Technical Integrity / Collaboration / Exceptional Results

Development of Regulatory Toxicity Criteria for Lindane and Isomers

Integral toxicologists evaluated the potential carcinogenicity of the pesticide lindane and two of its related isomers, and developed alternate toxicological criteria that were accepted by the State of Nevada for use in risk assessment. This project incorporated recent advances in the approach to carcinogenic risk assessment recommended by EPA, as well as new data that were published since the original toxicity criteria were developed. Integral performed a technical review of toxicological literature for three hexachlorocyclohexane (HCH) isomers (lindane, alpha-HCH, beta-HCH) with the aim of determining the critical effect and deriving scientifically based toxicity criteria to use as a metric for evaluating human health risks. The assessment included the critical review of more than 200 studies from the primary literature, an evaluation of the most sensitive target endpoint, a review of the carcinogenicity, and an assessment of the mode of action by which each isomer elicits toxicity. Using principles and frameworks set forth by EPA and the International Programme on Chemical Safety, Integral synthesized the weight of evidence for the carcinogenic potential and the mode of action for toxicity. Toxicity criteria were determined using several approaches including EPA’s benchmark dose modeling software. Criteria were reviewed and accepted by the Nevada State regulatory agency for use. This state-of-the-science technical evaluation resulted in a significantly better understanding of the risks posed by these chemicals, leading to the development of the alternate toxicity criteria.


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