Transboundary Air Pollution
Although most air pollution problems are caused by local or regional sources of emissions, air pollution does not stop at national borders. Transboundary flows of pollutants occur between the United States and our closest neighbors, Mexico and Canada, as well as between North America, other continents, and sources in the global commons such as international shipping and aviation. Some air pollutants are known to circulate globally and deposit on land and water bodies far from their sources.
EPA is engaged in a variety of efforts to better understand the impact of air pollution sources outside the United States on health and environmental quality in the United States, and to enable and motivate the mitigation of these sources in other countries.
Addressing Transboundary Flows in North America
EPA works closely with our colleagues in Mexico and Canada through several bilateral and multi-lateral forums, including:
- U.S.-Mexico Border 2020 Program
- U.S.-Canada Air Quality Agreement
- North American Commission for Environmental Cooperation
Understanding Intercontinental Flows of Air Pollution
EPA has taken a leading role in focusing attention on the intercontinental transport of air pollutants:
Starting with the First International Conference on Trans-Pacific Transport of Atmospheric Contaminants in July 2000, EPA has sponsored a series of workshops and conferences to focus the attention of the research community on quantifying intercontinental flows of air pollution.
- View the consensus statement of the meeting’s findings: The 2000 Aljoya Consensus Statement on Long-Range Transport in the North Pacific (PDF)
EPA, along with NOAA, NASA, and NSF, sponsored a 2009 report of the National Research Council entitled Global Sources of Local Pollution: An Assessment of Long-Range Transport of Key Air Pollutants to and from the United States. Washington, DC: The National Academies Press, 2009.
Since 2005, EPA has co-chaired, along with the European Commission, the Task Force on Hemispheric Transport of Air Pollution (TF HTAP) Exit organized under the UNECE Convention on Long-Range Transboundary Air Pollution. Exit
- In 2010, TF HTAP produced the first comprehensive assessment report Exit on the intercontinental transport of air pollution across the Northern Hemisphere, covering ozone and its precursors, fine particles and their components and precursors, mercury, and persistent organic pollutants.
Fostering Global and Regional Cooperation
In addition to working with key countries bilaterally, EPA works to address global and international flows and sources of air pollution through various international forums. This work includes:
- Work under the Minamata Convention on Mercury and the UNEP Global Mercury Partnership.
- Work through the International Maritime Organization to quantify and reduce air pollution emissions from international maritime transport. The most notable element of this work is the creation of the North American Emission Control Area (ECA) and U.S. Caribbean ECA to provide for far greater emissions reductions around most of the U.S. territory than are possible through the globally-applicable standards set out in MARPOL Annex VI.
- Work through the International Civil Aviation Organization (ICAO) to quantify and reduce air pollution emissions from international aviation. Learn more about EPA's work with ICAO.
- Involvement in the Stockholm Convention on Persistent Organic Pollutants.
- Involvement in the Arctic Council and its Arctic Contaminants Action Program.