Mutagenicity of some congeners of benzidine in the Salmonella typhimurium assay system

The analogs of benzidine were assay for mutagenicity using Salmonella typhimurium TA-98 and TA-100 and a mouse liver enzyme preparation. Only 4-aminobiphenyl produced both frameshift and base pair substitution mutations and 3,3'-dichlorobenzidine was the only compound which was mutagenic without the mammalian enzyme factor. When hydrochloride salts of the parent compounds were made to improve their stability for animal feeding experiments, the mutagenicity for the Salmonella tester strains was reduced except for 3,3'-dimethylbenzidine. Animal feeding trials in mice are underway to determine the dose response relationship of tumor incidence and molecular configuration.