretation of analytical data against the GQS values is a staged process. If an initial study
indicates the values are being exceeded, a more detailed site specific risk assessment is required to
determine the contribution of soil contamination at a particular site to the groundwater. The risk
assessment can comprise up to three stages:
1. Mixing model close to source area which comprises a simple calculation of contaminant
concentrations in groundwater directly below the affected area. If these calculated values
exceed the GQS, remedial action needs to be taken or Step 2 needs to be carried out.
2. Mixing model downgradient of source area which is based on compliance with the GQS at
a point in the aquifer located within 100m downgradient or at a distance equalling one
years groundwater flow. The width of the mixing zone in the aquifer is determined as
vertical dispersion. If these calculated values exceed the GQS, remedial action needs to be
taken or Step 3 needs to be carried out.
3. Downgradient model based on sorption and natural degradation is based on compliance
with the GQS at the same distance as in Step 2 but the concentrations of the contaminants
are reduced due to degradation in the aquifer. If the concentrations of contaminants are
below the GQS, the specific degradation rate shall be determined either by field
PAGE 96
GUIDELINE AMBIENT ENVIRONMENT STANDARDS FOR ETHIOPIA
measurements or in the laboratory, and samples from monitoring wells must confirm that
degradation is actually taking place at the site.
Table 3 Standards for groundwater beneath contaminated sites.
Substance Groundwater Quality Standard
µg/l
Acetone 10
Arsenic 8
Benzene 1
Boron 300
Butylacetates 10
Cadmium 0.5
Chlorinated solvents (not vinyl chloride) 1
Chloroform As low as possible
Chromium, total 25
Chromium VI 1
Copper 100
Cyanide, total 50
DEHP 1
Detergents, anionic 100
1,2-dibromomethane 0.01
Diethylether 10
Isopropyl alcohol 10
PAH 1 0.2
Lead 1
Methylisobutylketone 10
Methyl-tert-butylether (MTBE) 30
Mineral oil, total 9
Molybdenum 20
Naphthalene 1
Nickel 10
Nitrophenols 0.5
Pentachlorophenol 0.01
Pesticides, total
Pesticides
Pesticides, persistent chlorinated
0.5
0.1
0.03
Phenols 0.5
Phthalates (not DEHP) 10
Styrene 1
Toluene 5
Vinyl chloride 0.2
Xylenes 5
Zinc 100
1 Sum of fluoranthene, benzo(b)fluoranthene, benzo(k)fluoranthene, benzo(a)pyrene,
benzo(g,h,i)perylene, indeno(1,2,3-cd)pyrene.
PAGE 97
GUIDELINE AMBIENT ENVIRONMENT STANDARDS FOR ETHIOPIA
3.1 CATIONS/ANIONS
This section presents proposals for the setting of environmental quality objectives and standards for
groundwater through the use of ‘guideline values’. It is not possible to assign a universal set of
standards for groundwater due to the natural variation in hydrochemistry. Therefore, indicators can
be used to assess groundwater status, which takes account of natural variation in quality. It should
be noted that a guideline value may not be applicable in some cases due to the widely variable
nature of groundwater bodies. This variability in groundwaters, in pristine condition, is due to the
influence exerted by the particular geology of the area. Where a guideline value is not applicable
the natural background quality of the groundwater should be taken into consideration instead.
Where there is interaction between groundwater and surface water and more sensitive standards
exist for the receiving water body, these should then apply. The guideline values can be used to
assist with the characterisation of groundwater bodies and to establish the need for additional
investigations or further action in the event of guideline values being exceeded.
Table 4 Standards for Cations and Anions.
Parameter Groundwater Guideline Value
(mg/l)
Alkalinity No abnormal change to background
Aluminium 0.2
Ammonia (as NH4) 0.15
Barium 0.1
Bicarbonate/Carbonate No abnormal change to background
Calcium 200
Chloride 30
Dissolved Oxygen No abnormal change to background
Fluoride 1
Iron 0.2
Magnesium 50
Manganese 0.05
Mercury 0.001
Nitrate (as NO3) 25
Nitrite (as NO2) 0.1
Orthophosphate 0.03
Potassium 5
Silica No abnormal change to background
Sodium 150
Sulphate 200
PAGE 98
GUIDELINE AMBIENT ENVIRONMENT STANDARDS FOR ETHIOPIA
4 SAMPLING
Soil and water sampling is carried out in the investigation phase and as part of monitoring
strategies to demonstrate compliance with an agreed remedial plan. The objective of sampling is to
obtain representative samples to describe the nature and extent of contamination, the soil and
groundwater. This enables a risk assessment to be carried out so that there is an adequate
foundation for managing the contamination.
A written sampling strategy should be agreed and should include provision for the following:
• Sample locations
• Targeted sampling of hot spots on the basis of knowledge of the historical activities at the
site.
• Near boundaries of known contaminated areas to identify the extent of contamination.
• In areas of a contamination-sensitive land use.
• Non-targeted sampling at the rest of the site. In order to reveal unknown contamination
and to achieve the best statistical coverage of the site, it may be beneficial to locate
investigation points according to specific rules. In such cases, sample fields/grids/nets
can be defined.
• Sampling depth
Guidance on soil and groundwater sampling is provided in BS ISO 10175:2001 Investigation of
Potentially Contaminated Sites.
4.1 - SOIL SAMPLING
Two soil samples are recommended to provide for geological descriptions and for chemical
analyses. Surface samples can be taken in the top 0.15m for direct ingestion and inhalation risks.
Sample sets are usually collected every 0.5m and one should be taken per soil layer or to reflect
any strata/contamination changes as a minimum. Depths should also take into account proposed
activities at the site e.g. removal of topsoil, main sewer services etc. Three or four samples should
be taken through the soil profile with the deepest sample being natural strata. If contamination has
penetrated the natural strata sampling should continue to depths where contamination is at
background concentrations or it is not physically possible to sample.
4.2 - METHODS OF INVESTIGATION FOR SAMPLING
• Shallow investigations using hand augers
• Trial pits/trench excavations for depths up to 3m
• Percussion hammer probehole for depth up to 10m
• Shell and auger/rotary cored or open boreholes for deeper samples
Shallow investigations up to 1m may be backfilled with the excavated material. Deeper
investigations should be sealed with a low permeability material to prevent possible cross
contamination.
BS ISO 10381:2 Soil Quality – Sampling Techniques specified standard methods of sampling.
PAGE 99
GUIDELINE AMBIENT ENVIRONMENT STANDARDS FOR ETHIOPIA
4.3 WATER SAMPLING
The objective of sampling is to obtain a water sample from the well which is representative of the
groundwater in the aquifer with regard to the parameters to be investigated. A monitoring well
should be screened at the depth of interest in the aquifer and an impermeable seal installed through
any low permeability layers penetrated by the borehole to prevent cross contamination. After
installation a well is developed to clear the screen and to achieve the best possible well efficiency.
A minimum of three wells should be installed in a triangular patter to provide an estimate of
groundwater flow direction. The depth to the water level and depth of the well should be taken
prior to sampling using a dip meter. The thickness of any dense non-aqueous phase liquids
(DNAPL) and light non-aqueous phase liquids (LNAPL) should be taken prior to purging.
Prior to sampling, a well should be purged to ensure that water from the aquifer surrounding the
monitoring well is sampled. As a general rule, the amount purged is a minimum of three well
volumes or until groundwater quality measurements (electrical conductivity, pH, temperature, Eh,
DO) have stabilised. In cases where a borehole is purged dry, the sample may be taken from the
groundwater that subsequently enter the borehole.
BS ISO 5667:11 Water Quality – Groundwater Sampling details standard methods of sampling.
Bailers or pumps can be used to take a sample. Low flow methods are particularly appropriate
where general parameters (e.g.Eh, DO) are important to the overall assessment of biogeochemical
conditions. Samples should be carefully transferred from the bailer or pump to the sample
container (appropriate to the contaminant). Samples should be filtered or preserved where relevant
(e.g. metals).
Methods of sampling, packing, handling, and storage should be adapted to the types of
contaminants being investigated e.g volatile organics, to ensure that there is no loss of contaminant
during the sampling and analysis procedure. Water samples should be stored in the dark at 4 OC.
The time from sampling to analysis should be kept to a minimum and in any case should not
exceed the recommended duration as specified in Standard Methods for the Examination of Water
and Wastewater, 1998. As far as possible, samples should be delivered to the laboratory on the
same day they are collected. If this is not possible, it should be noted on the analysis form.
Sampling field sheets and chain of custody forms should be completed, dated and signed and
should accompany the samples.
Three important considerations that should be taken into account when sampling include the
following:
• The equipment should not contaminate the sample.
• The equipment should not be made of materials which ad/absorb substances.
• The method should not bias the contaminant content of the sample.
It is good practice to take field measurement of general water quality parameters on site at the time
of sampling (O2, CO2, Eh (redox potential) and pH), as these may change with time.
5 INFORMATION SOURCES
The following information sources were utilised in the preparation of these standards:
• BSI (1999) BS 5930. Code of Practice for Site Investigations. BSI, London.
• BSI (2002) BS 15176. Characterisation of excavated soil for reuse. BSI, London.
• BSI (2001) BS 10175. Investigation of Potentially Contaminated Sites. Code of Practice.
BSI, London.
PAGE 100
GUIDELINE AMBIENT ENVIRONMENT STANDARDS FOR ETHIOPIA
• BSI (2002) BS 10381-2 Soil Quality – Sampling – Part 2 Guidance on Sampling
Techniques. BSI, London.
• ISO (1993) 5667-11 Water Quality – Sampling – Part 11 Guidance on the sampling of
groundwaters.
• Nathanail, J., Bardos, P. and Nathanail, P, 2002, Contaminated Land Management, Ready
Reference, Land Quality Press and EPP Publications. [ISBN 1 900995 06 9].
• Aspinwall & Co. for Scottish Environment Protection Agency, 1999, Review of
International Guideline and Intervention Values (Contaminated Land) Report.
• Standard Methods for the Examination of Water and Wastewater, 1998, (prepared and
published jointly by A.P.H.A., A.W.W.A & W.E.F) 20th Ed., American Public Health
Association, 1015 Fifteenth Street, N.W., Washington DC 20005, USA.
PAGE 101
GUIDELINE AMBIENT ENVIRONMENT STANDARDS FOR ETHIOPIA
APPENDIX 4
NOISE STANDARDS
PAGE 102
GUIDELINE AMBIENT ENVIRONMENT STANDARDS FOR ETHIOPIA
1 NOISE STANDARDS TO BE ACHIEVED AT NOISE SENSITIVE
LOCATIONS
The generation of excessive noise in the community can have undesirable effects on the population.
It can cause annoyance and disturbance to people at work or during leisure activities, disturbance to
sleep and possibly a deleterious effect on general physical and mental well being. All people are
not equally sensitive to the disturbing aspects of noise. There is a small but significant minority
which is more sensitive than others.
The objective of these guidelines is to minimise the amount of noise to which people, living or
working in sensitive locations, are exposed. Examples of such areas include domestic dwellings,
hospitals, schools, places of worship, or areas of high amenity.
The sensitivity to noise is usually greater at night-time than it is during the day, by about
10dB(A). Ideally, if the total noise level from all sources is taken into account, the noise level at
sensitive locations should be kept within the following values:
Limits in dB (A) Leq
Area Code Category of area Day timeNote 1 Night timeNote 2
A Industrial area 75 70
B Commercial area 65 55
C Residential area 55 45
Note-1: Day time reckoned in between 6.00 am to 9.00p.m
Note 2: Night time reckoned in between 9.00p.m. to 6.00am
In some particularly quiet areas, such as pastoral, rural settings, where the background noise levels
are very low, lower noise limits may be more appropriate. Audible tones and impulsive noise at
sensitive locations at night should be avoided, irrespective of the noise level. Because of the
variability in sensitivity to noise from one area to the next, it may be desirable to establish formal
noise zoning criteria under the planning code.
2 VIBRATION AND AIR OVERPRESSURE
In the case of quarrying and mining operations, the vibration levels from blasting should not exceed
a peak particle velocity of 12 mm/sec, measured in any three mutually orthogonal directions at a
receiving location when blasting occurs at a frequency of once per week, or less. For more
frequent blasting the peak particle velocity should not exceed 8mm/sec. These levels are for low
frequency vibration, i.e., less than 40 Hertz.
Blasting should not give rise to air overpressure values at sensitive locations which are in excess of
125 dB (Lin)max peak.*Ambient Noise Standards
PAGE 103
Page 1
Page 2
Page 3
Page 4
Page 5
Page 6
Page 7
Page 8
Page 9
Page 10
Page 11
Page 12
Page 13
Page 14
Page 15
Page 16
Page 17
Page 18
Page 19
Page 20
Page 21
Page 22
Page 23
Page 24
Page 25
Page 26
Page 27
Page 28
Page 29
Page 30
Page 31
Page 32
Page 33
Page 34
Page 35
Page 36
Page 37
Page 38
Page 39
Page 40
Page 41
Page 42
Page 43
Page 44
Page 45
Page 46
Page 47
Page 48
Page 49
Page 50
Page 51
Page 52
Page 53
Page 54
Page 55
Page 56
Page 57
Page 58
Page 59
Page 60
Page 61
Page 62
Page 63
Page 64
Page 65
Page 66
Page 67
Page 68
Page 69
Page 70
Page 71
Page 72
Page 73
Page 74
Page 75
Page 76
Page 77
Page 78
Page 79
Page 80
Page 81
Page 82
Page 83
Page 84
Page 85
Page 86
Page 87
Page 88
Page 89
Page 90
Page 91
Page 92
Page 93
Page 94
Page 95
Page 96
Page 97
Page 98
Page 99
Page 100
Page 101
Page 102
Page 103
Page 104
Page 105
Page 106
Page 107
Page 108
GUIDLINE
AMBIENT
ENVIRONMENT
STANDARDS
FOR
ETHIOPIA
Prepared By:
The Environmental Protection
Authority
And
The United Nations Industrial
Development Organization
Prepared Under the
Ecologically Sustainable
Industrial Development (ESID)
Project
US/ETH/99/068/ETHIOPIA
August 2003
ADDIS ABABA
Parts of this publication may be reproduced without further permission provided the source is
acknowledged.
ISBN
Unique No.
Price V 1.1
GUIDELINE AMBIENT ENVIRONMENT STANDARDS FOR ETHIOPIA
Acknowledgements
The Environmental Protection Authority would like to acknowledge the United Nations Industrial
Development Organisation for their assistance under the Ecologically Sustainable Industrial Development
(ESID) Project US/ETH/99/068/ETHIOPIA in the preparation of these standards.
The Environmental Protection Authority would also like to take this opportunity to thank the following
bodies who were consulted during the drafting of these standards:
The Ministry of Water Resources
The Ministry of Health
The Ministry of Agriculture
The National Metrology Service Agency
Addis Ababa Administration Environmental Protection Authority
And
All participants of the workshop held for review of this document in Addis Ababa July 24 th 2003
GUIDELINE AMBIENT ENVIRONMENT STANDARDS FOR ETHIOPIA
PREFACE
The Federal Government of Ethiopia, through Proclamation 9/1995, established the Federal
Environmental Protection Authority. The Authority is mandated to protect and preserve ecosystems
of the Ethiopian environment.
It is in fulfilment of this mandate that these provisional standards for industrial pollution control are
hereby presented. These are guideline standards, which will be periodically reviewed and updated
in the light of additional information and knowledge.
It is now globally accepted that where there are threats of serious irreversible environmental
damages, lack of scientific certainty should not be used as a reason for postponing measures to
prevent environmental degradation.
The survival of man, and of any nation for that matter, depends on the ability to manage wastes in
an environmentally sound manner. This can only be achieved through establishment and
enforcement of appropriate standards and guidelines set to ensure that we do not destroy our
environment and indeed the very basis of our existence.
Dr. Telwode Brehan Gebre Egziabieher
General manager
Environmental Protection Authority
GUIDELINE AMBIENT ENVIRONMENT STANDARDS FOR ETHIOPIA
Contents
1 INTRODUCTION.....................................................................................................................1
2 GUIDELINE AMBIENT ENVIRONMENTAL STANDARDS FOR ETHIOPIA........................................3
APPENDIX 1 GUIDLINE AIR QUALITY STANDARDS................................................................12
APPENDIX 2 WATER QUALITY STANDARDS (SURFACE WATERS).........................................35
APPENDIX 3 SOIL AND GROUNDWATER QUALITY STANDARDS..............................................92
APPENDIX 4 NOISE STANDARDS.........................................................................................102
GUIDELINE AMBIENT ENVIRONMENT STANDARDS FOR ETHIOPIA
1 INTRODUCTION
Ambient environmental quality standards are set with a goal of safeguarding public health and
protecting the environment. Both objectives have very high quality requirements which
complement each other to a great extent. For example, in general terms, if a river or lake water
meets the most stringent fishery requirements it will meet all or virtually all other environmental
quality objectives.
It is appropriate then for the government of Ethiopia to set standards which will ensure that the
ambient environment of the country is protected and ensure environmental quality is not degraded
while also ensuring a healthy environment within people must live.
The government of Ethiopia has mandated the Environmental Protection Authority to set such
standards and this document represent the Authorities guideline standards with respect to the
ambient environment..
In practice, standards can be set from either first principles or based on existing national or
international guidelines.
Deriving such standards from first principles requires classification, and prioritisation of pollutants,
derivation of pollutant exposure processes and their ecological effects, determine. predicted
environmental concentrations and predicted no effect concentration for the receiving environment.
Given the resources required to derive country specific standards from first principles, standards
are generally derived based on existing published guidelines as is the case in this instance. The
information upon which international guidelines are based are derived predominantly from
extensive epidemiological and toxicological studies to determine the observed health and
environmental effects of the compound in question. As such, there are a limited number of
international sources who collate and interprets this data in order to prepare guideline for such
parameters. The principle international and national guidelines used in the preparation of these
guideline standards for Ethiopia are referenced throughout the document.
Where sufficient national baseline information is available, the guideline values prepared by
international bodies may be further modified at to take account of particular national criteria prior
to their implementation as a national standard. Additional baseline data collection is then
undertaken to improve or adapt the initial standards to own country situation. Baseline data is
important for the implementation of environmental quality standards particularly with regard to the
following:
• forming a basis for zoning; where general or special standards should apply;
• assessing the assimilative capacity of the receiving environment;
• identifying the areas which require stringent or less stringent application of standards; and,
• formulating rehabilitation and/or conservation measures.
There is currently insufficient baseline data available within Ethiopia to allow modification of
international guidelines for ambient environmental quality. As such many of the guideline
standards have been adopted directly as recommended for developing countries.
These guideline standards are being introduced to be used all throughout the country subjected to
amendment, as more information on the state or pollution is made available through the
Ecologically Sustainable Industrial Development (ESID) project. The regional states can establish
more stringent standards taking into consideration particular ecological conditions in their localities
provided EPA’s standards are used as the minimum. .
PAGE 1
GUIDELINE AMBIENT ENVIRONMENT STANDARDS FOR ETHIOPIA
These guideline standards are primarily aimed at protection of ambient environmental quality
within all components of the Ethiopian Environment. The guideline standards provided within this
document with regard to water quality are not based on use related criteria e.g water for abstraction
as a source of drinking water, or for example irrigation purposes. It is anticipated that such
standards will be prepared by the Ministry of Water resources at a later date.
1.1 STRUCTURE OF THE DOCUMENT
The Guideline Standards are presented in summary form in the following section. Additional
appendices are included which provides detailed information and background for the guideline
standards in each area as follows.
Appendix 1: Air Quality Standards
Appendix 2: Water Quality Standards
Appendix 3: Soil and Groundwater Quality Standards
Appendix 4: Noise Standards
PAGE 2
GUIDELINE AMBIENT ENVIRONMENT STANDARDS FOR ETHIOPIA
2 GUIDELINE AMBIENT ENVIRONMENTAL STANDARDS FOR ETHIOPIA
The guideline environmental standards for Ethiopia are presented below in summary form.
Additional information is given on each parameter in a set of Appendixes attached to this
document.
2.1 GUIDELINE AIR QUALITY STANDARDS
Guideline standards for priority ambient atmospheric pollutants are given below. Information on
additional parameters is provided in Appendix 1.
Compound Guideline Value [µg/m3] Averaging time
Sulphur dioxide 500
125
50
10 minutes
24 hours
1 year
Nitrogen dioxide 200
40
1 hour
1 year
Carbon monoxide 100 000
60 000
30 000
10 000
15 minutes
30 minutes
1 hour
8 hours
Ozone 120 8 hours
Suspended Particulate Matter
PM10 50 1 year
150 24 hours
PM2.5 15 1 year
65 24 hours
Lead 0.5 1 year
2.2
PAGE 3
GUIDELINE AMBIENT ENVIRONMENT STANDARDS FOR ETHIOPIA
GUIDELINE SURFACE WATER QUALITY STANDARDS
Guideline standards for priority surface water pollutants with regard to protection of aquatic
species are given below. Detailed information on each parameter is provided in Appendix 2
Compound Limit
Aluminium 200 µg/l Al;
Ammonium 20 µg/l NH
3
un-ionised
25 µg/l NH
3
un-ionised
Antimony 20 µg/l Sb
Arsenic 50 µg/l As
Barium 100 µg/l Ba
Benzene 10.0 µg/l
Benzo(A)Pyrene 0.01 µg/l
BOD
5
[Biochemical oxygen demand] < 5 mg/l O
2
Cadmium 5.0 µg/l Cd [Total];
Chloride 250 mg/l Cl
Chlorine, Residual 5 µg/l as HOCl
Chromium 50 µg/l Cr
Conductivity 1000 µS/Cm (@ 20 °C)
Copper 5-112 µg/l dissolved Cu for hardness
range 10-500 mg/l CaCO
3
Cyanide 50 µg/l CN
Dissolved oxygen Game Fish - 50% samples > 9 mg/l
O
2
[minimum 6 mg/l O
2
]
Course Fish - 50% samples > 7 mg/l
O2[minimum 4 mg/l O2]
Fluoride 1.0 mg/l F
Iron 1.0 mg/l dissolved Fe
Lead 50 µg/l Pb
Manganese 300 µg/l Mn
Mercury 1 µg/l Hg
Methylene Blue Active
Substances[(Anionic) Detergents]
200 µg/l lauryl-SO
4
Nickel 100 µg/l Ni AM
Nitrate 50 mg/l NO
3
Nitrite Game Fish - 200 µg/l NO
2
Course Fish - 400 µg/l NO
2
PAGE 4
GUIDELINE AMBIENT ENVIRONMENT STANDARDS FOR ETHIOPIA
Compound Limit
Nitrogen, Kjeldahl 2 mg/l N
PCBs and PCTs 1 µg/l AM
Pesticides
Aldrin 0.01 µg/l
Dieldrin 0.01 µg/l
Endrin 0.005 µg/l
Isodrin 0.005 µg/l
Atrazine 1.0 µg/l
Chloridazon 0.1 µg/l
2,4-D 0.005 µg/l
DDT (y-isomer) 10 µg/l
DDT (all isomers) 25 µg/l
Diazinon 5 µg/l
Dichlorbenil 10µg/l
Dichlorvos 0.001 µg/l
Diuron 25 µg/l
Endosulphan 0.001 µg/l
Fenitrothion 0.01 µg/l
Isoproturon 0.5 µg/l
Lindane 0.1 µg/l
Linuron 1.0 µg/l
Malathion 0.01 µg/l
MCPA 10 µg/l
Mecoprop 10 µg/l
Parathionethyl 0.01 µg/l
Pentachlorophenol 2.0 µg/l
Simazine 1.0 µg/l
Tributyltin oxide 0,001 µg/l
Trifuralin 0.1 µg/l
Triphenyltin acetate 0.01 µg/l
Triphenyltin hydroxide 0.01 µg/l
pH 6 to 9, but no change more than 0.2 units
from natural level in 95% of samples
Phenols [non specific/total] 0.5 µg/l C
6
H
5
OH AM
PAGE 5
GUIDELINE AMBIENT ENVIRONMENT STANDARDS FOR ETHIOPIA
Compound Limit
Polycyclic aromatic hydrocarbons [PAH] 2 µg/l [Total for 6 specified
compounds**] AM
Selenium 10 µg/l Se
Silver 10 µg/l Ag
Total Suspended Solids, < 25 mg/l [annual mean]
50 mg/l [maximum value]
Sulphate 200 mg/l SO
4
Temperature Game Fish - Discharge must not result in
variation of more than 1.5
o
C; temperature
down stream of thermal discharge
Course Fish - Discharge must not result in
variation of more than 3
o
C; temperature
down stream of thermal discharge
Thallium 5 µg/l Tl AM
Toluene 10.0 µg/l AM
1,1,1-Trichloroethane 500 µg/l AM
Tetrachloroethylene 10 µg/l AM
Trichloroethylene 10 µg/l AM
Uranium 20 µg/l U AM
Vinyl chloride 10 µg/l AM
Zinc 30 µg/l to 500 µg/l Zn @ hardness 10 to
500 mg/l
2.3
PAGE 6
GUIDELINE AMBIENT ENVIRONMENT STANDARDS FOR ETHIOPIA
GUIDELINE SOIL AND GROUNDWATER STANDARDS
Guideline standards for soil quality are provided below. These standards represent “clean-up”
values for soils and groundwater’s which have been contaminated as a result of anthropogenic
activity. These values are based on a generic “risk assessment” and as such should be regarded as
guideline values. A detailed risk assessment should be undertaken to obtain site specific values for
the parameters in question. Additional information on this approach and the guideline standards is
presented in Appendix 3.
2.3.1 Guideline Soil Quality Standards.
Substance Guideline Standard
(mg/kg dry weight)
Acetone 8
Arsenic 201(2)
Benzene 1.52
BTEX, total 102
Cadmium 0.52
Chloroform 502
Chlorophenols, total 32
Pentachlorophenol 0.15
Chromium, total 500
Chromium (VI) 20
Copper 5001
Cyanide, total 500
Cyanide, acid volatile 102
DDT 1
Detergents, anionic 1,5002
1,2-dibromomethane 0.022
1,2-dichloroethane 1.42
1,1-dichloroethylene 52
1,2-dichloroethylene 852
Dichloromethane 82
Fluorides, inorganic 201
Gas oil (Total hydrocarbons (C5–C35)
5) 100
Lead 402
Mercury 1
Molybdenum 5
MTBE 5002
Nickel 301
PAGE 7
GUIDELINE AMBIENT ENVIRONMENT STANDARDS FOR ETHIOPIA
Substance Guideline Standard
(mg/kg dry weight)
Nickel 301
Nitrophenols
Mono- 1252
Di- 102
Tri- 302
PAH, total 1.52,3
Benzo(a)pyrene 0.12
Dibenzo(a,h) anthracene 0.12
Petrol (C5-C10) 25
Petrol (C9-C16) 25
Phenols, total 701
Phthalates, total 2502
DEHP 252
Styrene 402
Turpentine, mineral (C7 – C12) 25
Tetrachloroethylene 52
Tetrachloromethane 52
1,1,1-trichloroethane 2002
Trichloroethylene 52
Vinyl chloride 0.42
Zinc 500
1: Based on acute harmful effects
2: Based on chronic harmful effects
3PAH, total defined as the sum of individual components: fluoranthene, benzyl(b+j+k)fluoranthene, benzyl(a)pyrene,
dibenzyl(a,h)anthracene, and ideno(1,2,3-cd)pyrene.
2.3.2 Guideline Standards for Groundwater Beneath Contaminated Sites
Substance Groundwater Quality Standard µg/l
Acetone 10
Arsenic 8
Benzene 1
Boron 300
Butylacetates 10
Cadmium 0.5
PAGE 8
GUIDELINE AMBIENT ENVIRONMENT STANDARDS FOR ETHIOPIA
Chlorinated solvents (not vinyl chloride) 1
Chloroform As low as possible
Chromium, total 25
Chromium VI 1
Copper 100
Cyanide, total 50
DEHP 1
Detergents, anionic 100
1,2-dibromomethane 0.01
Diethylether 10
Isopropyl alcohol 10
PAH 1 0.2
Lead 1
Methylisobutylketone 10
Methyl-tert-butylether (MTBE) 30
Mineral oil, total 9
Molybdenum 20
Naphthalene 1
Nickel 10
Nitrophenols 0.5
Pentachlorophenol 0.01
Pesticides, total
Pesticides
Pesticides, persistent chlorinated
0.5
0.1
0.03
Phenols 0.5
Phthalates (not DEHP) 10
Styrene 1
Toluene 5
Vinyl chloride 0.2
Xylenes 5
Zinc 100
1 Sum of fluoranthene, benzo(b)fluoranthene, benzo(k)fluoranthene, benzo(a)pyrene,
benzo(g,h,i)perylene, indeno(1,2,3-cd)pyrene.
2.3.3 Guideline Standards for Cations and Anions*
* It is not possible to assign a universal set of standards for groundwater due to the natural
variation in hydrochemistry. Therefore, indicators can be used to assess groundwater
status, which takes account of natural variation in quality. It should be noted that a
PAGE 9
GUIDELINE AMBIENT ENVIRONMENT STANDARDS FOR ETHIOPIA
guideline value may not be applicable in some cases due to the widely variable nature of
groundwater bodies.
Parameter Groundwater Guideline Value (mg/l)
Alkalinity No abnormal change to background
Aluminium 0.2
Ammonia (as NH4) 0.15
Barium 0.1
Bicarbonate/Carbonate No abnormal change to background
Calcium 200
Chloride 30
Dissolved Oxygen No abnormal change to background
Fluoride 1
Iron 0.2
Magnesium 50
Manganese 0.05
Mercury 0.001
Nitrate (as NO3) 25
Nitrite (as NO2) 0.1
Orthophosphate 0.03
Potassium 5
Silica No abnormal change to background
Sodium 150
Sulphate 200
2.4 GUIDELINE STANDARDS FOR NOISE
The objective of these guidelines is to minimise the amount of noise to which people, living or
working in sensitive locations, are exposed. Examples of such areas include domestic dwellings,
hospitals, schools, places of worship, or areas of high amenity.
The sensitivity to noise is usually greater at night-time than it is during the day, by about
10dB(A). Ideally, if the total noise level from all sources is taken into account, the noise level at
sensitive locations should be kept within the following values:
Limits in dB (A) Leq
Area Code Category of area Day timeNote 1 Night timeNote 2
A Industrial area 75 70
B Commercial area 65 55
C Residential area 55 45
PAGE 10
GUIDELINE AMBIENT ENVIRONMENT STANDARDS FOR ETHIOPIA
Note-1: Day time reckoned in between 6.00 am to 9.00p.m
Note 2: Night time reckoned in between 9.00p.m. to 6.00am
Additional information on noise and vibration standards is provided in Appendix 4.
PAGE 11
GUIDELINE AMBIENT ENVIRONMENT STANDARDS FOR ETHIOPIA
APPENDIX 1
GUIDLINE AIR QUALITY STANDARDS
PAGE 12
GUIDELINE AMBIENT ENVIRONMENT STANDARDS FOR ETHIOPIA
1 SULPHUR DIOXIDE
Chemical Symbol or Formula: SO2
Standard*: Averaging Time
500 µg/m3 10 minutes
125 µg/m3 24 hours
50 µg/m3 1 year
* The volume must be standardised at a temperature of 293 °K and a pressure of 101,3 kPa.
1.1 HEALTH EFFECTS1
1.1.1 Short-period exposures (less than 24 hours)
Most information on the acute effects of SO2 comes from controlled chamber experiments on
volunteers exposed to SO 2 for periods ranging from a few minutes up to one hour (WHO 1999a).
Acute responses occur within the first few minutes after commencement of inhalation. Further
exposure does not increase effects. Effects include reductions in the mean forced expiratory volume
over one second (FEV1), increases in specific airway resistance (sRAW), and symptoms such as
wheezing or shortness of breath. These effects are enhanced by exercise that increases the volume
of air inspired, as it allows SO2 to penetrate further into the respiratory tract.
A wide range of sensitivity has been demonstrated, both among normal subjects and among those
with asthma. People with asthma are the most sensitive group in the community. Continuous
exposure-response relationships, without any clearly defined threshold, are evident. To develop a
guideline value, the minimum concentrations associated with adverse effects in asthmatic patients
exercising in chambers have been considered.
1.1.2 Exposure over a 24-hour period
Information on the effects of exposure averaged over a 24-hour period is derived mainly from
epidemiological studies in which the effects of SO2, SPM and other associated pollutants are
considered. Exacerbation of symptoms among panels of selected sensitive patients seems to arise in
a consistent manner when the concentration of SO 2 exceeds 250 µg/m
3 in the presence of SPM.
Several more recent studies in Europe have involved mixed industrial and vehicular emissions now
common in ambient air. At low levels of exposure (mean annual levels below 50 µg/m3; daily
levels usually not exceeding 125 µg/m3 ) effects on mortality (total, cardiovascular and respiratory)
and on hospital emergency admissions for total respiratory causes and chronic obstructive
pulmonary disease (COPD), have been consistently demonstrated. These results have been shown,
in some instances, to persist when black smoke and SPM levels were controlled for, while in others
no attempts have been made to separate the pollutant effects. In these studies no obvious threshold
levels for SO2 has been identified.
1 For further information on health effects see Guidelines for Air Quality, WHO, Geneva, 2000
PAGE 13
GUIDELINE AMBIENT ENVIRONMENT STANDARDS FOR ETHIOPIA
1.1.3 Long-term exposure
Earlier assessments examined findings on the prevalence of respiratory symptoms, respiratory
illness frequencies, or differences in lung function values in localities with contrasting
concentrations of SO2 and SPM, using data from the coal-burning era in Europe. The lowest-
observed- adverse-effect level of SO 2 was judged to be at an annual average of 100 µg/m
3, when
present with SPM. More recent studies related to industrial sources of SO2, or to the changed urban
mixture of air pollutants, have shown adverse effects below this level. But a major difficulty in
interpretation is that long-term effects are liable to be affected not only by current conditions, but
also by the qualitatively and quantitatively different pollution of earlier years. However, cohort
studies on differences in mortality between areas with contrasting pollution levels indicate that
mortality is more closely associated with SPM, than with SO2.
1.2 MONITORING
As the main source of this pollutant is the combustion of fossil fuels containing sulphur, either in
power stations or domestic/commercial space heating, the major local source types strongly
influences monitoring and assessment strategies. Automatic analyzers need to be used if
compliance against a short-term guideline is to be determined; a variety of active samplers are
suitable for comparison with daily or annual guidelines. Passive samplers may be used to provide
data for comparison with the long-term annual guideline.
1.2.1 Passive samplers
There are currently no national or international standards governing the application of SO2
diffusion tubes to ambient air monitoring, nor for their laboratory preparation and analysis.
Protocols for sample preparation and analysis by spectrophotometry and ion exchange
chromatography have, however, been published in scientific literature (Bennett et al. 1992;
Downing et al. 1994; Hargreaves and Atkins 1988).
A variety of passive sampling techniques are available (UNEP/WHO 1994b). The most widely
used include:
• The triethanolamine (TEA)/glycol/spectrophotometry method (Hangartner et al. 1989).
• The potassium hydroxyde (KOH)/glycerol/spectrophotometry method (Hargreaves and
Atkins 1988).
• The sodium carbonate (Na2CO3)/glycerine/ion-exchange chromatography method (Ferm
1991).
Hybridization of these techniques is widespread. In the UK, for instance, KOH or NaOH is used as
absorbent, but with the tube membrane proposed by Ferm (1991) and using ion-exchange
chromatography as the analysis method. In practice, the ion-exchange chromatographic technique
has been informally accepted as the standard method for SO2 diffusion tube analysis. The typical
sensitivity of this hybrid technique is ±8.5 mg/m 3 : some under-reading against automatic
analysers has been observed (about 30%), although agreement with active samplers is better
(Downing et al. 1994).
1.2.2 Active samplers
The equipment required for sampling gaseous sulphur compounds in ambient air is described in full
in International Standard ISO 4219 (ISO 1979). This standard gives details of the equipment
necessary to sample gaseous pollutants by absorption in a liquid bubbler. The standard also
includes guidance for siting and installation of the apparatus. The principle of active-sampling
PAGE 14
GUIDELINE AMBIENT ENVIRONMENT STANDARDS FOR ETHIOPIA
methodologies is to draw ambient air through a collecting medium (typically a liquid bubbler), for
a specified time, typically 24 hours. The volume of air is metered. The collecting medium is
subsequently analysed and the concentration of pollutant in the sampled air determined. This
proven method is well established, and has been used in many monitoring networks worldwide for
a number of years. In consequence, there is a long history of active sampler SO2 measurements
available for trend assessment.
There are several methods of SO2 monitoring based on this principle, which can be carried out
using the apparatus specified in ISO 4219. They differ with respect to the solutions used in the
bubblers for SO2 absorption and the method of analysis. The four most widely used methods are
described below.
Acidimetric (total acidity) method.
This method, given in ISO 4220 (ISO 1983), is used to determine a gaseous acid air pollution
index. Although this method measures total acidity, and is not specific for SO2, it is adequate for
general use. The simplicity of the method, and the fact that the reagents are relatively safe, makes it
a popular choice for routine monitoring (AEA 1997). An accuracy of ±10% has been estimated for
SO2 measurements using the total acidity method, taking account of all contributory factors. A
precision of ±4 mg/m 3 is achievable for this widely-used method (AEA 1997).
Ion-exchange chromatography.
A variation on the above technique. The exposed peroxide solutions are analysed for sulphate ions
by means of ion-exchange chromatography, rather than titration. This has the advantage of being
sulphate-specific, but requires the use of an expensive ion-exchange chromatograph.
Tetrachloromercurate (TCM) method.
This is also known as the Pararosaniline method ISO 6767 (ISO 1990). This is the reference
method specified in the EC Directive on SO2 and suspended particulate matter(EC 1980).
However, the reagents used are very toxic, and for this reason the method is not widely used.
Thorin method.
This method is given in ISO 4221 (ISO 1980). The reagents used include perchloric acid, barium
perchlorate, dioxane and thorin. These are hazardous and must be handled and disposed of with
care. Accordingly, this method is not commonly used world-wide.
1.2.3 Automatic analysers
The measurement of SO2 in ambient air using automatic analysers is covered by ISO/DIS 10498
(ISO/DIS 1999). Well-established automatic monitoring techniques are available. The most widely
used method for automatic SO2 measurement is ultraviolet fluorescence (UVF). SO2 molecules in
the sample airstream are excited to higher, unstable energy states by UV radiation at 212 nm. These
energy states decay, causing an emission of secondary fluorescent radiation with an intensity
proportional to the concentration of SO2 in the sample.
The accuracy of data from automatic SO2 analysers depends on a range of factors encompassing
the entire measurement chain. These include accuracy of calibration standards, analyser stability
and sample losses in the measurement system. An accuracy of ±10% has been estimated for SO2
measurements in UK national automatic networks, taking account of all contributory factors. The
precision of SO2 measurements, determined from long-term variations in baseline response of in-
service analysers, is estimated to be ±3 mg/m3 (AEA 1996).
1.2.4 Remote sensors
Remote optical sensor systems, such as the Differential Optical Absorption System (DOAS), use a
long-path spectroscopic technique to make real-time measurements of the pollutant concentration
by integrating readings along a path between a light source and a detector. Long-path monitoring
PAGE 15
GUIDELINE AMBIENT ENVIRONMENT STANDARDS FOR ETHIOPIA
systems can be used to measure SO2, but the methodology is less well established than that for
automatic point monitors. The accuracy and precision of the data from these instruments are,
therefore, much more difficult to determine. The method does not conform to ISO 7996 (ISO
1985b). Particularly careful attention needs to be paid to instrument calibration and quality
assurance to obtain meaningful data from remote sensing instruments.
PAGE 16
GUIDELINE AMBIENT ENVIRONMENT STANDARDS FOR ETHIOPIA
2 NITROGEN DIOXIDE
Chemical Symbol or Formula: NO2
Standard*: Averaging Time
200 µg/m3 24 hours
40 µg/m3 1 year
* The volume must be standardised at a temperature of 293 °K and a pressure of 101,3 kPa.
2.1 HEALTH EFFECTS2
2.1.1 Short-term exposure effect
Available data from animal toxicology experiments indicate that acute exposure to NO2
concentrations of less than 1880 µg/m 3 (1 ppm) rarely produce observable effects. Normal healthy
humans, exposed at rest or with light exercise for less than two hours to concentrations above 4700
µg/m3 (2.5 ppm), experience pronounced decreases in pulmonary function; generally, normal
subjects are not affected by concentrations less than 1880 µg/m 3 (1.0 ppm). One study showed that
the lung function of subjects with chronic obstructive pulmonary disease is slightly affected by a
3.75-hour exposure to 560 µg/m3 (0.3 ppm).
A wide range of findings in asthmatics has been reported. Asthmatics are likely to be the most
sensitive subjects, although uncertainties exist in the health database. The lowest concentration
causing effects on pulmonary function was reported from two laboratories that exposed mild
asthmatics for 30-110 minutes to 565 µg/m 3 (0.3ppm) NO2 during intermittent exercise. However,
neither of these laboratories was able to replicate these responses with a larger group of asthmatic
subjects. One of these studies indicated that NO2 can increase airway reactivity to cold air in
asthmatic subjects. At lower concentrations, the pulmonary function of asthmatics was not changed
significantly.
NO2 increases bronchial reactivity, as measured by the response of normal and asthmatic subjects
following exposure to pharmacological bronchoconstrictor agents, even at levels that do not affect
pulmonary function directly in the absence of a bronchoconstrictor. Some, but not all, studies show
increased responsiveness to bronchoconstrictors at NO 2 levels as low as 376-565 µg/m
3
(0.2 to 0.3
ppm); in other studies, higher levels had no such effect. Because the actual mechanisms of effect
are not fully defined and NO2 studies with allergen challenges showed no effects at the lowest
concentration tested (188 µg/m3; 0.1 ppm), full evaluation of the health consequences of the
increased responsiveness to bronchoconstrictors is not yet possible. Recent studies have shown an
increased reactivity to natural allergens in the same concentration range. The results of repetitive
exposures of such individuals, or the impact of single exposures on more severe asthmatics, are not
known.
2.1.2 Long-term exposure effects
Studies with animals have clearly shown that several weeks to months of exposure to N O2
concentrations of less than 1880 µg/m 3 (1ppm) causes a range of effects, primarily in the lung, but
also in other organs such as the spleen and liver, and in blood. Both reversible and irreversible lung
2 For further information on health effects see Guidelines for Air Quality, WHO, Geneva, 2000.
PAGE 17
GUIDELINE AMBIENT ENVIRONMENT STANDARDS FOR ETHIOPIA
effects have been observed. Structural changes range from a change in cell type in the
tracheobronchial and pulmonary regions (at a lowest reported level of 640 µg/m 3), to emphysema-
like effects. Biochemical changes often reflect cellular alterations, with the lowest effective NO 2
concentrations in several studies ranging from 380-750 µg/m3.
NO2 levels of about 940 µg/m
3
(0.5ppm) also increase susceptibility to bacterial and viral infection
of the lung. There are no epidemiological studies that can be confidently used to quantify a long-
term NO2 exposure or concentration likely to be associated with the induction of unacceptable
health risks in children or adults. Homes with gas cooking appliances have peak levels of NO2 in the
same range as levels causing effects in some animal and human clinical studies. Epidemiological
studies evaluating the effects of NO2 exposures in such homes have been conducted. In general,
epidemiological studies of adults and infants (less than 2years old) show no significant effect of the
use of gas cooking appliances on respiratory illness; nor do the few available studies of infants and
adults show any associations between pulmonary function changes and gas stove use. However,
children 5-12 years old are estimated to have a 20% increased risk for respiratory symptoms and
disease for each increase of 28 µg/m3 NO2 (2-week average), where the weekly average
concentrations are in the range of 15-128 µg/m 3 or possibly higher. However, the observed effects
cannot clearly be attributed to either the repeated short-term high level peak, or to long-term
exposures in the range of the stated weekly averages (or possibly both).
The results of outdoor studies consistently indicate that children with long-term ambient NO2
exposures exhibit increased respiratory symptoms that are of longer duration, and show a decrease
in lung function. However, outdoor NO 2 epidemiological studies, as with indoor studies, provide
little evidence that long-term ambient NO 2 exposures are associated with health effects in adults.
None of the available studies yields confident estimates of long-term exposure-effect levels, but
available results most clearly suggest respiratory effects in children at annual average NO2
concentrations in the range of 50-75 µg/m3 or higher.
2.2 MONITORING
Automatic analysers must be used for the direct determination of compliance against the hourly
guideline, although much useful information can be inferred using passive samplers (see section
4.5). Either technique is applicable for comparing ambient levels against the annual guideline.
2.2.1 Passive samplers
Monitoring ambient NO2 concentrations using passive diffusion tube samplers is now well
established. This method provides an integrated, average concentration for the pollutant over the
exposure period (typically 2-4 weeks) and is particularly well suited to baseline and screening
studies for assessing the spatial distribution of NO2 concentrations in an urban environment. The
most widely used techniques are variants on the Palmes-type sampler, originally developed for the
assessment of occupational exposure. This uses a tube sampler, employing TEA as absorbent.
Sample analysis, after thermal desorption, is by spectrophotometry or ion-exchange
chromatography (Palmes et al. 1976). Very large scale mapping surveys are possible using
diffusion tubes, but careful attention both to the harmonization of analytical procedures and to the
outputs from different analytical laboratories is essential for the success of large-scale passive
sampler surveys.
Although extensively used throughout the UK and Europe there are, at present, no national or
international standards governing the application of diffusion tubes for ambient air quality
monitoring, nor for the laboratory preparation and analysis of diffusion tubes. Protocols for sampler
preparation and analysis by spectrophotometry have, however, been published in the scientific
literature (Palmes et al. 1976; Atkins et al. 1986); these have been informally accepted as standard
procedures for NO2 diffusion tube preparation and analysis.
PAGE 18
GUIDELINE AMBIENT ENVIRONMENT STANDARDS FOR ETHIOPIA
Recent comparisons of NO2 diffusion tube measurements with co-located chemiluminescent NOx
analysers show good agreement (Smith et al. 1997; Gerboles and Amantini 1993). Over the range
of concentrations generally encountered in urban areas (20-80 mg/m 3 ), it was found that on
average NO2 diffusion tubes, exposed for one month, tended to overestimate ambient NO2 by
approximately 10% compared with a chemiluminescent NOx analyser. Precision estimates of the
diffusion tube technique have been quoted as 5-8% in similar studies.
2.2.2 Active samplers
A variety of active sampler technologies are available (UNEP/WHO 1994b). The best known of
these is the Griess-Saltzman method, covered by ISO 6768 (ISO 1985a). Although this method is
sensitive and requires a relatively simple, inexpensive sampling apparatus, there are a number of
disadvantages. It is a relatively skilled and labour-intensive technique, uses corrosive chemicals
and is not readily applicable to sampling periods longer than 1-2 hours. There also remain doubts
about calibration methods, collection efficiency and possible side-reactions. In consequence, this
method cannot be recommended for general baseline monitoring applications.
2.2.3 Automatic analysers
The reference method for automatic measurement of nitrogen oxide concentrations, as defined for
compliance with EC Directive 85/203/EEC (EC 1985), is the automatic chemiluminescence
method described in ISO standard 7996 (ISO 1985b). This method is widely used world wide. The
method is based on the chemiluminescence energy emitted when NO in the sample airstream reacts
with O3 in an evacuated chamber to form an excited energy state of NO2. The chemiluminescent
reaction is:
NO + O3 = NO2* + O2
Emitted light from the excited NO 2* is converted to an output voltage by a photomultiplier tube
and amplifier.
Automatic NO2 analysers based on liquid-phase chemiluminescence, produced by reacting NO2
with a chemical solution, are also available. These highly sensitive but relatively fragile
instruments are mostly employed for research applications and are not generally regarded as being
suitable for routine baseline monitoring purposes.
The accuracy of data from automatic NO2 analysers depends on a range of factors encompassing
the entire measurement chain. These include the accuracy of calibration standards, analyser
stability and sample losses in the measurement system. Final accuracy can therefore vary from
network to network. An accuracy of ± 8% has been estimated for NO2 measurements in well-run
automatic networks, taking account of all contributory factors (AEA 1996). The precision of NO2
measurements is estimated to be ±6.5 mg/m 3 , determined from long-term variations in the
baseline responses of in-service analysers.
2.2.4 Remote sensors
Long-path monitoring systems are available for the measurement of NO2, but the methodology is
less well established than that for automatic point monitors. The accuracy and precision of the data
from these instruments are, therefore, much more difficult to determine. The method does not
conform to ISO 7996 (ISO 1995b) and, as noted previously, careful attention needs to be given to
instrument calibration and quality assurance to obtain meaningful data.
PAGE 19
GUIDELINE AMBIENT ENVIRONMENT STANDARDS FOR ETHIOPIA
3 CARBON MONOXIDE
Chemical Symbol or Formula: CO
Standard*: Averaging Time
100,000 µg/m3 15 minutes
60,000 µg/m3 15 minutes
30,000 µg/m3 1 hour
10,000 µg/m3 8 hours
* The volume must be standardised at a temperature of 293 °K and a pressure of 101,3 kPa.
3.1 HEALTH EFFECTS3
CO diffuses rapidly across alveolar, capillary and placental membranes. Approximately 80-90 % of
the absorbed CO binds with hemoglobin to form carboxyhemoglobin (COHb), which is a specific
biomarker of exposure in blood. The affinity of hemoglobin for CO is 200-250 times that for
oxygen. During exposure to a fixed concentration of CO, the COHb concentration increases rapidly
at the onset of exposure, starts to level off after 3 hours, and reaches a steady-state after 6-8 hours
of exposure. It is noted that the elimination half-life in the fetus is much longer than in the pregnant
mother. The binding of CO with hemoglobin to form COHb reduces the oxygen-carrying capacity
of the blood and impairs the release of oxygen from hemoglobin. These are the main causes of
tissue hypoxia produced by CO at low exposure levels. At higher concentrations, the rest of the
absorbed CO binds with other heme proteins such as myoglobin and with cytochrome oxidase and
cytochrome P-450. The toxic effects of CO first become evident in organs and tissues with high
oxygen consumption, such as the brain, heart, exercising skeletal muscle and the developing fetus.
Severe hypoxia due to acute CO poisoning may cause both reversible, short-lasting, neurological
deficits and severe, often delayed, neurological damage. The neurobehavioural effects include
impaired coordination, tracking, driving ability, vigilance and cognitive performance at COHb
levels as low as 5.1-8.2%. In apparently healthy subjects, the maximal exercise performance
decreases at COHb levels as low as 5%. The regression between the percentage decrease in
maximal oxygen consumption and the percentage increase in COHb concentration appears to be
linear, with a fall in oxygen consumption of approximately 1% for each 1% rise in COHb level
above 4%.
In controlled studies involving patients with documented coronary artery disease, mean pre-
exposure COHb levels of 2.9-5.9% (corresponding to post-exercise COHb levels of 2.0-5.2%) have
been associated with a significant shortening in the time to onset of angina, with increased
electrocardiographic changes and with impaired left ventricular function during exercise. In
addition, ventricular arhythmias may be increased significantly at the higher range of mean post-
exercise COHb levels. Epidemiological and clinical data indicate that CO from smoking and
environmental or occupational exposures may contribute to cardiovascular mortality and to the
early course of myocardial infarction. Current data from epidemiological studies and experimental
animal studies indicate that common environmental exposures to CO in the developed world would
not have atherogenic effects on humans (WHO 1999a).
During pregnancy, endogenous production of CO is increased so that maternal COHb levels are
usually about 20% higher than the non-pregnant values. At steady-state, the fetal COHb levels are
3 For further information on health effects see Guidelines for Air Quality, WHO, Geneva, 2000.
PAGE 20
GUIDELINE AMBIENT ENVIRONMENT STANDARDS FOR ETHIOPIA
as much as 10-15% higher than the maternal COHb levels. There is a well-established and probably
causal relationship between maternal smoking and low birth weight at fetal COHb levels of 2-10%.
In addition, maternal smoking seems to be associated with a dose-dependent increase in perinatal
deaths and with behavioural effects in infants and young children.
3.2 MONITORING
CO in urban areas results almost entirely (typically ~90%) from road traffic emissions. Since CO is
a primary pollutant, its ambient concentrations closely follow emissions. In urban areas,
concentrations are therefore highest at the kerbside and decrease rapidly with increasing distance
from the road. Mostly automatic analysers are being used for the direct assessment of ambient
levels against guidelines.
3.2.1 Passive samplers
A passive sampler has been developed for CO, utilizing a zeolite absorber and a narrow filamental
diffusion passage to optimize uptake, and involving GC/FID analysis after thermal desorption (Lee
et al. 1992). This technique may be useful for screening, mapping and ‘hot-spot’ identification. Its
use does not, however, appear to be widespread at the present time. Active samplers
Grab samples may be collected for subsequent laboratory analysis. However, this technique is not
known to be widely used.
3.2.2 Automatic analysers
The measurement of CO in ambient air is covered by international standards ISO/FDIS 4224
(ISO/FDIS 1999a) and ISO 8186. (ISO 1989) .
Baseline ambient CO monitoring is normally carried out using IR analysers. A number of
electrochemical CO analysers are available, but these are generally of low sensitivity and not
suitable for routine ambient monitoring. However, they may have application in areas of high
concentrations. A version of this sensor is incorporated in a commercially available roadside
pollution monitoring system.
CO analysis is based on the absorption of IR radiation at wavelengths of 4.5-4.9 micrometres.
Since other gases and particles can also absorb IR, the analyser must distinguish between
absorption by CO and absorption by interferences. In the most common analyser type, this is done
using a gas filter correlation wheel containing a cell of pure nitrogen and a cell of nitrogen plus
CO. The cell containing CO removes the CO-sensitive wavelengths before the IR signal enters the
absorption chamber, whilst all wavelengths are transmitted by the other cell. The difference in the
intensity of the two absorption signals, divided by the intensity of the IR source, provides a
measure of the ambient CO concentration.
The accuracy of data from automatic CO analysers depends on a range of factors encompassing the
entire measurement chain. These include accuracy of calibration standards, analyser stability and
sample losses in the measurement system. An accuracy of ± 8% and a precision of ±0.5 mg/m 3
may be achieved using this technique in well-managed and quality-assured programmes.
PAGE 21
GUIDELINE AMBIENT ENVIRONMENT STANDARDS FOR ETHIOPIA
4 OZONE AND OTHER PHOTOCHEMICAL OXIDANTS
Chemical Symbol or Formula: O3
Standard*: Averaging Time
120 µg/m3 8 hours
* The volume must be standardised at a temperature of 293 °K and a pressure of 101,3 kPa.
4.1 HEALTH EFFECTS4
O3 toxicity occurs in a continuum in which higher concentrations, longer exposure duration, and
greater activity levels during exposure cause greater effects. Short-term acute effects include
pulmonary function changes, increased airway responsiveness and airway inflammation, and other
symptoms. These health effects are statistically significant at 160 µg/m 3 (0.08 ppm) for 6.6 hour
exposures in a group of healthy exercising adults, with the most sensitive subjects experiencing a
more than 10% functional decrease within 4-5 hours. Controlled exposure of heavily exercising
adults, or children to an O3 concentration of 240 µg/m
3
(0.l2 ppm) for 2 hours, also produced
decreases in pulmonary function. There is no question that substantial acute adverse effects occur
during exercise with one hour exposure to concentrations of 500 µg/m 3 or higher, particularly in
susceptible individuals or subgroups.
Field studies in children, adolescents, and young adults have indicated that pulmonary function
decrease can occur as a result of short term exposure to O3 concentrations in the range 120-240
µg/m3 and higher. Mobile laboratory studies have observed changes in pulmonary function in
children or asthmatics exposed to O3 concentrations of 280-340 µg/m 3 (0.14-0.17 ppm) for several
hours. Respiratory symptoms, especially coughing, have been associated with O3 concentrations as
low as 300 µg/m 3 (0.15 ppm). O3 exposure has also been reported to be associated with increased
respiratory hospital admissions and exacerbation of asthma. The effects are observed with
exposures to ambient O3 (and co-pollutants) and with controlled exposures to O3 alone. This
demonstrates that the functional and symptomatic responses can be attributed primarily to O3.
A number of studies evaluating animals (rats and monkeys) exposed to O 3 for a few hours or days
have shown alterations in the respiratory tract, in which the lowest-observed-effect levels were in
the range of 160-400 µg/m3 (0.08-0.2 ppm). These included the potentiation of bacterial lung
infections, inflammation, morphological alterations in the lung, increases in the function of lung
enzymes active in oxidant defenses, and increases in collagen content. Long-term exposure to O3 in
the range of 240-500 µg/m3 (0.12 to 0.25 ppm) causes morphological changes in the epithelium and
interstitium of the centri-acinar region of the lung, including fibrotic changes.
4.2 MONITORING
O3 is not emitted directly from man-made sources in any significant quantities, but is formed in the
atmosphere by sunlight-driven chemical reactions involving NOx and VOC (see Section 2.1.2).
These reactions are not immediate, but may take from hours to days to complete. O3 is chemically
scavenged by primary NOx emissions from traffic, and is also removed from the atmosphere by
deposition to the ground.
4 For further information on health effects see Guidelines for Air Quality, WHO, Geneva, 2000
PAGE 22
GUIDELINE AMBIENT ENVIRONMENT STANDARDS FOR ETHIOPIA
Both spatial and temporal distributions of O3 differ markedly from those of other pollutants. In
particular, significant impacts may occur in areas up to hundreds of kilometres downwind of the
original precursor emissions, as a result of long-range as a result of long-range transport. Ambient
concentrations and population exposure may often be maximized in suburban and rural areas. This
has important implications for monitoring system design.
4.2.1 Passive samplers
A variety of techniques are available (UNEP/WHO 1994b). These include:
1,2,di-(4-pyridyl) ethylene absorbent- spectrophotometry (Monn and Hangartner 1990).
KI –spectrophotometry (Grosjean and Hisham 1992).
NaNO2/Na2CO3/glycerine -ion chromatography (Koutrakis et al. 1990).
Indigo carmine-reflectance (Alexander et al. 1991).
These methods are not as widely used or validated as corresponding samplers for NO2 and no clear
consensus as to a standard technique has yet emerged.
4.2.2 Active samplers
The most widely used active sampler technique was the Neutral Buffered Potassium Iodide (NKBI)
method. Although relatively simple and inexpensive, there are practical problems with
deterioration of the iodine complex and interference (most notably from NO2 and SO2). These
issues have reduced its use to the extent that the technique may now be regarded as obsolete.
4.2.3 Automatic analysers
ISO 10313 (ISO 1993a) is not of real relevance, as the chemiluminescence detection technique it
describes is no longer widely used. The most commonly used technology is now that of UV
absorption; this is specified as the reference method for the purposes of EC Directive 92/72/EEC
(EC 1992). An ISO standard is being developed for the UV method.
UV absorption is a robust, well-developed technique. Ambient O3 concentrations are calculated
from the absorption of UV light at 254 nm wavelength. The sample passes through a detection cell
of known length (l). An O3-removing scrubber is used to provide a zero reference light intensity,
I0. The analyser alternately measures the absorption of air in the cell with no O3 present and the
absorption in the experimental sample cell, Is. The ambient O3 concentration, c, may be simply
calculated using the Beer-Lambert equation:
Is = I0e
-alc
where a is the relevant absorption coefficient at 254 nm.
Given appropriate attention to system design, calibration and equipment support a typical
measurement accuracy of ±11% and a precision of ±4 mg/m 3 should be readily achievable in well-
run automatic networks.
4.2.4 Remote sensors
Open-path optical remote sensing techniques such as DOAS are available for O3, although the
associated practical issues noted in previous sections are applicable.
PAGE 23
GUIDELINE AMBIENT ENVIRONMENT STANDARDS FOR ETHIOPIA
5 SUSPENDED PARTICULATE MATTER
Chemical Symbol or Formula: Not Applicable
Standard: Averaging Time
PM10 50 µg/m3 1 Year
150 µg/m3 24 hours
PM2.5 15 µg/m3 1 Year
65 µg/m3 24 hours
5.1 HEALTH EFFECTS5
Health effects of SPM in humans depend on particle size and concentration, and can fluctuate with
daily fluctuations in PM10 or PM2.5 levels. They include acute effects such as increased daily
mortality, increased rates of hospital admissions for exacerbation of respiratory disease,
fluctuations in the prevalence of bronchodilator use and cough and peak flow reductions. Long-
term effects of SPM refer also to mortality and respiratory morbidity, but only few studies on the
long-term effects of SPM exist. Air pollution by particulate matter has been considered to be
primarily an urban phenomenon, but it is now clear that in many areas of developed countries,
urban-rural differences in PM10 are small or even absent, indicating that PM exposure is widespread.
This is not to imply that exposure to primary, combustion-related PM may not be higher in urban
areas.
A variety of methods exist to measure different fractions of particulate matter in air, with different
health significance. This evaluation has tended to focus on studies in which PM exposure was
expressed as PM10 and PM2.5. Health effect studies conducted with various TSP and BS as exposure
indicators have provided valuable additional information. However, they are less suitable for
deriving exposure-response relationships for PM because TSP includes particles that are too large
to be inhaled, or because the health significance of particle opacity as measured by the Black
Smoke method is uncertain.
The current time-series epidemiological studies are unable to define a threshold below which no
effects occur. Recent studies suggest that even at low levels of PM (less than 100 µg/m 3), short-
term exposure is associated with health effects. At low levels of PM 10 (0 - 100 µg/m
3), the short-
term exposure-response curve fits a straight line reasonably well. However, there are indications
from several studies that at higher levels of exposure (several hundreds of µg/m3 of PM10), at least
for effects on mortality, the curve is flatter than at low levels of exposure. This is discussed later in
this section.
Although many studies have obtained acute effect estimates for PM10 that are reasonably
consistent, this does not imply that particle composition or size distribution within the PM10
fraction is unimportant. Limited evidence from studies on dust storms indicates that such PM10
particles are much less toxic than those associated with combustion sources. Recent studies in
which PM10 size fractions and/or constituents have been measured suggest that the observed effects
of PM10 are largely associated with fine particles and not with the coarse fraction (PM10 minus
PM2.5). In some areas strong aerosol acidity or sulphate may be the cause of the effects associated
with PM2.5.
5 For further information on health effects see Guidelines for Air Quality, WHO, Geneva, 2000
PAGE 24
GUIDELINE AMBIENT ENVIRONMENT STANDARDS FOR ETHIOPIA
Evidence is also emerging that long-term exposure to low concentrations of PM in air is associated
with mortality and other chronic effects, such as increased rates of bronchitis and reduced lung
function. Two cohort studies conducted in the U.S.A. suggest that life expectancy may be 2-3 years
shorter in communities with high PM than in communities with low PM. This is consistent with
earlier cross-sectional studies, which compared age-adjusted mortality rates across a range of long-
term average PM concentrations. The results showed that long-term average exposures to low PM
levels, starting at about 10 µg/m3 of fine particulate matter, were associated with a reduction in life
expectancy. Whilst such observations require further corroboration, preferably also from other
areas in the world, these new studies suggest that the public health implications of PM exposure
may be large.
5.2 MONITORING
SPM is a generic term embracing all airborne particulate matter. This therefore encompasses a
wide range of size fractions, morphologies and chemical compositions, as discussed in Chapter 2.
Although coarse particle size ranges may cause significant local nuisance or soiling, it is the finer
fractions, such as PM2.5, that are capable of deep lung/airway penetration. Concern about the
potential health impacts of fine particulate matter has increased rapidly over recent years.
SPM monitoring is fundamentally different from the measurement of gaseous pollutants, and the
methods are generally less precise. A wide variety of different sampling and detection
methodologies is available, including the Tapered Element Oscillating Microbalance (TEOM), b-
ray analysis, gravimetric sampling (low or high-volume) and a number of indirect optical, particle
counting and light-scattering methods. The sampling system strongly affects the measurement
process and appropriate aerodynamically designed inlets are essential for proper sample-
fractionated determinations (UNEP/WHO 1994c).
5.2.1 Active samplers
Gravimetric samplers collect particulate matter onto a filter using high-volume (about 100 m 3
/hour) or low-volume (about 1 m 3 /hour) pumped sample flows. The weight of particulate matter
deposited on the filter is used to calculate a 24-hour average mass concentration. No ISO or CEN
standards have yet been promulgated for ambient measurement of PM10 particulate matter using
gravimetric samplers, although these are under development at the present time. An ISO standard
for evaluating PM10 inlet heads is, however, available (EN 1999). A United States Environmental
Protection Agency procedure for PM10 using the high-volume sampler is given in Federal Register
40 CFR Part 50 (CFR 1993). However, compliance with this procedure does not ensure consistency
with the anticipated CEN standards.
The various SPM monitoring techniques may not necessarily produce comparable measurements.
Different sampling systems, operating temperature, filter media and filter history may also
potentially affect measurement equivalence. The accuracy and precision of any measured mass
concentration is, therefore, liable to a wide margin of error. A target accuracy of <10 µg/m 3 and a
precision of <5 µg/m 3 (for daily average concentrations <100 µg/m 3 ) are given for PM10
measurements by EN 12341 (EN 1999).
Medium- or low-volume gravimetric samplers are more portable and less noisy than high-volume
samplers, making them more suitable for use in urban areas. However, the mass of particles
collected is far less than with high-volume samplers, giving a greater potential for errors due to
filter weighing. According to a recent large-scale instrument comparison, a number of
commercially available high- and medium-volume samplers are equivalent to a reference Wide
Ranging Aerosol Collector (WRAC) (EN 1999).
Correct filter handling, documentation and analysis is fundamental for obtaining valid data. The
filters must be conditioned in a temperature- and humidity-controlled environment, typically 20 o C
PAGE 25
GUIDELINE AMBIENT ENVIRONMENT STANDARDS FOR ETHIOPIA
and 50% relative humidity, for at least 24 hours before and after exposure. The filters must be
accurately weighed using a suitable balance, that has been calibrated using an accredited method.
5.2.2 Automatic analysers
Instruments are commercially available using the following techniques:
Tapered Element Oscillating Microbalance (TEOM).
Beta-ray absorption analysers (ISO/FDIS 1999b).
Light scattering systems.
Of the automatic instrument types available, the TEOM and b-ray systems have been operated
widely for many years and are well tested in the field. The light scattering type of instrument has
been developed more recently, and is therefore less well proven in service. Operating experience
and co-located measurement campaigns indicate that measurements from the different instruments
are not always equivalent or comparable
For traceable and robust measurements, samplers must be fitted with a tested PM10 inlet head and
an accurate flow control system. The PM10 sampling inlet should be tested to ISO Standard 7708
(ISO 1995) to ensure accurate size fractionation at the point of sampling. A target accuracy figure
of <10µg/m 3 and precision of <5µg/m 3 (for daily average concentrations <100 µg/m 3 ) are given
in EN 12341 (EN 1999). Tests on in-service TEOM analysers deployed in UK networks
demonstrate these figures to be realistic and achievable.
PAGE 26
GUIDELINE AMBIENT ENVIRONMENT STANDARDS FOR ETHIOPIA
6 LEAD
Chemical Symbol or Formula: Pb.
Standard: Averaging Time
0.5 µg/m3 1 Year
6.1 HEALTH EFFECTS6
The level of lead in blood is the best available indicator of current and recent past environmental
exposure and, with stable exposures, may also be a reasonably good indicator of lead body-burden.
The biological effects of lead can therefore be related to blood lead levels as an indicator of internal
exposure. The relationship between blood lead concentrations and exposure to lead in air exhibits
downward curvilinearity where the range of exposures is sufficiently large. At low levels of
exposure the deviation from linearity is negligible and linear models of the relationship between
intake and blood lead levels are satisfactory approximations.
The LOAEL for hematological and neurological effects of lead in adults and children can be
summarized as follows. Frank anemia is exhibited in adults at blood lead levels above 800 µg/l,
and in children above about 700 µg/l. Hemoglobin production is reduced in adults at blood lead
levels above 500 µg/l and in children above 250-300 µg/l. The presence of lead in the blood also
inhibits delta-aminolaevulinic acid dehydrase (ALAD), an enzyme involved in heme biosynthesis,
resulting in an accumulation of its substrate, ALA, in blood, plasma and urine (WHO 1987).
Urinary ALA and coproporyphyrin are elevated in both adults and children above blood lead levels
of about 400 µg/l. Erythrocyte protoporphyrin is found to increase in male adults at blood lead
levels above 200-300µg/l, and in female adults and children above 150-200 µg/l. A reduction in
vitamin D3 occurs in children at blood lead levels above 100-150 µg/l. Consequently, inhibition of
ALAD in adults and children is likely to occur at blood lead levels of about 100 µg/l. However,
because of its uncertain biological significance for the functional reserve capacity of the heme
biosynthetic system, ALAD inhibition is not treated as an adverse effect here. Encephalopathic
signs and symptoms appear not to occur in adults at lead concentrations in blood below 1000-1200
µg/l, and in children below 800-1000 µg/l.
Cognitive effects in lead workers have not been observed at blood lead levels below 500 µg/l,
although reductions in nerve conduction velocity were found at concentrations as low as 300 µg/l.
Elevation of free erythrocyte protoporphyrin has been observed at blood lead levels of 200- 300
µg/l. Central nervous system effects, as assessed by neurobehavioural endpoints, appear to occur in
children at levels below 200 µg/l. Consistent effects have been reported for global measures of
cognitive functioning, such as the psychometric intelligence quotient, at blood lead levels between
100-150 µg/l. Some epidemiological studies have indicated effects such as hearing impairment at
blood lead levels below 100 µg/l. Animal studies provide qualitative support for the claim that lead
is a causative agent for hearing impairment.
6.2 MONITORING
The main sources of lead in air are the combustion of petrol containing lead-based additives and
industrial emissions.
6 For further information on health effects see Guidelines for Air Quality, WHO, Geneva, 2000
PAGE 27
GUIDELINE AMBIENT ENVIRONMENT STANDARDS FOR ETHIOPIA
6.2.1 Active samplers
These are based on pumped sampling of large quantities of ambient air, capturing fine ambient
particulate matter on a filter for subsequent analysis. Analysis of filters for lead is covered by ISO
9855 (E), which specifies atomic absorption spectroscopy as the standard analytical method (ISO
1993b). There is no standard sampling method, although the EC Directive does specify some
relevant sampling and filter criteria (EC 1982).
A variety of sampling methods are used, including high-, medium-, and low-volume samplers.
There is no standard or reference sampling method. The UK method is broadly typical: this utilises
an “M Type” sampler designed specifically for this purpose. Its flow rate is controlled to 5.4-7.1 m
3 /day, and Millipore Aerosol Field Monitor filters are exposed and changed weekly. Passive
sampling methods are not applicable.
PAGE 28
GUIDELINE AMBIENT ENVIRONMENT STANDARDS FOR ETHIOPIA
7 GUIDELINES FOR AIR QUALITY: COMPOUNDS WITH NON-
CARCINOGENIC HEALTH ENDPOINTS
Compound Guideline Value (GV) or Tolerance
Concentration (TC)
µg/m3
Averaging Time
Acetaldehyde 2 000 (TC) 24 hours
50 (TC) 1 year
Acrolein 50 (GV) 30 min
Acrylic acid 54 (GV) 1 year
2-Butoxyethanol 13100 (TC) 1 week
Cadmium 5 x 10-3(GV) 1 year
Carbon disulphide 100 (GV) 24 hours
20 (GV) odour annoyance 30 min
Carbon Tetrachloride 6.1 (TC) 1 year
1,4 Dichlorobenzene 1000 (TC) 1 year
Dichloromethane 3000 (GV) 24 hours
Diesel exhaust 5.6 (GV) 1 year
Ethylbenzene 22 000 (GV) 1 year
Fluorides 1 (GV) 1 year
Formaldehyde 100 (GV) 30 min
Hydrogen sulphide 150 (GV) 24 hrs
7 (GV) Odour annoyance 30 min
Manganese 0.15 (GV) 1 year
Mercury, inorganic 1 (GV) 1 year
Methyl Methacrylate 200 (TC) 1 year
Monochlorobenzene 500 (TC) 1 year
Styrene 260 (GV) 1 week
7 (GV) Odour annoyance 30 minutes
Tetrachloroethylene 250 (GV) 24 hours
8000 (GV) Odour annoyance 30 minutes
Toluene 260 (GV) 1 week
1000 (GV) Odour annoyance 30 minutes
1,3,5 Trichlorobenzene 200 (TC) 1 year
1,2,4 Trichlorobenzene 50 (TC) 1 year
Vanadium 1 (GV) 24 hours
Xylenes 4800 (GV) 24 hours
870 (GV) 1 year
PAGE 29
GUIDELINE AMBIENT ENVIRONMENT STANDARDS FOR ETHIOPIA
Compound Tolerable Daily Intake (TDI or
ADI)
µg/kg bw d
Averaging Time (Over lifetime)
Chloroform 15 (TDI) 24 hours
Cresol 170 (ADI) 24 hours
Di-n-butyl Phthalate 66 (ADI) 24 hours
Dioxin-like compounds 1-4 (TDI) [TEQ/kg bw d] 24 hours
8 GUIDELINES FOR AIR POLLUTANTS WITH CARCINOGENIC HEALTH
ENDPOINTS
See Table 8.1
PAGE 30
GUIDELINE
Table 8.1 8 Guidelines For Air Pollutants With Carcinogenic Health Endpoints
Compound Average ambient air
concentration
µg/m3
Health endpoint
Acetaldehyde 5 Nasal tumours in rats
Acrylonitrile 0.01-10 Lung cancer in workers
Arsenic (1-30) x 10-3 Lung cancer in exposed humans
Benzene 5.0-20.0 Leukaemia in exposed workers
Benzo[a]pyrene Lung cancer in humans
Bis(chloromethyl)ether No data Epitheliomas in rats
Chloroform 0.3-10 Kidney tumours in rats
Chromium VI (5-200) x 10-3 Lung cancer in exposed workers
1,2-Dichloroethane 0.07-4 Tumour formation in rodents
Diesel exhaust 1.0-10.0 Lung cancer in rats
ETS 1-10 Lung cancer in exposed humans
Nickel 1-180 Lung cancer in exposed humans
PAH (BaP) (1-10) x 10-3 Lung cancer in exposed humans
1,1,2,2-Tetrachloroethane 0.1-0.7 Hepatocellular carcinomas in mice
Trichloroethylene 1-10 Cell tumours in testes of rats
Vinychloride 0.1-10 Hemangiosarkoma in exposed workers. Liver cancer in
exposed workers
GUIDELINE AMBIENT ENVIRONMENT STANDARDS FOR ETHIOPIA
9 INFORMATION SOURCES
The following information sources were utilised in the preparation of these standards:
• Guidelines for Air Quality, WHO, Geneva, 2000
• DEAT Guideline Values for Ambient Air Quality in South Africa
• The United Kingdom National Air Quality Strategy (March 1997 - Command no. 3587)
• USEPA National Ambient Air Quality Standards
• European Union, Directive 1999/30/EC relating to limit values for sulphur dioxide,
nitrogen dioxide, and oxides of nitrogen, particulate matter and lead in ambient air.
10 REFERENCES
AEA 1996 Site Operator’s Manual Automatic Urban Monitoring Network. AEA Technology plc,
National Environmental Technology Centre, Culham, Abingdon OX14 3ED, UK and
.http://www.aeat.co.uk/netcen/airqual/reports/lsoman/lsoman.html.
AEA 1997 Instruction Manual: UK Smoke and Sulphur Dioxide Networks. Report AEAT-1806,
AEA Technology plc, National Environmental Technology Centre, Culham, Abingdon OX14 3ED
UK and http://www.aeat.co.uk/netcen/airqual/reports/smkman/shead.html.
Alexander J, Drueke M, Traem R and Rumpel K-J. 1991 Ozon-Messungen mit SAM- kein Einfluss
Meteorologischer Groessen. Staub-Reinhaltung der Luft 51: 307-308.
Atkins CHF, Sandalls J, Law DV, Hough A, Stevenson K 1986 The measurement of nitrogen
dioxide in the outdoor environment using passive diffusion samplers. Environment & Medical
Sciences Division Report, Harwell Laboratory, N o AERE-R 12133, February 1986. AEA
Technology plc, National Environmental Technology Centre, Culham Abingdon OX14 3ED, UK.
Bennett SL, Lee DS, Sandalls FJ, Nason P, Atkins DHF 1992 The measurement of sulphur dioxide
in the outdoor environment using passive diffusion tube samplers: A second report. Environmental
Physics Department, AEA Environment and Energy. Report N o AEA-EE-0323, May 1992. AEA
Technology plc, National Environmental Technology Centre, Culham Abingdon OX14 3ED, UK.
CFR 1993 Code of Federal Regulations, Protection of Environment, National Primary and
Secondary Ambient Air Quality Standards, CFR Title 40 Part 50, Appendix J. Reference Method
for the Determination of Particulate Matter as PM10 in the Atmosphere. Office of the Federal
Register, National Archives and Records Administration, Washington DC, USA.
Downing CEH, Campbell GW, Bailey JC 1994 A survey of sulphur dioxide, ammonia and
hydrocarbon concentrations in the United Kingdom using diffusion tubes: July to December 1992.
Warren Spring Laboratory Report, Report N o LR 964, AEA Technology plc, National
Environmental Technology Centre, Culham Abingdon OX14 3ED, UK. EA 1997: Environment
Agency, Air Quality Bureau. Report of a continuous survey of the health effects of nitrogen oxides
in 1992-1995, Government of Japan.
EC 1982 Council Directive of 3 December 1982 on a Limit Value for Lead in Air 82/884/EEC.
Council of the European Communities, Brussels.
EC 1985 Council Directive 85/203/EEC of 7 March 1985 on air quality standards for nitrogen
dioxide. Official Journal of the European Communities, No. L372, p. 36.
PAGE 32
GUIDELINE AMBIENT ENVIRONMENT STANDARDS FOR ETHIOPIA
EC 1992 Council Directive 92/72/EEC of 12 September 1992 on air pollution by ozone. Official
Journal of the European Communities, No. L297, Vol. 34.
EN 1999 Air quality. Determination of the PM10 fraction of suspended particulate matter.
Reference method and field test procedure to demonstrate reference equivalence of measurement
methods – EN 12341. Available as BS EN 12341 from BSI 389 Chiswick High Road, London, W4
4AL or as a national standard from any CEN member country.
Ferm M 1991 A Sensitive Diffusional Sampler. Report No. IVL B-1020, Swedish Environmental
Research Institute, IVL Biblioteket, Stockholm, Sweden.
Grosjean, D, Hisham, MWM 1992 A passive sampler for atmospheric ozone. Journal of the Air
and Waste Management Association 42: 169-173
Hangartner M, Burri P, Monn C 1989 Passive Sampling of Nitrogen Dioxide, Sulphur Dioxide and
Ozone in Ambient Air. Proceedings of the 4th World Clean Air Congress, Hague, the Netherlands,
September 1989, Vol. 3, pp. 661-666.
Hargreaves, KJ, Atkins DHF 1988 The measurement of sulphur dioxide in the outdoor
environment using passive diffusion tube samplers: A first report. Environmental and Medical
Sciences Division, Harwell Laboratory. Report N o AERE-R-12569, July 1988. AEA Technology
plc, National Environmental Technology Centre, Culham Abingdon OX14 3ED, UK.
ISO 1979 Air Quality - Determination of gaseous sulphur compounds in ambient air- Sampling
equipment. International Standard ISO 4219. International Organization for Standardization,
Geneva
ISO 1980 Ambient Air - Determination of the mass concentration of sulfur dioxide in ambient air -
Thorin spectrophotometric method. International Standard ISO 4221. International Organization
for Standardization, Geneva
ISO 1983 Ambient Air - Determination of a gaseous acid air pollution index - Titrimetric method
with indicator or potentiometric end-point detection. International Standard ISO 4220. International
Organization for Standardization, Geneva
ISO 1985a Ambient Air - Determination of mass concentration of nitrogen dioxide – Modified
Griess-Saltzman Method. International Standard ISO 6768. International Organization for
Standardization, Geneva
ISO 1985b Ambient Air - Determination of mass concentration of nitrogen oxides –
Chemiluminescence method. International Standard ISO 7996. International Organization for
Standardization, Geneva
ISO 1989 Ambient Air - Determination of the mass concentration of carbon monoxide: Gas
chromatographic method, 8186. International Organization for Standardization, Geneva
ISO 1990 Ambient Air - Determination of the mass concentration of sulfur dioxide –
Tetrachloromercurate TCM / pararosaniline method. International Standard ISO 6767. International
Organization for Standardization, Geneva
ISO 1993a Ambient Air - Determination of the Mass Concentration of Ozone-Chemiluminescence
Method. International Standard ISO 10313. International Organization for Standardization, Geneva
ISO 1993b Ambient Air - Determination of the particulate lead content of aerosols collected in
filters. Atomic absorption spectroscopy method. International Standard ISO 9855 E . International
Organization for Standardization, Geneva
ISO 1995 Air Quality - Particle size fraction definitions for health-related sampling. International
Standard ISO 7708. International Organization for Standardization, Geneva
ISO/DIS 1999 Ambient Air - Determination of sulfur dioxide Ultraviolet fluorescence method.
International Standard ISO/DIS 10498. International Organization for Standardization, Geneva
PAGE 33
GUIDELINE AMBIENT ENVIRONMENT STANDARDS FOR ETHIOPIA
ISO/FDIS 1999a Ambient Air - Determination of carbon monoxide - Non-dispersive infrared
spectrometric method. International Standard ISO/FDIS 4224. International Organization for
Standardization, Geneva
ISO/FDIS 1999b Ambient Air - Measurement of particulate matter on a filter medium - Beta-ray
absorption method. International Standard ISO/FDIS 10473. International Organization for
Standardization, Geneva
Junker A, Schwela D 1998 Air quality guidelines and standards based on risk considerations. In:
Papers of the 11 th World Clean Air and Environment Congress, Vol. 6, paper 17D1, National
Association for Clean Air, South Africa.
Koutrakis P, Wolfson JM, Slater JL, Mulik JD, Kronmiller KJ and Williams DD 1990
Measurements of Ozone Exposure. Proceedings of the 1990 EPA-AWMA International
symposium on Measurement of Toxic and related Air Pollutants. Pittsburgh, pp. 468-474.
Monn C, Hangartner M 1990: Passive Sampling for Ozone, Journal of the Air and Waste
Management Association 40: 357-358.
Palmes ED, Gunnison AF, DiMattio J, Tomczyk C 1976 Personal sampler for nitrogen dioxide.
American Industrial Hygiene Association Journal 37: 570-577.
UNEP/WHO 1994a GEMS/Air Methodology Review Handbook Series, Vol.1- Quality Assurance
in Air Quality Measurements. WHO/EOS/94.1, UNEP /GEMS /94.A.2, United Nations
Environment Programme, Nairobi, Kenya, World Health Organization, Geneva.
UNEP/WHO 1994b: GEMS/Air Methodology Reviews Vol. 4: Passive and Active Sampling
Methodologies for Measurement of Air Quality. WHO/EOS 94.4, UNEP /GEMS/94.A.5, United
Nations Environment Programme, Nairobi, Kenya, World Health Organization, Geneva.
UNEP/WHO 1994c: GEMS/Air Methodology Reviews Vol. 3. Measurement of Suspended
Particulate matter in Ambient Air. WHO/EOS 94.3, UNEP/GEMS/94.A.4, United Nations
Environment Programme, Nairobi, Kenya, World Health Organization, Geneva.
WHO 1987 Air Quality Guidelines for Europe. WHO Regional Publications, European Series No.
23. Regional Office for Europe, World Health Organization, Copenhagen.
WHO 1999a. Air Quality Guidelines for Europe. WHO Regional Publications, European Series.
World Health Organization, Regional Office for Europe, Copenhagen, in press. Internet address:
http://www.who.dk
PAGE 34
GUIDELINE AMBIENT ENVIRONMENT STANDARDS FOR ETHIOPIA
APPENDIX 2
WATER QUALITY STANDARDS
(Surface Waters)
PAGE 35
GUIDELINE AMBIENT ENVIRONMENT STANDARDS FOR ETHIOPIA
PRESENTATION OF THE DATA
For convenience in reference each parameter included in this volume is covered in a standard
format consisting of a template in which important explanatory and background information is
summarised. The parameters are dealt with in one alphabetical. The elements of the template are
as follows, in the order in which they appear:
Chemical Symbol or Formula: These are in the conventional chemical notation, e.g. Antimony is
Sb, Silver is Ag, Zinc is Zn, and so on. In many cases the entry is "Not Applicable" as there is
either no chemical formula at all, as for microbiological parameters, or else the parameter, although
chemical, is a bulk one, e.g. Pesticides, so that the use of formulae is precluded on practical
grounds.
Units used for Analytical Results: For several key parameters the results of analysis may be
reported in terms other than those of the chemical formulae of the entities being determined.
Examples are nitrate, NO3
–, reported often as N, and phosphate, PO4
– – commonly reported as P.
Reference Methods of Analysis: Reference methods are specified for the parameter in question.
The references given relate to Standard Methods for the Examination of Water and Wastewater,
1998, (prepared and published jointly by A.P.H.A., A.W.W.A & W.E.F) 20th Ed., American Public
Health Association, 1015 Fifteenth Street, N.W., Washington DC 20005, USA, a standard text used
in most water laboratories.
As a guide, to the complexity of the method specified the following letters [A], [B], [C] and [D]
have been used throughout to indicate, respectively, an increasing degree of sophistication of the
technique and/or of the equipment used. Thus, [A] indicates a method suitable for use in a more
basic water laboratory, [B] implies a method more demanding of staff expertise or equipment, [C]
implies an elaborate laboratory set-up, with advanced instrumentation, and [D] denotes a specialist
laboratory with state-of-the-art equipment. A dual designation, e.g. [B/C], is used for those
methods which may be practicable at different levels of instrumentation or expertise. It may be
noted that these designations are quite in for mat and are offered for guidance only. In reality, there
may often be no clear gradations between the capabilities of different laboratories.
With regard to sampling, a sample should be collected such that the sample is representative of the
condition being investigated and in a manner consistent with the collection, handling and
preservation principles enunciated in the above publication section 1060.
Introduction: This section contains adequate detail to set the significance of each parameter in
perspective. In some important cases, notably " Biochemical Oxygen Demand," "Hardness" and "
Dissolved Oxygen," the entries are fairly lengthy, but this is in line with one of the primary aims of
this volume, namely to act as a "free-standing" reference for the engineer, environmentalist or
scientist.
Occurrence: A brief indication is given as to whether substances covered by the parameter occur
in rock, are constituents of sewage or industrial wastes, or are synthetic materials. It is assumed
throughout that substances attributed to industrial wastes could equally well arise from tiphead
leachates, this is not always specified.
Effect: Brief reference is made to known toxic or physiological effects - or the lack of them - of
each parameter. It must be stressed that such references are not in any way exhaustive, but are
merely indicative. This volume does not purport in any way to deal with medical matters or with
any material connection between a given parameter and the health of the user/consumer of a water
containing it.
PAGE 36
GUIDELINE AMBIENT ENVIRONMENT STANDARDS FOR ETHIOPIA
1 ALUMINIUM
Chemical Symbol or Formula: Al.
Standard: 0.2 mg/l
Percentage Compliance Required: 95% of all monitoring data must comply with the
standard.
Units Used for Analytical Results: mg/l Al.
Reference Method(s) of Analysis:
Method Type Complexity APHA Reference
Colorimetry B 3500-Al-D
Atomic Absorption Spectrometry Method B/C. 3500-Al-B
Inductively Coupled Plasma Method D 3500-Al-C
Introduction Aluminium is the third most abundant element in the earth's crust. It occurs
primarily as aluminosilicate minerals which are too insoluble to participate
readily in bio-geochemical reactions. Aluminium is a strongly hydrolysing
metal and is relatively insoluble in the neutral pH range. Under acidic (pH <
6.0) or alkaline (pH > 8.0) conditions, or in the presence of complexing ligands,
elevated concentrations may be mobilised to the aquatic environment.
The solubility of aluminium in water is strongly pH dependent. Under acid
conditions, it occurs as soluble, available and toxic hexahydrate (aquo) species.
At intermediate pH values, it is partially soluble and probably occurs as
hydroxy- and polyhydroxo- complexes. At alkaline pH values, aluminium is
present as soluble but biologically unavailable hydroxide complexes or as
colloids and flocculants.
Aluminium is described as a non-critical element, though there is growing
concern over the effects of elevated concentrations of aluminium in the
environment, primarily that mobilized as a result of acid mine drainage and acid
precipitation. Studies of the environmental chemistry and toxicity of aluminium
provide a limited understanding of the processes regulating the aqueous
concentration, speciation and bio-availability of this element. Clearly, the
toxicity of aluminium depends on the chemical species involved.
Occurrence Aluminium can be mobilised from soils and sediments by both natural
weathering and accelerated acidification processes, resulting in detectable
concentrations in surface waters. Although aluminium is found in waters made
naturally acidic by humic and fulvic acids, it usually adsorbs onto these and is
therefore not available in soluble form in such waters, even at low pH.
Aluminium is found in soluble forms mainly in acid mine drainage waters and
is also of concern in natural waters affected by acid rain. Aluminium is one of
the principal particulates emitted from the combustion of coal, and aluminium
fluoride is emitted from aluminium smelters. Industries using aluminium in
their processes or in their products include the following:
• the paper industry,
• the metal construction industry,
• the leather industry, and
PAGE 37
GUIDELINE AMBIENT ENVIRONMENT STANDARDS FOR ETHIOPIA
• the textile industry.
In addition to liquid effluents that may be generated from the above industries,
alum or aluminium sulphate is used in most water treatment processes as a
flocculating agent for suspended solids, including colloidal materials, micro-
organisms and "humic rich" dissolved organics.
Effects Elevated concentrations of bio-available aluminium in water are toxic to a wide
variety of organisms. There is, however, uncertainty as to the form(s) of bio-
available aluminium as well as to the mechanism(s) of toxicity. The toxic
effects are dependent on the species and life stage of the organism, the
concentration of calcium in the water, and pH. The pH may not only affect the
chemistry of aluminium but may also determine how the organism responds to
dissolved aluminium. In acidic waters, aluminium is generally more toxic over
the pH range of 4.4 - 5.4, with maximum toxicity occurring about pH 5.0 - 5.2.
The mechanism of toxicity in fish seems to be related to interference with ionic
and osmotic balance and with respiratory problems resulting from coagulation
of mucus on the gills. It has also been suggested that aluminium interferes with
calcium metabolism, thereby altering the functioning of the calcium regulating
protein, calmodulin. Aluminium has been shown to interfere with ion exchange
sites, in particular those involved in sodium homeostasis. This in turn may lead
to neuromuscular dysfunction.
2 AMMONIA
Chemical Symbol or Formula: NH3
Standard: Game Fishing: 0.02 mg/l NH3 (Non-ionised Ammonia)
Game Fishing: 0.04 mg/l NH4 (Total Ammonia)
Coarse Fishing: 0.025 mg/l NH3 (Non-ionised Ammonia)
Coarse Fishing: 0.2 mg/l NH4 (Total Ammonia)
Percentage Compliance Required: 95% of all monitoring data must comply with the
standard.
Units Used for Analytical Results: mg/l N.
Reference Method(s) of Analysis:
Method Type Complexity APHA Reference
Preliminary Distillation Step B 4500 NH3 B
Titrimetric Method B 4500 NH3 C
Ammonia – Selective Electrode Method B 4500 NH3 D
Colorimetric Method (Phenate) B 4500 NH3 F
Introduction Un-ionized ammonia (NH3) is a colourless, acrid-smelling gas at ambient
temperature and pressure. It is produced naturally by the biological degradation
of nitrogenous matter and provides an essential link in the nitrogen cycle.
Ammonia may be present in the free, un-ionized form (NH 3) or in the ionized
form as the ammonium ion (NH4
+). Both are reduced forms of inorganic
PAGE 38
GUIDELINE AMBIENT ENVIRONMENT STANDARDS FOR ETHIOPIA
nitrogen derived mostly from aerobic and anaerobic decomposition of organic
material. They exist either as ions, or can be adsorbed onto suspended organic
and inorganic material.
The toxicity of ammonia is directly related to the concentration of the un-
ionized form (NH3), the ammonium ion (NH4
+) having little or no toxicity to
aquatic biota. The ammonium ion does, however, contribute to eutrophication.
Modifying factors may alter the acute toxicity by altering the concentration of
un-ionized ammonia in the water through changes in the ammonia-ammonium
ion equilibrium, or may increase the toxicity of the un-ionized ammonia to
organisms.
Occurrence Ammonia is present in small amounts in air, soil and water, and in large
amounts in decomposing organic matter. Natural sources of ammonia include
gas exchange with the atmosphere; the chemical and biochemical
transformation of nitrogenous organic and inorganic matter in the soil and
water; the excretion of ammonia by living organisms; the nitrogen fixation
processes whereby dissolved nitrogen gas enters the water and ground water.
Ammonia, associated with clay minerals enters the aquatic environment through
soil erosion. Bacteria in root nodules of legumes fix large amounts of nitrogen
in the soil and this may be leached into surrounding waters.
Ammonia is a common pollutant and is one of the nutrients contributing to
eutrophication. Commercial fertilizers contain highly soluble ammonia and
ammonium salts. Following application of fertilizer, if the concentration of such
compounds exceeds the immediate requirements of the plant, transport via the
atmosphere or irrigation waters can carry these nitrogen compounds into aquatic
systems. Other sources of ammonia include:
• fish-farm effluent (un-ionized ammonia);
• sewage discharge;
• discharge from industries that use ammonia or ammonium salts in their
cleaning operations;
• manufacture of explosives and use of explosives in mining and
construction; and
• atmospheric deposition of ammonia from distillation and combustion of
coal, and the biological degradation of manure.
Effects The most significant factors that affect the proportion and toxicity of un-ionized
ammonia in aquatic ecosystems are water temperature and pH. An increase in
either results in an increase in the relative proportion of un-ionized ammonia in
solution, and hence an increase in toxicity to aquatic organisms, as given in
Table 1.
PAGE 39
GUIDELINE AMBIENT ENVIRONMENT STANDARDS FOR ETHIOPIA
Contribution of Un-ionised Ammonia to Total Ammonia (expressed as
percentage) as function of pH Value and Water Temperature
Water Temperature °C
pH 0 5 10 15 20 25 30 35
6.0 0.0083 0.012 0.019 0.027 0.039 0.056 0.079 0.11
6.5 0.026 0.039 0.059 0.086 0.12 0.18 0.25 0.35
7.0 0.083 0.12 0.18 0.27 0.39 0.56 0.79 1.1
7.5 0.26 0.39 0.58 0.85 1.2 1.7 2.4 3.4
8.0 0.82 1.2 1.8 2.6 3.8 5.3 7.3 9.9
8.5 2.6 3.8 5.5 7.9 11 15 20 26
9.0 7.6 11 16 21 28 36 44 52
9.5 21 28 37 46 55 64 71 78
Ammonia toxicity is also affected by the concentrations of dissolved oxygen,
carbon dioxide and total dissolved solids, and the presence of other toxicants,
such as metal ions. The acute toxicity of ammonia to fish increases as dissolved
oxygen decreases. Ammonia is oxidized to nitrate in well oxygenated waters.
Ammonia may also be adsorbed onto suspended and bed sediments and to
colloidal particles.
Un-ionized ammonia affects the respiratory systems of many animals, either by
inhibiting cellular metabolism or by decreasing oxygen permeability of cell
membranes. Acute toxicity to fish may cause a loss of equilibrium, hyper-
excitability, an increased breathing rate, an increased cardiac output and oxygen
intake, and in extreme cases convulsions, coma and death.
Chronic effects include a reduction in hatching success, reduction in growth rate
and morphological development, and pathological changes in tissue of gills,
liver and kidneys. An increased ventilation of the gills following exposure to
ammonia indicating a respiratory effect has been observed in mayfly larvae
Ecdyonurus dispar.
PAGE 40
GUIDELINE AMBIENT ENVIRONMENT STANDARDS FOR ETHIOPIA
3 ANTIMONY
Chemical Symbol or Formula: Sb
Standard: 20 µg/l.
Percentage Compliance Required: 95% of all monitoring data must comply with the
standard.
Units Used for Analytical Results: µg/l Sb.
Reference Method(s) of Analysis:
Method Type Complexity APHA Reference
Atomic Absorption Spectrometry Method B/C 3500-Sb-B
Inductively Coupled Plasma Method D 3500-Sb-C
Occurrence Naturally occurring trace element used in metal industry and in flame retardant
materials. Antimony can occur naturally in water from weathering of rocks but
is more likely to arise from effluents.
Effects Significance: Although the health effects of antimony have not been established
definitively, there is evidence of actual or potential carcinogenicity of some
antimony compounds. Accordingly, concentrations are limited in drinking
water.
4 ARSENIC
Chemical Symbol or Formula: As.
Standard: 0.05 mg/l
Percentage Compliance Required: All monitoring data must comply with the standard.
Units Used for Analytical Results: mg/l As.
Reference Method(s) of Analysis:
Method Type Complexity APHA Reference
Atomic Absorption Spectrometry Method C/D. 3500-As-B
Inductively Coupled Plasma Method D 3500-As-D
Introduction Arsenic is a metalloid element which is toxic to marine and freshwater aquatic
life and is a known carcinogen. Elemental arsenic is insoluble in water, but
many of its compounds are highly soluble. Arsenic occurs in several oxidation
states, namely, III, IV, V and III, -depending on the pH and redox potential of
the water. The two most common forms are arsenic (III) and arsenic (V), both
of which form stable compounds with carbon, resulting in numerous organo-
arsenical compounds. Elemental arsenic also combines readily with many
metals to form arsenide salts, which are toxic to organisms.
PAGE 41
GUIDELINE AMBIENT ENVIRONMENT STANDARDS FOR ETHIOPIA
Most forms of arsenic, including the arsenical gases arsine (AsH3) and trimethyl
arsine, are very toxic. The USEPA has classified arsenic as "very toxic and
relatively accessible" to aquatic organisms.
Occurrence Elemental arsenic is found to a limited extent in nature, mostly as a result of
weathering of arsenic-containing rocks and of volcanic activity. Arsenic most
commonly occurs as arsenides of metals or as arsenopyrite. Inorganic arsenic
occurs in aquatic ecosystems primarily as arsenic (III) and as arsenic (V),
depending on pH and redox potential. Arsenic readily adsorbs onto sediments
and suspended solids, and is lipid-soluble.
Arsenic may occur at high concentrations in water bodies subject to industrial
pollution, or in the vicinity of industrial activities utilising or discharging
arsenic or arsenal compounds.
Manufacturers that use arsenic in their processes, or in their products, include:
• the mining industry,
• the metal processing industry,
• producers of pesticides and fertilizers,
• producers of glass and ceramics,
• tanneries,
• dye manufacturers,
• producers of wood preservation products,
• the chemical industry,
• producers of detergents.
Effects Arsenic has been reported to have a variety of adverse effects on both vertebrate
and invertebrate aquatic organisms; the type and severity of adverse effects
being dependent on the life stages of the organisms concerned. Exposure to
arsenic results in reduced growth and reproduction in both fish and invertebrate
populations. Arsenic also causes behavioural changes such as reduced migration
in fish.
Organic arsenal compounds have been shown to be less toxic than inorganic
forms of arsenic to fish. In fresh water, there is little evidence to suggest that
different inorganic forms of arsenic vary significantly in their toxicity to aquatic
biota. Arsenic (V) is more toxic to plants than arsenic (III). Arsenates, although
not particularly toxic, interfere with energy metabolism, whereas arsenites
inhibit the activity of a variety of essential enzymes.
Increased duration of exposure to arsenic at a given concentration leads to a
reduction in adverse effects experienced by aquatic organisms, and they have
been shown to develop tolerance. The response of organisms to arsenic is
reduced by pre-exposure, and organisms may become gradually acclimated to
high concentrations of arsenic in aquatic ecosystems.
Although inorganic arsenic does not accumulate in aquatic organisms, various
forms of arsenic are lipid-soluble and therefore accumulate, in fatty tissue.
Arsenic accumulation is usually higher in algae and invertebrates than in fish,
though bottom-feeding fish are most likely to accumulate arsenic. Humans are
more sensitive to arsenic than are aquatic organisms; therefore, consumption of
contaminated products can pose a health risk to humans. Arsenic can be bio-
concentrated in aquatic organisms because it has a high affinity for organic
substances.
PAGE 42
GUIDELINE AMBIENT ENVIRONMENT STANDARDS FOR ETHIOPIA
Many of the toxic effects of arsenic on aquatic organisms can be reversed if
arsenic concentrations are reduced and maintained at very low levels.
5 BARIUM
Chemical Symbol or Formula: Ba.
Standard: 0.1 mg/l
Percentage Compliance Required: All monitoring data must comply with the standard.
Units Used for Analytical Results: mg/l Ba.
Reference Method(s) of Analysis:
Method Type Complexity APHA Reference
Atomic Absorption Spectrometry Method B/C 3500-Ba-B
Inductively Coupled Plasma Method D 3500-Ba-C
Occurrence Naturally occurring mineral (e.g. in barytes. According to the WHO
Guidelines, while food is the main source of barium intake by humans, where
barium occurs in drinking water supplies the latter can contribute a significant
proportion of total intake.
In normal surface waters levels are likely to be low as traces of barium will
react with sulphate present to form the highly insoluble barium sulphate.
Effects Significance: Excessive amounts of barium can cause muscular, cardiovascular
and renal damage. Although not markedly toxic, barium in excess quantities is
clearly undesirable.
6 BENZENE
Chemical Symbol or Formula: C6H6
Standard: 10 µg/l
Percentage Compliance Required: All monitoring data must comply with the standard.
Units Used for Analytical Results: µg/l compound.
Reference Method(s) of Analysis:
Method Type Complexity APHA Reference
Purge and Trap Gas Chromatographic Method I C 6220-B
Purge and Trap Gas Chromatographic Method II C 6220-C
Purge and Trap Gas Chromatographic/Mass Spectrometric
Method
D 6220-D
PAGE 43
GUIDELINE AMBIENT ENVIRONMENT STANDARDS FOR ETHIOPIA
Background: Emissions from motor vehicles account for most of the benzene in the air,
which can in due course reach the aquatic environment. Pollution from
industrial sources can also introduce benzene to water.
Benzene is not a naturally-occurring constituent of water.
Occurrence Constituent of some petroleum products; industrial raw material; solvent.
Effects Carcinogenic substance which also affects the central nervous system adversely.
7 BENZO(A)PYRENE
Chemical Symbol or Formula: C20H12
Standard: 0.01 µg/l
Percentage Compliance Required: All monitoring data must comply with the standard.
Units Used for Analytical Results: µg/l compound.
Reference Method(s) of Analysis:
Method Type Complexity APHA Reference
Liquid-Liquid Extraction Gas Chromatographic/Mass
Spectrometric Method
D 6410-B
Liquid-Liquid Extraction Gas Chromatographic Method C 6431-B
Occurrence Synthetic complex aromatic organic compound formed by pyrolysis or
combustion of organic materials.
Effects Benzo(a)pyrene is a carcinogenic and mutagenic substance which is considered
to be highly undesirable in drinking water, even though the WHO Guidelines
indicate that food is the main source of human exposure to this type of
substance.
8 BENZENE
Chemical Symbol or Formula: C6H6
Standard: 10 µg/l
Percentage Compliance Required: All monitoring data must comply with the standard.
Units Used for Analytical Results: µg/l compound.
Reference Method(s) of Analysis:
Method Type Complexity APHA Reference
Purge and Trap Gas Chromatographic Method I C 6220-B
Purge and Trap Gas Chromatographic Method II C 6220-C
Purge and Trap Gas Chromatographic/Mass Spectrometric
Method
D 6220-D
PAGE 44
GUIDELINE AMBIENT ENVIRONMENT STANDARDS FOR ETHIOPIA
Background: Emissions from motor vehicles account for most of the benzene in the air,
which can in due course reach the aquatic environment. Pollution from
industrial sources can also introduce benzene to water.
Benzene is not a naturally-occurring constituent of water.
Occurrence Constituent of some petroleum products; industrial raw material; solvent.
Effects Carcinogenic substance which also affects the central nervous system adversely.
9 BIOCHEMICAL OXYGEN DEMAND (BOD5)
Chemical Symbol or Formula: Not applicable [Bulk parameter]
Standard: ≤ 5 mg/l
Percentage Compliance Required: 95% of all monitoring data must comply with the
standard.
Units Used for Analytical Results: mg/l O2.
Reference Method(s) of Analysis:
Method Type Complexity APHA Reference
5-Day BOD Test B 5210-B
Background When organic matter is discharged into a watercourse it serves as a food source
for the bacteria present there. These will sooner or later commence the
breakdown of this matter to less complex organic substances and ultimately to
simple compounds such as carbon dioxide and water. If previously unpolluted,
the receiving water will be saturated with dissolved oxygen (DO), or nearly so,
and the bacteria present in the water will be aerobic types. Thus the bacterial
breakdown of the organic matter added will be an aerobic process - the bacteria
will multiply, degrading the waste and utilising the DO as they do so. If the
quantity of waste present is sufficiently large, the rate of bacterial uptake of
oxygen will outstrip that at which the DO is replenished from the atmosphere
and from photosynthesis, and ultimately the receiving water will become
anaerobic.
Bacterial degradation of the waste will continue but now the products will be
offensive in nature -for example, hydrogen sulphide. Even if the uptake of
oxygen is not sufficient to result in anaerobic conditions there will be other
undesirable effects as the DO level falls, notably damage to fisheries and,
ultimately, fish deaths. Where levels are around 50 per cent saturation for
significant periods there may be adverse, though non-lethal, effects on game
fish. Coarse fish will be likewise affected if levels are regularly around 30 per
cent saturation.
Because of the potential danger to the oxygen levels in receiving waters from
waste discharges considerable emphasis is placed in the laboratory on the
estimation of the oxygen demand of wastes: i.e. the amount of oxygen which
will be required in their breakdown. This is done chemically and biologically,
by a variety of tests which are also employed to assess the actual effects of
waste discharges on receiving water, as discussed below. As in most cases the
oxygen demand of a waste on the DO level of a receiving water results from
biological action, it follows that the most important analytical method should
PAGE 45
GUIDELINE AMBIENT ENVIRONMENT STANDARDS FOR ETHIOPIA
also depend on a biological process, to measure the biochemical oxygen
demand or BOD. The principle of this test, which was devised some 85 years
ago, is straightforward. The (five-day) BOD of a water is the amount of
dissolved oxygen taken up by bacteria in degrading oxidisable matter in the
sample, measured after 5 days incubation in the dark at 20°C. The BOD is
simply the amount by which the DO level has dropped during the incubation
period. This technique is the basis of BOD analyses for all types of sample even
though considerable extensions of procedure are necessary in dealing with
wastewaters and polluted surface waters.
Current scientific opinion is that waters with a BOD failing within the range of
0 - 4 mg/l O 2 are of satisfactory quality for sensitive species such as salmonid
fish and thus for other beneficial uses. If an upper limit for BOD of 4 mg/l O2 is
adopted as a criterion of satisfactory quality then it is possible to assess the
degree to which waters are polluted by reference to this datum. It is most
important to remember, however.. that a BOD figure for a receiving water
indicates the maximum extent to which the oxygen level may be depleted by the
organic matter present. In reality, no appreciable deoxygenation may occur
because of factors such as low temperatures, reaeration at weirs or shallows,
dilution by tributaries and so on. Conversely, in some waters which do not have
high BOD levels, but which are eutrophic, there may be severe night-time DO
depletions caused by algal respiration. Notwithstanding the many often
contradictory considerations which govern the interpretation of BOD data the
analysis is one of the most important elements in river quality surveillance and
it seems unlikely to be superseded for a long time yet.
Somewhat different considerations apply to the BOD analysis of effluents. BOD
data are normally required for one of two purposes. Firstly, it is necessary to
know the strength of a waste which is to be treated by biological means, as in an
oxidation ditch or percolating filter. This is essential so that adequate treatment
capacity may be provided for in the design of the plant. Secondly.. where wastes
are being discharged to receiving waters a knowledge of their strength and the
magnitude of the river discharge will permit the dilution to be calculated and
hence the maximum potential change in the river BOD at the boundary of the
mixing zone. A factor which must be borne in mind in obtaining and in
assessing BOD results is nitrification. This is the oxidation of ammonia to
nitrate by suitable micro-organisms and if the process is occurring under test
conditions high oxygen uptake values will be recorded. For normal river waters
the onset of nitrification under BOD test conditions does not occur within the 5-
day period of the analysis but in the case of waters or wastewaters containing
nitrifying organisms this phenomenon will take place much more promptly.
Unless suitable precautions are taken the result is an apparently very high BOD
level which, if the analysis is being used to check the performance of a waste
treatment works (with respect to the removal of organic matter), for example,
may lead to serious errors in the interpretation and use of the data.
Occurrence Natural or introduced organic matter in water.
Effects An indicator of overall water quality.
PAGE 46
GUIDELINE AMBIENT ENVIRONMENT STANDARDS FOR ETHIOPIA
10 CADMIUM
Chemical Symbol or Formula: Cd.
Standard: 5 µg/l
Percentage Compliance Required: 95% of all monitoring data must comply with the
standard.
Units Used for Analytical Results: µg/l Cd.
Reference Method(s) of Analysis:
Method Type Complexity APHA Reference
Atomic Absorption Spectrometric Method B/C 3500-Cd-B
Inductively Coupled Plasma Method D 3500-Cd-C
Dithizone Method B 3500-Cd-D
Introduction Cadmium is a metal element which is highly toxic to marine and fresh water
aquatic life. Elemental cadmium is insoluble in water though many of its
organic and inorganic salts are highly soluble. Cadmium occurs primarily in
fresh waters as divalent forms including free cadmium (II) ion, cadmium
chloride and cadmium carbonate, as well as a variety of other inorganic and
organic compounds.
Cadmium is defined by the United States Environmental Protection Agency as
potentially hazardous to most forms of life, and is considered to be toxic and
relatively accessible to aquatic organisms.
Occurrence Cadmium is present in the earth's crust at an average concentration of 0.2
mg/kg, usually in association with zinc, lead and copper sulphide ore bodies.
Due to its abundance, large quantities of cadmium enter the global environment
annually as a result of natural weathering processes. Cadmium is found at trace
concentrations in fresh waters and mostly a result of industrial activity.
The main sources of cadmium in the environment are due to:
• emissions to air and water from mining, metal (zinc, lead and copper)
smelters, and industries involved in manufacturing alloys, paints, batteries
and plastics;
• agricultural use of sludges, fertilizers and pesticides containing cadmium;
• burning of fossil fuels (very limited effect); and
• the deterioration of galvanized materials and cadmium-plated containers.
Effects Cadmium is easily absorbed by mammals, where it is concentrated by binding
with the protein metallothionein. Many plant and animal tissues contain
cadmium, but there is no evidence that cadmium is biologically essential or
beneficial. Cadmium is chemically similar to zinc, and its physiological effects
are often due to its replacement of zinc in some enzymes, thereby impairing
enzyme activity. Cadmium is known to inhibit bone repair mechanisms, and is
teratogenic, mutagenic and carcinogenic.
Bioavailable cadmium may be accumulated by macrophytes, phytoplankton,
zooplankton, invertebrates and fish. Bioavailability is dependent on cadmium
speciation; for example, the free ion, Cd , is readily taken up by aquatic plants,
PAGE 47
GUIDELINE AMBIENT ENVIRONMENT STANDARDS FOR ETHIOPIA
whereas organo-cadmium complexes are 2+ not absorbed. Lethal concentrations
of cadmium also vary depending on the test animal, water hardness and
temperature, and time of exposure. The level of bio-accumulation is dependent
on the species and age of the organism. Cadmium bio-accumulates in the food
chain due to its tendency to bind strongly to sulphydryl groups.
Bio-concentration factors range from 10 to 10 for both invertebrates and fish.
However, 2 5 there is no evidence for cadmium bio-magnification through the
aquatic food web.
11 CHLORIDE
Chemical Symbol or Formula: Cl−.
Standard: 250 mg/l
Percentage Compliance Required: 95% of all monitoring data must comply with the
standard.
Units Used for Analytical Results: mg/l Cl.
Normal Method(s) of Analysis: Titration (Mohr Method: Silver Nitrate) [A]
Reference Method(s) of Analysis:
Method Type Complexity APHA Reference
Mercuric Nitrate Method B 4500-Cl--C
Potentiometric Method B 4500-Cl--D
Ion Chromatographic Method B/C 4500-Cl--F
Introduction At levels above 250 mg/l Cl water will begin to taste salty and will become
increasingly objectionable as the concentration rises further. However, external
circumstances govern acceptability and in some arid areas waters containing up
to 2,000 mg/l Cl are consumed, though not by people unfamiliar with such
concentrations. High chloride levels may similarly render freshwater unsuitable
for agricultural irrigation.
Because sewage is such a rich source of chloride, a high result may indicate
pollution of a water by a sewage effluent. Natural levels in rivers and other
fresh waters are usually in the range 15-35 mg/l Cl - much below drinking water
standards. What is normally important to note in a series of results from a river,
for example, is not the absolute level, but rather the relative levels from one
sampling point to another.
An increase of even 5 mg/l at one station may give rise to suspicions of a
sewage discharge, especially if the free ammonia levels (q.v.) are also elevated.
Normal raw water treatment processes do not remove chloride.
Occurrence Chloride exists in all natural waters, the concentrations varying very widely and
reaching a maximum in sea water (up to 35,000 mg/l Cl). In fresh waters the
sources include soil and rock formations, sea spray and waste discharges.
Sewage contains large amounts of chloride, as do some industrial effluents.
Effect Chloride does not pose a health hazard to humans and the principal
consideration is in relation to palatability
PAGE 48
GUIDELINE AMBIENT ENVIRONMENT STANDARDS FOR ETHIOPIA
12 CHLORINE
Chemical Symbol or Formula: Cl2.
Standard: 5 µg/l
Percentage Compliance Required: 95% of all monitoring data must comply with the
standard.
Units Used for Analytical Results: µg/l Cl.
Reference Method(s) of Analysis:
Method Type Complexity APHA Reference
Iodometric Method I B 4500-Cl-B
Amperometric Titration Method B/C 4500-Cl-D
DPD Colorimetric Method A 4500-Cl-G
Introduction Elemental chlorine (Cl2) is a greenish-yellow gas that dissolves readily in water.
It is not normally a constituent of natural waters since chlorine is too reactive to
persist in the aquatic environment..
Occurrence Free forms of chlorine such as HOCl and OCl -, or combined available chlorine
(chloramines), occurs in aquatic ecosystems as a result of:
• chlorination of drinking water (to remove unwanted tastes and odours, and
for the purposes of disinfection);
• the textile industry (bleaching, slimicide);
• the pulp and paper industry (bleaching, slimicide);
• sewage treatment (reduce odour, algicide, bactericide);
• cooling waters (slimicide); and
• swimming pools (disinfection).
Effluents containing ammonia, organic matter or cyanides convert chlorine into
substances such as chloramines, which may be less toxic but more persistent
than chlorine, thereby posing a long-term threat to aquatic life..
Effects The toxic effects of chlorine are usually irreversible. Free chlorine is more toxic
but less persistent than combined chlorine. Diatoms are more sensitive to
chlorine than are green algae, which, in turn, are more sensitive than blue-green
algae. Newly hatched fish larvae are more sensitive to chlorine than are fish
eggs.
Avoidance behaviour, adverse changes in the blood chemistry, damage to gills,
decreased growth rate, restlessness preceding loss of equilibrium and death have
been observed for fish exposed to chlorine. Invertebrates become immobile, and
exhibit reduced reproduction and reduced survival on exposure to chlorine.
Aquatic plants may become chlorotic, whilst reduced rates of photosynthesis
and respiration are observed for phytoplankton.
Acclimation to sublethal chlorine concentrations leads to increased resistance.
Chlorine itself does not accumulate, but chlorinated organic substances may
bio-concentrate in aquatic organisms.
PAGE 49
GUIDELINE AMBIENT ENVIRONMENT STANDARDS FOR ETHIOPIA
13 CHROMIUM
Chemical Symbol or Formula: Cr.
Standard: 50 µg/l
Percentage Compliance Required: 95% of all monitoring data must comply with the
standard.
Units Used for Analytical Results: µg/l Cr.
Reference Method(s) of Analysis:
Method Type Complexity APHA Reference
Atomic Absorption Spectrometric Method B/C 3500-Cr-B
Inductively Coupled Plasma Method D 3500-Cr-C
Colorimetric Method B 3500-Cr-D
Ion Chromatographic Method B 3500-Cr-E
Introduction Chromium is a relatively scarce metal, and the occurrence and amounts thereof
in aquatic ecosystems are usually very low. Chromium ions occur in a variety of
forms:
• chromium (II) - chromous ion (Cr2+),
• chromium (III) - chromic ion (Cr3+, trivalent),
• chromium (III) - chromite ion (CrO3
3-, trivalent),
• chromium (VI) - chromate ion (CrO4
2- , hexavalent),
• chromium (VI) - dichromate ion (Cr2O7
2- , hexavalent)
Chromium(VI) is a highly oxidized state and occurs as the yellow dichromate
salt in neutral or alkaline media, and as the orange chromate salt in acid
medium. Both of these chromium(VI) salts are highly soluble at all pH values.
The reduced forms, chromium(II) and chromium(III) are reported as being less
toxic and therefore less hazardous than chromium(VI)..
Occurrence The most common ore of the metal chromium is chromite, in which chromium
occurs in the trivalent state. Other minerals containing chromium do occur, but
are not common. Most elevated levels of chromium in aquatic ecosystems are a
consequence of industrial activity.
In the aquatic environment chromous compounds tend to be oxidized to
chromic forms, whilst the chromium(VI) form can be reduced to chromium(III)
by heat, in the presence of organic matter and by reducing agents.
Of the trivalent chromium salts, the chloride, nitrate and sulphate salts are
readily soluble, whereas the hydroxide and carbonate salts are relatively
insoluble. Of the hexavalent chromate salts only the sodium, potassium, and
ammonium chromates and dichromates are soluble.
Hexavalent chromium salts are used extensively:
• in metal pickling and plating;
• in the leather industry as tanning agents; and
• in the manufacture of paints, dyes, explosives, ceramics and paper.
PAGE 50
GUIDELINE AMBIENT ENVIRONMENT STANDARDS FOR ETHIOPIA
Trivalent chromium salts are used much less frequently, but are important as:
• fixatives in textile dye manufacture;
• in the ceramic and glass industry; and
• in photography.
Chromium compounds may also be discharged in chromium-treated cooling
waters where chromium has been used as a corrosion inhibitor.
Effects Chromium exerts a toxic effect at different concentrations in different groups of
aquatic organisms. Fish are the most resistant, and in some cases the toxicity of
chromium(VI) is no greater than for chromium(III). A temporarily reduced
growth phase has been reported for young fish at low chromium concentrations.
Invertebrates are usually at least an order of magnitude more sensitive, with
daphniids showing the greatest sensitivity to chromium. Green algae are also
more sensitive than fish, whilst bacterial responses to chromium are variable.
14 CONDUCTIVITY
Chemical Symbol or Formula: Not Applicable [Physical parameter].
Standard: 1000 µS/Cm (@ 20°C)
Percentage Compliance Required: 95% of all monitoring data must comply with the
standard.
Units Used for Analytical Results: µS/cm
Reference Method(s) of Analysis:
Method Type Complexity APHA Reference
Field Method (Electrometric) A -
Laboratory Method B 2510
Introduction Also referred to as electrical conductivity and, not wholly accurately, as specific
conductance, the conductivity of a water is an expression of its ability to
conduct an electric current. As this property is related to the ionic content of the
sample which is in turn a function of the dissolved (ionisable) solids
concentration, the relevance of easily performed conductivity measurements is
apparent. In itself conductivity is a property of little interest to a water analyst
but it is an invaluable indicator of the range into which hardness and alkalinity
values are likely to fall, and also of the order of the dissolved solids content of
the water. While a certain proportion of the dissolved solids (for example, those
which are of vegetable origin) will not be ionised (and hence will not be
reflected in the conductivity figures) for many surface waters the following
approximation will apply: Conductivity (µS/cm) x 2/3 = Total Dissolved
Solids (mg/l).
In samples from a source which is regularly tested a rapid conductivity analysis
may be an adequate replacement for other, longer determinations.
It is important to note that there is an interrelationship between conductivity and
temperature, the former increasing with temperature at a rate of some 2 per cent
per degree C rise. There is a regrettable lack of uniformity in the terms in which
PAGE 51
GUIDELINE AMBIENT ENVIRONMENT STANDARDS FOR ETHIOPIA
conductivity is reported. Some UK methods manuals report the results at 20°C
while the standard US reference manual uses 25°C. A difference of 10 percent
can therefore arise depending on how the results are quoted. An error of this
magnitude could not be tolerated, especially where conductivity readings are
being used to estimate salinity.
Occurrence Reflects mineral salt content of water.
Effect No direct significance.
15 COPPER
Chemical Symbol or Formula: Cu.
Standard: Copper (µg/l) Hardness (mg/l CaCO3)
5 10
22 50
40 100
112 500
Percentage Compliance Required: 95% of all monitoring data must comply with the
standard.
Units Used for Analytical Results: µg/l Cu.
Reference Method(s) of Analysis:
Method Type Complexity APHA Reference
Atomic Absorption Spectrometric Method B/C 3500-Cu-B
Inductively Coupled Plasma Method D 3500-Cu-C
Neocuproine Method B 3500-Cu-D
Introduction Copper is one of the world's most widely used metals. Although copper occurs
naturally in most waters, it is regarded as potentially hazardous by the USEPA.
Copper occurs in four oxidation states, namely, 0, I, II and III. The two most
common forms are cuprous copper(I) and cupric copper(II). Cuprous copper is
unstable in aerated aqueous solutions and will normally be oxidized to cupric
copper..
Occurrence Copper is a common metallic element in the rocks and minerals of the earth's
crust, and is commonly found as an impurity in mineral ores. Chalcopyrite
(CuFeS2) is the most abundant of the copper minerals. Crustal (igneous) rocks
contain more copper (23 - 55 mg/kg) than sedimentary rocks (4 - 45 mg/kg).
The occurrence of natural sources of copper in the aquatic environment is due to
weathering processes or from the dissolution of copper minerals and native
copper. Metallic copper is insoluble in water, but many copper salts are highly
soluble as cupric or cuprous ions. Anthropogenic sources account for 33 - 60 %
of the total annual global input of copper to the aquatic environment.
The main anthropogenic sources of copper in the aquatic environment are:
• corrosion of brass and copper pipes by acidic waters;
PAGE 52
GUIDELINE AMBIENT ENVIRONMENT STANDARDS FOR ETHIOPIA
• sewage treatment plant effluents;
• copper compounds used as aquatic algicides;
• runoff and ground water contamination from the use of copper as fungicides
and pesticides in the treatment of soils; and
• liquid effluents and atmospheric fallout from industrial sources such as
mining, smelting and refining industries, coal-burning, and iron- and steel-
producing industries.
Effects Copper is a micronutrient and an essential component of enzymes involved in
redox reactions and is rapidly accumulated by plants and animals. It is toxic at
low concentrations in water and is known to cause brain damage in mammals.
Copper exerts its effect by forming stable co-ordinate bonds in proteins, where
it functions as a catalyst in redox reactions. Metabolically, copper interacts with
zinc, molybdenum, arsenic and selenium.
The effect of elevated copper concentrations on aquatic organisms is also
related to factors such as the duration of exposure and life stage of the
organism. Studies have shown that species richness and species composition of
invertebrate communities and changed as copper concentrations increased.
Early life stages of organisms appear to be more sensitive than adults to copper
pollution.
Nitrogen fixation by blue-green algae is reduced by the addition of trace
amounts of copper. Although bio-concentration factors range from 100 - 26
000, there is no evidence to suggest that copper is bio-magnified.
16 CYANIDE
Chemical Symbol or Formula: CN−.
Standard: 50 µg/l
Percentage Compliance Required: 95% of all monitoring data must comply with the
standard.
Units Used for Analytical Results: µg/l CN
Normal Method(s) of Analysis: Colorimetric (after distillation) [B];
Specific Ion Electrode (after distillation) [B].
Reference Method(s) of Analysis:
Method Type Complexity APHA Reference
Preliminary Treatment of Samples B 4500-CN--B
Total Cyanide after Distillation B 4500-CN--C
Titrimetric Method B 4500-CN--D
Colorimetric Method B 4500-CN--E
Cyanide Selective Electrode Method B 4500-CN--F
Introduction Hydrocyanic acid (HCN) which is the most toxic form of cyanide reacts with
water to release cyanide ions (CN-).
PAGE 53
GUIDELINE AMBIENT ENVIRONMENT STANDARDS FOR ETHIOPIA
Occurrence Most of the cyanide in water is in the hydrocyanic acid form which is largely
undissociated at pH values of 8 or less. Cyanide in the environment is usually
found complexed with metals. Cyanides are present in effluents from gas works
and coke ovens, scrubbing of gases at steel plants, metal cleaning, electroplating
and chemical industries. Cyanide is a common reagent in gold extraction
processes and large quantities of cyanide are found in gold mine tailing dams.
Cyanide is sometimes present in phenolic wastes..
Effects Cyanide interferes with aerobic respiration and is therefore toxic only to aerobic
organisms. Cyanide is thus not as toxic to "lower" organisms (invertebrates) as
it is to fish and other vertebrates. There is a greater variability in sensitivities of
invertebrates than there is in fish species. Embryos, sac larvae and warm-water-
adapted species of fish are more resistant to cyanide than are other life stages or
species of fish. The gills of fish suffering from cyanide poisoning are bright red
in colour.
17 DISOLVED OXYGEN
Chemical Symbol or Formula: O2.
Standard: Game Fish 50% Samples ≥ 9 mg/l
Minimum 6 mg/l
Course Fish 50% Samples ≥ 7 mg/l
Minimum 4 mg/l
Units Used for Analytical Results: mg/l O2
Reference Method(s) of Analysis:
Method Type Complexity APHA Reference
Iodometric (Winkler) Method B 4500-O-B
Azide Modification B 4500-O-C
Permanganate Modification B 4500-O-D
Membrane Electrode (may be modified for filed work) A 4500-O-G
Introduction Gaseous oxygen (O2) from the atmosphere dissolves in water and is also
generated during photosynthesis by aquatic plants and phytoplankton. Oxygen
is moderately soluble in water. Equilibrium solubility, termed the saturation
solubility, varies non-linearly with temperature, salinity and atmospheric
pressure, and with other site-specific chemical and physical factors.
The maintenance of adequate dissolved oxygen (DO) concentrations is critical
for the survival and functioning of the aquatic biota because it is required for the
respiration of all aerobic organisms. Therefore, the DO concentration provides a
useful measure of the health of an aquatic ecosystem. Measurement of the
biochemical oxygen demand (BOD) or the chemical oxygen demand (COD) are
inappropriate for aquatic ecosystems, but are useful for determining water
quality requirements of effluents discharged into aquatic systems, in order to
limit their impact.
PAGE 54
GUIDELINE AMBIENT ENVIRONMENT STANDARDS FOR ETHIOPIA
Occurrence In unpolluted surface waters, dissolved oxygen concentrations are usually close
to saturation. Typical saturation concentrations at sea level, and at TDS values
below 3 000 mg/l, are: 12.77 mg/l at 5 °C; 10.08 mg/R at 15 °C; 9.09 mg/l at 20
°C.
There is a natural diel variation (24 hour cycle) in dissolved oxygen associated
with the 24-hour cycle of photosynthesis and respiration by aquatic biota.
Concentrations decline through the night to a minimum near dawn, then rise to
a maximum by mid afternoon. Seasonal variations arise from changes in
temperature and biological productivity.
Reduction in the concentration of dissolved oxygen can be caused by several
factors:
• Resuspension of anoxic sediments, as a result of river floods or dredging
activities.
• Turnover or release of anoxic bottom water from a deep lake or reservoir.
• The presence of oxidizable organic matter, either of natural origin (detritus)
or originating in waste discharges, can lead to reduction in the concentration
of dissolved oxygen in surface waters. The potential for organic wastes to
deplete oxygen is commonly measured as biochemical oxygen demand
(BOD) and chemical oxygen demand (COD). The COD is used as a routine
measurement for effluents, and is measure of the amount of oxygen likely to
be used in the degration of organic waste. However, in aquatic ecosystems
it is unlikely that all organic matter will be fully oxidised.
• The amount of suspended material in the water affects the saturation
concentration of dissolved oxygen, either chemically, through the oxygen-
scavenging attributes of the suspended particles, or physically through
reduction of the volume of water available for solution.
Dissolved oxygen concentrations can be increased by natural diffusion of
gaseous oxygen from the atmosphere into water. Diffusion continues until the
saturation concentration is reached. The rate of increase of dissolution of
oxygen can be accelerated if turbulence of the water increases, causing
entrainment of air from the atmosphere.
Effects Aerobic organisms are dependent for respiration on the presence of dissolved
oxygen in water. Anoxic or hypoxic conditions may be lethal within short time
scales (minutes to hours).
The sensitivity of many species, especially fish and invertebrates, to changes in
dissolved oxygen concentrations depends on the species and the life stages
(eggs, larvae or adult) and behavioural changes (feeding and reproduction)
Juveniles of many aquatic organisms are more sensitive to physiological stress
arising from oxygen depletion, and in particular to secondary effects such as
increased vulnerability to predation and disease. Where possible, many species
will avoid anoxic or oxygen-depleted zones.
Cold-water-adapted species such as salmonids (e.g., trout) are especially
sensitive to depletion of dissolved oxygen. Reproduction and growth in these
species is reduced under continuous exposure to oxygen concentrations less
than 100 % saturation.
Oxygen concentrations above saturation may cause gas bubble disease in fish.
Super-saturated conditions also tend to inhibit photosynthesis in green algae,
favouring instead blue-green algae, which are more tolerant of super-saturation,
but which may become a nuisance to other water users.
PAGE 55
GUIDELINE AMBIENT ENVIRONMENT STANDARDS FOR ETHIOPIA
The reversibility of toxic effects on organisms depends on the duration,
frequency and timing of the occurrence of oxygen depletion. Physiological
stress effects in adult or less sensitive life stages may be rapidly reversed if
oxygen depletion is short-lived. Prolonged exposure of aquatic communities to
dissolved oxygen concentrations less than 50 % of saturation can cause
significant changes in community composition, as more tolerant species are
favoured.
18 FLORIDE
Chemical Symbol or Formula: F−.
Standard: 1 mg/l
Percentage Compliance Required: 95% of all monitoring data must comply with the
standard.
Units Used for Analytical Results: mg/l F.
Normal Method(s) of Analysis: Colorimetric (after distillation) [B];
Specific Ion Electrode [B].
Reference Method(s) of Analysis:
Method Type Complexity APHA Reference
Preliminary Distillation Step B 4500-F--B
Ion Selective Electrode Method B/C 4500-F--C
SPADNS Method B 4500-F--D
Introduction Fluoride is a halogen gas which is highly reactive with a variety of substances.
It is seldom found as free fluorine gas in nature, but occurs either as the fluoride
ion or in combination with calcium, potassium and phosphates.
Occurrence Fluoride occurs in the earth's crust at an average concentration of 0.3 g/kg, most
often as a constituent of fluorite (CaF2), often known as fluorspar or calcium
fluoride, in sedimentary rocks. Other important occurrences of fluoride are
cryolite and fluorapatite in igneous rocks. Traces of fluoride (< 1 mg/l) occur in
many aquatic ecosystems, whilst higher concentrations (often > 10 mg/l) can be
found in ground waters derived from igneous rocks.
Fluoride is used in:
• the manufacture and use of insecticides;
• disinfecting brewery apparatus;
• fluxes used in the manufacture of steel;
• wood preservatives;
• glass and enamel manufacture;
• chemical industries;
• water treatment, where fluoride may be added for dental purposes; and
• other minor uses.
PAGE 56
GUIDELINE AMBIENT ENVIRONMENT STANDARDS FOR ETHIOPIA
Effects Low concentrations of fluoride (< 1 000 µg/l) strengthen tooth enamel and
bones in mammals. Skeletal fluorosis may occur if exposure to intermediate
fluoride concentrations occurs over long periods.
19 HYDROCARBONS, DISSOLVED & EMULSIFIED
Chemical Symbol or Formula: Not Applicable [Bulk parameter].
Standard: 10 µg/l
Percentage Compliance Required: 95% of all monitoring data must comply with the
standard.
Units Used for Analytical Results: µg/l material.
Reference Method(s) of Analysis:
Method Type Complexity APHA Reference
Hydrocarbons (followed by Gas chromatography) C 5520-F
Introduction This heading includes petroleum, oil, grease and related materials. Problems
caused by these substances include interference with such vital processes as the
mass transfer of oxygen from air to water (essential in river reaeration, for
example), blockage of pipes, fouling of plant and animal life, odour and taste
problems, and the like
It is worth reiterating that this parameter as herein defined is an overall
aggregate (or bulk) parameter which is nonetheless limited in its scope by the
generalised nature of the relevant analytical methods. A large number of
specific (and potentially undesirable) hydrocarbon compounds are thus
excluded from its coverage
Occurrence Effluent discharges, oil spillages etc.
Effect The main implications are organoleptic in the context of this parameter, but
many complex hydrocarbon materials are carcinogenic (e.g. polycyclic aromatic
hydrocarbons, q.v.).
PAGE 57
GUIDELINE AMBIENT ENVIRONMENT STANDARDS FOR ETHIOPIA
20 IRON
Chemical Symbol or Formula: Fe.
Standard: 1 mg/l
Percentage Compliance Required: 95% of all monitoring data must comply with the
standard.
Units Used for Analytical Results: mg/l Fe Dissolved.
Reference Method(s) of Analysis:
Method Type Complexity APHA Reference
Atomic Absorption Spectrometric Method B/C 3500-Fe-B
Inductively Coupled Plasma Method D 3500-Fe-C
Phenanthroline Method B 3500-Fe-D
Introduction Iron is the fourth most abundant element in the earth's crust and may be present
in natural waters in varying quantities depending on the geology of the area and
other chemical properties of the water body. The two common states of iron in
water are the reduced (ferrous, Fe 2+) and the oxidised (ferric, Fe 3+) states. Most
iron in oxygenated waters occurs as ferric hydroxide in particulate and colloidal
form and as complexes with organic, especially humic, compounds. Ferric salts
are insoluble in oxygenated waters, and hence iron concentrations are usually
low in the water column. In reducing waters, the ferrous form, which is more
soluble, may persist and, in the absence of sulphide and carbonate anions, high
concentrations of ferrous iron may be found.
The toxicity of iron depends on whether it is in the ferrous or ferric state, and in
suspension or solution. Although iron has toxic properties at high
concentrations, inhibiting various enzymes, it is not easily absorbed through the
gastro-intestinal tract of vertebrates. On the basis of iron's limited toxicity and
bio-availability, it is classified as a non-critical element.
Iron is an essential micronutrient for all organisms, and is required in the
enzymatic pathways of chlorophyll and protein synthesis, and in the respiratory
enzymes of all organisms. It also forms a basic component of haeme-containing
respiratory pigments (for example, haemoglobin), catalyses, cytochromes and
peroxidases. Under certain conditions of restricted availability of iron,
photosynthetic productivity may be limited.
Occurrence Iron is naturally released into the environment from weathering of sulphide ores
(pyrite, FeS2) and igneous, sedimentary and metamorphic rocks. Leaching from
sandstones releases iron oxides and iron hydroxides to the environment. Iron is
also released into the environment by human activities, mainly from the burning
of coke and coal, acid mine drainage, mineral processing, sewage, landfill
leachates and the corrosion of iron and steel. Various industries that also use
iron in their processes, or in their products, include:
• the chlor-alkali industry,
• the household chemical industry,
• the fungicide industry,
• the petro-chemical industry.
PAGE 58
GUIDELINE AMBIENT ENVIRONMENT STANDARDS FOR ETHIOPIA
Streams may be negatively impacted by high levels of iron in acid mine
drainage. Pyrite, iron sulphide, is often found in close association with coal
deposits. Upon exposure to moisture and atmospheric oxygen, the ferrous iron
is oxidised to the ferric state, a reaction which is frequently accelerated by
bacteria of the Thiobacillus-Ferrobacillus group. If the mine drainage results in
acid conditions in the stream, the rate of oxidation will be slow. If, however, the
acid is neutralized (the rate of neutralization depends on the surface geology)
and pH rises to between 7 and 8, the rate of oxidation will increase and ferric
hydroxide will precipitate. A layer of ferric hydroxide precipitate, so-called
"yellowboy", on stream bottoms and structures is a common sight in areas
affected by acid mine drainage. The receiving water is often also oxygen
deficient.
Effects Data on the acute and chronic toxicity of iron to both invertebrates and
vertebrates are rather limited.
21 LEAD
Chemical Symbol or Formula: Pb.
Standard: 0.05 mg/l
Percentage Compliance Required: 95% of all monitoring data must comply with the
standard.
Units Used for Analytical Results: mg/l Pb.
Reference Method(s) of Analysis:
Method Type Complexity APHA Reference
Atomic Absorption Spectrometric Method B/C 3500-Pb-B
Inductively Coupled Plasma Method D 3500-Pb-C
Dithiozone Method B 3500-Pb-D
Introduction Lead exists in several oxidation states, that is, 0, I, II and IV, all of which are of
environmental importance. Lead occurs as metallic lead, inorganic compounds,
and organometallic compounds. The divalent form, lead (II), is the stable ionic
species present in the environment and is thought to be the form in which most
lead is bio-accumulated by aquatic organisms. In fresh waters lead is generally
present as PbCO3 and as lead-organic complexes, with a small proportion in the
form of free lead ions. Lead may also be complexed with organic ligands,
yielding soluble, colloidal and particulate compounds. Lead is defined by the
USEPA as potentially hazardous to most forms of life, and is considered toxic
and relatively accessible to aquatic organisms.
Occurrence Lead is principally released into the aquatic environment through the
weathering of sulphide ores, especially galena. Since metallic lead and common
lead minerals such as sulphides, sulphates, oxides, carbonates and hydroxides
are almost insoluble, levels of dissolved lead (acetate and chloride salts) in
aquatic ecosystems are generally low. Most of the lead entering aquatic
ecosystems is associated with suspended sediments, while lead in the dissolved
phase is usually complexed by organic ligands.
PAGE 59
GUIDELINE AMBIENT ENVIRONMENT STANDARDS FOR ETHIOPIA
The photolysis of lead compounds is an important process in the removal of
lead from the atmosphere. The products of this photo-degradation are lead
oxides and halides, which enter the aquatic ecosystems via direct deposition or
surface runoff.
The major sources of lead in the aquatic environment are anthropogenic, these
include:
• precipitation, fallout of lead dust and street runoff (associated with lead
emissions from gasoline-powered motor vehicles);
• industrial and municipal wastewater discharge;
• mining, milling and smelting of lead and metals associated with lead, e.g.
zinc, copper, silver, arsenic and antimony; and
• combustion of fossil fuels.
Effects Lead is a common and toxic trace metal which readily accumulates in living
tissue. Metabolically, lead interacts with iron and therefore interferes with
haemoglobin synthesis. It also affects membrane permeability by displacing
calcium at functional sites, and inhibits some of the enzymes involved in energy
metabolism. Lead that has been absorbed by vertebrate organisms is largely
deposited in the bony skeleton, where it does not usually exhibit toxic effects. If
stress results in decalcification or deossification, lead deposits may result in
toxic effects. It has been shown that rainbow trout develop spinal deformities
after exposure to lead in soft water, while no deformities were evident in hard
water.
Low concentrations of lead affect fish by causing the formation of a film of
coagulated mucous over the gills and subsequently over the entire body. This
has been attributed to a reaction between lead and an organic constituent of the
mucous. Death of fish is due to suffocation brought about by the mucous layer
since insoluble lead is apparently not toxic to fish.
Lead is bio-accumulated by benthic bacteria, freshwater plants, invertebrates
and fish. Bio-concentration factors for four species of invertebrates and two
species of fish ranged from 42 - 1 700, though lead does not appear to bio-
magnify through the aquatic food web.
PAGE 60
GUIDELINE AMBIENT ENVIRONMENT STANDARDS FOR ETHIOPIA
22 MANGANESE
Chemical Symbol or Formula: Mn.
Standard: 0.3 mg/l
Percentage Compliance Required: 95% of all monitoring data must comply with the
standard.
Units Used for Analytical Results: mg/l Mn.
Reference Method(s) of Analysis:
Method Type Complexity APHA Reference
Atomic Absorption Spectrometric Method B/C 3500-Mn-B
Inductively Coupled Plasma Method D 3500-Mn-C
Persulphate Method B 3500-Mn-D
Introduction Manganese is an essential micronutrient for plants and animals. It is a functional
component of nitrate assimilation and an essential catalyst of numerous enzyme
systems in animals, plants and bacteria. When manganese is not present in
sufficient quantities, photosynthetic productivity may be limited and plants may
exhibit chlorosis (a yellowing of the leaves) or failure of leaves to develop
properly. A deficiency in manganese in vertebrates leads to skeletal deformities
and reduced reproductive capabilities.
High concentrations of manganese are toxic, and may lead to disturbances in
various metabolic pathways, in particular disturbances of the central nervous
system caused by the inhibition of the formation of dopamine (a
neurotransmitter).
Occurrence Manganese is the eighth most abundant metal in nature, and occurs in a number
of ores. In aquatic ecosystems, manganese does not occur naturally as a metal
but is found in various salts and minerals, frequently in association with iron
compounds. It may exist in the soluble manganous (Mn 2+) form, but is readily
oxidised to the insoluble manganic (Mn4+) form. The Mn2+ ion occurs at low
redox potentials and low pH. Permanganates (Mn 7+) do not persist in the
environment. They rapidly oxidise organic materials and are therefore reduced.
Nitrate, sulphate and chloride salts of manganese are fairly soluble in water,
whereas oxides, carbonates, phosphates, sulphides and hydroxides are less
soluble.
Soils, sediments and metamorphic and sedimentary rocks are significant natural
sources of manganese. Industrial discharges also account for elevated
concentrations of manganese in receiving waters. Various industries use
manganese, its alloys and manganese compounds in their processes, or in their
products, examples of which are given below:
• the steel industry, in the manufacture of dry cell batteries;
• the fertilizer industry (manganese is used as a micro-nutrient fertilizer
additive); and
• the chemical industry in paints, dyes, glass, ceramics, matches and
fireworks.
PAGE 61
GUIDELINE AMBIENT ENVIRONMENT STANDARDS FOR ETHIOPIA
Acid mine drainage also releases a large amount of the manganese. Iron and
steel foundries release manganese into the atmosphere, where it is then
redistributed through atmospheric deposition.
Effects Information on the acute and chronic toxicity effects of manganese to algae,
invertebrates and vertebrates are very limited..
23 MERCURY
Chemical Symbol or Formula: Hg.
Standard: 1 µg/l
Percentage Compliance Required: 95% of all monitoring data must comply with the
standard.
Units Used for Analytical Results: µg/l Hg.
Reference Method(s) of Analysis:
Method Type Complexity APHA Reference
Cold-Vapor Atomic Absorption Spectrometric Method C 3500-Hg-B
Inductively Coupled Plasma Method D 3500-Hg-C
Dithizone Method B 3500-Hg-D
Introduction Mercury is a heavy metal that is of quite rare geological occurrence, and its
concentration in the environment is normally very low. Mercury occurs in three
oxidation states in the natural aquatic environment, namely: as the metal, as
mercury(I), and as mercury(II). The dissolved forms of mercury and those
adsorbed onto particulate material are included in the guideline since they are
both available for uptake by aquatic organisms. Mercury is also found as
organo-mercurial salts, the most important of which is methyl mercury.
Mercury and mercury-organic complexes are of concern in the natural aquatic
environment because of their extreme toxicity to aquatic organisms and the
potential to bio-accumulate in the food chain. Intake of mercury can occur via
air, food and water.
Occurrence Mercury may occur at high concentrations in water bodies subject to industrial
pollution, or in the vicinity of industrial activities utilising or discharging
mercury or compounds thereof. Important industries that use mercury in their
processes, or in their products, include:
• the chlor-alkali industry,
• the paint industry,
• the fungicide industry,
• the paper and pulp industry,
• medical and dental industries, and
• the electrical equipment industry.
Mercury has a strong affinity for sediments and suspended solids. Under
anaerobic conditions, bacteria readily transform inorganic mercury into methyl
PAGE 62
GUIDELINE AMBIENT ENVIRONMENT STANDARDS FOR ETHIOPIA
mercury. Dissolved mercury salts are also easily absorbed by aquatic organisms
and can be bio-accumulated.
Methyl mercury, the most common form of mercury found in aquatic
organisms, is lipid soluble (readily passes through plant and animal membranes)
and is stored within the bodies of organisms. In aquatic animals, bio-
accumulated mercury is stored in fatty tissues, whilst in aquatic plants, mercury
is usually stored in roots and stems.
Effects Because of its neuro- and renal toxicity, mercury is severely poisonous to
mammals. Poisoning by mercury takes the form of neurological disturbances,
particularly in the case of organo-mercurial salts such as methyl mercury, and of
renal dysfunction in the case of inorganic mercury. The kidneys are the main
route of excretion of inorganic mercury. De-methylation is a slow process, and
methyl mercury is only excreted over a long period.
Methyl mercury accumulated in fatty tissue or storage organs can be mobilized
rapidly into the nervous and reproductive systems. This bio-accumulated
mercury increases the risk of mercury toxicity to aquatic and terrestrial
organisms in the food chain.
Organic forms of mercury are approximately ten times more toxic than
inorganic forms because they pass rapidly through biological membranes. Solid
inorganic forms of mercury have relatively low toxicity to vertebrates since
solids are not easily absorbed by the gastrointestinal tract. In contrast, dissolved
mercury salts are easily absorbed by aquatic organisms and can be bio-
accumulated.
The toxic effects of mercury on aquatic organisms cannot be reversed.
24 METHYLENE BLUE – ACTIVE SUBSTANCES
Chemical Symbol or Formula: Not applicable [Bulk parameter].
Standard: 0.2 mg/l
Percentage Compliance Required: 95% of all monitoring data must comply with the
standard.
Units Used for Analytical Results: mg/l reference material (Lauryl sulphate).
Normal Method(s) of Analysis: Methylene Blue/Solvent Extraction [B]
Reference Method(s) of Analysis:
Method Type Complexity APHA Reference
Anionic Surfactants as MBAS B 5540-C
Introduction Often abbreviated to MBAS, the designation of this parameter is the chemically
correct term for the group of compounds commonly known as anionic
detergents. To cloud the issue further, the non-specific terms surf octants
(surface active agents) and syndets (synthetic detergents) are also used on
occasion, the former more frequently. Synthetic detergents fall into three
groups - anionic, cationic and non-ionic. The last-mentioned are all substituted
polymers of ethylene oxide which do not ionise in water. They are more
expensive than the anionic type but are coming into greater use. The cationic
PAGE 63
GUIDELINE AMBIENT ENVIRONMENT STANDARDS FOR ETHIOPIA
types are salts of quaternary ammonium hydroxide and are known for their
properties of disinfection. The major group comprises the anionic detergents
which are all sodium salts of organic sulphates or sulphonates. Such entities
form ion pairs with the reagent methylene blue, a property which forms the
basis of their estimation. The results are quoted as mg/l standard reference
material. Some authorities specify lauryl sulphate which is used increasingly as
a standard.
It is worth noting that other terms have been used in connection with synthetic
detergents. "Hard" and "soft" detergents are those which are biodegraded with
difficulty and with ease, respectively. The designations have nothing to do with
the hardness of the waters in which they are used. Some of the original anionic
detergents were very hard; structurally they were of the "ABS"
(alkylbenzenesulphonate) type. Later, there was a move towards the much more
biodegradable ("soft") linear alkylate sulphate/sulphonate ("LAS") detergents.
This was to help eliminate the major problem of foaming. In the US very
severe foaming problems were encountered in the days of first use of synthetic
detergents. Other disadvantages associated with them include interference with
the reaeration of water which is low in dissolved oxygen, and the synergistic
foaming effects which can arise when waters containing sub-foaming
concentrations of different types of detergents are mixed. Most detergent
preparations contain around 20 per cent surface active agent (which is all that is
determined in this test): the rest of the formulation consists of so-called
"builders" which enhance the properties of the active constituent. Chief among
these are phosphates which are of major environmental significance (see
below).
It should be noted that, as there may be some extraneous matter which will also
react with methylene blue, the analysis is more correctly designated as
"methylene blue active substances" than as anionic detergents, even though the
latter may in fact represent 100 per cent of levels found
Occurrence Synthetic materials in domestic and industrial wastes.
Effect No immediate implications as other problems will prevent consumption of
waters with these materials present.
25 NICKEL
Chemical Symbol or Formula: Ni.
Standard: 0.1 mg/l
Percentage Compliance Required: 95% of all monitoring data must comply with the
standard.
Units Used for Analytical Results: mg/l Ni.
Normal Method(s) of Analysis: Atomic Absorption Spectrometry [B/C]
Reference Method(s) of Analysis:
Method Type Complexity APHA Reference
Atomic Absorption Spectrometric Method B/C 3500-Ni-B
Inductively Coupled Plasma Method D 3500-Ni-C
PAGE 64
GUIDELINE AMBIENT ENVIRONMENT STANDARDS FOR ETHIOPIA
Introduction This is another metallic element which is of moderate concern because of
possible carcinogenicity as far as humans are concerned; it also has variable
harmful effects on aquatic life. It is toxic to plant life, too, and is a hazard to fish
(generally in the mg/l concentration range).
Occurrence Principal sources are minerals and industrial wastes.
Effect Very limited.
26 NITRATE
Chemical Symbol or Formula: NO3
–
Standard: 50 mg/l
Percentage Compliance Required: 95% of all monitoring data must comply with the
standard.
Units Used for Analytical Results: mg/l NO3
–.
Reference Method(s) of Analysis:
Method Type Complexity APHA Reference
Ultraviolet Spectrophotometric Screening Method B 4500-NO3
--B
Ion Chromatographic Method B/C 4500-NO3
--C
Nitrate Electrode Method B/C 4500-NO3
--D
Titanous Chloride Reduction Method B 4500-NO3
--G
Introduction Relatively little of the nitrate found in natural waters is of mineral origin, most
coming from organic and inorganic sources, the former including waste
discharges and the latter comprising chiefly artificial fertilisers. However,
bacterial oxidation and fixing of nitrogen by plants can both produce nitrate.
Interest is centred on nitrate concentrations for various reasons. Most
importantly, high nitrate levels in waters to be used for drinking will render
them hazardous to infants as they induce the "blue baby" syndrome
(methaemoglobinaemia). The nitrate itself is not a direct toxicant but is a health
hazard because of its conversion to nitrite [see also below] which reacts with
blood haemoglobin to cause methaemoglobinaemia.
Of increasing importance is the degree to which fertiliser run-off can contribute
to eutrophication problems in lakes. Sewage is rich in nitrogenous matter which
through bacterial action may ultimately appear in the aquatic environment as
nitrate. Hence, the presence of nitrate in ground waters, for example, is cause
for suspicion of past sewage pollution or of excess levels of fertilisers or
manure slurries spread on land. (High nitrite levels would indicate more recent
pollution as nitrite is an intermediate stage in the ammonia-to-nitrate oxidation).
In rivers high levels of nitrate are more likely to indicate significant run-off
from agricultural land than anything else and the parameter is not of primary
importance per se. However, it should be noted that there is a general tendency
for nitrate concentrations in rivers to increase as a result of enhanced nutrient
run-off; this may ultimately lessen their utility as potential sources of public
water supply. Nitrite concentrations in rivers are rarely more than 1 - 2 per cent
of the nitrate level so that it may therefore be acceptable to carry out the
PAGE 65
GUIDELINE AMBIENT ENVIRONMENT STANDARDS FOR ETHIOPIA
analytically convenient determination of nitrate + nitrite at the same time. This
determination is correctly referred to as total oxidised nitrogen
Occurrence Oxidation of ammonia: agricultural fertiliser run-off.
Effect Hazard to infants above 50 mg/l NO3.
27 NITRITE
Chemical Symbol or Formula: NO2
–
Standard: 0.1 mg/l
Percentage Compliance Required: 95% of all monitoring data must comply with the
standard.
Units Used for Analytical Results: mg/l NO2
–.
Normal Method(s) of Analysis: Manual or Automated Colorimetry [A/B]
Reference Method(s) of Analysis:
Method Type Complexity APHA Reference
Colorimetric Method B 4500-NO2
--B
Ion Chromatographic Method B/C 4500-NO2
--C
Introduction Nitrite exists normally in very low concentrations and even in waste treatment
plant effluents levels are relatively low, principally because the nitrogen will
tend to exist in the more reduced (ammonia; NH3) or more oxidised (nitrate;
NO3 ) forms
Because nitrite is an intermediate in the oxidisation of ammonia to nitrate,
because such oxidation can proceed in soil, and because sewage is a rich source
of ammonia nitrogen, waters which show any appreciable amounts of nitrite are
regarded as being of highly questionable quality. Levels in unpolluted waters
are normally low, below 0.03 mg/l NO 2. Values greater than this may indicate
sewage pollution.
The significance of nitrite (at the low levels often found in surface waters) is
mainly as an indicator of possible sewage pollution rather than as a hazard itself
although, as mentioned above under "Nitrate" (q.v.), it is nitrite rather than
nitrate which is the direct toxicant. There is, accordingly, a stricter limit for
nitrite in drinking waters. In addition, nitrites can give rise to the presence of
nitrosamines by reaction with organic compounds and there may be
carcinogenic effects.
Occurrence Generally from untreated or partially treated wastes.
Effect Methaemoglobinaemia-causing agent [cf. Nitrate]..
PAGE 66
GUIDELINE AMBIENT ENVIRONMENT STANDARDS FOR ETHIOPIA
28 NITROGEN (KJELDAHL)
Chemical Symbol or Formula: Not Applicable [Bulk parameter]
Standard: 1 mg/l
Percentage Compliance Required: 95% of all monitoring data must comply with the
standard.
Units Used for Analytical Results: mg/l N.
Reference Method(s) of Analysis:
Method Type Complexity APHA Reference
Macro-Kjeldahl Method B 4500-Norg-B
Semi-Micro- Kjeldahl Method B 4500-Norg-C
Introduction This determination is for organically-bound nitrogen and, under the normal test
conditions (without ammonia removal), it includes ammonia. However, the
results do not include oxidised nitrogen. The sum of the organically-bound
nitrogen and ammonia figures is the "Kjeldahl nitrogen" value; if the ammonia
has been excluded the result is "organic nitrogen." The term "total nitrogen"
refers to the sum of the Kjeldahl and total oxidised nitrogen figures.
In past years much reliance was placed on the so-called albuminoid nitrogen
determination which was frequently carried out in conjunction with the manual
distillation technique for measuring ammonia. In this test the ammonia-free
residue from the initial distillation is treated with alkaline potassium
permanganate and then distilled again to give a further quantity of ammonia
which is derived from proteinaceous matter and is a reflection of the organic
content. Although alternative procedures have superseded the albuminoid
nitrogen determination, it may still be found useful especially in assessing water
with possible sewage contamination. While high values are themselves
indicative of pollution, the albuminoid nitrogen results are most often
considered in conjunction with the figures for ammonia. This is because in
natural waters the ratio of free/saline ammonia nitrogen to albuminoid nitrogen
is normally significantly less than unity (frequently of the order of 0.2-0.4),
being a reflection of the fact that albuminoid nitrogen sources (principally
vegetable) occur with a natural frequency. When the ratio approaches or
exceeds unity an extraneous source of free ammonia is indicated and in many
cases this is a sewage discharge. Thus, by scrutinising this nitrogen ratio the
analyst can get an early indication of possible sewage contamination of a water,
an indication which may be reinforced by elevated chloride values (q.v.).
In the Kjeldahl nitrogen determination the sample is subjected to quite severe
digestion conditions which break down proteins and other organic matter and
convert the nitrogen to ammonia, in which form it is actually measured.
Occurrence Principally from organic matter naturally present (e.g. falling leaves etc.) or
added in discharges.
Effects Site-specific conditions, especially the availability of phosphorus, are critically
important in modifying the influence of inorganic nitrogen on eutrophication.
Inorganic nitrogen toxicity is not considered to be important for setting
inorganic nitrogen water quality guidelines for protection of aquatic ecosystems.
PAGE 67
GUIDELINE AMBIENT ENVIRONMENT STANDARDS FOR ETHIOPIA
Total nitrogen concentrations below 0.5 mg N/l are considered to be sufficiently
low that they can limit eutrophication and reduce the likelihood of nuisance
growths of blue-green algae and other plants. However, in the presence of
sufficient available phosphorus, nitrogen-fixing organisms will be able to fix
atmospheric nitrogen, thereby compensating for any deficit caused by low total
nitrogen concentrations.
The information given in the table below illustrates typical symptoms
associated with selected ranges of total nitrogen concentrations, if all other
nutrients and environmental conditions are within favourable ranges for the
organisms concerned.
Average Summer
Inorganic Nitrogen
Concentration(mg/l)
Effects
<0.5 Oligotrophic conditions; usually moderate levels of species
diversity; usually low productivity systems with rapid nutrient
cycling; no nuisance growth of aquatic plants or the presence of
blue-green algal blooms.
0.5 – 2.5 Mesotrophic conditions; usually high levels of species
diversity; usually productive systems; nuisance growth of
aquatic plants and blooms of blue-green algae; algal blooms
seldom toxic.
2.5 – 10 Eutrophic conditions; usually low levels of species diversity;
usually highly productive systems, nuisance growth of aquatic
plants and blooms of blue-green algae; algal blooms may
include species which are toxic to man, livestock and wildlife.
>10 Hypertrophic conditions; usually very low levels of species
diversity; usually very highly productive systems; nuisance
growth of aquatic plants and blooms of blue-green algae, often
including species which are toxic to man, livestock and
wildlife.
PAGE 68
GUIDELINE AMBIENT ENVIRONMENT STANDARDS FOR ETHIOPIA
29 PESTICIDES
Chemical Symbol or Formula: Not applicable [Bulk parameter].
Standard:
Aldrin 0.01 µg/l Fenitrothion 0.01 µg/l
Dieldrin 0.01 µg/l Isoproturon 0.5 µg/l
Endrin 0.005 µg/l Lindane 0.1 µg/l
Isodrin 0.005 µg/l Linuron 1.0 µg/l
Atrazine 1.0 µg/l Malathion 0.01 µg/l
Chloridazon 0.1 µg/l MCPA 10 µg/l
2,4-D 0.005 µg/l Mecoprop 10 µg/l
DDT (y-isomer) 10 µg/l Parathionethyl 0.01 µg/l
DDT (all isomers) 25 µg/l Pentachlorophenol 2.0 µg/l
Diazinon 5 µg/l Simazine 1.0 µg/l
Dichlorbenil 10µg/l Tributyltin oxide 0,001 µg/l
Dichlorvos 0.001 µg/l Trifuralin 0.1 µg/l
Diuron 25 µg/l Triphenyltin acetate 0.01 µg/l
Endosulphan 0.001 µg/l Triphenyltin hydroxide 0.01 µg/l
Percentage Compliance Required: 100% of all monitoring data must comply with the
standard.
Units Used for Analytical Results: µg/l specified compound
Normal Method(s) of Analysis: Chromatographic techniques (GLC/HPLC) [C]
Reference Method(s) of Analysis:
Method Type Complexity APHA Reference
Carbamate Pesticides
High Performance Liquid Chromatographic Method C/D 6610-B
Organochlorine Pesticides
Liquid-Liquid Extraction Gas Chromatographic Method C/D 6630-B
Liquid-Liquid Extraction Gas Chromatographic Method II C/D 6630-C
Liquid-Liquid Extraction Gas Chromatographic/Mass
Spectrometric Method
D 6630-D
Acidic Herbicide Compounds
Micro Liquid-Liquid Extraction Gas Chromatographic
Method
C/D 6640-B
Glyphosate Herbicides
Liquid Chromatographic Post-Column Florescence Method D 6651-B
PAGE 69
GUIDELINE AMBIENT ENVIRONMENT STANDARDS FOR ETHIOPIA
Introduction This broad designation encompasses a large group of compounds with either
related uses or similar chemical composition. The substances covered comprise
insecticides (organo-chlorine and organo-phosphorus), herbicides, fungicides,
PCBs (polychlorinated biphenyls) and PCTs (polychlorinated terphenyls).
Compounds such as pesticides are among those which cause mortality or severe
reproductive or genetic problems in fauna and which also qualify for inclusion
under the broad heading of substances which possess carcinogenic, mutagenic
or teratogenic properties. As such, they are highly undesirable in waters of
virtually any type. Even if levels in, say, a river water are very low there is the
probability of bioaccumulation in fish or other living tissue and, to compound
the matter, of retention on the in-situ sediments..
Occurrence Synthetic compounds - agricultural discharges, spillages or runoff, industrial
waste discharges
Effect Compounds of great acute or chronic toxicity.
30 PH (ACIDITY AND ALKALINITY)
Chemical Symbol or Formula: Not applicable [Physical parameter].
Standard: 6-9 (but no change of more than 0.2 units from natural
level)
Percentage Compliance Required: 95% of all monitoring data must comply with the
standard.
Units Used for Analytical Results: pH units.
Normal Method(s) of Analysis: Electrometry [pH electrode] [A/B]
Reference Method(s) of Analysis:
Method Type Complexity APHA Reference
Electrometric Method B 4500-H+-B
Introduction The pH value is a measure of the hydrogen ion activity in a water sample. It is
mathematically related to hydrogen ion activity according to the expression:
pH = -log10 [H
+], where [H+] is the hydrogen ion activity. The pH of pure water
(that is, water containing no solutes) at a temperature of 24 °C is 7.0, the
number of H+ and OH− ions are equal and the water is therefore
electrochemically neutral. As the concentration of hydrogen ions [H+] increases,
pH decreases and the solution becomes more acid. As [H+] decreases, pH
increases and the solution becomes more basic.
The equilibrium between H+ and OH− ions is influenced by reactions with acids
and bases introduced into the aqueous system. In general, acidity is the number
of OH− ions that have reacted over a given pH range during a base titration, that
is, a measure of the water's ability to neutralise base. Similarly, alkalinity is a
measure of the number of H+ ions that have reacted over a given pH range
during an acid titration, that is, a measure of the water's ability to neutralise
acid.
Alkalinity is primarily controlled by carbonate species and is therefore usually
expressed in terms of equivalence to calcium carbonate (CaCO 3). Briefly,
PAGE 70
GUIDELINE AMBIENT ENVIRONMENT STANDARDS FOR ETHIOPIA
carbon dioxide dissolves in water to form carbonic acid (H 2CO3) which,
depending on pH, dissociates to form carbonate, bicarbonate and hydrogen ions:
CO2 + H2O ' H2CO3 ' HCO3
− + H+ ' CO3
2− + 2H+
At a pH value of less than 4.0, carbonate species are mostly in the form of
H2CO3 , whilst between pH values of 6.4 and 8.6 they are in the form HCO 3
−.
As the pH increases to greater than 8.6, so the proportion of CO 3
2− increases,
and above pH 10.3 CO3
2− predominates.
The rate of change of pH, on addition of a given quantity of an acid or base,
depends on the buffering capacity of the water. The most important buffering
system in fresh waters is the carbonate-bicarbonate one, and between pH values
of 6.4 - 10.3 the hydrogen carbonate ion predominates. In naturally acid waters,
complex polyphenolic organics and their salts may form the major buffering
system, while aluminium and its salts become effective buffering agents in
waters subject to acid precipitation.
Occurrence For surface water, pH values typically range between 4 and 11. The relative
proportions of the major ions, and in consequence the pH, of natural waters, are
determined by geological and atmospheric influences. Most fresh waters, are
relatively well buffered and more or less neutral, with pH ranges between 6 and
8. Very dilute sodium-chloride-dominated waters are poorly buffered because
they contain virtually no bicarbonate or carbonate. If they drain catchments
containing certain types of vegetation (for example, fynbos), the pH may drop
as low as 3.9 owing to the influence of organic acids (for example, humic and
fulvic acids).
The pH may also vary both diurnally and seasonally. Diurnal fluctuations occur
in productive systems where the relative rates of photosynthesis and respiration
vary over a 24- hour period, because photosynthesis alters the
carbonate/bicarbonate equilibrium by removing CO from the water. Seasonal
variability is largely related to the hydrological 2 cycle, particularly in rivers
draining catchments with vegetation such as fynbos, where the concentration of
organic acids is consistently lower during the rainy season.
Industrial activities generally cause acidification rather than alkalinization of
rivers. Acidification is normally the result of three different types of pollution,
namely:
• low-pH point-source effluents from industries, such as pulp and paper and
tanning and leather industries;
• mine drainage, which is nearly always acid, leading to the pH of receiving
streams dropping to below 2; and
• acid precipitation resulting largely from atmospheric pollution caused by
the burning of coal (and subsequent production of sulphur dioxide (SO2))
and the exhausts of combustion engines (nitrogen oxides). Both sulphur
oxides (SOx) and nitrogen oxides (NOx) form strong mineral acids when
dissolved in water. When acid rain falls on a catchment, the strong acids
leach calcium and magnesium from the soil and also interfere with nutrient
availability.
Elevated pH values can be caused by increased biological activity in eutrophic
systems. The pH values may fluctuate widely from below 6 - above 10 over a
24-hour period as a result of changing rates of photosynthesis and respiration.
Effects A change in pH from that normally encountered in unimpacted streams may
have severe effects upon the biota. The extent of acidification or alkalinization
PAGE 71
GUIDELINE AMBIENT ENVIRONMENT STANDARDS FOR ETHIOPIA
is important in determining the severity of the effects, which do not vary
linearly either with pH or over time. When assessing the potential effect of a
change in pH, it is important to note that some streams are naturally more acidic
than others and their biotas are often adapted to these conditions.
Direct effects of pH changes consist of alterations in the ionic and osmotic
balance of individual organisms, in particular changes in the rate and type of ion
exchange across body surfaces. This requires greater energy expenditure, with
subsequent effects such as slow growth and reduced fecundity becoming
apparent. Aquatic organisms, however, generally have well developed
mechanisms for maintaining ionic and osmotic balance. Impacts of indirect pH
changes include changes in the availability of toxic substances such as
aluminium and ammonia.
Acidic pH
Gradual reductions in pH may result in a change in community structure, with
acid-tolerant organisms replacing less tolerant organisms.
Streams with acidic pH values have different periphyton (micro flora and fauna
living on solid surfaces) communities and lower overall production compared
with less acidic streams.
The discharge of acid wastes into water containing bicarbonate alkalinity results
in the formation of free carbon dioxide. If the water is alkaline, free CO2 may be
liberated and be toxic to fish even though the pH does not drop to a level
normally considered toxic.
Alkaline pH
Limited information is available on the effects of elevated pH.
31 PHENOLS
Chemical Symbol or Formula: Not applicable [Physical parameter].
Standard: 0.5 µg/l.
Percentage Compliance Required: 95% of all monitoring data must comply with the
standard.
Units Used for Analytical Results: mg/l C6H5OH [Phenol].
Reference Method(s) of Analysis:
Method Type Complexity APHA Reference
Liquid-Liquid Extraction Gas Chromatographic Method B 6420-B
Liquid-Liquid Extraction Gas Chromatographic/Mass
Spectrometric Method
B 6420-C
Introduction Phenol itself is an organic compound consisting of a hydroxyl group attached to
a benzene ring.
Occurrence In unimpacted water systems phenols are only found in very low
concentrations, usually in the µg/l range or less. Phenols are produced as by-
products in many industrial processes where organic chemicals are used.
Phenols are also used as a disinfectant, and as a starting material for a wide
PAGE 72
GUIDELINE AMBIENT ENVIRONMENT STANDARDS FOR ETHIOPIA
variety of synthetic organic processes. Phenolic wastes arise from the
distillation of wood and coal, from oil refineries, chemical plants, pulp and
paper industries, livestock dips and human and animal wastes. Phenol is often
present in sewage at levels between 0.07 - 0.1 mg/l. Phenols are generally
biodegraded in water.
Effects Phenols are thought to be a nerve poison which gives rise to an increased blood
supply to the gills and heart cavities. Fish exposed to phenol become excited,
swim more rapidly, become more sensitive to stimuli and show increased
respiratory rates, colour changes and increased secretion of mucus. Death may
occur quickly or follow a period of depressed activity and loss of equilibrium,
with occasional convulsions. Fish surviving long-term exposure to low phenol
concentrations show general inflammation and necrosis of tissues. This is
possibly due to irreversible changes in protein structure. Histopathological
changes in the blood, liver, heart, skin and spleen may also occur. Reduction in
growth and sexual activity and a loss of balance and co-ordination have been
observed in some fish species. Phenol affects some aquatic organisms directly
by increasing their demand for oxygen.
Reduction in oxygen consumption occurs in some invertebrates. Avoidance
behaviour has been observed in leeches. Phenols have also been shown to
reduce rates of photosynthesis in aquatic plants.
32 PHOSPHATES
Chemical Symbol or Formula: PO4–
Standard The inorganic phosphorus concentration for a specific
system must be based on the existing trophic status of the
system. It is undesirable to allow inorganic phosphorus
concentrations to rise to a level which will change the
trophic status of the system. A standard for each water
body should be derived only after case- or site-specific
studies.
• Inorganic phosphorus concentrations should not be
changed by > 15 % from that of the water body under
local, unimpacted conditions at any time of the year;
and
• The trophic status of the water body should not
increase above its present level, though a decrease in
trophic status is permissible (see Effects); and
• The amplitude and frequency of natural cycles in
inorganic phosphorus concentrations should not be
changed.
PAGE 73
GUIDELINE AMBIENT ENVIRONMENT STANDARDS FOR ETHIOPIA
Percentage Compliance Required: 95% of all monitoring data must comply with the
standard.
Units Used for Analytical Results: mg/l P.
Normal Method(s) of Analysis: Manual or Automated Colorimetry [B/C].
Reference Method(s) of Analysis:
Method Type Complexity APHA Reference
Sample Preparation B 4500-P-B
Vanadomolybdophosphoric Acid Colorimetric Method B 4500-P-C
Stannous Chloride Method B 4500-P-D
Ascorbic Method B 4500-P-E
Introduction Phosphorus can occur in numerous organic and inorganic forms, and may be
present in waters as dissolved and particulate species. Elemental phosphorus
does not occur in the natural environment. Orthophosphates, polyphosphates,
metaphosphates, pyrophosphates and organically bound phosphates are found in
natural waters. Of these, orthophosphate species H2PO4 and HPO4
2− are the only
forms of soluble inorganic phosphorus directly utilizable by aquatic biota.
Soluble Reactive Phosphate (SRP), or orthophosphate, is that phosphorus which
is immediately available to aquatic biota which can be transformed into an
available form by naturally occurring processes.
The forms of phosphorus in water are continually changing because of
processes of decomposition and synthesis between organically bound forms and
oxidised inorganic forms. The phosphorus cycle is influenced by the exchange
of phosphorus between sedimentary and aqueous compartments. In turn this is
affected by various physical, chemical and biological modifying factors such as
mineral-water equilibria, water pH values, sorption processes, oxygen-
dependent redox interactions, and the activities of living organisms.
Phosphorus is an essential macronutrient, and is accumulated by a variety of
living organisms. It has a major role in the building of nucleic acids and in the
storage and use of energy in cells. In unimpacted waters it is readily utilized by
plants and converted into cell structures by photosynthetic action. Phosphorus is
considered to be the principle nutrient controlling the degree of eutrophication
in aquatic ecosystems.
Occurrence Natural sources of phosphorus include the weathering of rocks and the
subsequent leaching of phosphate salts into surface waters, in addition to the
decomposition of organic matter. Spatial variation is high and is related to the
characteristics of regional geology. Phosphorus levels are generally lowest in
mountainous regions of crystalline rocks and levels increase in lowland waters
derived from sedimentary deposits.
Phosphorus is seldom present in high concentrations in unimpacted surface
waters because it is actively taken up by plants. Concentrations between 10 and
50 µg/l are commonly found, although concentrations as low as 1 µg/l of
soluble inorganic phosphorus may be found in "pristine" waters and as high as
200 mg/l of total phosphorus in some enclosed saline waters.
Elevated levels of phosphorus may result from point-source discharges such as
domestic and industrial effluents, and from diffuse sources (non-point sources)
in which the phosphorus load is generated by surface and subsurface drainage.
PAGE 74
GUIDELINE AMBIENT ENVIRONMENT STANDARDS FOR ETHIOPIA
Non-point sources include atmospheric precipitation, urban runoff, and drainage
from agricultural land, in particular from land on which fertilizers have been
applied.
Effects The most significant effect of elevated phosphorus concentrations is its
stimulation of the growth of aquatic plants. Both phosphorus and nitrogen limit
plant growth, and of these, phosphorus is likely to be more limiting in fresh
water. The effect is dependent on the form of phosphorus present in the water,
since not all forms are available for uptake by plants. Other factors, such as
water temperature, light and the availability of other nutrients, also play an
important role in limiting plant growth.
Inorganic phosphorus concentrations of less than 5 µg P/l are considered to be
sufficiently low to reduce the likelihood of algal and other plant growth.
The information given in the table below illustrates typical symptoms
associated with selected ranges of inorganic phosphorus concentrations, if all
other nutrients and environmental conditions are within favourable ranges for
the organisms concerned.
Average Summer
Inorganic
Phosphorous
Concentration
(µg/l)
Effects
<5 Oligotrophic conditions; usually moderate levels of species
diversity; usually low productivity systems with rapid nutrient
cycling; no nuisance growth of aquatic plants or blue-green
algae.
5-25 Mesotrophic conditions; usually high levels of species
diversity; usually productive systems; nuisance growth of
aquatic plants and blooms of blue-green algae; algal blooms
seldom toxic.
25-250 Eutrophic conditions; usually low levels of species diversity;
usually highly productive systems, nuisance growth of aquatic
plants and blooms of blue-green algae; algal blooms may
include species which are toxic to man, livestock and wildlife.
>250 Hypertrophic conditions; usually very low levels of species
diversity; usually very highly productive systems; nuisance
growth of aquatic plants and blooms of blue-green algae,
often including species which are toxic to man, livestock and
wildlife.
PAGE 75
GUIDELINE AMBIENT ENVIRONMENT STANDARDS FOR ETHIOPIA
33 POLYCHLORINATED BIPHENYLS & TERPHENYLS
Chemical Symbol or Formula: Not applicable [Physical parameter].
Standard: 1 µg/l.
Percentage Compliance Required: 100% of all monitoring data must comply with the
standard.
Units Used for Analytical Results: µg/l reference PCB/PCT (mixture) used.
Reference Method(s) of Analysis:
Method Type Complexity APHA Reference
Liquid-Liquid Extraction Gas Chromatographic Method C/D 6431-B
Liquid-Liquid Extraction Gas Chromatographic/Mass
Spectrometric Method
D 6431-C
Introduction Commonly termed PCBs/PCTs, this parameter covers those chlorinated
compounds which have been used as mixtures in transformer coolant oils. The
mixtures are normally designated by a proprietary name, for example "Aroclor,"
to which is suffixed a number, e.g. 1254 or 1260. The first two digits represent
the number of carbon atoms in the molecule and the second two the percentage
by weight of chlorine. The basic molecules present are biphenyl, which is
C12H10 and comprises two benzene rings joined together, or terphenyl (C 18H14,
consisting of three fused benzene rings).
When these are chlorinated a whole range of polychlorinated compounds is
produced and the mixtures are of such complexity that no effort is made to
identify the individual components. The mixtures are dense and extremely
stable, resisting biodegradation and conventional incineration procedures.
The best process currently available for their destruction is very high
temperature "flash" incineration. It is not without significance that, according
to current estimates, about 90% of the total world production of these materials
since the 1940s, when they were introduced, is still extant.
Occurrence Synthetic components of transformer coolant oils which gain access to water by
spillages or industrial discharges.
Effect Compounds of marked chronic toxicity; they are actual or potential carcinogens.
PCBs/PCTs are toxic, causing genetic effects and mortality to fauna. They are
accumulated to a very great extent by fauna and there are many literature
references to concentration factors of over 100,000 - in other words, an
infinitesimal concentration in a water may be matched by 100,000 times that
amount in the tissue of fish or animals normally resident in that water. When
these toxicants enter the food chain, through consumption of fish for example,
there is a health risk to man.
PAGE 76
GUIDELINE AMBIENT ENVIRONMENT STANDARDS FOR ETHIOPIA
34 POLYCYCLIC AROMATIC HYDROCARBONS
Chemical Symbol or Formula: Not applicable [Physical parameter].
Standard: 2 µg/l (Total of 6 specified).
Percentage Compliance Required: 100% of all monitoring data must comply with the
standard.
Units Used for Analytical Results: mg/l PAH [or specific PAH compound(s)].
Reference Method(s) of Analysis:
Method Type Complexity APHA Reference
Liquid-Liquid Extraction Chromatographic Method D 6440-B
Liquid-Liquid Extraction Gas Chromatographic/Mass
Spectrometric Method
D 6440-C
Introduction This term, while strictly applicable to very many substances, has been defined
as applying to six specific compounds:
• Fluoranthene
• 3,4-benzofluoranthene [benzo(b)fluoranthene]
• 11,12-benzofluoranthene [benzo(k)fluoranthene]
• 3,4-benzopyrene [benzo(a)pyrene]
• 1,12-benzoperylene [benzo(ghi)perylene]
• indeno(l,2,3-cd)pyrene
The compounds covered are the six originally identified by the WHO.
It may be useful to comment on the nomenclature of these compounds and
related materials. They are so-called aromatic compounds, the term being used
for those substances containing the "aromatic ring" (i.e. the cyclic molecular
structure of benzene) a basic element of their composition. As the substances
contain more than one such ring, they are termed polycyclic (or sometimes,
poly- aromatic compounds). The compounds are hydrocarbons - i.e. they consist
of the elements carbon and hydrogen only.
The alternative often-used designation - "polynuclear aromatic hydrocarbons" •
arises from the (inaccurate) use by organic chemists of the word "nucleus" to
refer to the benzene ring structure. As there is more than one such ring in these
compounds they are termed "polynuclear."
All of these materials are complex organic molecules which originate typically
in the combustion of organic compounds. Their analysis, like that of many other
so-called micropollutants, is difficult, but the procedures are justified because of
the potential health hazards posed by the PAH. The listed compounds can be
determined relatively easily, albeit with advanced instrumental techniques, and
their presence is also taken as indicative of the possible occurrence of other
undesirable aromatic compounds. While all have been regarded previously as
carcinogens, the six listed compounds comprising the most widely found such
group in the environment, by far the most hazardous compound among them is
benzo(a)pyrene [3,4-benzopyrene].
PAGE 77
GUIDELINE AMBIENT ENVIRONMENT STANDARDS FOR ETHIOPIA
Occurrence Synthetic compounds occurring in soot, tar, vehicle exhausts, combustion
products of hydrocarbon fuels
Effect Carcinogens of greater or lesser potency.
35 SELENIUM
Chemical Symbol or Formula: Se.
Standard: 10 µg/l (Total of 6 specified).
Percentage Compliance Required: 100% of all monitoring data must comply with the
standard.
Units Used for Analytical Results: µg/l Se.
Reference Method(s) of Analysis:
Method Type Complexity APHA Reference
Sample Preparation B 3500-Se-B
Atomic Absorption Spectrometric Method C 3500-Se-C
Inductively Coupled Plasma Method D 3500-Se-I
Colorimetric Method B 3500-Se-D
Introduction Selenium is a non-metallic element similar to sulphur. Selenium occurs in five
oxidation states, namely, -II, 0, II, IV and VI, of which the tetravalent state is
the most common. Small quantities of selenium are essential to animals and
bacteria, where it is important in certain enzyme systems, but selenium is
apparently not essential for plants.
Occurrence Selenium occurs naturally as ferric selenite, calcium selenate, as elemental
selenium and in organic compounds derived from decayed plant tissue.
Although selenium occurs in some natural waters, it is usually in nanogram
quantities.
Selenium may occur at increased concentrations in water bodies subject to
industrial pollution, or in the vicinity of industrial activities utilising or
discharging selenium or selenium compounds. Industries that use selenium in
their processes, or in their products, include:
• the paint industry;
• the food processing industry;
• the steel industry;
• vehicle and aircraft plating industries;
• the pesticide industry;
• the glass and ceramics industries;
• the dye manufacturing industry;
• the rubber industry; and
• the metal alloy and electrical apparatus industries.
PAGE 78
GUIDELINE AMBIENT ENVIRONMENT STANDARDS FOR ETHIOPIA
Effects Because these are chemical similarities between selenium and sulphur, selenium
can replace sulphur in some biologically important substances and thereby
cause toxic effects. The toxic effects are similar in cold- and warm-water
adapted fish.
Selenium toxicity effects observed in fish include changes in feeding behaviour
and equilibrium, pathological changes, deformities, haematological (blood)
changes and death. Fish are generally less sensitive to selenium than are
invertebrates. Toxic effects of selenium that have been recorded in invertebrates
include immobilisation, reduced survival and reduced reproduction.
Selenium is passed up through the aquatic food chain and accumulates in the
liver of mammals and fish; it may therefore pose a threat to predators. Selenium
undergoes biological methylation in sediments, a process similar to mercury
methylation. Selenomethionine is ten times more toxic than inorganic selenium.
36 SILVER
Chemical Symbol or Formula: Ag.
Standard: 10 µg/l.
Percentage Compliance Required: 100% of all monitoring data must comply with the
standard.
Units Used for Analytical Results: µg/l Ag..
Reference Method(s) of Analysis:
Method Type Complexity APHA Reference
Atomic Absorption Spectrometric Method B/C 3500-Ag-B
Inductively Coupled Plasma Method D 3500-Ag-C
Dithizone Method B 3500-Ag-D
Introduction This metal is toxic, especially to micro-organisms, and its soluble salts are
excellent disinfectants. It is not considered particularly toxic to humans and, as
it is likely to be found only in very low levels (such that it would be practically
impossible to reach hazardous levels through consumption of water and food),
few limits have been set. However, it has been reported that restrictions on its
use were introduced to discourage the use of silver as a disinfectant because of
possible health effects if used unduly liberally. Nowadays, economic
considerations are likely to restrict the discharge of silver.
Occurrence Ores, industrial wastes (e.g. photographic effluents).
Effect Metal of varying toxicity.
PAGE 79
GUIDELINE AMBIENT ENVIRONMENT STANDARDS FOR ETHIOPIA
37 SULPHATE
Chemical Symbol or Formula: SO4
– –.
Standard: 200 mg/l.
Percentage Compliance Required: 100% of all monitoring data must comply with the
standard.
Units Used for Analytical Results: mg/l SO4
Reference Method(s) of Analysis:
Method Type Complexity APHA Reference
Ion Chromatographic Method C 4500-SO4
---B
Turbidimetric Method B/C 4500-SO4
---E
Introduction Sulphates exist in nearly all natural waters, the concentrations varying
according to the nature of the terrain through which they flow. They are often
derived from the sulphides of heavy metals (iron, nickel, copper and lead). Iron
sulphides are present in sedimentary rocks from which they can be oxidised to
sulphate in humid climates; the latter may then leach into watercourses so that
ground waters are often excessively high in sulphates. As magnesium and
sodium are present in many waters their combination with sulphate will have an
enhanced laxative effect of greater or lesser magnitude depending on
concentration. The utility of a water for domestic purposes will therefore be
severely limited by high sulphate concentrations, hence the limit of 250 mg/l
SO4.
Occurrence Rocks, geological formations, discharges and so on .
Effect In polluted waters in which the dissolved oxygen i.e. zero, sulphate is very
readily reduced to sulphide causing noxious odours.
38 TEMPERATURE
Chemical Symbol or Formula: Not applicable [Physical parameter]
Standard: Game fish Discharge must not result in
variation of more than 1.5 °C
temperature down stream of
the thermal discharge
Coarse fish Discharge must not result in
variation of more than 3 °C
temperature down stream of
the thermal discharge
PAGE 80
GUIDELINE AMBIENT ENVIRONMENT STANDARDS FOR ETHIOPIA
Percentage Compliance Required: 100% of all monitoring data must comply with the
standard.
Units Used for Analytical Results: Degrees Celsius [°C].
Reference Method(s) of Analysis:
Method Type Complexity APHA Reference
Laboratory and Field Method A 2550-B
Introduction Temperature may be defined as the condition of a body that determines the
transfer of heat to, or from, other bodies. As temperature increases viscosity,
surface tension, compressibility, specific heat, the ionization constant and the
latent heat of vaporization decrease, whereas thermal conductivity and vapour
pressure increase. The solubilities of the following gasses, H 2, N2, CO2 and O 2
decrease with increasing temperature.
Temperature plays an important role in water by affecting the rates of chemical
reactions and therefore also the metabolic rates of organisms. Temperature is
therefore one of the major factors controlling the distribution of aquatic
organisms. Natural variations in water temperature occur in response to
seasonal and diel cycles and organisms use these changes as cues for activities
such as migration, emergence and spawning. Artificially-induced changes in
water temperature can thus impact on individual organisms and on entire
aquatic communities.
Occurrence The temperatures of inland waters generally range from 5 - 30 °C. Thermal
characteristics of running waters are dependent on various features of the region
and catchment area, including:
• the latitude and altitude of the river;
• hydrological factors such as the source of water, the relative contribution of
ground water, and the rate of flow or discharge;
• climatic factors such as air temperature, cloud cover, wind speed, vapour
pressure and precipitation events; and
• structural characteristics of the river and catchment area, including
topographic features, vegetation cover, channel form, water volume, depth
and turbidity.
Surface waters exhibit daily and annual periodicity patterns, in addition to
longitudinal changes along a river course, and vertical stratification in deeper
waters. The minimum and maximum temperatures, and temperature ranges vary
depending on the factors mentioned above.
Anthropogenic sources which result in changes in water temperature include:
• discharge of heated industrial effluents;
• discharge of heated effluents below power stations;
• heated return-flows of irrigation water;
• removal of riparian vegetation cover, and thereby an increase in the amount
of solar radiation reaching the water;
• inter-basin water transfers; and
• discharge of water from impoundments.
PAGE 81
GUIDELINE AMBIENT ENVIRONMENT STANDARDS FOR ETHIOPIA
Effects The effects of temperature on aquatic organisms have been the subject of a
number of literature reviews, predominantly conducted in the northern
hemisphere. There is however, little information on the thermal tolerances of
the African aquatic organisms, or their responses to temperature change.
Aquatic organisms have upper and lower thermal tolerance limits, optimal
temperatures for growth, a preferred temperature range in thermal gradients, and
temperature limitations for migration, spawning and egg incubation. All
organisms associated with freshwater, excluding birds and mammals, are
poikilothermic. In other words, they are unable to control their body
temperatures and are therefore highly dependent on ambient water temperature
and very susceptible to changes in water temperature. Consequently, rapid
changes in temperature may severely affect aquatic organisms and lead to mass
mortality. Causes of thermal mortality in fish from acute exposure to elevated
temperatures are basically the result of metabolic malfunctions (including fluid-
electrolyte imbalance, alterations in gaseous exchange and osmoregulation,
hypoxia of the central nervous system and inactivation of enzyme systems).
Less severe temperature changes in water bodies may have sub-lethal effects or
lead to an alteration in the existing aquatic community. The qualitative and
quantitative composition of the biota can change as a result of population shifts
caused by the disappearance of stenothermal species (organisms adapted to a
very narrow range of temperatures) from heated waters, and replacement by
heat-tolerant species which increase in number and supplant the original species
in the ecosystem.
Many organisms have life cycles in which temperature acts as a cue for the
timing of migration, spawning or emergence. Artificial changes in temperature
can interfere with temperature cues, thereby altering normal development.
39 TOTAL DISSOLVED SALTS/SOLIDS
Chemical Symbol or Formula: Not applicable [Bulk parameter].
Standard: TDS concentrations should not be changed by > 15 %
from the normal cycles of the water body under
unimpacted conditions at any time of the year; and
The amplitude and frequency of natural cycles in TDS
concentrations should not be changed.
Percentage Compliance Required: 100% of all monitoring data must comply with the
standard.
Units Used for Analytical Results: mg/l solids (Dried at stated temperature).
Reference Method(s) of Analysis:
Method Type Complexity APHA Reference
Total Dissolved Solids Dried at 180 °C A 2540-C
Introduction The total dissolved solids concentration , is a measure of the quantity of all
compounds dissolved in water. The total dissolved salts concentration is a
measure of the quantity of all dissolved compounds in water that carry an
electrical charge. Since most dissolved substances in water carry an electrical
PAGE 82
GUIDELINE AMBIENT ENVIRONMENT STANDARDS FOR ETHIOPIA
charge, the TDSalts concentration is usually, used as an estimate of the
concentration of total dissolved solids in the water.
The TDSalts concentration is directly proportional to the electrical conductivity
(EC) of water. Because EC is much easier to measure than TDSalts, it is
routinely used as an estimate of the TDSalts concentration. Therefore, it has
become common practise to use the total dissolved salts concentration, as a
measure for the total dissolved solids.
Electrical conductivity (EC) is a measure of the ability of water to conduct an
electrical current. This ability is a result of the presence in water of ions such as
carbonate, bicarbonate, chloride, sulphate, nitrate, sodium, potassium, calcium
and magnesium, all of which carry an electrical charge. Many organic
compounds dissolved in water do not dissociate into ions (ionise), and
consequently they do not affect the EC.
Occurrence Natural waters contain varying quantities of TDS as a consequence of the
dissolution of minerals in rocks, soils and decomposing plant material, the TDS
concentrations of natural waters therefore being dependent at least in part on the
characteristics of the geological formations which the water has been in contact
with. The TDS concentration also depends on physical processes such as
evaporation and rainfall.
The TDS concentrations are generally
• Low in rainwater, less than 1 mg/l;
• Low in water in contact with granite, siliceous sand and well-leached soils,
less than 30 mg/l;
• Greater than 65 mg/l in water in contact with precambrian shield areas; and
• In the range of 200 - 1100 mg/l in water in contact with palaeozoic and
mesozoic sedimentary rock formations.
• High as a result of evapoconcentration, usually greater than 1100 mg/ml.
Salts accumulate as water moves downstream because salts are continuously
being added through natural and anthropogenic sources whilst very little is
removed by precipitation or natural processes. Domestic and industrial effluent
discharges and surface runoff from urban, industrial and cultivated areas are
examples of the types of sources that may contribute to increased TDS
concentrations. Evaporation also leads to an increase in the total salts.
Effects Plants and animals possess a wide range of physiological mechanisms and
adaptations to maintain the necessary balance of water and dissolved ions in
cells and tissues. This ability is extremely important in any consideration of the
effects of changes in total dissolved solids on aquatic organisms.
The individual ions making up the TDS also exert physiological effects on
aquatic organisms.
Changes in the concentration of the total dissolved solids can affect aquatic
organisms at three levels, namely:
• effects on, and adaptations of, individual species;
• effects on community structure; and
• effects on microbial and ecological processes such as rates of metabolism
and nutrient cycling.
PAGE 83
GUIDELINE AMBIENT ENVIRONMENT STANDARDS FOR ETHIOPIA
The rate of change of the TDS concentration, and the duration of change,
appears to be more important than absolute changes in the TDS concentration,
particularly in systems where the organisms may not be adapted to fluctuating
levels of TDS. Seasonal timing of the change in TDS concentration may also
have important synergistic effects with water temperature on the total
community composition and functioning. Organisms adapted to low-salinity
habitats are generally sensitive to changes in the TDS concentration.
40 TOTAL SUSPENDED SOLIDS
Chemical Symbol or Formula: Not applicable [Physical parameter].
Standard: ≤ 25 mg/l (annual mean)
50 mg/l (maximum value)
Units Used for Analytical Results: mg/l solids (Dried at stated temperature).
Reference Method(s) of Analysis:
Method Type Complexity APHA Reference
Total Suspended Solids Dried at 103-105 °C A 2540-D
Introduction The total suspended solids (TSS) concentration is a measure of the amount of
material suspended in water. This definition includes a wide range of sizes of
material, from colloids (0.1 µm) through to large organic and inorganic
particulates.
The concentration of suspended solids increases with the discharge of sediment
washed into rivers due to rainfall and resuspension of deposited sediment. As
flow decreases the suspended solids settle out, the rate of which is dependent on
particle size and the hydrodynamics of the water body.
Water turbidity in the southern hemisphere is generally considered to be
equivalent to some measure of the concentration of suspended solids. Turbidity
is an expression of the optical property that causes light to be scattered and
absorbed rather than transmitted in straight lines through a water sample. The
scattering of light is caused by suspended matter such as clay, silt and finely
divided organic material, while the absorption of light is caused by inorganic
matter, plankton and other microscopic organisms and soluble coloured organic
compounds, such as fulvic, humic and tannic acids.
Correlation of turbidity with the concentration of suspended solids (mass/unit
volume) is difficult because the size, shape and refractive index of particulates
affects the light scattering properties of the suspension. The relationship
between turbidity and suspended solids may however, be determined on a site-
specific basis. A turbidimeter, calibrated with consideration of the site-specific
characteristics, may then potentially be used to monitor suspended solids.
Occurrence Natural variations in rivers often result in changes in the TSS, the extent of
which is governed by the hydrology and geomorphology of a particular region.
In general, all rivers become highly turbid and laden with suspended solids
during the rainy season. The major part of suspended material found in most
natural waters is made up of soil particles derived from land surfaces. Erosion
of land surfaces by wind and rain is a continuous and natural process. However,
PAGE 84
GUIDELINE AMBIENT ENVIRONMENT STANDARDS FOR ETHIOPIA
land use practices such as overgrazing, non-contour ploughing, removal of
riparian vegetation and forestry operations accelerate erosion and result in
increased loads of suspended solids in rivers.
Increases in total suspended solids may also result from anthropogenic sources,
including:
• discharge of domestic sewage,
• discharge of industrial effluents (such as the pulp/papermill, china-clay, and
brick and pottery industries),
• discharge from mining operations,
• fish-farm effluents (mostly organic suspended solids) and
• physical perturbations from road, bridge and dam construction.
Effects In turbid waters light penetration is reduced, leading to a decrease in
photosynthesis. The resultant decrease in primary production reduces food
availability for aquatic organisms higher up the food chain. Suspended solids
may interfere with the feeding mechanisms of filter-feeding organisms such as
certain macroinvertebrates, and the gill functioning, foraging efficiency (due to
visual disturbances) and growth of fish.
Suspended solids that settle out may smother or abrade benthic plants and
animals, and may result in changes to the nature of the substratum. This may
then lead to changes in the structure of the biotic community by the decline of
these organisms, through the replacement with organisms which burrow in soft
sediments. Sensitive species may be permanently eliminated if the source of the
suspended solids is not removed.
The recovery of a stream from sediment deposition is dependent on the
elimination of the sediment source and the potential for the deposited material
to be flushed out by stream flow.
PAGE 85
GUIDELINE AMBIENT ENVIRONMENT STANDARDS FOR ETHIOPIA
41 TETRACHLOROETHYLENE
Chemical Symbol or Formula: C2Cl4.
Standard: 10 µg/l.
Percentage Compliance Required: 100% of all monitoring data must comply with the
standard.
Units Used for Analytical Results: µg/l C2Cl4.
Normal Method(s) of Analysis: Gas Chromatography [B/C].
Reference Method(s) of Analysis:
Method Type Complexity APHA Reference
Purge and Trap Packed-Column Gas Chromatographic/Mass
Spectrometric Method I
C 6210-B
Purge and Trap Packed-Column Gas Chromatographic/Mass
Spectrometric Method II
C 6210-C
Purge and Trap Capillary Column Gas
Chromatographic/Mass Spectrometric Method
C 6210-D
Purge and Trap Packed-Column Gas Chromatographic
Method I
C 6230-B
Purge and Trap Packed-Column Gas Chromatographic
Method II
C 6230-C
Purge and Trap Capillary Column Gas Chromatographic
Method
C 6230-D
Introduction Information: Synonyms for tetrachloroethylene are tetrachloroethene and
perchloroethylene. It is the most commonly used dry-cleaning solvent. As with
all chlorinated solvents, this substance should be handled with care, and in well-
ventilated areas.
Occurrence Synthetic solvent used extensively in dry-cleaning industry; also used to a
significant extent for degreasing metals.
Effect Toxic solvent which can cause narcosis, dermatitis and ultimately fatal
intoxication. However, when handled according to proper procedures and with
adequate ventilation, tetrachloroethylene may be used without problems.
PAGE 86
GUIDELINE AMBIENT ENVIRONMENT STANDARDS FOR ETHIOPIA
42 THALLIUM
Chemical Symbol or Formula: Tl.
Standard: 5 µg/l.
Percentage Compliance Required: 100% of all monitoring data must comply with the
standard.
Units Used for Analytical Results: µg/l Tl.
Reference Method(s) of Analysis:
Method Type Complexity APHA Reference
Atomic Absorption Spectrometric Method B/C 3500-Tl-B
Inductively Coupled Plasma Method D 3500-Tl-C
Introduction The metal is used at 2-3% concentration in rodent poisons, and is also used in
the electrical components industry.
Occurrence Minerals, but more often from discharges.
Effect Causes a wide variety of effects including nausea, vomiting, pain and,
ultimately, death.
43 TRICHLOROETHYLENE
Chemical Symbol or Formula: C2HCl3.
Standard: 5 µg/l.
Percentage Compliance Required: 100% of all monitoring data must comply with the
standard.
Units Used for Analytical Results: µg/l C2HCl3.
Reference Method(s) of Analysis:
Method Type Complexity APHA Reference
Purge and Trap Packed-Column Gas Chromatographic/Mass
Spectrometric Method I
C 6210-B
Purge and Trap Packed-Column Gas Chromatographic/Mass
Spectrometric Method II
C 6210-C
Purge and Trap Capillary Column Gas
Chromatographic/Mass Spectrometric Method
C 6210-D
Purge and Trap Packed-Column Gas Chromatographic
Method I
C 6230-B
Purge and Trap Packed-Column Gas Chromatographic
Method II
C 6230-C
Purge and Trap Capillary Column Gas Chromatographic
Method
C 6230-D
PAGE 87
GUIDELINE AMBIENT ENVIRONMENT STANDARDS FOR ETHIOPIA
Introduction Trichloroethylene is used in the manufacture of organic chemicals and
pharmaceuticals, and it also has some medical uses.
Occurrence Synthetic solvent used in various industrial and manufacturing processes (e.g.
solvent for paints, varnishes, resins etc); used in dry-cleaning and in metals
degreasing.
Effect Potential carcinogen. Causes narcosis and effects similar to alcohol inebriation.
See also "Tetrachloroethylene," which is a very similar compound.
44 URANIUM
Chemical Symbol or Formula: U.
Standard: 5 µg/l.
Percentage Compliance Required: 100% of all monitoring data must comply with the
standard.
Units Used for Analytical Results: mg/l U.
Normal Method(s) of Analysis: Radiometric or Fluorometric techniques [D]
There are atomic absorption spectrometric procedures for
uranium analysis but (ICP analysis excepted) their
sensitivity is generally inadequate for very low levels.
Reference Method(s) of Analysis:
Method Type Complexity APHA Reference
Radiochemical Method D 7500-U-B
Introduction This radioactive element is used in the nuclear industry and is thus far from
being universally encountered.
Occurrence Rare natural occurrence; equally rare in effluents
Effect Highly toxic, with a variety of effects leading ultimately to death.
PAGE 88
GUIDELINE AMBIENT ENVIRONMENT STANDARDS FOR ETHIOPIA
45 VINYL CHLORIDE
Chemical Symbol or Formula: C2H3Cl.
Standard: 5 µg/l.
Percentage Compliance Required: 100% of all monitoring data must comply with the
standard.
Units Used for Analytical Results: µg/l C2H3Cl.
Reference Method(s) of Analysis:
Method Type Complexity APHA Reference
Purge and Trap Packed-Column Gas Chromatographic/Mass
Spectrometric Method I
C 6210-B
Purge and Trap Packed-Column Gas Chromatographic/Mass
Spectrometric Method II
C 6210-C
Purge and Trap Capillary Column Gas
Chromatographic/Mass Spectrometric Method
C 6210-D
Purge and Trap Packed-Column Gas Chromatographic
Method I
C 6230-B
Purge and Trap Packed-Column Gas Chromatographic
Method II
C 6230-C
Purge and Trap Capillary Column Gas Chromatographic
Method
C 6230-D
Introduction Although a very reactive monomer which forms plastic polymers very easily, it
is almost inevitable that in some cases the resultant polymer - the most common
of which is polyvinyl chloride or PVC - will contain vestigial amounts of vinyl
chloride itself. Thus, in the first use, in particular, of vessels made of PVC there
is the possibility of residual monomer gaining access to water..
Occurrence Synthetic gaseous compound which polymerises very readily and is an
important raw material in the manufacture of plastics. It is also used as a
refrigerant.
Effect It is a suspected causative agent of liver cancer.
46 ZINC
Chemical Symbol or Formula: Zn.
Standard: Zinc (µg/l) Hardness (mg/l CaCO3)
30 10
200 50
300 100
500 500
PAGE 89
GUIDELINE AMBIENT ENVIRONMENT STANDARDS FOR ETHIOPIA
Percentage Compliance Required: 100% of all monitoring data must comply with the
standard.
Units Used for Analytical Results: µg/l Zn
Reference Method(s) of Analysis:
Method Type Complexity APHA Reference
Atomic Absorption Spectrometric Method B/C 3500-Zn-B
Inductively Coupled Plasma Method D 3500-Zn-C
Dithizone Method II B 3500-Zn-E
Zincon Method B 3500-Zn-F
Introduction Zinc, a metallic element, is an essential micronutrient for all organisms as it
forms the active site in various metalloenzymes. Zinc occurs in two oxidation
states in aquatic ecosystems, namely as the metal, and as zinc(II).
In aquatic ecosystems the zinc(II) ion is toxic to fish and aquatic organisms at
relatively low concentrations.
Occurrence Zinc occurs in rocks and ores and is readily refined into a pure stable metal. It
can enter aquatic ecosystems through both natural processes such as weathering
and erosion, and through industrial activity.
In aqueous solutions zinc is amphoteric, that is, it dissolves in acids to form the
hydrated cations Zn 2+ and in strong bases it forms zincate anions (probably of
the form Zn(OH2−)4 ). Organozinc complexes and compounds can also be
formed. In most natural waters zinc exists mainly as the divalent cation, which
is the potentially toxic form. The proportion of other forms such as inorganic
compounds like ZnCO3 ; stable organic complexes like Zn-cysteinate; or
colloids like Zn2+ -clay or Zn2+ -humic acid, depends on the chemistry of the
water. The greatest dissolved zinc concentrations will occur in water with low
pH, low alkalinity and high ionic strength. Chemical speciation of zinc is
affected primarily by pH and alkalinity.
Soluble zinc salts (for example, zinc chloride and zinc sulphate) or insoluble
precipitates of zinc salts (for example, zinc carbonate, zinc oxide and zinc
sulphide) occur readily in industrial wastes. The carbonate, hydroxide and oxide
forms of zinc are relatively resistant to corrosion and are used extensively in the
following industries:
• metal galvanising;
• dye manufacture and processing;
• pigments (paints and cosmetics);
• pharmaceuticals; and
• fertilizer and insecticide.
Effects Zinc is a trace metal which is also an essential micronutrient in all organisms.
The requirement for trace elements frequently varies substantially between
species, but the optimal concentration range is generally narrow. Severe
imbalances can cause death, whereas marginal imbalances contribute to reduced
fitness.
The lethal effect of zinc on fish is thought to be from the formation of insoluble
compounds in the mucus covering the gills. Sub-lethal concentrations at which
PAGE 90
GUIDELINE AMBIENT ENVIRONMENT STANDARDS FOR ETHIOPIA
toxic effects are evident depend on the concentration ratio of zinc to copper,
since zinc interferes with copper absorption. Observed symptoms include
depressed white blood cell-thrombocyte counts. Observed effects of prolonged
exposure to sublethal concentrations of zinc in fish fry include oedema and liver
necrosis.
Although invertebrate responses to zinc toxicity vary, molluscs are generally
more resilient than are other organisms. Sub-lethal effects include reduced rates
of shell growth, oxygen uptake and larval development. Algal photosynthesis
can be inhibited by zinc.
47 INFORMATION SOURCES
The following information sources were utilised in the preparation of these standards:
• The Setting of Water Quality Objectives for Chemicals Dangerous to the Aquatic
Environment – List 1 Chemicals –In accordance with European Directive 76/464/EEC.
CSTE, The Scientific Advisory Committee On Toxicity and Ecotoxicity of Chemicals,
October 1993.
• South African Water Quality Guidelines, Department of Water Affairs and Forestry, 1996.
• Canadian Water Quality Guidelines. Prepared by the Task Force on Water Quality of the
Canadian Council of Resources and Environmental Ministers. 1987.
• Quality Criteria for Water. United States Environmental Protection Agency Office of
Water Regulations and Standards, Washington DC 20460. 1986.
• Australian Water Quality Guidelines. Australian and New Zealand Environmental and
Conservation Council. ANZECC 1992.
• Water Quality Assessment, A Guide to the use of Biota, Sediment and Water in
Environmental Monitoring. UNESCO/WHO/UNEP, 1996.
• Parameters of Water Quality, Interpretation and Standards, Irish Environmental Protection
Agency, 2001.
• Dangerous Substances in Water, A Practical Guide. Environmental Data Services Ltd
(ENDS). 1992.
• Environmental Quality Objectives and Environmental Quality Standards for the Aquatic
Environment. Irish Environmental Protection Agency, 1997.
• Standard Methods for the Examination of Water and Wastewater, 1998, (prepared and
published jointly by A.P.H.A., A.W.W.A & W.E.F) 20th Ed., American Public Health
Association, 1015 Fifteenth Street, N.W., Washington DC 20005, USA.
PAGE 91
GUIDELINE AMBIENT ENVIRONMENT STANDARDS FOR ETHIOPIA
APPENDIX 3
SOIL AND GROUNDWATER QUALITY
STANDARDS
.
PAGE 92
GUIDELINE AMBIENT ENVIRONMENT STANDARDS FOR ETHIOPIA
1 RISK ASSESSMENT
A risk assessment is an evaluation of environmental and health-related effects of contamination.
The purpose is to assess the need for remediation or protective measures. If contamination is found
to pose a significant risk to human health or the environment, remedial work or other protective
measures should be put in place.
Risk assessments appraise the specific circumstances of the contaminants in question, transport and
exposure pathways and potential receptors at risk in each given situation. This is the source-
pathway-receptor model. The risk assessment must be based on:
• The results of the investigations, including the nature and extent of contamination as well
as prevailing geological, hydrogeological and hydrological conditions.
• A hazard assessment pertaining to the contaminants of interest.
• A survey of possible ways of transport and exposure pathways
• Knowledge of the potential receptors exposed.
• Conceptual Model of the site.
A conceptual model of the site is an essential component of a risk assessment and gives a
representation of the environmental processes at a contaminated site including details of the source
of contamination and the potential pathways and receptors at risk. A specific risk assessment will
highlight interconnected ways and effects that may constitute a hazard to the receptor. It may also
be necessary to take ecotoxicological aspects into consideration.
A hazard assessment is a review of the inherent characteristics of a potential contaminant.
Qualitatively, a hazard may be described as carcinogenic, corrosive, toxic, etc. and effects may be
characterised as acute and more long term (chronic effects). Whenever possible, the hazard is
quantified by determining the concentration level at which harmful effects arise. Determining the
inherent hazard of a given contamination incident entails a comprehensive assessment of toxicity,
biodegradability, bioavailability, and mobility.
Risk is also assessed by considering the possible transport and exposure pathways. Three of the
most important considerations include; health considerations in connection with land use,
groundwater protection considerations and considerations regarding surface-water recipients and
soil.
It is important that the risk assessment is planned as an integral part of the site investigation work.
Soil contamination cannot be clearly distinguished from soil gas or groundwater contamination. In
the saturated zone, the space between soil particles is filled with groundwater. The contaminants
are in a state of dynamic equilibrium between soil particles and groundwater. Similarly, there is air
and water between the soil particles in the unsaturated zone and the volatile substances will reach a
dynamic equilibrium between soil, soil gas, and water. Thus, while distinction between the
contamination of soil, groundwater and soil gas may be difficult in a purely physical sense, it may
still be useful to carry out separate risk assessments in connection with land use, groundwater and
evaporation.
Criteria for soil quality have been established to be used in risk assessments in relation to land use.
Sites where the soil fully lives up to these criteria can be used without restriction for all purposes
including those that are highly sensitive to contamination. Furthermore, cut-off criteria have been
established for several contaminants. These criteria state the level at which it is necessary to
prevent all contact with the soil. It should be noted that compliance with soil quality criteria does
not necessarily ensure compliance with evaporation and groundwater criteria.
PAGE 93
GUIDELINE AMBIENT ENVIRONMENT STANDARDS FOR ETHIOPIA
At contaminated sites, indoor air in buildings as well as outdoor air may be unacceptably affected
by underlying contamination of soil or groundwater. The effect on the indoor and outdoor air
should be assessed in stages by various methods that have been constructed. In several stages,
theoretical calculation models are included. Risk assessment should be based on evaporation to the
overlying air and must not exceed the acceptable contamination contribution.
The risk of methane gas explosions in buildings on or in the immediate proximity of landfill sites
can also be assessed in stages.
Risk assessment of groundwater should be used to assess whether contamination of either soil or
groundwater contributes unacceptably to the contamination of groundwater resources. Groundwater
quality criteria have been established for use in risk assessments. Risk assessments should be based
on the aquifer complying with groundwater criteria at all points. Risk assessment can be carried out
in stages, starting with a simple assessment. If this assessment does not provide enough evidence of
the lack of risk, a more detailed risk assessment should be carried out taking sorption, dispersion
and degradation of the contaminants into account. Furthermore, the assessment of the effect on the
groundwater should be used to perform a risk assessment for surface water receptors where
groundwater discharges to or is hydraulically connected to surface waters.
It should be emphasised that the soil and groundwater criteria do not represent a risk analysis. A
specific risk analysis should take account of the local geological conditions and the sensitivity of
land use (site and adjacent land).
If the risk assessment establishes a risk to human health or the environment, residents on or in the
proximity of the site should be advised as to how to act until remediation can be implemented.
2 SOIL QUALITY STANDARDS
Standards for soil have been identified for a range of contaminants. In addition, cut-off criteria
have been identified for ten contaminants (metals, total PAH and Benxzo(a)pyrene). The Soil
Quality Standard (SQS) values and cut-off values are largely based on human toxicological data.
Most values have been determined by means of a risk assessment process which assumes a two
year old child,consuming 0.2g of soil a day as a target. Ecotoxicologial data has been taken into
consideration for 16 of the compounds assessed. Soil quality standard (SQS), cut-off values and
background values (based on total soil concentrations) are listed in Table 1 and 2.
Remediation is required if the concentration of contaminants exceeds the cut-off value. If the
concentration is between the SQS and the cut-off values, remediation is not required however
measures to reduce exposure may have to be implemented. Cut-off values have been identified for
ten compounds due to their low mobility, making it relatively easy to implement measures to
reduce exposure. They are also the contaminants most frequently encountered in topsoil from both
point sources and non-point sources.
When interpreting analytical data against the SQS values, data from distinguishable soil horizons
should be assessed separately to prevent data from contaminated soil horizons becoming diluted.
Similarly data from hot spots should also be considered separately to data from other parts of the
site.
For compounds that can lead to adverse chronic health effects average concentrations need to meet
the SQS in order to avoid risk of contamination. In the case of compounds with acute health
effects such as arsenic, the average concentration should not exceed the SQS and no more than
10% of the samples analysed should exceed the SQS by more than 50%. If these criteria are not
met the area represented by the samples could pose an unacceptable risk and further investigation is
required to determine if remedial work or other isolation or protective measures are required.
PAGE 94
GUIDELINE AMBIENT ENVIRONMENT STANDARDS FOR ETHIOPIA
2.1 APPLICATION IN RELATION TO LAND USE .
Three categories of land use are identified:
• Very sensitive e.g. home with gardens, playgrounds, allotments
• Sensitive e.g. parks
• Non sensitive e.g. industrial areas
In the case of the very sensitive land uses there is considered to be no risk from exposure to
contamination provided that SQS are not exceeded up to 3m below ground level (bgl). If the SQS
are only met to a depth of 1m bgl there is considered to be no risk to site users under ordinary
conditions. If SQS are exceeded beyond 1m, any activities such as construction work should be
controlled to take the contaminated soil into account. Sensitive land uses can take place even if the
SQS are only met within the top 0.3m of soil provided the underlying soil in which the criteria are
exceeded is isolated. For sensitive and non-sensitive land uses SQS must be met in the depth of
utilisation, which is determined on a site by site basis. For parkland and other areas of open space
the depth of utilisation is generally considered to be 0.5m. For grassed and built up areas it is set at
0.25m.
Table 1 Soil Quality Standards. All units are in mg/kg dry weight (DW).
Substance Soil quality
criteria
Substance Soil quality
criteria
Acetone 8 Molybdenum 5
Arsenic 201(2) MTBE 5002
Benzene 1.52 Nickel 301
BTEX, total 102 Nickel 301
Cadmium 0.52 Nitrophenols
Chloroform 502 Mono- 1252
Chlorophenols, total 32 Di- 102
Pentachlorophenol 0.15 Tri- 302
Chromium, total 500 PAH, total 1.52,3
Chromium (VI) 20 Benzo(a)pyrene 0.12
Copper 5001 Dibenzo(a,h) anthracene 0.12
Cyanide, total 500 Petrol (C5-C10) 25
Cyanide, acid volatile 102 Petrol (C9-C16) 25
DDT 1 Phenols, total 701
Detergents, anionic 1,5002 Phthalates, total 2502
1,2-dibromomethane 0.022 DEHP 252
1,2-dichloroethane 1.42 Styrene 402
1,1-dichloroethylene 52 Turpentine, mineral (C7 – C12) 25
1,2-dichloroethylene 852 Tetrachloroethylene 52
Dichloromethane 82 Tetrachloromethane 52
Fluorides, inorganic 201 1,1,1-trichloroethane 2002
Gas oil (Total hydrocarbons (C5–C35)
5) 100 Trichloroethylene 52
Lead 402 Vinyl chloride 0.42
Mercury 1 Zinc 500
1: Based on acute harmful effects
2: Based on chronic harmful effects
3PAH, total defined as the sum of individual components: fluoranthene, benzyl(b+j+k)fluoranthene, benzyl(a)pyrene,
dibenzyl(a,h)anthracene, and ideno(1,2,3-cd)pyrene.
PAGE 95
GUIDELINE AMBIENT ENVIRONMENT STANDARDS FOR ETHIOPIA
Table 2 Criteria for necessary contamination cut-off, mg/kg, dry weight (DW)
Substance Level where
contamination cut off is
necessary
Arsenic 201
Cadmium 52
Chromium 1,000
Copper 5001
Lead 4002
Mercury 3
Nickel 301
Zinc 1,000
PAHs 152
Benzo(a)pyrene 12
Dibenzo(a,h)anthracene 12
1: Based on acute harmful effects
2: Based on chronic harmful effects
3 GROUNDWATER QUALITY STANDARDS
Groundwater Quality Standards (GQS) have been set with the objective of protecting groundwater
for the purposes of abstraction. They should be applied irrespective of whether there are any
abstractions in the area under consideration. Values have been set for a range of substances and are
listed in Table 3. Effectively the GQS values are concentrations of contaminants which can be
reduced to those of drinking water quality by means of standard water treatment processes
(oxidation and filtration).
The interpretation of analytical data against the GQS values is a staged process. If an initial study
indicates the values are being exceeded, a more detailed site specific risk assessment is required to
determine the contribution of soil contamination at a particular site to the groundwater. The risk
assessment can comprise up to three stages:
1. Mixing model close to source area which comprises a simple calculation of contaminant
concentrations in groundwater directly below the affected area. If these calculated values
exceed the GQS, remedial action needs to be taken or Step 2 needs to be carried out.
2. Mixing model downgradient of source area which is based on compliance with the GQS at
a point in the aquifer located within 100m downgradient or at a distance equalling one
years groundwater flow. The width of the mixing zone in the aquifer is determined as
vertical dispersion. If these calculated values exceed the GQS, remedial action needs to be
taken or Step 3 needs to be carried out.
3. Downgradient model based on sorption and natural degradation is based on compliance
with the GQS at the same distance as in Step 2 but the concentrations of the contaminants
are reduced due to degradation in the aquifer. If the concentrations of contaminants are
below the GQS, the specific degradation rate shall be determined either by field
PAGE 96
GUIDELINE AMBIENT ENVIRONMENT STANDARDS FOR ETHIOPIA
measurements or in the laboratory, and samples from monitoring wells must confirm that
degradation is actually taking place at the site.
Table 3 Standards for groundwater beneath contaminated sites.
Substance Groundwater Quality Standard
µg/l
Acetone 10
Arsenic 8
Benzene 1
Boron 300
Butylacetates 10
Cadmium 0.5
Chlorinated solvents (not vinyl chloride) 1
Chloroform As low as possible
Chromium, total 25
Chromium VI 1
Copper 100
Cyanide, total 50
DEHP 1
Detergents, anionic 100
1,2-dibromomethane 0.01
Diethylether 10
Isopropyl alcohol 10
PAH 1 0.2
Lead 1
Methylisobutylketone 10
Methyl-tert-butylether (MTBE) 30
Mineral oil, total 9
Molybdenum 20
Naphthalene 1
Nickel 10
Nitrophenols 0.5
Pentachlorophenol 0.01
Pesticides, total
Pesticides
Pesticides, persistent chlorinated
0.5
0.1
0.03
Phenols 0.5
Phthalates (not DEHP) 10
Styrene 1
Toluene 5
Vinyl chloride 0.2
Xylenes 5
Zinc 100
1 Sum of fluoranthene, benzo(b)fluoranthene, benzo(k)fluoranthene, benzo(a)pyrene,
benzo(g,h,i)perylene, indeno(1,2,3-cd)pyrene.
PAGE 97
GUIDELINE AMBIENT ENVIRONMENT STANDARDS FOR ETHIOPIA
3.1 CATIONS/ANIONS
This section presents proposals for the setting of environmental quality objectives and standards for
groundwater through the use of ‘guideline values’. It is not possible to assign a universal set of
standards for groundwater due to the natural variation in hydrochemistry. Therefore, indicators can
be used to assess groundwater status, which takes account of natural variation in quality. It should
be noted that a guideline value may not be applicable in some cases due to the widely variable
nature of groundwater bodies. This variability in groundwaters, in pristine condition, is due to the
influence exerted by the particular geology of the area. Where a guideline value is not applicable
the natural background quality of the groundwater should be taken into consideration instead.
Where there is interaction between groundwater and surface water and more sensitive standards
exist for the receiving water body, these should then apply. The guideline values can be used to
assist with the characterisation of groundwater bodies and to establish the need for additional
investigations or further action in the event of guideline values being exceeded.
Table 4 Standards for Cations and Anions.
Parameter Groundwater Guideline Value
(mg/l)
Alkalinity No abnormal change to background
Aluminium 0.2
Ammonia (as NH4) 0.15
Barium 0.1
Bicarbonate/Carbonate No abnormal change to background
Calcium 200
Chloride 30
Dissolved Oxygen No abnormal change to background
Fluoride 1
Iron 0.2
Magnesium 50
Manganese 0.05
Mercury 0.001
Nitrate (as NO3) 25
Nitrite (as NO2) 0.1
Orthophosphate 0.03
Potassium 5
Silica No abnormal change to background
Sodium 150
Sulphate 200
PAGE 98
GUIDELINE AMBIENT ENVIRONMENT STANDARDS FOR ETHIOPIA
4 SAMPLING
Soil and water sampling is carried out in the investigation phase and as part of monitoring
strategies to demonstrate compliance with an agreed remedial plan. The objective of sampling is to
obtain representative samples to describe the nature and extent of contamination, the soil and
groundwater. This enables a risk assessment to be carried out so that there is an adequate
foundation for managing the contamination.
A written sampling strategy should be agreed and should include provision for the following:
• Sample locations
• Targeted sampling of hot spots on the basis of knowledge of the historical activities at the
site.
• Near boundaries of known contaminated areas to identify the extent of contamination.
• In areas of a contamination-sensitive land use.
• Non-targeted sampling at the rest of the site. In order to reveal unknown contamination
and to achieve the best statistical coverage of the site, it may be beneficial to locate
investigation points according to specific rules. In such cases, sample fields/grids/nets
can be defined.
• Sampling depth
Guidance on soil and groundwater sampling is provided in BS ISO 10175:2001 Investigation of
Potentially Contaminated Sites.
4.1 - SOIL SAMPLING
Two soil samples are recommended to provide for geological descriptions and for chemical
analyses. Surface samples can be taken in the top 0.15m for direct ingestion and inhalation risks.
Sample sets are usually collected every 0.5m and one should be taken per soil layer or to reflect
any strata/contamination changes as a minimum. Depths should also take into account proposed
activities at the site e.g. removal of topsoil, main sewer services etc. Three or four samples should
be taken through the soil profile with the deepest sample being natural strata. If contamination has
penetrated the natural strata sampling should continue to depths where contamination is at
background concentrations or it is not physically possible to sample.
4.2 - METHODS OF INVESTIGATION FOR SAMPLING
• Shallow investigations using hand augers
• Trial pits/trench excavations for depths up to 3m
• Percussion hammer probehole for depth up to 10m
• Shell and auger/rotary cored or open boreholes for deeper samples
Shallow investigations up to 1m may be backfilled with the excavated material. Deeper
investigations should be sealed with a low permeability material to prevent possible cross
contamination.
BS ISO 10381:2 Soil Quality – Sampling Techniques specified standard methods of sampling.
PAGE 99
GUIDELINE AMBIENT ENVIRONMENT STANDARDS FOR ETHIOPIA
4.3 WATER SAMPLING
The objective of sampling is to obtain a water sample from the well which is representative of the
groundwater in the aquifer with regard to the parameters to be investigated. A monitoring well
should be screened at the depth of interest in the aquifer and an impermeable seal installed through
any low permeability layers penetrated by the borehole to prevent cross contamination. After
installation a well is developed to clear the screen and to achieve the best possible well efficiency.
A minimum of three wells should be installed in a triangular patter to provide an estimate of
groundwater flow direction. The depth to the water level and depth of the well should be taken
prior to sampling using a dip meter. The thickness of any dense non-aqueous phase liquids
(DNAPL) and light non-aqueous phase liquids (LNAPL) should be taken prior to purging.
Prior to sampling, a well should be purged to ensure that water from the aquifer surrounding the
monitoring well is sampled. As a general rule, the amount purged is a minimum of three well
volumes or until groundwater quality measurements (electrical conductivity, pH, temperature, Eh,
DO) have stabilised. In cases where a borehole is purged dry, the sample may be taken from the
groundwater that subsequently enter the borehole.
BS ISO 5667:11 Water Quality – Groundwater Sampling details standard methods of sampling.
Bailers or pumps can be used to take a sample. Low flow methods are particularly appropriate
where general parameters (e.g.Eh, DO) are important to the overall assessment of biogeochemical
conditions. Samples should be carefully transferred from the bailer or pump to the sample
container (appropriate to the contaminant). Samples should be filtered or preserved where relevant
(e.g. metals).
Methods of sampling, packing, handling, and storage should be adapted to the types of
contaminants being investigated e.g volatile organics, to ensure that there is no loss of contaminant
during the sampling and analysis procedure. Water samples should be stored in the dark at 4 OC.
The time from sampling to analysis should be kept to a minimum and in any case should not
exceed the recommended duration as specified in Standard Methods for the Examination of Water
and Wastewater, 1998. As far as possible, samples should be delivered to the laboratory on the
same day they are collected. If this is not possible, it should be noted on the analysis form.
Sampling field sheets and chain of custody forms should be completed, dated and signed and
should accompany the samples.
Three important considerations that should be taken into account when sampling include the
following:
• The equipment should not contaminate the sample.
• The equipment should not be made of materials which ad/absorb substances.
• The method should not bias the contaminant content of the sample.
It is good practice to take field measurement of general water quality parameters on site at the time
of sampling (O2, CO2, Eh (redox potential) and pH), as these may change with time.
5 INFORMATION SOURCES
The following information sources were utilised in the preparation of these standards:
• BSI (1999) BS 5930. Code of Practice for Site Investigations. BSI, London.
• BSI (2002) BS 15176. Characterisation of excavated soil for reuse. BSI, London.
• BSI (2001) BS 10175. Investigation of Potentially Contaminated Sites. Code of Practice.
BSI, London.
PAGE 100
GUIDELINE AMBIENT ENVIRONMENT STANDARDS FOR ETHIOPIA
• BSI (2002) BS 10381-2 Soil Quality – Sampling – Part 2 Guidance on Sampling
Techniques. BSI, London.
• ISO (1993) 5667-11 Water Quality – Sampling – Part 11 Guidance on the sampling of
groundwaters.
• Nathanail, J., Bardos, P. and Nathanail, P, 2002, Contaminated Land Management, Ready
Reference, Land Quality Press and EPP Publications. [ISBN 1 900995 06 9].
• Aspinwall & Co. for Scottish Environment Protection Agency, 1999, Review of
International Guideline and Intervention Values (Contaminated Land) Report.
• Standard Methods for the Examination of Water and Wastewater, 1998, (prepared and
published jointly by A.P.H.A., A.W.W.A & W.E.F) 20th Ed., American Public Health
Association, 1015 Fifteenth Street, N.W., Washington DC 20005, USA.
PAGE 101
GUIDELINE AMBIENT ENVIRONMENT STANDARDS FOR ETHIOPIA
APPENDIX 4
NOISE STANDARDS
PAGE 102
GUIDELINE AMBIENT ENVIRONMENT STANDARDS FOR ETHIOPIA
1 NOISE STANDARDS TO BE ACHIEVED AT NOISE SENSITIVE
LOCATIONS
The generation of excessive noise in the community can have undesirable effects on the population.
It can cause annoyance and disturbance to people at work or during leisure activities, disturbance to
sleep and possibly a deleterious effect on general physical and mental well being. All people are
not equally sensitive to the disturbing aspects of noise. There is a small but significant minority
which is more sensitive than others.
The objective of these guidelines is to minimise the amount of noise to which people, living or
working in sensitive locations, are exposed. Examples of such areas include domestic dwellings,
hospitals, schools, places of worship, or areas of high amenity.
The sensitivity to noise is usually greater at night-time than it is during the day, by about
10dB(A). Ideally, if the total noise level from all sources is taken into account, the noise level at
sensitive locations should be kept within the following values:
Limits in dB (A) Leq
Area Code Category of area Day timeNote 1 Night timeNote 2
A Industrial area 75 70
B Commercial area 65 55
C Residential area 55 45
Note-1: Day time reckoned in between 6.00 am to 9.00p.m
Note 2: Night time reckoned in between 9.00p.m. to 6.00am
In some particularly quiet areas, such as pastoral, rural settings, where the background noise levels
are very low, lower noise limits may be more appropriate. Audible tones and impulsive noise at
sensitive locations at night should be avoided, irrespective of the noise level. Because of the
variability in sensitivity to noise from one area to the next, it may be desirable to establish formal
noise zoning criteria under the planning code.
2 VIBRATION AND AIR OVERPRESSURE
In the case of quarrying and mining operations, the vibration levels from blasting should not exceed
a peak particle velocity of 12 mm/sec, measured in any three mutually orthogonal directions at a
receiving location when blasting occurs at a frequency of once per week, or less. For more
frequent blasting the peak particle velocity should not exceed 8mm/sec. These levels are for low
frequency vibration, i.e., less than 40 Hertz.
Blasting should not give rise to air overpressure values at sensitive locations which are in excess of
125 dB (Lin)max peak.*Ambient Noise Standards
PAGE 103
Page 1
Page 2
Page 3
Page 4
Page 5
Page 6
Page 7
Page 8
Page 9
Page 10
Page 11
Page 12
Page 13
Page 14
Page 15
Page 16
Page 17
Page 18
Page 19
Page 20
Page 21
Page 22
Page 23
Page 24
Page 25
Page 26
Page 27
Page 28
Page 29
Page 30
Page 31
Page 32
Page 33
Page 34
Page 35
Page 36
Page 37
Page 38
Page 39
Page 40
Page 41
Page 42
Page 43
Page 44
Page 45
Page 46
Page 47
Page 48
Page 49
Page 50
Page 51
Page 52
Page 53
Page 54
Page 55
Page 56
Page 57
Page 58
Page 59
Page 60
Page 61
Page 62
Page 63
Page 64
Page 65
Page 66
Page 67
Page 68
Page 69
Page 70
Page 71
Page 72
Page 73
Page 74
Page 75
Page 76
Page 77
Page 78
Page 79
Page 80
Page 81
Page 82
Page 83
Page 84
Page 85
Page 86
Page 87
Page 88
Page 89
Page 90
Page 91
Page 92
Page 93
Page 94
Page 95
Page 96
Page 97
Page 98
Page 99
Page 100
Page 101
Page 102
Page 103
Page 104
Page 105
Page 106
Page 107
Page 108
Phone numbers
- 100100
- 6000083001200190027003900560079011
- 7502603905808512172434
- 204601986
- 64103
- 10026
- 1900995069
- 952128374655647178
- 852638557911152026
- 2001100
- 70008301201802703905607911
- 650026003900590086012018025035
- 8008212182638537399
- 421700
- 1993566711
- 300802
- 907611162128364452
- 3014017
- 5101520253035
Phone numbers
- 3 (0.08-0.2
- 3 (0.14-0.17
- 8.5 2.6 3.8 5.5 7.9 11 15 20 26
- 8.0 0.82 1.2 1.8 2.6 3.8 5.3 7.3 9.9
- 6.5 0.026 0.039 0.059 0.086 0.12 0.18 0.25 0.35
- 6.0 0.0083 0.012 0.019 0.027 0.039 0.056 0.079 0.11
- 9.5 21 28 37 46 55 64 71 78
- 7.0 0.083 0.12 0.18 0.27 0.39 0.56 0.79 1.1
- 7.5 0.26 0.39 0.58 0.85 1.2 1.7 2.4 3.4
- 100 - 26
- 9.0 7.6 11 16 21 28 36 44 52
- 6.4 - 10.3
- 42 - 1 700
- 10 (0 - 100
- 200 - 1100
- 20460. 1986
- 5 10 15 20 25 30 35
- 1 900995 06 9
- (1993) 5667-11
Law clause
- section 1060
- section 4.5)
- Section 2.1.
- art 2
- art 50
- art 11
Filename extension
pdfCountries
etl_file_b:
1
1
etl_enhance_mapping_id_time_millis_i:
0
0
etl_enhance_mapping_id_b:
1
1
etl_filter_blacklist_time_millis_i:
0
0
etl_filter_blacklist_b:
1
1
etl_filter_file_not_modified_time_millis_i:
12
12
etl_filter_file_not_modified_b:
1
1
etl_enhance_file_mtime_time_millis_i:
0
0
etl_enhance_file_mtime_b:
1
1
etl_enhance_path_time_millis_i:
0
0
etl_enhance_path_b:
1
1
etl_enhance_entity_linking_time_millis_i:
1008
1008
etl_enhance_entity_linking_b:
1
1
etl_enhance_multilingual_time_millis_i:
2
2
etl_enhance_multilingual_b:
1
1
etl_export_solr_time_millis_i:
3
3
etl_export_solr_b:
1
1
etl_export_queue_files_time_millis_i:
1
1
etl_export_queue_files_b:
1
1
etl_time_millis_i:
3375
3375
etl_enhance_extract_text_tika_server_ocr_enabled_b:
1
1
etl_count_images_yet_no_ocr_i:
0
0
X-Parsed-By:
- org.apache.tika.parser.DefaultParser
- org.apache.tika.parser.pdf.PDFParser
- [org.apache.tika.parser.DefaultParser, org.apache.tika.parser.ocr.TesseractOCRParser, org.apache.tika.parser.jpeg.JpegParser]
etl_enhance_extract_text_tika_server_time_millis_i:
1159
1159
etl_enhance_extract_text_tika_server_b:
1
1
etl_enhance_pdf_ocr_time_millis_i:
9
9
etl_enhance_pdf_ocr_b:
1
1
etl_enhance_detect_language_tika_server_time_millis_i:
68
68
etl_enhance_detect_language_tika_server_b:
1
1
etl_enhance_contenttype_group_time_millis_i:
0
0
etl_enhance_contenttype_group_b:
1
1
etl_enhance_pst_time_millis_i:
1
1
etl_enhance_pst_b:
1
1
etl_enhance_csv_time_millis_i:
0
0
etl_enhance_csv_b:
1
1
etl_enhance_extract_hashtags_time_millis_i:
20
20
etl_enhance_extract_hashtags_b:
1
1
etl_enhance_warc_time_millis_i:
9
9
etl_enhance_warc_b:
1
1
etl_enhance_zip_time_millis_i:
1
1
etl_enhance_zip_b:
1
1
etl_clean_title_time_millis_i:
0
0
etl_clean_title_b:
1
1
etl_enhance_rdf_annotations_by_http_request_time_millis_i:
39
39
etl_enhance_rdf_annotations_by_http_request_b:
1
1
etl_enhance_rdf_time_millis_i:
0
0
etl_enhance_rdf_b:
1
1
etl_enhance_regex_time_millis_i:
70
70
etl_enhance_regex_b:
1
1
etl_enhance_extract_email_time_millis_i:
70
70
etl_enhance_extract_email_b:
1
1
etl_enhance_extract_phone_time_millis_i:
65
65
etl_enhance_extract_phone_b:
1
1
etl_enhance_extract_law_time_millis_i:
162
162
etl_enhance_extract_law_b:
1
1
etl_export_neo4j_time_millis_i:
668
668
etl_export_neo4j_b:
1
1
X-TIKA_content_handler:
ToTextContentHandler
ToTextContentHandler
X-TIKA_embedded_depth:
- 0
- 1
X-TIKA_parse_time_millis:
- 1091
- 50
X-TIKA_embedded_resource_path:
/image0.jpg
/image0.jpg
