U.S.-Canada Air Quality Agreement
In 1991, the U.S. and Canada entered into an agreement to address transboundary air pollution, whereby pollutants released at one location can travel long distances, affecting air quality at their sources, as well as many miles away. The 1991 Agreement led to reductions in acid rain in the 1990s, and was expanded in 2000 to reduce transboundary smog emissions under the Ozone Annex.
View additional information about the U.S.-Canada Air Quality Agreement
View U.S. - Canada Air Quality Agreement Progress Reports
Additional Resources
Review and Assessment of the Canada-US AQA (pdf)
This 2023 document details a review of what the Air Quality Agreement or AQA has accomplished to date, including whether it is meeting its current objectives and whether emission reductions mandated by the Agreement have met the AQA objectives to: reduce the transboundary flow of air pollution, reduce acid deposition, reduce concentrations of ground-level ozone, and improve air quality in Canada and the U.S. It also assesses whether the emissions reduction targets and measures included in Annex 1 (acid rain) and in Annex 3 (ozone) and the commitments in Annex 2 (scientific cooperation) remain appropriate for Canada/U.S. policy and science needs and examines whether new actions such as commitments and/or measures would be appropriate.
Canada-United States Transboundary Particulate Matter Science Assessment 2013
This 2013 document summarizes the findings of the Canada-U.S. subcommittee on Scientific Cooperation concerning the transboundary transport of particulate matter (PM) and PM precursors between the two countries.
Meeting the Challenge of Cleaner Air
This general audience brochure supplements the biennial U.S.-Canada progress report, released in 2008. The brochure provides an overview of the U.S.-Canada Air Quality Agreement and features recent progress made by the United States and Canada to control transboundary air pollution.
U.S. - Canada Border Air Quality Pilot Projects
Provides a summary of joint projects that have been completed under the Canada-U.S. Border Air Quality Strategy, including two airshed projects and a study examining the feasibility of emissions trading for sulfur dioxide (SO2) and nitrogen oxides (NOx).
Canada – U.S. Transboundary PM Science Assessment
This 2004 document summarizes the findings of the Canada-U.S. subcommittee on Scientific Cooperation concerning the transboundary transport of particulate matter (PM) and PM precursors between the two countries.
Cleaner Air through Cooperation, Progress under the Air Quality Agreement
This brochure summarizes progress made by Canada and the United States under the 1991 Air Quality Agreement and highlights key issues from the 2002 U.S.-Canada Air Quality Agreement Progress Report. This document provides an overview of the 1991 Agreement, followed by key commitments and progress, including air quality programs and scientific cooperation between the two nations.
Ground-Level Ozone: Occurrence and Transport in Eastern North America
This 1999 report, prepared for the Air Quality Committee under the U.S.-Canada Air Quality Agreement, presents results of cooperative efforts set in motion in April 1997 to describe ground-level ozone concentration and transport in the border region of the eastern United States and Canada.
U.S.-Canada Air Quality Agreement Notification Table
Summarizes facility permitting information.
Environment Canada – Canada-U.S. Air Quality Issues
Government of Canada – Canada-United States Air Quality Agreement: overview