Ammonia

Ammonia is a both a common naturally occuring chemical and is manufactured by man. It is very toxic to water-dwelling organisms. It is one of the gases important in "acid rain", playing an important part in the long range transport of the acidic pollutants. It can also contribute to localised soil acidification.

How is it released?

The majority of ammonia released to the environment is formed through natural processes during the degradation of animal wastes. Smaller man-made sources of ammonia include the use of fertilisers and the decomposition of wastes, as well as from some industrial processes.

Detailed information

Scientific name:

Ammonia (anhydrous); NH3

Other names:

Ammonia gas, ammonium hydroxide, aqua ammonia, ammonia water, aqueous ammonia, 0.88 ammonia (refers to the density of the saturated solution in water).

CAS Number:

7664-41-7

Ammonia is an important substance in the natural nitrogen cycle. The substance is formed from decaying organic matter, especially proteins. In aerobic soils and water, it is converted to nitric acid, which, along with dissolved ammonia itself, is the main form in which land plants take up the nitrogen they need for their growth. Land animals (including humans) excrete excess nitrogen in the form of urea - a compound of ammonia and carbon dioxide. Urea readily breaks down through microbial action, releasing ammonia. High levels of ammonia in babies' nappies can give rise to skin irritation ('nappy rash'). The total UK emissions of ammonia to the air reported to the UN/ECE was 350 ktonnes. Under the Gothenburg Protocol (1999) the UK is committed to reduce ammonia emissions to below 297 ktonnes for 2010.

Ammonia is commonly used for bleaching and cleaning, both industrially and in the home. It is used in many and varied industrial processes including the production of fertilisers, plastics, pharmaceuticals, explosives, rubber and petrochemicals. Ammonia also has anti-fungal properties and is used in the control of fungal growth on fruit.

In its pure state and under usual environmental conditions, ammonia exists as a colourless, pungent-smelling gas. It is alkaline, caustic and an irritant. Under high pressure, ammonia can be stored as a liquid. It is highly soluble in water. It reacts with acids to form ammonium salts.

Where is it released?

The majority of ammonia released to the atmosphere in the UK comes from the degradation of animal and human wastes (74%). Smaller man-made sources of release of ammonia include the use of fertilisers and the decomposition of vegetation and waste, as well as some industrial processes. Minor releases of ammonia include cigarette smoke and infants nappies; humans also emit ammonia in very low levels through sweating and breathing.

Local environmental effects

Ammonia is very toxic to aquatic organisms. Toxic concentrations of ammonia can be liberated from decomposing manure that is confined to a slurry pit or chicken house. Animals confined nearby may then inhale the gas. Vegetation may also be harmed by high local concentration of ammonia from animal excreta. Other local air impacts are likely to be restricted to odour issues as ammonia can be smelled in the air at quite low concentrations. The biological transformation of ammonium ions (formed when ammonia dissolves in water) to nitrate ions in soils (nitrification) and plant uptake both release acidity into the soil, contributing to soil acidification. Significant quantities released into the water can have severe short-term effects as ammonia is highly toxic to fish. In well-aerated waters, ammonia is converted to far less toxic nitrate ions by nitrifying bacteria. Low concentrations of ammonia occur normally in soils as part of the nitrogen cycle. It is an important source of nitrogen to crops and other plants. High levels of nitrogenous fertiliser use (as urea, ammonium nitrate etc) can result in the leaching of large quantities of nitrate into ground water, which may then be rendered unfit for human consumption, or require expensive treatment to reduce nitrate concentrations to acceptable levels before consumption.

Global environmental effects

Ammonia plays an important part in transporting acidic pollutants by the formation of relatively stable particles of ammonium sulphate and ammonium nitrate. Although ammonia is an alkaline gas, it contributes to acidification of soil through nitrification, and by combining with acid gases to form ammonium sulphate and nitrate aerosol particles, that then deposit from the atmosphere faster than either the acid gas or ammonia would deposit separately.

Possible health concerns

Excessive exposure to ammonia may affect the eye, lung, nose, skin and throat. The Environment Agency aims to ensure that environmental exposures are too low to harm human health.

Legislation

Why was this substance selected for the Pollution Inventory?

Included in : European Pollutant Emission Register (EPER) reporting requirements.

Standard risk phrases for the pure substance

The standard risk phrases provided here are generally those used by suppliers of chemicals to describe substances - for example on packaging materials. The most important source of these phrases are the CHIP Regulations - Chemicals (Hazard Information and Packaging for Supply) - provided by the Health and Safety Executive. Some substances do not have CHIP risk phrases and in these circumstances we have used other risk phrases, the sources of which are indicated.

CHIP Phrase(s) : T: Toxic; N: Dangerous to the Environment; C: Corrosive; R10: Flammable; R23: Toxic by inhalation; R34: Causes burns; R50: Very toxic to aquatic organisms

Controlling legislation and international agreements

Releases of ammonia are controlled under the UK Pollution Prevention and Control (PPC) Regulations 2000, which implement the EC Directive 96/61 on Integrated Pollution Prevention and Control. Its release to water is regulated under the are the 'Surface Waters (Dangerous Substances) (Classification) Regulations, 1997 (SI 1997/2560). In Europe ammonia releases to water are regulated under EC Directive 76/464: ?Pollution of the aquatic environment by dangerous substances? (plus daughter directives). Air emissions are also regulated under EC Directive 84/360/EEC Combating of air pollution from industrial plants. Relevant international legislation to air release of ammonia includes the UN/ECE Convention on Long-Range Transboundary Air Pollution and the Gothenburg UN/ECE Protocol to Abate Acidification, Eurtrophication and Ground-level Ozone.