Canada-United States Air Quality Agreement

The Canada-United States Air Quality Agreement signed by Canada and the United States in 1991 to address transboundary air pollution leading to acid rain. Both countries agreed to reduce emissions of sulphur dioxide (SO2) and nitrogen oxides (NOx), the primary precursors to acid rain, and to work together on acid rain-related scientific and technical cooperation.

The Ozone Annex was added to the Canada-United States Air Quality Agreement (December 2000) to address transboundary air pollution leading to high ambient levels of ground-level ozone, a major component of smog. The long-term goal of the Ozone Annex is the attainment of the ozone air quality standards in both countries. Where there are transboundary flows of the pollution that create ozone, the Ozone Annex commits both countries to reduce their emissions of nitrogen oxides and volatile organic compounds, the precursor pollutants to ground-level ozone.