CHRONIC AND INITIATION PROMOTION SKIN BIOASSAYS OF PETROLEUM REFINERYSTREAMS/

Nine refinery streams were tested in both chronic and initiation/promo tion (I/P) skin bioassays. In the chronic bioassay, groups of 50 C3H/H eJ 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, gro ups of CD-1 mice received an initiating dose of 50 mu l of test articl e for 5 consecutive days, followed by promotion with 50 mu l of phorbo l-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 w eekly for 25 weeks. The most volatile of the streams, sweetened naphth a, and the least volatile, vacuum residuum, were noncarcinogenic in bo th 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 m ineral 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 tha t the I/P bioassay, which takes 6 months to complete, may be a good qu alitative 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.