U.S. Water News Online
OTTAWA, Ontario -- 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
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 recently by the Integrated Atmospheric Deposition
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
``Think of the lakes as giant lungs that have been sucking in
polluted air for the last 50 years,'' he said. ``Now that atmospheric
levels of many of these pollutants have dropped below the equilibrium
point, the lakes are starting to exhale.''
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 the
evaporation, Puckett said there was no threat to public health.
``Most of what you get (in toxic contamination) comes in the food
that you eat rather than the air you breathe,'' he said. ``I don't
think this is a significant concern.''
Scientists say air pollution remains a significant threat to the
Great Lakes, and Puckett called for increased efforts to control
pollution from power plants, vehicles, and other sources.
PCBs, industrial compounds used to insulate electrical
transformers and capacitors, have been banned in the United States
and Canada since the mid-1970s but are still widely used in the Third
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