Ammonia is a colorless gas with a strong pungent odor.
It is formed from the natural breakdown of manure, plants and animals. It is present in water, soil and air and acts as a source of nitrogen for plants and animals. Ammonia is also produced industrially, largely as a raw material in fertilizers. A smaller proportion is used to manufacture plastics, synthetic fibers and explosives. It is not persistent in the environment, but high levels may build up around waste disposal sites.