High microsome-mediated mutagenicity of the 3,4-dihydrodiol of 7-methylbenz[a]anthracene in S. typhimurium TA 98.

7-Methylbenz[a]anthracene and the 1,2-, 3,4-, 5,6- and 8,9-dihydrodiols derived from this hydrocarbon have been tested for mutagenicity towards S. typhimurium TA 98 in the presence of rat-liver post-mitochondrial supernatant. At non-toxic concentrations, the mutagenicity of the non-K-region 3,4-dihydrodiol was more than ten-fold higher than that of the other K-region and non-K-region dihydrodiols and more than three-fold higher than that of the parent hydrocarbon. 1,1,1-Trichloropropene 2,3-oxide, an inhibitor of epoxide hydratase, increased the microsome-mediated mutagenicity of 7-methylbenz[a]anthracene but did not alter that of the four related dihydrodiols.