OTTAWA — Toxic chemicals absorbed over decades by the Great Lakes are now being exhaled from the waters years after the source of the pollution was cut, according to a study by an environmental group.
Lake Ontario alone released almost two tons of the now-banned PCBs (polychlorinated biphenyls) into the air from 1992 to 1996, said a study released Friday by the Integrated Atmospheric Deposition Network.
The five lakes decreased their combined levels of PCBs by 10 tons during the four-year period, while levels of the banned pesticide Deildren decreased four tons, the study said.
Keith Puckett, a researcher with Canada’s environment ministry who led the study, said the outgassing of the chemicals only involved banned substances — those no longer present in the atmosphere in significant concentrations.
Puckett said the news shows that the lakes can cleanse themselves once the source of polluting chemicals has been cut.
"It came as quite a surprise to us," he said. "Traditionally, we always thought of the Great Lakes as the ultimate destination for many of these toxic chemicals that we find in the atmosphere. It seems now they no longer behave as a repository, but are indeed releasing them back into the air."
Despite the release of toxic chemicals in the air through evaporation, Puckett said there was no threat to public health.
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