Toxicity Profile for Nitrates (sodium and potassium salts) (1991)

Abstract

Nitrates have generally demonstrated a low acute oral toxicity in rats, mice and rabbits but may be moderately toxic in man, producing the blood disorder methaemoglobmaemia. Ingestion of a nitrate/nitrite mixture exacerbated the dermatitis of some patients, and the ingestion of nitrate has caused pains in the joints of two individuals. In studies involving repeated oral administration to a range of laboratory animal species, the principal site of toxic attack (particularly in rats) was the blood. Effects on the lung and thyroid have been reported in some studies. There is no convincing evidence that nitrate has adversely affected human reproduction. In guinea-pigs treated orally, adverse effects on reproduction (decreased numbers of litters and live births) were only seen at toxic maternal doses. Repeated oral doses induced chromosomal damage in rats and mice, and sperm head abnormalities in mice. Nitrates were also genotoxic in mammalian cells in culture and caused DNA damage in bacteria, but no evidence of mutagenicity was found in Ames bacterial tests. Studies of human populations have failed to show any convincing association between nitrate intake and cancer, the inconsistency of the findings from studies of stomach cancer arguing against a causative link. Negative results in rat and mouse feeding studies support the view that nitrate itself is non-carcinogenic. Nitrate may, however, be reduced in the body to nitrite which in turn may react with certain dietary components to form carcinogenic nitrosamines.