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Carcinogenicity

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Description of key information

Key value for chemical safety assessment

Justification for classification or non-classification

In conclusion, the available carcinogenicity data give no indication of a carcinogenic potential of sodium nitrite. Therefore, a classification concerning carcinogenity is not warranted.

Additional information

In a two-year chronic toxicity/carcinogenicity study [NTP, 2001] male and female F344/N rats were exposed to 0, 750, 1500 or 3000 ppm sodium nitrite (equivalent to average daily doses of approximately 0, 35, 70 or 130 mg/kg bw/day in males and 0, 40, 80 or 150 mg/kg bw/day in females) in drinking water. There were no clinical findings related to exposure. Methaemoglobin levels were measured at two weeks and three months. At both 2 weeks and three months, methaemoglobin levels were high at night when the rats were actively feeding and drinking and low during the day when the rats were less active. Methaemoglobin levels tended to increase with increasing dosage.

In a second two-year study [NTP, 2001] male and female B6C3F1 mice were exposed to 0, 750, 1500 or 3000 ppm sodium nitrite (equivalent to average daily doses of approximately 0, 60, 120 or 220 mg/kg bw/day for males and 0, 45, 90 or 165 mg/kg bw/day for females) in drinking water. There were no clinical findings related to exposure. At 12 months, no significant increase in methaemoglobin level was observed in either sex at any dose.

Based on the two-year studies, the NOAELs for rats were 130 mg/kg bw/day in males and 150 mg/kg bw/day in females. For mice the NOAELs were 220 mg/kg bw/day in males and 165 mg/kg bw/day in females.

Maekawa et al. (1982) reported about the carcinogenicity of sodium nitrite and sodium nitrate. Male and female rats were offered continuously concentrations of 0.25 or 0.125% sodium nitrate/rat/day via the drinking water over a study period of 2 years. The authors concluded that sodium nitrite did not have carcinogenic activity in rats.