Airshed Science
Cooperation among scientists in the Puget Sound Georgia Basin ecosystem is improving knowledge of the actions needed to protect human health and the environment and prevent future deterioration of air quality.

Introduction to Airshed Science

This section addresses air pollutants, emissions and emissions inventories, and ongoing air quality research in the Puget Sound Georgia Basin region. Growth within this region continues to put stress on the environment. Expansion of suburban development, increasing transportation demands and developments in the energy sector are just a few of the challenges faced in managing air quality in the area.

What is an airshed?

An airshed is the air within a particular geographic area. The term “airshed” has been borrowed from aquatic science, in which a watershed is defined as the “land area from which water drains toward a common watercourse in a natural basin.” The Puget Sound Georgia Basin International Airshed refers to the air in the crossboundary coastal regions of Northwest Washington and Southwest British Columbia.

What is the quality of air in the PSGB airshed?

The air quality in the PSGB airshed currently meets relevant national standards in the U.S. and Canada. However, many agencies, organizations and communities are making an effort to improve regional air quality because research has not yet determined a clear threshold for health effects, particularly with respect to ozone and particulate matter. Research has shown that visibility is degraded by air pollution levels currently monitored in the region. Furthermore, the Health and Air Quality 2002 (PDF, 133 pp.) report by the British Columbia Lung Association shows that significant social and economic benefits can be achieved from continuous improvement efforts in air quality. Finally, the significant growth projected for the region threatens to overwhelm past successful efforts to improve air quality in the PSGB airshed.

For real-time information about the quality of the air where you live and work, visit AirNow.

What are the air pollutants of primary concern in the PSGB airshed?

Ground-level ozone: Ground level ozone is a gas that occurs within the air from the Earth's surface to approximately 10 miles above. It is a main ingredient of urban smog that forms via a chemical reaction between oxides of nitrogen (NOx) and volatile organic compounds (VOC) in the presence of sunlight. It is a significant health risk, especially for people with asthma and other chronic respiratory conditions. It also damages crops, trees and other vegetation.

Fine particulate matter (PM_2.5): Particles suspended in the air, including dust, dirt, soot, smoke, and liquid droplets, are known as particulate matter. PM_2.5 is particulate matter 2.5 micrometers in diameter and smaller. PM is linked to a variety of health and environmental impacts, including aggravated asthma, impaired visibility, damaging sensitive forests and crops through atmospheric deposition, and aesthetic damage caused by soot, a type of PM.

What are the sources of air pollutant emissions in the PSGB airshed?

In Southwest BC and Northwest Washington, sources of air pollutants include area sources, transportation, industry, and agriculture.

PSGB emissions sources
Pollutants	Puget Sound	Georgia Basin (Lower Fraser Valley)
Oxides of Nitrogen (NOx)	On-road mobile, marine vessels	On-road mobile, marine vessels
Volatile Organic Compounds (VOC)	On-road mobile, natural sources	On-road mobile, solvent evaporation, stationary sources, natural sources
Sulfur Dioxide (SO2)	Point industrial sources, marine vessels	Point industrial sources, marine vessels
Ammonia (NH3)	Agriculture	Agriculture
Particulate Matter (PM10)	Agriculture, woodstoves and fireplaces, transportation (diesel)	Agriculture, woodstoves and fireplaces, transportation (diesel)
Fine Particulate Matter (PM2.5)	Woodstoves and fireplaces, transportation (diesel)	Transportation (diesel)

Source: Washington State Department of Ecology, Greater Vancouver Regional District and Fraser Valley Regional District

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Air Quality