CHRONIC AND INITIATION/PROMOTION SKIN BIOASSAYS OF PETROLEUM REFINERY STREAMS

Nine refinery streams were tested in both chronic and initiation/promotion (I/P) skin bioassays. In the chronic bioassay, groups of 50 C3H/HeJ mice received twice weekly applications of 50 mu l of test article for at least 2 years. In the initiation phase of the I/P bioassay, groups of CD-1 mice received an initiating dose of 50 mu l of test article for 5 consecutive days, followed by promotion with 50 mu l of phorbol-12-myristate-13-acetate (0.01%) w/v in acetone) for 25 weeks. In the promotion phase of the I/P bioassay, CD-1 mice were initiated with 50 mu l of 7,12-dimethylbenzanthracene (0.1%) w/v in acetone) or acetone, followed by promotion promotion with 50 mu l of test article twice weekly for 25 weeks. The most volatile of the streams, sweetened naphtha, and the least volatile, vacuum residuum, were noncarcinogenic in both assays. Middle distillates, with a boiling range of 150 degrees-370 degrees C, demonstrated carcinogenic activity in the chronic biossay and acted as promoters but not-initiators in the bioassay. Untreated mineral oil streams displayed initiating activity and were carcinogenic in the chronic bioassay, presumably due to the presence of polycyclic aromatic hydrocarbons of requisite size and A highly solvent-refined mineral stream lacked initiating activity. These, results indicate that the I/P bioassay, which takes 6 months to complete, may be a good qualitative predictor of the results of a chronic bioassay, at least for petroleum streams. Furthermore, the I/P bioassay provide insight into possible mechanisms of tumor development.