Air Pollution Increases Blood Clot Risk

Air pollution increases the risk of deep vein thrombosis (DVT) -- dangerous blood clots in the veins -- even at pollution levels the EPA deems "acceptable."

Harvard researcher Andrea Baccarelli, MD, PhD, and colleagues in Italy studied 870 people diagnosed with DVT from 1995 to 2005. They compared their particulate air pollution exposure in the year before their diagnosis to that of 1,210 matched people without DVT.

They found that DVT risk goes up 70% for every 10 microgram-per-cubic-meterrise in particulate air pollution above 12 micrograms per cubic meter of air (the lowest pollution level measured in the study).

The U.S. EPA standard for particulate air pollution is 150 micrograms per
cubic meter of air. However, it's likely that fine and very fine particles cause most of the health risks linked to particulate air pollution. The EPA sets much lower standards for these smaller particles, which Baccarelli and colleagues did not specifically measure.

"Our findings introduce a novel and common risk factor into the pathogenesis of DVT and, at the same time, give further substance to the call for tighter standards and continued efforts aimed at reducing the impact of urban air pollutants on human health," Baccarelli and colleagues conclude.

Air pollution affects the heart and blood vessels even more than the lungs, notes Robert D. Brook, MD, a University of Michigan expert on the cardiovascular effects of air pollution. An editorial by Brook accompanies the Baccarelli report in the May 12 issue of Archives of Internal Medicine.

The study, Brook notes, adds DVT to a long list of cardiovascular illnesses linked to air pollution that includes heart attacks, heart failure, stroke, and sudden death.

However, Brook warns that while Baccarelli and colleagues link air pollution to a huge increase in DVT risk, part of this result may be due to chance or the unique circumstances of the population studied. Other studies are needed to better determine the absolute risk.

Even so, Brook says, we don't have to wait for these studies -- we already know that air pollution, even at current levels, is not healthy.

"You do not need to know every last detail about the archer who shot you with a poison arrow before you know you need to pull the arrow out," he writes.

By Daniel DeNoon
Reviewed by Elizabeth Klodas
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