New Toxicology Data for Chloroform: Implications for the Pulp and Paper Industry, 1996 Environmental Conference Proceedings

EPA currently classifies chloroform as a possible human carcinogen. Chloroform, like all other chemicals classified as carcinogenic, is regulated based on the assumption that any dose, no matter how small, carries with it a finite risk of developing cancer. Using this assumption, a risk-based concentration for chloroform associated with a one in one million risk of contracting cancer is 8 ppt in air. Recent, as yet unpublished, studies performed by the Chemical Industry Institute of Toxicology and others indicate that this non-threshold cancer model is not appropriate for chloroform. The data indicate that a threshold exists for the carcinogenic potential of chloroform and that exposures below this threshold can be considered safe. A health-protective estimate of that threshold for humans is between l0-30 ppb - many orders of magnitude greater than EPA’s risk-based concentration. The purpose of this paper is to provide a review of these recent research advances, and to discuss how these results may affect the regulation of chloroform.