Fractionation of skin tumor-initiating activity in coal liquids.

Narrow temperature range distillates from biologically active solvent refined coal-I and -II heavy-end coal liquids were fractionated according to chemical class and assayed for initiation of skin carcinogenesis in CD-1 mice. In addition, instrumental chemical analyses were performed on the distillates and their chemical fractions. Results showed that initiation activity in these complex fuel mixtures could be segregated both by boiling point and chemical class. Neutral polycyclic aromatic hydrocarbon fractions were the most active of the chemical classes, with some initiating activity being shown by nitrogen-containing polycyclic aromatic hydrocarbon. Aliphatic and hydroxylated polycyclic aromatic hydrocarbon fractions showed little or no initiating activity. For the two solvent refined coal-II distillates studied, initiating activity was substantially higher in the material boiling above 850 degrees F than in that boiling 800-850 degrees F, although both contained essentially the same concentrations of benzo[a]pyrene. These data indicate that the overall initiating activity of these complex mixtures is highly dependent on interactions of the many chemical carcinogens and that relative concentrations of known carcinogenic polycyclic aromatic hydrocarbons, such as benzo[a]pyrene and dimethylbenz[a]anthracene, are not the sole determinants of initiating activity.