Chemical impurity as the possible cause of nitrofen mutagenicity

The results of Salmonella mutagenicity tests with the herbicide nitrofen (2,4-dichlorophenyl-4-nitrophenyl ether, CAS 1836-75-5) reported in the literature seem to vary according to source or lot of the technical product. This behaviour could be reproduced in our experiments, and it could be traced to the varying content of bis(4-nitrophenyl) ether in nitrofen. Nitrofen samples with the highest bis(4-nitrophenyl) ether concentrations proved to exhibit also the highest mutagenic activities, while the one containing no bis(4-nitrophenyl) ether was also devoid of mutagenic activity towards Salmonella typhimurium TA 100.