Agriculturally-related carcinogenic risk

Although all people are exposed throughout life to pesticides (during manufacture and use, in the environment, via the food chain), with the exception of vinyl chloride and the arsenic compounds, no human carcinogen pesticide is known. In experimental animals and short-term tests, however, many pesticides have proved to be carcinogenic or genotoxic. In order to elucidate possible modes of action related to genotoxicity (short-term tests) and carcinogenicity, data on 83 pesticides were analysed. A definitive promoter effect was demonstrated for five compounds, and a suspected promoter effect could be attributed to 16 compounds. Almost all were organohalogens. Ethylenthiourea and aminotriazole are also carcinogens, which induce tumours through hormonal imbalance. Ethylenthiourea is the degradation product and metabolite of certain ethylene-bisdithiocarbamate pesticides. Chlorphenol and chlorophenoxyacetic acid-type pesticides contain 2,3,7,8-tetrachlorodibenzo-paradioxin (TCDD) as a contaminant. TCDD has definite promoter action. Seventeen tumorigenic pesticides could be regarded as genotoxic, and similar activity could be suspected in three other carcinogenic pesticides. Many pesticides contain N-nitroso impurities in various amounts. Nitrosation of the original pesticide or its derivative, such as dialkylamines, alkyl-arylamines, methyleneimines, gives rise to the formation of N-nitroso compounds. Amides containing secondary amines, such as ethylcarbamate and alkylurea, could be nitrosated in vivo and in vitro. Most nitrosated pesticides are strong genotoxic carcinogens.