Air pollution from other countries, both on a regional and hemispheric scale, has an impact on Canada's domestic air quality.  For this reason, Canada and the United States participate in the Commission for Environmental Cooperation (CEC) North American Air Working Group and the United Nations Economic Commission for Europe where acid rain, smog and other transboundary air issues are a focus of concern.

Commission for Environmental Cooperation (CEC) North American Air Working Group

In June 2002, under the North American Agreement on Environmental Cooperation (NAAEC), the Commission for Environmental Cooperation (CEC) established a trilateral North American Air Working Group with Mexico, the United States and Canada as its members. The working group is to support the three governments in addressing the widespread harm that air pollution such as ground level ozone, acid rain, and particulate aerosols pose over large regions of North America.

United Nations Economic Commission for Europe (UN ECE)

Canada, the United States and Europe participate in the United Nations Economic Commission for Europe where acid rain, smog and other transboundary air issues have been a focus of concern since the 1970s.

Convention on Long-Range Transboundary Air Pollution - This is the address for the Convention on Long-Range Transboundary Air Pollution and the recent Protocol to Abate Acidification, Eutrophication and Ground-level Ozone signed in Gothenburg in December 1999 which includes commitments for sources of emissions of NOxand VOC emissions similar to those used in the Canada-U.S. Ozone Annex

Scientific evidence of the influence of hemispheric transport of particulate matter is growing and is expected to play a key role in future discussions of intercontinental transport of air pollution.  For example, the United Nations Economic Commission for Europe Convention on Long-Range Transboundary Air Pollution recently established an expert group on particulate matter to review the characteristics of particulate matter as a transboundary pollutant (to consider issues such as particulate matter contribution to ambient concentrations from local, national, regional and hemispheric sources, and consider the implications of choosing different particle size fractions).