Nitrosated methylcarbamate insecticides: effect on the DNA of human cells

Normal human skin cells were treated with six insecticide esters of N-methylcarbamic acid or their N-nitroso derivatives. The DNA of the cells was sedimented in alkaline sucrose gradients at various times after treatment. The insecticides used were aldicarb, baygon, BUX-TEN, carbofuran, landrin, and methomyl. Numerous single-strand breaks were apparent in the DNA of all the nitroso derivative-treated cells but not in the DNA of those treated with the parent insecticides. Since the effect of the nitroso derivatives on the DNA could be observed for at least 20 h after removal of the chemical from the cultures, the DNA repairing events normally occurring in human cells after damage initiated by these chemical agents was not repaired as UV-type DNA damage or ionizing-type DNA damage in human cells. These observations suggest that the human cellular DNA in vivo is irreversibly altered by nitrosated N-methyl carbamate insecticides resulting in numerous alkali-sensitive bonds.