Backgrounder: Ammonia in the aquatic environment

What is Ammonia?

Ammonia is a naturally occurring compound made up of nitrogen and hydrogen which exists in two basic forms in the environment. It is required by most organisms for protein synthesis, and is a waste product of animal, fish and microbial metabolism.

What are common sources of Ammonia?

The principal releases of ammonia to the environment from human activity come from a number of industries, municipal wastewater effluents and agricultural activities.

The major sources of ammonia released to the aquatic environment are municipal wastewater treatment plants, which discharge a total of approximately 62 000 tonnes/year.

Ammonia is also released in large quantities into the environment by many industries such as pulp and paper mills, mines, food processing and fertilizer production. The majority of these releases go to the atmosphere.

Large agricultural releases of ammonia may result from two principal sources: fertilizer application, and intensive animal-rearing facilities. Both activities may results in significant releases of ammonia to the air, whereas intensive livestock activities may result in direct runoff to watercourses. The latter are not easily quantified, partly because of the diffuse nature of agriculture in Canada.

The largest quantifiable industrial releases come from ammonia produced in the manufacture of fertilizer, while municipalities are the largest non-industrial source due to their release of sewage effluents.

Why has ammonia been found to be toxic to the environment?

Under some conditions, depending on water pH and temperature, ammonia can become highly toxic to fish and other animals living in the water. These substances are not found to be bioaccumulative, or to transfer up the food chain.

Freshwater organisms are most at risk from releases of ammonia in the aquatic environment. Rainbow trout, freshwater scud, walleye, mountain whitefish and fingernail clams are some of the most sensitive species. Some of the observed effects include reduced reproductive capacity and reduced growth of young.

At several point sources in Canada, concentrations exceed the threshold levels of sensitive species such as rainbow trout. Concentrations of ammonia between 0.158 - 1.090 mg/L (158 and 1,090 µg/L) have been shown to be lethal to rainbow trout in 48 hour and 96 hour exposures.

Ammonia is considered to be entering the aquatic environment in a quantity or concentration or under conditions that have or may have an immediate or long-term harmful effect on the environment or its biological diversity.

Why was ammonia only assessed for environmental toxicity and not human health?

Evaluation of information at the outset of the assessment indicated that action taken to reduce release on the basis of effects on more sensitive environmental organisms would be protective for human health. The assessment focused on effects on more sensitive environmental organisms, exposed directly to ammonia in the aquatic environment, as recommended by the Ministers' Expert Advisory Panel on the Second Priority Substances List.

What are the next steps for the federal government to reduce the effects of ammonia the environment?

The conclusions of the scientific assessment of ammonia are based on an analysis of risks from releases of ammonia from municipal wastewater treatment plants. The assessment report recommends that options to reduce exposure to ammonia from municipal wastewater systems should be explored.

The assessment suggests that releases of ammonia from several other sources, such as runoff from manure-fertilized fields and intensive livestock operations, may also be causing environmental harm. However, it was not possible to quantify the extent and magnitude of these releases. The report recommends additional research on whether options to reduce exposure to ammonia from such sources should be undertaken.

Under the Canadian Environmental Protection Act, 1999 (CEPA), the federal government has two years to develop preventive or control measures for ammonia , and a further 18 months to finalize them.

A range of options is available to reduce or minimize releases of substances that are found to be toxic. They include regulatory and voluntary initiatives, economic measures, environmental quality or release guidelines, codes of practice and pollution prevention plans.

For more information please contact: Danie Dubé Environment Canada (819) 953-0356

Robert Liteplo Health Canada (613) 957-1880