Airborne Toxic Substances
IJC Recommendation
"The Parties should take the following measures to
deal with airborne pollutants:
(i) identify both in-basin and out-of-basin sources of atmospheric
deposition of persistent toxic substances to the Great Lakes, quantify
their contribution to the total burden of these substances to the lakes,
and use this information to formulate and implement appropriate prevention
and control measures; and
(ii) adopt a source-receptor computer model, improve emissions
inventory information, and add dioxin and mercury to the Integrated Atmospheric
Deposition Network to improve the data bases for these two substances."
Response to Recommendation
The IJC calls for the identification and quantification of the atmospheric
sources of pollutants entering the Great Lakes. The Government of Canada
supports the measures recommended by the IJC and is satisfying the recommendation
through meeting existing obligations. Specifically, Annex 15 - Air Borne
Toxic Substances - of the GLWQA calls on the Parties to develop models
of the intermediate and long-range movement and transformation of toxic
substances. The purpose of the models is (1) to determine the significance
of atmospheric loadings to the Great Lakes system relative to other pathways
and (2) to determine the sources of such substances from outside the Great
Lakes system. Canada has been developing source-receptor models, in keeping
with the IJC recommendation, and has applied them to address the issue
of the contribution from in-basin and out-of-basin sources. Canada will
continue to use these and other models to deal with this concern.
The Government of Canada agrees with the IJC that it is desirable to
improve knowledge about air emissions of substances targeted by the Binational
Toxics Strategy. Not only is such information needed to formulate control
measures, but it is critical for the application of the source-receptor
models discussed above.
One test of the effectiveness of prevention and control measures to address
substances of concern is whether environmental levels show changes in
concert with changes in emissions. The U.S./Canada Integrated Atmospheric
Deposition Network (IADN) is well placed to address this question. Measures
to reduce mercury and dioxins emissions are discussed in the Great Lakes
Binational Toxics Strategy. In order to measure the environmental response,
Canada has been monitoring atmospheric mercury (the vapour phase) at the
two Canadian IADN master stations since 1997; with the recent purchase
of the necessary equipment, Canada will begin routine measurements of
mercury in precipitation in fiscal year 2001- 2002. Dioxins and furans
have been measured at one IADN master station since 1996, and additional
measurements are planned. The results of these measurements will significantly
assist in quantifying the deposition of these substances in the Great
Lakes.
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