The cancer-causing toxin known as PCB is entering Lake Michigan from land in much greater amounts than previously thought, a massive federal study has found.
The U.S. Environmental Protection Agency study identified the Chicago and Gary areas as major sources of the toxin, a researcher said Thursday.
"It looks like the atmospheric inputs are largely due to the two industrial areas and are significantly larger than previously thought," said Tom Holsen, a leader of the study and former engineering professor at the Illinois Institute of Technology.
Samples taken from 1993 through 1999 show that PCB concentrations from Chicago are five to 10 times as high as those from Kankakee, for example.
Current cleanup efforts are concentrated on digging up PCBs trapped in lake-bottom sediment. The study underlines the need to curb airborne PCBs as well.
PCBs in lakes and rivers are of particular concern because they concentrate in fish and move up the food chain. People, especially pregnant women, are warned not to eat too many Great Lakes fish.
Consumption of fish from the Indiana Harbor waters--15 miles from downtown Chicago--has been restricted by the U.S.-Canadian International Joint Commission, while Waukegan Harbor has experienced loss of fish and wildlife habitat.
The beach at Hammond, Ind., near Indiana Harbor, has been closed because of PCB contamination. The beaches near Waukegan Harbor, off limits for a time, have been cleaned of PCBs and other contaminants. Chicago area beaches have not been affected.
The chemical industry stopped making PCBs--polychlorinated biphenyls--20 years ago, after scientists learned how harmful they are. A 17-year federal cleanup at Waukegan Harbor ended in 1993, although a $16 million dredging job to finish that work is planned. It will take about $250 million to dig up PCB-laced sediments at Indiana Harbor near Gary.
Holsen, now an environmental engineering professor at Clarkson University in Potsdam, N.Y., said scientists have known for some time that PCBs from land sources were a problem, "but it was not documented, or not very well, before."
Holsen and his colleagues suspect the toxin is wafting into the air from old electrical transformers, improperly capped dumps, disposal sites for sediment dredged from rivers and shipping canals and other sources.
PCB concentrations in Lake Michigan "are a lot better than 20 years ago, but the rate of improvement has certainly slowed down," Holsen said.
Cameron Davis, executive director of the Lake Michigan Federation, said, "The evidence shows that the greater Chicago area impacts the entire Great Lakes basin through the atmosphere. What we do as far as cleaning up contaminated sediments and PCB deposits will have a strong benefit on the entire Great Lakes region."
But Holsen emphasized that airborne PCBs are entering the lake from everywhere.
"They go back and forth between the air and the ground and plants . . . around the world," the researcher said. "We found PCBs everywhere we looked--in the arctic, antarctic, polar bear fat, everywhere."
High concentrations also have been found since 1995 near Detroit, Baltimore and in England, Holsen said.
The study results, to be fully analyzed and converted into a model by the end of the year, will help policymakers decide what resources to put into landfill cleanup, sediment removal and other options.
On the Web: www.epa.gov/glnpo
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