Differential toxicity and environmental fates of hexachlorocyclohexane isomers

The differential environmental fates and toxicities of the various hexachlorocyclohexane (HCH) isomers including lindane and isomers in the technical mixture will be the focus of this review. HCHs are one of the most widely used and most readily detected organochlorine pesticides in environmental samples. The relatively high volatility of HCH has led to global transport, even into formerly pristine locations such as the Arctic. Certain HCHs cause central nervous system, reproductive, and endocrine damage. Because gamma-HCH is rapidly metabolized, the beta-HCH isomer is consistently found in higher concentrations in human fat, blood,and breast milk. In contrast, alpha- and gamma-HCH are the most prevalent isomers in soil, water, and air samples. The ratio of the alpha- to gamma-isomers can be used to track global transport of HCHs. A new area of HCH research focuses on the selective degradation of the two alpha-HCH enantiomers in various environmental matrices. These HCH issues and recommendations for future HCH research are presented in this review.