Mutagenicity and tumor initiating activity of methylated benzo[b]fluoranthenes

The mutagenicity toward S. typhimurium TA 100 and tumor initiating activity on mouse skin of benzo[b]fluoranthene (BbF), 1-methylbenzo[b]fluoranthene (1-MeBbF), 3-MeBbF, 7-MeBbF, 8-MeBbF, 9-MeBbF, 12-MeBbF, 5,6-dimethylbenzo[b]fluoranthene (5,6-diMeBbF) and 1,3-diMeBbF were assayed. Dose-dependent mutagenic activity was observed for BbF, 3-MeBbF, and 1,3-diMeBbF; the other compounds were inactive at the doses tested. 3-MeBbF and 1,3-diMeBbF were strong tumor initiators, with activity greater than that of BbF. All the other compounds were less tumorigenic than BbF. The results suggest that the structural features favoring tumorigenicity of methylated non-alternant polynuclear aromatic hydrocarbons such as BbF are different from those favoring tumorigenicity of methylated alternant polynuclear aromatic hydrocarbons such as benzo[a]pyrene, chrysene and benz[a]anthracene.