HEXACHLOROBUTADIENE: HAZARD CHARACTERIZATION AND EXPOSURE–RESPONSE ANALYSIS

Abstract

Hexachlorobutadiene (HCBD) has been assessed as a Priority Substance under the Canadian Environmental Protection Act. Based on results of studies conducted in experimental animals, the proximal tubules of the kidney are the principal target sites for HCBD-induced non-neoplastic lesions. Kidney tumours have also been observed in rats following long-term exposure to HCBD, but only at doses associated with significant nephrotoxicity. A tolerable intake of 0.34 μg/kg body weight per day has been derived, based upon the benchmark dose for renal tubular regeneration in female mice. This value is also considered protective for potential carcinogenicity.

ACKNOWLEDGMENTS

To ensure transparency and defensibility of the health assessments, a cut-off date for consideration of new data is specified so as not to compromise the integrity of several stages of internal and external review. Data obtained after December 1996 were not considered for inclusion in this assessment.

Sections of the Assessment Report and supporting documentation on genotoxicity were reviewed by D. Blakey of the Environmental Health Directorate of Health Canada. Sections related to evaluation of the effects on human health were externally reviewed by staff of BIBRA International and a peer review panel convened by Toxicology Excellence in Risk Assessment (TERA), composed of J. Christopher, California Environmental Protection Agency; M. Dourson, TERA; M. Friedman, Cytec Industries, Inc.; M. Gargas, ChemRisk Division of MacLaren/Hart; P. McGinnis, Syracuse Research Corporation; E. Ohanian, Environmental Protection Agency; and J. Reid, University of Cincinnati.