Ammonia gas is a severe respiratory tract irritant. It is noticeable by smell at 0.6 to 53 ppm. Volunteers have first noticed nose and throat irritation at concentrations as low as 24 ppm after 2-6 hours exposure. A 10-minute exposure to 30 ppm was considered faintly irritating by 2/6 volunteers, while 50 ppm was considered moderately irritating by 4/6. Irritation of the nose and throat was noticeable in 5/10 and 10/10 volunteers after a 5-minute exposure to 72 or 134 ppm. At 500 ppm, immediate and severe irritation of nose, and throat occurs. Brief exposure to concentrations above 1500 ppm can cause pulmonary edema, a potentially fatal accumulation of fluid in the lungs. The symptoms of pulmonary edema (tightness in the chest and difficulty breathing) may not develop for 1-24 hours after an exposure. Numerous cases of fatal ammonia exposure have been reported, but actual exposure levels have not been well documented. If the victim survives, complete recovery may occur depending on the extent of injury to the respiratory tract and lungs. However, long-term respiratory system and lung disorders have been observed following severe short-term exposures to ammonia.

People repeatedly exposed to ammonia may develop a tolerance (or acclimatization) to the irritating effects after a few weeks. Tolerance means that higher levels of exposure are required to produce effects earlier seen at lower concentrations.

High levels of airborne ammonia gas dissolve in moisture on the skin, forming corrosive ammonium hydroxide. At 10000 ppm, ammonia is mildly irritating to moist skin. At 20000 ppm, the effects are more pronounced and 30000 ppm may produce chemical burns with blistering. These same exposure levels would be almost certainly fatal due to inhalation health effects.

Direct contact with liquified gas can cause frostbite and corrosive burns. Symptoms of mild frostbite include numbness, prickling and itching in the affected area. Symptoms of more severe frostbite include a burning sensation and stiffness of the affected area. The skin may become waxy white or yellow. Blistering, tissue death and gangrene may also develop in severe cases. Corrosive burns of the skin have resulted from direct contact with a jet of liquefied ammonia. Permanent scarring of the skin may result.

Exposure to 50 ppm or less for 5 minutes was not considered irritating by volunteers, while exposure to 72 ppm was irritating to a few individuals and 134 ppm was irritating and caused tearing. At 700 ppm, the gas is immediately and severely irritating.

Direct contact with the liquefied gas can cause frostbite and corrosive injury to eye. Permanent eye damage or blindness could result. Severe, permanent eye injury, including an almost complete loss of vision, has been reported following direct contact with liquefied ammonia gas.

Ingestion is not an applicable route of exposure for gases.

INHALATION; Despite design limitations, the small number of human population studies available have not shown significant effects in people with long-term occupational exposure to ammonia. No significant differences in lung function were observed in 58 workers exposed to 9.2 ppm ammonia for an average of 12.2 years compared to controls with very low exposure (less than 1 ppm). No conclusions can be drawn from one case report which described lung injury following long-term exposure to ammonia because the person was a long-term smoker. People with repeated exposure to ammonia may develop a tolerance (or acclimatization) to the irritating effects after a few weeks.

SKIN SENSITIZATION: Insufficient details are available to evaluate two single case reports of hives which developed in people occupationally exposed to ammonia. Previous history of allergies is not discussed and allergic sensitivity was not confirmed by patch testing in either case.

RESPIRATORY SENSITIZATION: One case report describes a chemical worker who developed an increased respiratory sensitivity to ammonia, inert iron yellow dust and cold air following a cold. It is unlikely that this case represents true respiratory sensitivity.

There is no credible evidence that ammonia can cause cancer. Very limited human information is available. A poorly conducted and reported study found an increased rate of lung, stomach, urinary tract and lymphatic cancer among workers in two ammonia plants. A single case report of nasal cancer was observed in a person exposed to an ammonia/oil mixture. No conclusions can be drawn from one poorly conducted animal study.

There is no human or animal information available.

There is no human or animal information available.

There is no information available.

Ammonia does not accumulate in the body. It is a normal body component and is normally present in all tissues constituting a metabolic pool. It is a by- product of protein and nucleic acid metabolism, and is a minor component of the diet. The ammonia-nitrogen is incorporated into amino acids, proteins and nucleic acids in the body. Ammonia may be excreted in the urine, principally as urea and ammonium salts, with some free ammonia, and there is also some elimination through sweat glands. Respiratory and fecal excretion is not significant.