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Indiana University

SPEA policy brief: Research shows pollutant levels decline slowly

March 31, 2010
Bloomington, Indiana --

It has been almost 35 years since the manufacture of polychlorinated biphenyls was banned in the United States, but the chemicals, known as PCBs, are still very much with us, according to research from the Indiana University School of Public and Environmental Affairs.

Professor HitesThe research results are reported in the latest issue of SPEA Insights, a series of policy briefs from the school. The March 2010 brief, by SPEA Distinguished Professor Ronald A. Hites, 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," Hites writes. Data from Eagle Harbor, Mich., a remote site on Lake Superior, show atmospheric levels of PCBs were about the same in 2000-02 as they were in 1992-96. Careful analysis shows that it takes 30 years for PCB concentrations to decrease by half.

Other findings from the research include:

  • Levels of most pollutants measured in the project tend to peak in warm summer months.
  • Concentrations of pollutants are highly correlated with population density.
A statistical analysis of IADN data by Hites and Marta Venier, a post-doctoral associate in the School of Public and Environmental Affairs, was published in a recent issue of the journal Environmental Science & Technology. The article, "Regression Model of Partial Pressures of PCBs, PAHs, and Organochlorine Pesticides in the Great Lakes Atmosphere," analyzes the influence of urbanization, temperature, wind speed and direction, and regulation on concentrations of several persistent organic pollutants.

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

According to the SPEA Insights brief, one of the researchers' earliest observations was that concentrations of most of the chemicals peaked in the warm summer months. This has been true for all the pollutant groups except polycyclic aromatic hydrocarbons, which are 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, but 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," he says. "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."

Researchers also observe that concentrations of the chemicals are strongly dependent on the human population living and working within 25 miles of the sampling site -- they were much higher at Chicago and Cleveland than at the rural sites. The strongest correlation with population was for PAH, produced by combustion and industrial activity, and the weakest was for lindane, a pesticide used primarily in agriculture."

"This general observation has important implications for pollution prevention and control: Focus pollution remediation in cities, and give the farmers a pass for now," Hites writes.

An Indiana University team led by Hites has been in charge of the U.S. part of the IADN project since 1994. The Environmental Protection Agency in November 2009 awarded IU $5 million to continue the work for five more years. The Canadian part of the project is operated by Environment Canada.

To speak with Hites, contact Jana Wilson at the School of Public and Environmental Affairs, 812-856-5490 or wilsonjs@indiana.edu, or Steve Hinnefeld at University Communications, 812-856-3488 or slhinnef@indiana.edu.


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