Web Release Date: November 4,
Factors Influencing the Distribution of Lindane and Other Hexachlorocyclohexanes in the Environment
U.S. EPA, National Center for Environmental Assessment, 401 M Street SW, Mail Code 8601-D, Washington, D.C. 20460
U.S. EPA, National Exposure Research Laboratory, Research Triangle Park, North Carolina 27711
Received for review June 7, 1999
Revised manuscript received October 4, 1999
Accepted October 12, 1999
Abstract:
This review examines the potential for 
-hexachlorocyclohexane (HCH) to be transformed into other isomers of
HCH. HCH 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 -HCH to transform into
other isomers is essential to the development of an effective
regional management program. The high relative concentrations of 
-HCH in the Arctic suggest that -HCH may be
transformed into other isomers in the environment.
Laboratory studies show that significant photoisomerization
of -HCH to -HCH is possible. However, field studies
do not find evidence for significant isomerization of -HCH,
and recent environmental samples suggest that -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.
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