Issue Date: September 24, 2007
Persistent Organic Pollutants
I read Celia Arnaud's News of the Week item with considerable interest (C&EN, July 16, page 6). The scientific investigation undertaken by Frank A. P. C. Gobas and Barry C. Kelly has gone a long way to help explain the continuing persistence of hexachlorocyclohexane (HCH) isomers in the environment and traditional food sources for inhabitants of northern regions.
In 2004, The North American Commission for Environmental Cooperation was mandated by the Council of Ministers of Environment for Canada, the U.S., and Mexico to develop and implement a North American Regional Action Plan on Lindane & Other Hexachlorocyclohexane Isomers. The expert panel consisting of renowned scientists from these three countries provided the scientific evidence for the resulting plan, which is now being implemented by the three countries (www.cec.org). In our deliberations, we wrestled intensely with the apparent contradiction of high levels of HCH that demonstrated relatively low octanol-water partition coefficient (Kow) and high octanol-air partition coefficient (Koa).
Our scientific team noted that β-HCH seemed to be endemic throughout the northern region. Our experts have also concluded that isomeric transformations between the six HCH isomers are not a major source of the β-HCH concentrations found in the north. We have come to believe that the major sources of HCH isomers in the northern environment may be the legacy of years of HCH production, pesticidal application of technical HCH until the 1970s, and subsequent indiscriminate disposal of 80% of the HCH isomers in an effort to capture only the γ-HCH isomer for commercial pesticidal purposes. The long-range atmospheric transport of persistent organic pollutants then provided the transport mechanism for these contaminants to enter the northern ecosystems.
The production and disposal of HCH isomers is detailed by John Vijgen of the International HCH & Pesticides Association. The main report and Annex can be downloaded free from the IHPA library at www.ihpa.info/library_access.php.
Luke J. Trip
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