MUTAGENICITY OF CYCLOPENTA-FUSED POLYNUCLEAR AROMATIC-HYDROCARBONS AND A NONPOLAR FRACTION FROM A FUEL COMBUSTION SAMPLE IN A SALMONELLA FORWARD MUTATION ASSAY WITHOUT EXOGENOUS METABOLIC-ACTIVATION

A series of cyclopenta-fused polynuclear aromatic hydrocarbons (PAH) w ere tested for mutagenicity in a bacterial forward mutation assay base d on resistance to 8-azaguanine (8-AG) in Salmoneila typhimurium TM677 in the absence of Aroclor-induced rat liver postmitochondrial superna tant (PMS). All of the aceanthrylenes tested were mutagenic in the abs ence of PMS, whereas none of the acephenanthrylenes were active. The f ollowing mutagenic potency series expressed as the minimum detectable mutagen concentration (MDMC) in nmol/ml was obtained: aceanthrylene (A A) (5.5); cyclopent[h,i]aceanthrylene (CPAA) (18.2); 6-methylaceanthry lene (6-MeAA) (112); 1,2,6,7-tetrahydrocyclopent[ h,i]aceanthrylene (T HCPAA) (166); 1,2-dihydroaceanthrylene (DHAA) (298). Saturation of the cyclopenta rings or methylation at the 6-position of AA reduced, but did not eliminate, mutagenicity measured in the absence of PMS. AA was unusual because it was approximately 4-fold more mutagenic in the abs ence of PMS than in its presence. The other aceanthrylenes tested were 1.3-10.7 times more mutagenic in the presence of PMS than in its abse nce to give an MDMC potency series of: CPAA (3.8); 6-MeAA (10.5); AA ( 19.9); THCPAA (52.9); DHAA (229). Approximately 20% of the PMS-indepen dent mutagenicity in a combustion sample from ethylene burned under fu el-rich conditions was found in a fraction containing only non-polar, 4-7 ring PAHs, widely attributed to be mutagenic only in the presence of PMS, None of this mutagenicity could be attributed to aceanthrylene s, thus other non-polar PAHs appear to possess significant PMS-indepen dent mutagenicity as well.