Bacteria found that eats PCBs

By AMANDA BENSEN
Published in The Post-Star (A1)
March 12, 2007

Researchers at Rensselaer Polytechnic Institute announced last week they had discovered bacteria capable of naturally breaking down PCBs.

Dr. Donna Bedard, an RPI biology professor who led the work, said the research is "years away" from being a viable alternative to dredging, but it is a groundbreaking step. This is the first time bacteria have been found capable of dechlorinating complex commercial PCB mixtures, such as those found in contaminated river sediment, she said.

The bacteria, known as Dehalococcoides (Dhc), can grow only by removing chlorines from compounds known as halogenated organics, most of which are toxic, explained Bedard.

Dhc bacteria are anaerobic --they cannot survive in the presence of oxygen -- but seem to thrive on PCBs, a type of halogenated organic.

Bedard's research used sediment samples from the Housatonic River in western Massachusetts, which, like the Hudson River, was contaminated with PCBs from a General Electric factory several decades ago.

EPA and GE spokespeople said that while the new research is promising, it does not change the plan to dredge PCB-contaminated sediments from the Hudson beginning in 2009.

"I think it's exciting ... but it sounds like it's not commercially viable at this point," said David Kluesner, a spokesperson for EPA's Region 5 office. "We're always keeping our eyesand ears open for newtechnologies, but to our knowledge, there's nothing available that is proven to work on a large scale."

"We're moving ahead with the dredging project that EPA has selected," said Mark Behan, a GE spokesperson. He noted that GE has funded research about natural PCB dechlorination for years at its laboratory in Niskayuna, where Bedard worked until 2000. He said most scientists agree that PCBs break down in the environment over time.

"The good news is that these natural processes are occuring naturally every day, including, we believe, in the Hudson," he said.

Environmentalists dispute that assertion, however.

"The bad news is that they're just washing downriver," said Rich Schiafo, environmental project manager for Scenic Hudson. "They don't break down. That's why, even though they were banned more than 30 years ago, they're still a serious environmental problem."

Bedard said although "PCB dechlorinating bacteria occur naturally in PCB-contaminated sediments, the challenge is to learn enough about them to be able to promote their activity so they do the job."

The next step in the research process, she said, is to identify a second bacteria that can break down the rest of the chlorine molecules, since Dhc onlyworks on five to nine chlorines per molecule. Bedard also plans to study the particular enzymes in Dhc which appear to be linked to dechlorination, called reductive dehalogenases.