Despite 20-Year Ban, PCBs Still Seep Into Lake Michigan

More than 20 years after the manufacture of PCBs was banned, the cancer-causing toxins are still entering Lake Michigan from sources on land, according to a federal study that challenges long-held beliefs about the chemical.

Air tests indicate that the Chicago and Gary, Ind., areas are major sources of PCBs entering the lake, said Glenn Warren of the Environmental Protection Agency’s Great Lakes National Program Office in Chicago.

The findings came as a surprise to scientists who had long believed the lake’s PCB load was decreasing, and the study suggests the same thing is happening in industrial areas throughout the world.

PCBs--polychlorinated biphenyls--have been linked to cancer and birth defects. The chemical was widely used as a coolant in electrical transformers during the 1960s and ‘70s, to control dust on roads, as a wood preservative and in paint.

PCB pollution of lakes and rivers is of particular concern because contaminated sediment exposes fish to the toxin and speeds its movement up the food chain. Because PCBs don’t break down easily, the chemical builds up in fatty tissue, with each exposure putting a person at greater risk.

That has prompted the government to warn people, especially pregnant women, against eating too much Great Lakes fish.

It was widely believed that most PCBs in the environment had been there for years and were recirculating by evaporating and reentering the lake from the atmosphere--not necessarily coming from new sources.

“Conventional wisdom was . . . that Lake Michigan overall was losing PCBs to the atmosphere,” Warren said. “But because of the urban input, Lake Michigan is still taking in PCBs.”

Researchers suspect the toxin is coming from old electrical transformers, dumps that were not capped properly, sludge beds and disposal sites for PCB-laced sediment dredged from rivers and shipping canals, as well as a host of smaller sites, said Tom Holsen, an environmental engineering professor at Clarkson University in New York, who is leading the PCB study in Chicago.

PCBs evaporate from those sources and are deposited in the lake from the atmosphere, Holsen said. He said more extensive analyses of air data must be completed before researchers identify sources of new emissions. A report is expected by the end of the year.

But the extent of the problem is probably not yet known because higher-than-expected levels of PCBs are probably being released by industrial areas throughout the world, Holsen said.

Since 1995, tests also have found high levels of the toxin in the atmosphere near Baltimore and Detroit, and in England, he said.

Technology to allow routine testing of industrial areas became available only recently, he said. That means scientists and policymakers will have to revisit the PCB issue on an international scale, he said.

“These pollutants don’t respect state or national boundaries; they go everywhere,” he said. “If you just clean up the Great Lakes, it won’t solve the problem.”

The high levels of PCBs in the air near Gary and Chicago were found during testing for a different study of the source and movement of PCBs and three other toxins in Lake Michigan. That finding prompted the EPA to fund a separate study to pinpoint the toxin’s sources.

Holsen said levels in the air around Chicago and Gary were far higher than from non-urban areas --10 times higher in Chicago than in Kankakee, about 50 miles to the south, for example.

“It was clear that urban industrial areas were the source,” Holsen said.

The new information could help government agencies decide what steps to clean up PCBs should get top priority, said Warren and Cameron Davis, executive director of the Lake Michigan Federation, a citizens environment group.

Many government officials and advocacy groups support dredging contaminated sediment from lakes and rivers. Industry has resisted that as too expensive and has favored covering polluted sediment with clean fill such as clay to limit exposure, Warren said.

The land-based sources, from which PCBs evaporate or are washed into waterways, present a new concern, but cleanup of all sources of the toxin is important to reduce fish contamination, Warren and Davis said.

“It is my belief we will have to go after all sources if we want contamination levels low enough so [fish are] consumable by everyone,” Warren said.

*

On the Net:

Environmental Protection Agency: https://www.epa.gov/glnpo

Lake Michigan Federation: https://www.lakemichigan.org