Development of Regulatory Toxicity Criteria for Lindane and Isomers


Although lindane is no longer produced or used agriculturally in the United States, exposure to hexachlorocyclohexane (HCH) isomers is of continuing concern due to past usage and persistence in the environment.  The risk-based standards that were being applied for these compounds at our client’s site were derived using outdated toxicity criteria—namely these criteria did not consider the full set of toxicological data currently available for the compounds.


Our team performed a technical review of the toxicological literature for the HCH compounds and determined the most sensitive target endpoint, potential carcinogenicity, and mode of action by which each isomer elicits toxicity.  Our findings supported the derivation of threshold-based criteria, rather than those that assume linearity at low doses.  We performed dose-response evaluations to derive toxicity criteria.


Our recommended toxicity criteria were peer-reviewed and accepted by the Nevada State regulatory agency for use.  Our state-of-the-science technical evaluation resulted in a significantly better understanding of the risks posed by these chemicals, and lead to the development of alternative risk-based standards.