Factors influencing the distribution of lindane and other hexachlorocyclohexanes in the environment

This review examines the potential for gamma-hexachlorocyclohexane (HCH) to be transformed into other isomers of HCH. HGH residues are among the most widely distributed and frequently detected organochlorine contaminants in the environment. The potential environmental-and human health risks associated with these residues have prompted Canada, the United States, and Mexico to consider the development of a North American Regional Action Plan (NARAP) to assess and mitigate HCH pollution. More information on the propensity of gamma-HCH to transform into other isomers is essential to the development of an effective regional management program. The high relative concentrations of alpha-HCH in the Arctic suggest that gamma-HCH may be transformed into other isomers in the environment. Laboratory studies show th at significant photoisomerization of gamma-HCH to alpha-HCH is possible. However, field studies do not find evidence for significant isomerization of gamma-HCH, and recent environmental samples suggest that alpha-HCH residues are declining as the use of technical HCH has ended in most parts of the world. Alternative explanations for the patterns of isomer contamination are discussed.