o-toluidine

Abstract

This CICAD on ortho-toluidine (o-toluidine) was based on a review of primarily occupational human health concerns, prepared by the United Kingdom Health and Safety Executive (Gregg et al., 1996) and covering data identified up to March 1992. Additional information identified during the international peer review of this CICAD and following consideration by the Final Review Board has been incorporated as appropriate. Information on the preparation and peer review of the source document is presented in Appendix 1. Information on the peer review of this CICAD is presented in Appendix 2. This CICAD was approved for publication at a meeting of the Final Review Board, held in Brussels, Belgium, on 18-20 November 1996. Participants at the Final Review Board meeting are listed in Appendix 3. The International Chemical Safety Card (ICSC 0341) for o-toluidine, produced by the International Programme on Chemical Safety (IPCS, 1993), has also been reproduced in this document. o-Toluidine (CAS no. 95-53-4) is a synthetic chemical that is a light yellow liquid at ambient temperature. It is used primarily in the manufacture of dye-stuffs, although it is also used in the production of rubber, chemicals, and pesticides and as a curing agent for epoxy resin systems. o-Toluidine is of moderate to low acute toxicity and has the potential to produce minimal skin irritation and mild eye irritation. Information is not available on the skin or respiratory sensitization potential of o-toluidine. The principal signs of toxicity following acute and short-term exposure to this chemical are methaemoglobinaemia and related effects in the spleen. These effects have been observed in rats administered o-toluidine at 225 mg/kg body weight per day for 5 days; a no-observed- adverse-effect level has not been identified. In several carcinogenicity studies in which o-toluidine was administered orally to rats and mice, there was a significant increase in the incidence of benign and malignant tumours in various tissues. o-Toluidine is generally not mutagenic in standard bacterial mutagenicity tests, but it is clastogenic in mammalian cells in vitro. There is uncertainty concerning the genotoxicity of o-toluidine in vivo; however, some positive results have been reported. Based upon the wide distribution of tumours observed in o-toluidine-exposed animals, as well as the clastogenic activity observed in mammalian in vitro assays, o-toluidine may be acting as a genotoxic carcinogen. Information relevant to assessing the risks of reproductive or developmental effects of o-toluidine was not identified. Owing to the lack of relevant data on exposure, it was not possible to assess risks to human health associated with indirect exposure to o-toluidine present in the general environment. In the occupational environment, there is the potential for significant risks of carcinogenic and genotoxic effects. Useful data on concentrations of o-toluidine in various environmental media and on its effects on aquatic and terrestrial organisms were not identified, and therefore it was not possible to assess the risks of exposure of environmental organisms to o-toluidine.