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Description of key information

A number of non-standard acute inhalation toxicity studies in the rat and mouse indicate that the substance is toxic by inhalation.

Key value for chemical safety assessment

Acute toxicity: via oral route

Endpoint conclusion
Dose descriptor:
350 mg/kg bw

Additional information

Acute oral toxicity

A waiver is proposed as the substance is a gas. However data are available (Smyth et al, 1941) which report an oral LD50 value of 350 mg/kg bw in the rat for ammonium hydroxide (aqueous ammonia), which is an aqueous solution of the substance.

Acute dermal toxicity

No data are available. A waiver is proposed as the substance is classified as corrosive. Dermal exposure to anhydrous ammonia will be dominated by local effects at the site of contact and significant systemic toxicity is unlikely.

Acute inhalation toxicity

The acute inhalation toxicity of the substance has been investigated in a number of studies in rats and mice, using non-standard short exposure periods. Further testing is not proposed as the substance is corrosive.

The acute inhalation toxicity of ammonia was assessed by exposing groups of male and female Wistar rats were to atmospheric ammonia for 10, 20, 40 or 60 minutes. Following exposure surviving rats were housed 5 per cage and observed for 14 days.

Clinical symptoms included eye irritation, wet noses and nasal discharge. Autopsy revealed haemorrhagic lungs. The 60 minute LC50 in male rats was 9850 mg/m³ air. The 60 minute LC50 in female rats was 13770 mg/m³ air (Appelman et al, 1982). The acute inhalation toxicity of ammonia gas was assessed in male albino mice. 100% mortality occurred at the highest concentration of 4860 ppm. At higher concentration, mortality usually occurred within 30 minutes of exposure initiation. The lungs of mice that died during exposure were congested with evidence of haemorrhage. The lungs of animals from every treatment group sacrificed displayed a mild to moderate degree of chronic focal pneumonitis histologically. The liver and heart weights were increased in animals that died during exposure to 4860 ppm. The 1 hour LC50 of ammonia gas to male mice is 4230 ppm (Kapeghian et al, 1982). The acute inhalation toxicity of ammonia gas to rats was determined during single exposure times of 5, 15, 30 or 60 minutes. Ammonia concentrations ranged from 6000 to 100 mg/m³. Ammonia poisoning in high concentrations (6000, 3000, 1000 mg/m³) was characterised by dyspnoea, irritation of the respiratory passgaes and eyes and cyanosis of the limbs. The animals were highly excitable and convulsed; the convulsions caused death. The LC50 during exposures of 5 and 15 minutes were 18693 mg/m³ and 12160 mg/m³, respectively, while for 30 and 60 minute exposures the values were 7035 mg/m³ and 7939 mg/m³ (Prokop'eva et al, 1973).

Justification for classification or non-classification

Anhydrous ammonia is listed on Annex I of Directive 67/548/EEC with classification as (R23) 'Toxic by inhalation'. The results of the available studies are consistent with this classification: no change is therefore proposed.