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Description of key information

Human exposures to ammonia have been reported in a medical screening study, a retrospective epidemiological study, in clinical cases and in several volunteer studies.

Additional information

The chronic effects of ammonia inhalation on industrial workers have been investigated in a key medical screening study (Holness et al, 1989). In the study, the exposed workers and control comparisons experienced ammonia levels of 9.2 and 0.3 ppm, respectively. Three workers were noted to have time weighted average ammonia concentrations in excess of 25 ppm. There were no differences between the two groups in the reporting of respiratory or cutaneous symptoms, sense of smell, baseline lung function, or change in lung function over a work shift at the beginning and end of a work week. No relationships were observed between level or length of ammonia exposure and lung function results. It was therefore concluded that exposure to ammonia at concentrations of up to 25 ppm is without adverse effects.


A retrospective epidemiological supporting study was carried out in a large petrochemical complex in Beijing, China to assess the association between petrochemical exposure and spontaneous abortion (Xu et al, 1998). In total, 2853 non-smoking women who were 20-44 years of age and had been pregnant at least once participated in the study. Women and their husbands were interviewed collecting information on reproductive history, pregnancy outcomes, employment history, alcohol consumption, indoor air pollution, and demographic variables. 97 women were exposed to ammonia in the occupational setting. Data analyses did not show any effect on spontaneous abortion (Odds Ratio: 1.2; 95% CI: 0.5-2.6), but actual exposure levels were unknown.


Further weight-of-evidence and supporting clinical cases were reported.


In a clinical case study, a 28 year-old male suffered 45% total body surface area of second and third degree burns as well as inhalational injury from an anhydrous ammonia explosion. The initial skin pH after submission to the hospital was 10 (Amshel et al., 2000). The severity of symptoms and tissue damage produced was directly related to the concentration of hydroxyl ions (ammonium hydroxide). Liquefactive necrosis resulted in superficial to full-thickness tissue loss. Clinical symptoms observed in such cases include hemoptysis, pharyngitis, pulmonary oedema, and bronchiectasis. Resulting ocular sequelae include iritis, glaucoma, cataracts, and retinal atrophy.


In another case study, a tanker truck carrying anhydrous ammonia fell off a highway, and released a dense cloud of anhydrous ammonia gas (Cruz 2009). Fifty-four people inhaled the gas and after ninety days, three people were still experiencing hoarseness and were examined. The authors assessed three patients with laryngeal sequelae due to anhydrous ammonia inhalation burn. They found a case of hyperemia and oedema, one case of granuloma of the posterior third portion of the left vocal cord, and one case of vocal cord adhesion. Treatment included corticosteroid medication and phonoaudiological treatment.


Several volunteer studies have been carried out to investigate the effects of exposure to gaseous ammonia. In a review of these studies the Us National Research council (NRC, 1979) concluded that ammonia can elicit the following effects: 400 ppm (= 278 mg/m3; in air) = Immediate throat irritation ; 700 ppm (= 487 mg/m³; in air) = Eye irritation; 1700 ppm (= 1182 mg/m3; in air) = Coughing ; 2500 - 6500 ppm (= 1738-4519 mg/m³; in air) = Life threatening after 0.5 hour; 5000 - 10000 ppm (= 348-6953 mg/m³; in air) = Mortality.