Fractionation of Skin Tumor-initiating Activity in Coal Liquids1

Narrow temperature range distillates from biologically active solvent refined coal-l and -II heavy-end coal liquids were fraction ated according to chemical class and assayed for initiation of skin carcinogenesis in CD-1 mice. In addition, instrumental chem ical 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 hy drocarbon fractions showed little or no initiating activity. For the two solvent refined coal-ll distillates studied, initiating activity was substantially higher in the material boiling above 850°f than in that boiling 800-850°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 carcino gens 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. lation temperature. Microbial mutagenesis studies have resulted in convincing evidence implicating APAH as the determinant mutagens in coalderived liquids. For example, Pelroy and Stewart (16) have shown that most of the mutagenic activity in high-boiling SRC coal liquids can be eliminated by treatment with nitrous acid, a pro cedure which converts the primary aromatic amino functionality into an aromatic hydroxy group. Chemical fractionation studies using the method of Later ef al. (9, 22) have also shown that microbial mutagenic activity can be segregated into fractions enriched in APAH. Similar studies using SHE and CHO cells (11) show a somewhat different pattern of activity from that found with the Ames system. Although the fractions enriched in nitro gen-containing compounds, including APAH, contain significant activity in both the SHE and CHO cell systems, substantially higher activity was found in PAH fractions. Both the Ames assay and mammalian cell culture systems are now being evaluated for their ability to predict the potential carcinogenicity of complex synfuel mixtures. We have, therefore, tested fractions prepared from high-boiling distillation distillates of SRC-I and -II liquids for skin tumor initiating activity to deter mine correlations between in vitro and in vivo studies, as well as to evaluate the relative initiating activity of the major chemical classes present in the coal liquids.