The genetic toxicology of ortho-toluidine.

ortho-Toluidine, a monosubstituted aniline and an intermediate in the dyeing industry, with a number of uses in other fields such as rubber processing and pharmaceutical production, has been in production for over 100 years. It is metabolised in vivo into a number of compounds, some of which are active genotoxins. It has been demonstrated to be a carcinogen in mice and rats and is a suspected human carcinogen. o-Toluidine has a wide range of genetic effects. It is a weak bacterial, fungal and mammalian mutagen, although the conditions required are stringent. The metabolising system used is of particular importance. o-Toluidine is also a clastogen, generally on prolonged exposure. It induces aneuploidy in both fungi and mammalian cultured cells. It also produces DNA damage (single-strand breaks and unscheduled DNA synthesis, UDS) and causes cell transformation. o-Toluidine can be considered a general genotoxin demonstrable under special conditions, particularly with regard to metabolism.