April 14, 2003

Three-year review produces science-based guidance on particulates for policy makers

The final report culminating a three-year review of the current state of knowledge on particulate matter (PM) in North America was released at the annual conference of the American Association of Aerosol Researchers, held in Pittsburgh, Pennsylvania at the end of March.

The review was carried out by 42 air quality scientists from Canada, the U.S. and Mexico. . The contributing scientists included nine Canadians. Their report, Particulate Matter Science for Policy Makers, was produced to provide science-based guidance for governments and other agencies working to reduce air pollution throughout North America. It sets out a comprehensive overview of the situation across the continent, defines problem areas, and offers guidance for effective action to reduce PM, a recognized health concern.

The study concludes with a summary of current knowledge for nine key regions in North America, including smog-prone areas such as Los Angeles, Mexico City, the U.S East Coast, British Columbia's lower Fraser Valley, and the Windsor-to-Quebec City corridor. These descriptions provide a template for communicating science to air quality managers.

The report was co-ordinated by the North American Research Strategy for Tropospheric Ozone and Aerosols (NARSTO), a three-country agency of government, university and industry representatives. The review was co-chaired by Marjorie Shepherd of Environment Canada's Meteorological Service of Canada; Peter McMurry of the University of Minnesota's Department of Mechanical Engineering; and James Vickery of the U.S. Environmental Protection Agency's office of research and development.

Reducing particulates is a complex task, says the report, since they have a wide variety of sources, and can be formed under many different conditions. Some PM, such as from forest fires, is natural in origin. However, most of the finer airborne particles, which are the greatest health concern, originate from the burning of fossil fuels in motor vehicles, homes and industry.

The researchers cite a considerable and growing body of evidence pointing to an association between adverse health impacts, especially on the cardio-respiratory system, and short- and long-term exposures to airborne particles. The finer particles are of greatest concern, because they are so small that they can penetrate deeply into the lungs, and aggravate existing heart and lung disease.

The report demonstrates that the science is a key input in developing the most effective strategies to reduce airborne particles. These strategies will have to take into consideration both local and distant sources of air pollution, as well as prevailing weather conditions, topography and seasonal variations. Management plans will have to be tailored specifically to each region, since actions that are effective in one area may not work as well in another.

Finally, the new PM science assessment confirms that the regulatory and other measures that make up Canada's clean air agenda, including international co-operation, are on the right track and will contribute to improving air quality in Canada. The agenda is designed to meet the Canada-Wide Standards for PM, which were set in June 2000.

NARSTO's mission is to provide scientific advice to guide action to reduce smog, including ground-level ozone and airborne particles. The first NARSTO assessment, completed in 2000, focused on ground-level ozone across North America. Funding and in-kind support for its PM assessment were provided by the Canadian, U.S. and Mexican governments, as well as the North American Commission on Environmental Co-operation, and members of the U.S. energy and motor vehicle industry.

More information is available on the NARSTO Web site, www.cgenv.com/Narsto/, or from Heather Mackey at Environment Canada, 416/739-4766. A Canadian PM fact sheet may be viewed at www.ec.gc.ca/air/p-matter_e.html.

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