Current Intelligence Bulletin 53: Toluene Diisocyanate (TDI) and Toluenediamine (TDA): Evidence of Carcinogenicity

The purpose of this bulletin is to disseminate new information on the potential carcinogenicity of toluene diisocyanate (TDI) and toluenediamine (TDA). Recent data from studies of chronic toxicity in animals have produced evidence that cancer is associated with exposure to commercial-grade TDI (an 80:20 mixture of 2,4- and 2,6-TDI) and to 2,4-TDA, a reagent used in the manufacture of TDI and a hydrolysis product of TDI. The tumorigenic responses observed in both rats and mice treated with TDI and TDA meet the criteria of the Occupational Safety and Health Administration (OSHA) Cancer Policy for classifying a substance as a potential occupational carcinogen [Title 29 of the Code of Federal Regulations, Section 1990.112]. Because insufficient data exist to evaluate the carcinogenic potential of the other TDI and TDA isomers, NIOSH concludes that occupational exposure to all TDI and TDA isomers should be reduced. NIOSH therefore recommends that all the isomers of TDI and TDA be regarded as potential occupational carcinogens and that occupational exposures be limited to the lowest feasible concentrations. Although the potential for TDI- or TDA-induced cancer in humans has not been determined, reducing exposure to TDI and TDA in the workplace should reduce the risk.

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