Formation of mutagenic N-nitroso compounds from the pesticides prometryne, dodine and carbaryl in the presence of nitrite at pH 1

Environmental chemicals including pesticides carrying secondary and tertiary amino groups are suggested to be a health hazard to man since potentially carcinogenic nitroso compounds may be formed in the presence of nitrite at low pH values resembling conditions in the human stomach. Nitrosation of the isopropylamino-triazine Prometryne, the n-dodecyl guanidine Dodine and the N-methylcarbamate carbaryl was investigated in the presence of HCl and acetic acid at pH 1 and excess sodium nitrite for 4 h at 37°C. The reaction products were extracted with CCl₄ and were analyzed qualitatively by infrared spectroscopy, nuclear-resonance spectrometry, GC/mass spectrometry and by spectrophotometry. All compounds investigated formed N-nitroso derivatives in the following yields: carbaryl 67%, Dodine 12% and Prometryne 14%. The N-nitroso derivatives per se were not or only slightly mutagenic to Escherichia coli K12 of Salmonella typhimurium TA 1538. However, significantly increased mutation frequencies were seen after metabolic activation by mouse-liver microsomes. These results add to the observations that among environmental chemicals not only those containing methyl- or ethyl-substituted amino groups form potentially carcinogenic nitroso derivatives but also those with iso-propylamino groups as well as alkyl-substituted guanidine derivatives.