Mutagenicity of the cysteine S-conjugate sulfoxides of trichloroethylene and tetrachloroethylene in the Ames test

► DCVCS and TCVCS mutagenicity investigated in the Ames Salmonella typhimurium TA100 strain. ► DCVCS and TCVCS were definite but weak mutagens in TA100. ► DCVCS and TCVCS were less mutagenic than the precursors DCVC and TCVC. ► DCVC and TCVC metabolite reactivity may explain differences in mutagenicity.