Ammonia is a colorless gas with a repellent odor. It is a naturally occurring compound in the environment; however, it is also released into the environment from ammonia production facilities and during the manufacture and use of ammonia-containing products. It is a central compound in the environmental cycling of nitrogen and is involved in major processes such as mineralization, nitrification, and nitrogen fixation. Ammonia is a key metabolite in mammals and plays an essential role in acid-base regulation and biosynthesis of purines, pyrimidines, and nonessential amino acids. However, ammonia is a toxic gas and in experimental animals, effects from acute exposure to ammonia gas have ranged from mild irritation of the respiratory system and mucous membranes to convulsions, acute pulmonary edema, coma, and death. Continuous or repeated exposure of animals to sublethal concentrations of ammonia gas have produced adverse effects on the respiratory tract, liver, kidneys, and spleen. Quantitative data on the toxic effects of ammonia in humans is limited. Accidental exposure of humans to unspecified concentrations of ammonia has resulted in burns of the eyes, skin, and respiratory tract and in death.

"June 1989." "EPA/600-8-89-052F." Includes bibliographical references (pages 4-1-4-18).