Skin tumorigenic potential of crude and refined coal liquids and analogous petroleum products.

The skin tumorigenic potential of seven complex hydrocarbon mixtures was determined: a coal-derived raw blend composed of light and heavy oils, a low- and high-severity hydrotreated product of that blend, and naphthas and fuel oils from the raw blend or from natural petroleum. Male and female C3H/Bdf mice were exposed three times per week to each test mixture by dermal application of 50 microliters of neat, 50, or 25% (w/v) preparations. Room, vehicle, and benzo[alpha]pyrene control groups were run concurrently. The raw blend produced an almost 100% incidence of skin tumors at all three doses while tumorigenicity was considerably decreased by hydrotreating the blend both in terms of incidence and onset. The tumorigenicities of the naphthas and fuel oils derived from the raw blend or from petroleums were low relative to that of the parent mixture. Although tumorigens in the raw blend were much reduced by hydrotreatment, tumorigenicity of the other agents did not parallel the content of polycyclic aromatic hydrocarbons known to be good tumor initiators.