The effects of nitrous acid on the mutagenicity of two coal liquids and their genetically active chemical fractions.

The Ames/Salmonella assay was used to determine the effect of nitrous acid on the mutagenicity of solvent refined coal (SRC) distillates and distillate fractions. The SRC materials consisted of the higher-molecular-weight, high-boiling distillates, the process solvent (PS) and heavy distillate (HD), and also included the basic tar and neutral tar chemical fractions derived from these 2 distillates. Nitrosation products of each of the SRC materials were less mutagenic than the distillates of distillate fractions from which they were derived (untreated materials); in most cases they were less than 10% as mutagenic as that observed in the starting materials. The mutagenicity of the SRC materials after nitrous acid treatment was direct-acting, whereas all mutagenicity associated with the untreated SRC materials was indirect and required metabolic activation for expression in the Ames assay system.