In vivo induction of sister chromatid exchanges in mice by nitrosated coal dust extract

The genotoxicity of coal dust extract nitrosated with sodium nitrite (NaNO2) was investigated in mice with the in vivo sister chromatid exchange (SCE) assay system. The SCEs in bone marrow cells of mice were examined following single and double oral dosings of coal dust extract, NaNO2, and nitrosated coal dust extract. Coal dust extract and NaNO2 separately did not cause significant increases of SCEs either in single or in double dosings. Nitrosated coal dust extract in single doses did not increase SCEs but in two doses significant increases in SCEs were observed (P less than 0.02). The mutagenicity of the same extracts was tested in Salmonella typhimurium with the Ames tester strain TA98. Coal dust extract was either non- or weakly mutagenic and NaNO2 was nonmutagenic. The nitrosated coal dust extract caused pronouced increases in his+ revertants both with and without rat liver S9 activation. These findings provide additional evidence that nitrosation of ingested coal dust which may occur in the stomach environment could be one of the factors leading to the higher incidence of gastric cancer in coal miners.