February 12, 2007

Air Pollution Tied to Cardiovascular Risks in Women

A congested and polluted city highway

Where a woman lives — and how polluted the air is in her neighborhood — may affect her risk of developing or dying from cardiovascular disease, according to a recent study of nearly 66,000 older women in 36 metropolitan areas.

While previous research has identified a link between air pollution and heart disease, the new findings offer the first large-scale look at long-term exposure to air pollution in specific communities, rather than averaging data across an entire city. The new study is also unique in that it included only women who had no previously diagnosed cardiovascular conditions at the start, and then monitored their health and exposure to pollutants over time.

To conduct this study, Dr. Joel D. Kaufman of the University of Washington in Seattle and his colleagues took advantage of the wealth of patient-related data already collected through the Women's Health Initiative funded by NIH’s National Heart, Lung and Blood Institute (NHLBI). The researchers considered a specific subset of 65,893 women, ages 50-79, who had no history of cardiovascular events and who did not move from their original communities during about six years of follow-up evaluation.

The investigators relied on community air pollution data compiled by the U.S. Environmental Protection Agency (EPA), which funded the team's study along with NIH's National Institute of Environmental Health Sciences (NIEHS). Pollution monitors in each community measure levels of several air contaminants, including sulfur dioxide, nitrogen dioxide, carbon monoxide, ozone, and both fine and larger airborne particles. All of the study participants lived relatively close to 573 different fine-particle monitors in 36 cities.

In the February 1, 2007, issue of the New England Journal of Medicine, the researchers reported that cardiovascular risks differed depending on which city a woman lived in, with even greater variations observed among the different communities within each city. The women who had greater exposure to fine-particle air pollution were at increased risk for both fatal and nonfatal cardiovascular conditions, including heart attack, stroke and coronary bypass surgery. No other pollutants appeared to be associated with cardiovascular risk.

"Fine particles” are those up to 2.5 microns in size, or about 1/30th the width of a human hair. These fine particles generally come from power plants, industry and automobile exhaust. The researchers estimated that each increase in fine-particle concentration of 10-micrograms per cubic meter of air increased the risk of a cardiovascular event by 24% and increased the risk of death from cardiovascular disease by 76%.

The researchers say their study confirms and expands on earlier evidence linking fine-particle air pollution to cardiovascular risk. What's still not known — but under intensive study by Kaufman and others — are the mechanisms by which fine airborne particles damage arteries, the heart and cardiovascular tissues.

— by Vicki Contie

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