IARC Monographs evaluation of the carcinogenicity of 1,1,1-trichloroethane and four other industrial chemicals

The results of the recent IARC Monographs evaluation of the carcinogenicity of 1,1,1-trichloroethane, 1,2-diphenylhydrazine, diphenylamine, N-methylolacrylamide, and isophorone have now been published in The Lancet Oncology. This summary article presents the conclusions of IARC Monographs Meeting 130.

Three of these agents (1,2-diphenylhydrazine, diphenylamine, and isophorone) were evaluated by the Working Group for the first time.

1,1,1-Trichloroethane is a chlorinated hydrocarbon that was used widely before the implementation of the Montreal Protocol on Substances that Deplete the Ozone Layer, but that since the 1990s has been used mostly as a chemical feedstock in closed systems and for essential purposes, e.g. medical devices and aviation safety. Diphenylamine, N-methylolacrylamide, and isophorone are chemicals with a high production volume that have diverse uses in industry, including as intermediates. 1,2-Diphenylhydrazine was primarily used as an intermediate in the manufacture of benzidine dyes, which has ceased in the USA and European Union, although such use may continue elsewhere. For all agents, data were sparse regarding exposure levels, but indicated that exposures are higher in occupational situations than in the general population.

The Working Group evaluated 1,2-diphenylhydrazine, diphenylamine, N-methylolacrylamide, and isophorone as possibly carcinogenic to humans (Group 2B) mainly on the basis of sufficient evidence of carcinogenicity in experimental animals. 1,1,1-Trichloroethane was evaluated as probably carcinogenic to humans (Group 2A) on the basis of sufficient evidence of carcinogenicity in experimental animals and limited evidence of carcinogenicity in humans (positive associations were seen for multiple myeloma). For all agents, there was limited mechanistic evidence.

The full scientific assessment will be published as Volume 130 of the IARC Monographs.

IARC Monographs Volume 130 Working Group
Carcinogenicity of 1,1,1-trichloroethane and four other industrial chemicals
Lancet Oncol, Published online 11 November 2021;
https://doi.org/10.1016/S1470-2045(21)00659-8

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