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Air Pollution Linked to Heart Deaths

Risk May Be Higher Than Previous Studies Suggest
WebMD Health News
Reviewed by Louise Chang, MD

Jan. 31, 2007 -- Air pollution is a much bigger factor in death from heart disease or stroke than has previously been recognized, according to findings from one of the largest studies ever to examine the issue.

Researchers followed close to 66,000 women -- aged 50-79 -- living in 36 cities. All the women were enrolled in the ongoing health study, the Women’s Health Initiative.

After adjusting for other risk factors for heart disease and stroke, they found that air quality was a strong predictor of heart disease and stroke risks -- and an even stronger predictor of death from heart disease or stroke.

Fine particulate air pollution -- caused primarily by vehicle exhausts, coal-fired power plants, and other industrial sources -- was the sole type of air pollution associated with increased risk.

When all other risk factors were equal, the researchers found that women living in the most polluted cities had the highest heart disease and stroke risks, while women living in the cleanest cities had the lowest.

A resident of Birmingham, Ala., one of the smoggiest cities included in the study, would have roughly a 76% increased risk of dying from cardiovascular causes than someone living in Tucson, Ariz., which was among the cities with the cleanest air.

Researcher Joel Kaufman, MD, MPH, of the University of Washington, tells WebMD that the findings highlight the importance of taking steps to reduce levels of fine particulate pollution in the air.

The study, funded in part by the Environmental Protection Agency (EPA), is published in the Feb. 1 issue of The New England Journal of Medicine.

“We have to think seriously about pollution exposures,” Kaufman says. “Pollution is not just a nuisance, it affects human health. We should be working to reduce exposures in whatever ways we can.”

More Exposure, Greater Risk

The study included only postmenopausal women, and there is some suggestion that this group is particularly vulnerable to the effects of air pollution. That is because a woman’s heart disease and stroke risks rise dramatically with menopause.

But there is little reason to believe that heart disease and stroke risks associated with exposure to dirty air are dramatically different for women and men, Kaufman says.

A total of 65,893 women without a history of heart disease or stroke were followed for an average of six years. During this time, 1,816 of the women experienced fatal or nonfatal cardiovascular events.

EPA air quality data were examined to determine each woman’s level of exposure to air pollutants, depending on where she lived.

Fine particulate air pollution is measured in micrograms per cubic meter. According to the EPA, fine particles of 2.5 micrometers or smaller are in smoke and haze. They can occur because of gases from industrial plants and cars.

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