Fate and Degradation of POP-Hexachlorocyclohexane

Abstract

Hexachlorocyclohexane (HCH) and its isomers are one of the most frequently detected chlorinated contaminants in the environment. In spite of the ban on technical grade HCH and restricted use of γ-HCH (lindane), its residues have not stopped from entering the environment. Its extensive use in the past, present use of lindane in several countries, unused stockpiles of date-expired HCH from earlier manufacturing, as well as leachates from earlier disposal at dump sites continue to pollute the biosphere. Because HCH is a persistent organic pollution (POP) known to have several toxic and deleterious effects on human health and wildlife, it becomes imperative to remove this substance of serious concern to the global community. A better understanding on the fate and degradation of this POP in the environment will facilitate in drawing measures to mitigate this chemical and bring about bioremediation of already contaminated sites. This review focuses on the fate, contamination levels, abiotic and biotic degradation of HCH isomers, genes and enzymes involved in microbial degradation, and future research needs in this area.

KEY WORDS:

• hexachlorocyclohexane (HCH)
• γ-HCH (lindane)
• persistent organic pollutant (POP)
• contamination
• biodegradation

ACKNOWLEDGMENTS

The authors are grateful to the Director of the National Environmental Research Institute (NEERI) for his constant guidance and support. PB would like to thank the Council of Scientific and Industrial Research (CSIR), India, for an award of senior research fellowship.