Tumor initiation and promotion effects of petroleum streams in mouse skin

A furnace oil, a dewaxed heavy paraffinic distillate, and a solvent-extracted lubricant base oil induced skin tumors in 9/43, 26/48, and 1/47 male C3H mice, respectively, during lifetime skin-painting bioassays. An initiation/promotion (I/P) bioassay was conducted to assess the I/P potential of these materials. During a 28-week initiation bioassay, groups of 30 male CD-1 mice were first treated dermally once daily for 5 days with 25 or 50 microliter of test materials or 50 microliter of acetone, rested for 2 weeks, then treated twice per week for 25 weeks with 50 microliter (0.1 mg/ml) phorbol-12-myristate-13-acetate (PMA). Only groups treated with the heavy paraffinic distillate had a significantly higher incidence of papillomas relative to the acetone control group. During a 28-week promotion bioassay, groups of 30 male CD-1 mice were treated once with 50 microliter of either DMBA (1.0 mg/ml) or acetone, rested for 2 weeks, and then treated twice per week with test material for the remaining 25 weeks. The furnace oil and dewaxed heavy paraffinic distillate showed significantly higher incidences of carcinomas and papillomas in DMBA-initiated mice relative to their acetone-initiated controls. Together these bioassay data suggest that only the dewaxed heavy paraffinic distillate is a complete carcinogen, having both initiating and promoting activity; furnace oil is a promoter only, while the solvent-extracted lubricating oil is noncarcinogenic. Overall, the I/P bioassay correlated well with the results of the lifetime skin-painting bioassay.