Methylated derivatives of pyrene and fluorene: evaluation of genotoxicity in the hepatocyte/DNA repair test and tumorigenic activity in newborn mice.

The genotoxicity of 1-methylpyrene, 1,6-dimethylpyrene, 1-methylfluorene, 9-methylfluorene, and 1,9-dimethylfluorene was evaluated in the hepatocyte primary culture/DNA repair test, and the tumorigenic potency of these compounds was tested by bioassay in newborn mice. With the exception of 1-methylfluorene, all of these methylated polycyclic aromatic hydrocarbons are known mutagens in Salmonella typhimurium. Both 1-methylpyrene and 1,6-dimethylpyrene induced unscheduled DNA synthesis in rat hepatocytes. However, only 1-methylpyrene was tumorigenic when administered to newborn male mice. None of the methylated fluorenes assayed in the hepatocyte primary culture/DNA repair test induced unscheduled DNA synthesis. While 1,9-dimethylfluorene exhibited weak tumorigenic activity when administered by subcutaneous injection to newborn mice, 1-methylfluorene and 9-methylfluorene were inactive.