Ammonia
(endorsed 1996)
Guideline
Based on aesthetic considerations (corrosion of copper pipes and fittings), the concentration of ammonia (measured as ammonia) in drinking water should not exceed 0.5 mg/L.
No health-based guideline value is set for ammonia.
General description
Ammonia dissolves rapidly in water to form an equilibrium mixture of free ammonia and the ammonium cation. It may be present in unchlorinated drinking water due to contamination of source water or through microbial metabolism. Ammonia is used in conjunction with chlorine to form chloramines to disinfect water supplies. Some residual will be present in the water, particularly if the chlorinator is not operating properly.
Ammonia is used commercially in animal feeds and fertilisers, and in the manufacture of fibres, plastics and explosives. Ammonia products are widely used as cleaning agents and food additives.
Most uncontaminated source waters have ammonia concentrations below 0.2 mg/L. High concentrations (greater than 10 mg/L) have been reported where water is contaminated with animal waste. Ammonia is unlikely to be detected in chlorinated supplies as it reacts quickly with free chlorine.
Ammonia in water can result in the corrosion of copper pipes and fittings, causing copper stains on sanitary ware. It is also a food source for some microorganisms, and can support nuisance growths of bacteria and algae, often with a resultant increase in the nitrite concentration.
The odour threshold of ammonia in water is 1.5 mg/L.
Ammonia can be an important indicator of pollution as it can be formed as an intermediate product in the breakdown of nitrogen-containing organic compounds, or of urea from human or animal excrement.
Food can contain substantial amounts of ammonia/ammonium and is the principal source of intake.
Typical values in Australian drinking water
In major Australian reticulated supplies concentrations of ammonia range up to 0.4 mg/L, but are generally less than 0.02 mg/L.
Treatment of drinking water
Ammonia concentrations in drinking water supplies can be reduced by chemical or biological oxidation of ammonia to nitrate.
Measurement
The concentration of ammonia in water can be determined by a number of methods including colorimetric, titrimetric and potentiometric techniques. For determination of low concentrations, the phenate colorimetric method is commonly used (APHA 4500-NH3 Parts D or H, 1992). The limit of determination for this method is 0.02 mg/L. Alternatively, the ammonia selective electrode method can be used (APHA 4500-NH3 Part F, 1992) with a limit of determination of 0.03 mg/L.
Both of these methods determine the total free ammonia and ammonium ion measured as ammonia (NH₃).
Health considerations
Ammonia is an important metabolite in humans and animals. It is formed in the liver by the deamination of amino acids, and in the gastrointestinal tract by the breakdown of food by enzymes and bacterial flora.
Only an extremely small proportion of the ammonia absorbed in the intestinal tract originates directly from food or water. The major part is formed in the gut as a by-product of the breakdown of food. Almost all ammonia is absorbed. It is then transported to the liver and used mostly in the urea cycle.
An extensive review and summary of the human and animal toxicity data for ammonia is available (IPCS 1986).
Ammonia has a toxic effect on humans only if the intake becomes higher than the detoxification capacity of the body. At doses above 32 mg ammonium per kilogram body weight per day (over 1000 mg/L) ammonium chloride influences the metabolism by shifting acid-base equilibrium, affecting glucose tolerance and reducing tissue sensitivity to insulin.
In studies with animals, high doses of ammonia (over 100 mg/kg body weight per day) have generally not produced any significant toxic effects. Ammonium hydroxide did not result in an increase in the incidence of cancer when given to mice in their drinking water over a lifetime; however, there is some evidence that ammonia may act with cancer-causing compounds to increase the incidence of tumours.
Ammonia and ammonium chloride have shown mutagenicity in some tests with bacteria and animal cells.
Derivation of guideline
Ammonia concentrations above 0.5 mg/L may attack copper pipes and fittings, or result in nuisance growths of microorganisms. Concentrations of ammonia that may cause health effects are unlikely to occur in drinking water supplies; accordingly, no health-based guideline is set.
References
APHA Method 4500- Part D (1992). Nitrogen (ammonia): Phenate method. Standard Methods for the Examination of Water and Wastewater, 18th edition. American Public Health Association, Washington.
APHA Method 4500- Part F (1992). Nitrogen (ammonia): Ammonia-selective electrode method. Standard Methods for the Examination of Water and Wastewater, 18th edition. American Public Health Association, Washington.
IPCS (International Programme on Chemical Safety) (1986). Ammonia. Environmental Health Criteria, 54. World Health Organization, IPCS.
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