Mutagenicities of mono-nitrobenzene derivatives in the presence of norharman.

The mutagenicities of 22 mono-nitrobenzene derivatives, i.e., nitrobenzene [98-95-3] and the ortho, meta and para isomers of nitrotoluene [88-72-2, 99-08-1, 99-99-0], nitrophenol [88-75-5, 554-84-7, 100-02-7], nitroanisole [91-23-6, 555-03-3, 100-17-4], nitrochlorobenzene [88-73-3, 121-73-3, 100-00-5], nitrobenzoic acid [552-16-9, 121-92-6, 62-23-7], nitrobenzaldehyde [552-89-6, 99-61-6, 555-16-8] and nitrobenzonitrile [612-24-8, 619-24-9, 619-72-7], were tested with or without S9 mix and norharman [244-63-3] in the Salmonella assay system. None of the compounds was mutagenic without norharman. In the presence of norharman, however, nitrobenzene, nitrotoluene, nitroanisole, nitrochlorobenzene and nitrobenzaldehyde exhibited mutagenicity only to S. typhimurium TA98 with S9 mix. This induction of mutagenesis with norharman was strong for the ortho isomers of every nitro-compound, weak for the para isomers, and was not observed for the meta isomers.