Nitrosation in Vitro and in Vivo by Sodium Nitrite, and Mutagenicity of Nitrogenous Pesticides

37 nitrogenous pesticides, belonging to the chemical groups of amides, carbamates and ureas, were nitrosated with sodium nitrite in vitro. The nitrosated compounds were tested for mutagenic activity in the bacterial spot test with Salmonella typhimurium his G 46. Those pesticides reacting positively in this test after nitrosation were then fed to mice in combination with sodium nitrite in order to assess the formation and mutagenicity of these nitroso compounds in vivo. With the already known exception of ethylenethiourea (ETU), no pesticide produced enhanced numbers of micronuclei in mouse bone-marrow erythrocytes when fed together with nitrite. Dose-response experiments with intraperitoneal injection of N-nitroso-ETU revealed an apparent no-effect level of about 15--18 mg/kg. The findings are correlated with the pesticide residues actually present in the environment.