Vancouver-Seattle Air Pollution Harming Health, Environment

VANCOUVER, British Columbia, Canada, October 1, 2004 (ENS) - Rapid growth in population, transportation demands and energy consumption in the adjacent airsheds of southern British Columbia and northern Washington are stressing the region's environment and public health, according to a new study by scientists from Canada and the United States.

The Georgia Basin airshed and the Puget Sound airshed are separate, but linked, and both are impacted by air pollution blowing in from the other area as well as self-generated air pollution, according to the study "Characterization of theGeorgia Basin-Puget Sound Airshed Report," released on Thursday.

Environment Canada and the U.S. Environmental Protection Agency, released the study "in support of the development of an international airshed strategy between Canada and the United States," the agencies said.

Smog in the Lower Fraser River Valley of British Columbia (Photo courtesy Environment Canada)

Ambient concentrations of air pollution, at present levels, have "a negative impact on human health and the environment," writes Environment Canada Senior Scientist Bruce Thomson, who prepared the study for Canada. "These results support the need for continuous improvement of air quality," he concluded.

Population in the region has grown to over seven million people, mainly in the Greater Seattle and Greater Vancouver areas. The population has grown from about six million in 1991, and is expected to be as much as 50 percent larger - about nine million - by 2020.

Because wind flow patterns move pollutants across the international border in both directions through all seasons of the year, the management of air pollution in the Georgia Basin/Puget Sound airshed will require coordinated attention by both Canada and the United States, the study advises.

Polluting emissions from vehicles are projected to decrease over the next decade in both airsheds, the study found, but emissions from the marine sector are increasing, as are emissions from agricultural practices.

Emissions from cruise ships like this one contribute to the region's air pollution. (Photo courtesy Environment Canada)

The amount of ground-level ozone, or smog, in the air is primarily the result of photochemical reactions. Ozone and its precursors can be transported great distances, so the highest ambient ozone concentrations were found downwind of urban centers and at high elevations in rural areas.

Sulfur dioxide (SO2), organic carbon and nitrogen oxides (NOx) are the dominant pollutants responsible for degraded visibility, the analysis found.

SO2 and NOx emissions are transformed in the atmosphere to sulphates and nitrates, which combine chemically with ammonia from agricultural sources and with sodium from natural marine emissions to form fine particulate matter.

"Improving visibility will require attention to SO2, organic carbon, NOx and ammonia sources," the study concludes.

Seattle's growing population contributes to the region's air pollution. The Puget Sound Clean Air Agency maintains webcams supplying current air quality information three times each day. (Photo courtesy Puget Sound Clean Air Agency)

Natural emissions of volatile organic compounds (VOCs) from trees and other vegetation represent from one-third to one-half of the total VOC emissions in the Basin, the study found. VOCs are a component of smog.

The authors conclude that the magnitude of these natural emissions "poses limits on achievable reductions in total VOC emissions in the Basin. Natural VOC emission levels also limit the effectiveness of NOx emission controls in reducing ambient particulate matter and ozone concentrations.

Ozone concentrations of 40 to 50 parts per billion are often recorded at rural coastal locations in the spring and identified as "background" concentrations.

These concentrations are caused by emissions from both natural and human sources, including transport from outside the Basin. Because part of thisbackground ozone is generated by human activities it is somewhat "controllable," the study concludes.

The stagnant weather associated with episodes of poor air quality usually impacts the Georgia Basin and Puget Sound airsheds simultaneously. During these episodes, the movement of air pollutants between airsheds is limited. Still, strategies taken to address episodes of poor air quality will continue to require coordinated international action in the Georgia Basin airshed.

Environment Canada features the report on its website at: http://www.pyr.ec.gc.ca/Air/gb_ps_airshed/summary_e.htm.