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Carcinogenicity

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Description of key information

No evidence of carcinogenicity was seen in a study with ammonium sulphate.  An investigative study suggests that long-term exposure to drinking water containing ammonia (aqueous ammonia) may cause irritant gastritis which in turn may promote gastric carcinogenesis initiated by MNNG.  However there is no evidence that ammonia is carcinogenic.

Key value for chemical safety assessment

Carcinogenicity: via oral route

Endpoint conclusion
Dose descriptor:
NOAEL
67 mg/kg bw/day

Justification for classification or non-classification

No classification for carcinogenicity is proposed. there is no evidence that the substance is carcinogenic.

Additional information

No evidence of carcinogenicity was seen in a rat dietary study with ammonium sulphate (Ota et al, 2006). The NOAEL for this study was 0.6% (dietary level) equivalent to 256 and 284 mg/kg bw/day in males and females respectively [67 and 74 mg/kg bw/d ammonia equivalents].

In a non-standard mechanistic assay, Tsuji et al (1992) exposed MNNG-initiated rats to 0.01% ammonia solution via drinking water. Gastritis was seen in all animals, indicating a local irritnat effect. The incidence of gastric tumours was increased in treated animals, suggesting that ammonia may be acting as a promoter of carcinogenesis.

Solutions of hydrazine as 0.001%, methylhydrazine as 0.01%, methylhydrazine sulfate as 0.001%, and ammonium hydroxide as 0.3, 0.2 and 0.1% were administered continuously in the drinking water of 5- and 6-week-old randomly bred Swiss mice for their entire lifetime. Similarly ammonium hydroxide as a 0.1% solution was given to 7-week-old inbred C3H mice. Hydrazine and methylhydrazine sulfate significantly increased the incidence of lung tumors in Swiss mice, while methylhydrazine enhanced the development of this neoplasm by shortening its latent period. The ammonium hydroxide treatments in Swiss and C3H mice were, however, without carcinogenic effect, and did not inhibit the development of breast adenocarcinomas in C3H females, which are characteristic of these animals. The present study thus proves for the first time the carcinogenicity of methylhydrazine, provides further evidence of the tumor-inducing capability of hydrazine by itself and negates the possibility that the metabolite of hydrazine, ammonium hydroxide, could interfere in the development of neoplasia (Toth, 1972).