Study: Airborne Pollutants Increase Risk of Fatal Coronary Heart Disease in Women

Women who live in areas with greater air pollution have a higher susceptibility of developing and dying from coronary heart disease (CHD), according to a multi-decade study accepted on Aug. 2 for publication in the peer-reviewed journal Environmental Health Perspectives (EHP). When ozone combines with particulate matter (PM), women's risk of fatal CHD can increase up to twofold. According to the authors, this is the first study to return gender-specific results on this topic.

Researchers found statistically significant increases in the relative risk of fatal CHD in females as pollution levels increased when they analyzed PM levels alone. The risk estimates were strengthened when the study also considered ozone, and strengthened further when only postmenopausal females were included.

From 1977 to 1998, researchers obtained data from 3,239 nonsmoking, non-Hispanic white adults who participated in the Adventist Health Study on the health effects of smog. Upon enrollment, participants completed a comprehensive questionnaire detailing health status, lifestyle, and education. Researchers used data from subsequent questionnaires in 1977, 1987, 1992 and 2000 to obtain follow-up information related to residence and work location histories as well as essential characteristics regarding relative exposure to ambient air pollutants, occupational fumes and dust, and indoor pollutants such as secondhand tobacco smoke.

Subjects lived within an airshed (a geographic location in which an emitted contaminant is contained for a period of time) adjacent to one of nine California airports with available visibility measures. None had any history of CHD, stroke, or diabetes.

During the 22-year follow-up, there were 155 fatal CHD cases in females and 95 among males. According to the article, those who died of CHD were older at baseline, had fewer years of education, and were more likely to have hypertension. Further, a larger proportion of the females were postmenopausal, and of these, fewer had undergone hormone replacement therapy.

Based on past research, the authors speculate that air pollution may affect females more than males because females may have a greater deposition of inhaled particles in their lungs, leading to increased health risk due to inflammatory responses to oxidative stress. They also theorize that females may be more sensitive to airborne pollution since they have fewer red blood cells than males, and thus may be more sensitive to the toxicological influences of air pollutants.

This study adds to the body of evidence supporting the adverse effects of exposure to fine particulates, and is one of the few to examine that exposure in the long term, the researchers said.

According to the study authors, these findings are in line with findings by others of an effect of PM on cardiopulmonary mortality, but are of greater magnitude, possibly because the outcome was limited to fatal CHD with better control of confounding factors such as alcohol and tobacco.

The lead author of the study was Lie Hong Chen of the Department of Epidemiology and Biostatistics at Loma Linda University. Other authors included Synnove F. Knutsen, David Shavlik, W. Lawrence Beeson, Floyd Petersen, Mark Ghamsary, and David Abbey. Funding for the research was provided by EPA. The article is available free of charge at http://ehp.niehs.nih.gov/docs/2005/8190/abstract.html.

EHP is published by the National Institute of Environmental Health Sciences, part of the U.S. Department of Health and Human Services. EHP is an Open Access journal. More information is available online at http://www.ehponline.org.

This article originally appeared in the 08/01/2005 issue of Environmental Protection.

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