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Great Lakes Article:

Purdue scientists seek PCB destroyer
Tammy Webber
Indiana Star
11/15/2002

Imagine a bug that could gobble up one of the most widespread, persistent toxins in the environment.

Until recently, such a scenario has been wishful thinking for environmental officials trying to clean up polychlorinated biphenyls, which first contaminated industrial sites throughout the country and now are so widespread that they're found even in polar ice.

But within a year, researchers at Purdue University and the University of British Columbia expect to be closer to finding an enzyme that might be able to digest the most stubborn of PCB toxins, said Jeffrey T. Bolin, a Purdue biological sciences professor and a member of Purdue's Markey Center for Structural Biology and Cancer Center.

The result could lead to more effective and perhaps cheaper cleanups of the chemical, which is thought to cause a variety of health problems.

Those answers, according to research that will appear in the December issue of Nature Structural Biology, will come from understanding how microorganisms destroy toxins.

Although microorganisms, or "bugs," have been used to consume a host of other toxins, scientists haven't found one capable of destroying all PCBs.

Bolin's team has figured out why.

Their research has shown that PCB molecules either hopelessly bind to one of the enzymes in the bugs or cause the enzyme to self-destruct. And that discovery means it now may be possible to re-engineer a microorganism that finally works, he said.

Ironically, it was PCBs' indestructible nature and insulating qualities that made the chemicals popular for use as coolants and lubricants in transformers and electrical equipment.

But the chemicals' manufacture was banned in 1977 because of health concerns. PCBs can cause skin conditions and liver and respiratory problems and are believed to cause cancer and thyroid and reproductive problems. They also can cause developmental problems in children.

Still, PCBs have lingered at old industrial sites, in sediment at the bottom of lakes and rivers and in the food chain, where they settle in animals' and humans' fatty tissue. They also evaporate and fall back to earth, recontaminating soil and water.

The highest PCB concentrations are found at industrial sites -- 21 of which in Indiana are being cleaned up by state and local environmental agencies specifically because of PCBs -- and in waterway sediment.

Cleanup can be expensive and time-consuming. At one of the worst sites of PCB contamination in Indiana, the former Westinghouse plant in Bloomington, more than $200 million has been spent in the past five years to incinerate the toxin on-site or ship tainted soil to a hazardous waste landfill.

Neither method is perfect: Encasing PCBs in a landfill does not destroy the chemical; burning them creates other toxins. For now, though, they are the most commonly used methods to remove PCBs.

A PCB-munching bug might prove to be less costly and more effective in cleanups, said Tom Alcamo, the EPA project manager for the Westinghouse site.

"It would be fantastic," he said. "It could be an effective way to deal with PCBs."

But there still are significant challenges to finding a bug that works.

Bioremediation might not work in every situation, nor would it be practical for very high levels of contamination, such as on barrels of the chemical, said researcher Lindsay Eltis, associate professor of microbiology and biochemistry at the University of British Columbia. It mostly would be used on soil contaminated with an intermediate level of PCBs, he said.

And because PCBs consist of multiple compounds that are present in many different combinations, other problems could crop up in other steps involved in the destruction of the toxin, Bolin said.

Researchers will start with a version of enzyme that works best, then try to force that organism to undergo random mutations until they find one that works on PCBs, he said.

This information is posted for nonprofit educational purposes, in accordance with U.S. Code Title 17, Chapter 1,Sec. 107 copyright laws.

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