Green Car Congress: Study finds even moderate air pollution can raise stroke risks; risk rises within hours of exposure

Air pollution, even at levels generally considered safe by federal regulations, increases the risk of stroke by 34%, according to a new study by researchers at Beth Israel Deaconess Medical Center. Stroke is a leading cause of long-term disability and the third leading cause of death in the United States. An estimated 795,000 Americans suffer a new or recurrent stroke every year, resulting in more than 135,000 deaths and 829,000 hospital admissions.

Writing in the 14 Feb. 2012 issue of the Archives of Internal Medicine, researchers who studied more than 1,700 stroke patients in the Boston area over a 10-year period found exposure to ambient fine particulate matter, generally from vehicle traffic, was associated with a significantly higher risk of ischemic strokes on days when the EPA’s air quality index for particulate matter was yellow instead of green. The team focused on particles with a diameter of 2.5 millionths of a meter: PM_2.5.

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The link between increased stroke risk and these particulates can be observed within hours of exposure and are most strongly associated with pollution from local or transported traffic emissions. Any proposed changes in regulated pollution levels must consider the impact of lower levels on public health.

—Murray A. Mittleman, MD, DrPH, the study’s senior author