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PCB pollutant levels decline quite slowly.

It has been almost 35 years since the manufacture of polychlorinated biphenyls was banned in the U.S., but the chemicals, known as PCBs, still are very much with us. A series of policy briefs describes findings from the Integrated Atmospheric Deposition Network (IADN), a U.S.-Canada project that has measured pollution in the Great Lakes region for the past 20 years.

"PCB concentrations in the atmosphere are decreasing very slowly, if at all, even though their production was banned in 1976," writes Ronald A. Hites, coauthor of the research, whose analysis demonstrates that it takes 30 years for PCB concentrations to decrease by half. A statistical analysis of IADN data by Hites considers the influence of urbanization, temperature, wind speed and direction, and regulation on concentrations of several persistent organic pollutants.

In addition to PCBs, IADN has traced combustion-related pollutants such as polycyclic aromatic hydrocarbons (PAH), chlorinated pesticides like lindane, chlordane, DDT, and, more recently, brominated and chlorinated fire retardants. Air samples have been collected every 12 days at five sites: Chicago, Ill.; Cleveland, Ohio; Eagle Harbor and Sleeping Bear Dunes, Mich.; and Sturgeon Point, N.Y.

One of the researchers' earliest observations is that concentrations of most of the chemicals peak in the hot summer months. This is true for all the pollutant groups except PAH, which is produced by the combustion needed for space heating that occurs in winter.

As for the surprisingly slow rate at which PCBs are disappearing, Hites notes that, not only are the chemicals slow to break down, they continue to enter the environment despite the ban on production. "Tons of PCBs are still out there, especially in electrical gear, such as transformers and capacitors. In addition, 'decommissioned' PCBs have not really been removed from the environment either; rather, they have been placed in landfills and other disposal facilities that may be leaking into the atmosphere."

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Title Annotation:YOUR LIFE; polychlorinated biphenyls
Publication:USA Today (Magazine)
Geographic Code:1USA
Date:Jan 1, 2011
Words:314
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