Chandigarh,14 May:Long-term exposure to the tiny, dirty particles in polluted air may cause blood clots in the legs, the same condition aero plane / automobile travelers’ call – Economy Class Syndrome from immobility during flight and automobile traveling, researchers said on Monday. Air pollution from automobiles and industry can contain tiny particles of carbon, nitrates, metals and other materials that have been linked over the years to a variety of health problems. It is well-established that air pollution causes myocardial infarction [heart attack] and stroke, and this is the first time that anyone has connected air pollution with deep vein thrombosis.
Scientists say they have linked long-term exposure to air pollution to a greater risk of deep vein thrombosis, or blood clots in the leg specifically to the thighs.Dr. Andrea Baccarelli of the Harvard School of Public Health, Boston who led the study while at and associates said they found the link after looking at 870 people in Italy who had developed deep vein thrombosis between 1995 and 2005.
The scientists compared the exposure to such pollution on 870 residents of the Lombardy region of Italy who had been diagnosed with deep vein thrombosis, and 1,210 residents who did not have deep vein thrombosis. The researchers used the average concentration of particulate matter measured by monitors at 53 sites. Compensating for other environmental and health factors, the researchers found that the risk of deep vein thrombosis increased by 70 percent for every increase in particulate matter of 10 micrograms per square meter. Tests showed that the blood of people more exposed to such pollution took less time to form clots. They also found the blood of patients in both the study subjects and control group members showed a shorter clotting time with higher levels of exposure to particulate matter.
Until now particulate pollution had not been linked to blood clots in the veins. The mechanism that causes problems for some air travelers is related not to the blood itself but to impaired circulation when sitting in one place without exercise for long periods of time. The effect of air polluted with particulate matter smaller than 10 micrometers in diameter — about one-40th the width of a human hair. Such particles come from the exhaust of vehicles, especially those with diesel engines, and burning of fossil fuels, the researchers said.
Previous studies have suggested such a connection, said Baccarelli, who is now an assistant professor of environmental health at the University of Milan. "Several studies in animal models and in humans have shown that particulate matter, inhaled into the lungs, causes inflammation in the lungs," he said. "The inflammation can expand the cell body, so that the incidence of coagulation is increased." The findings introduce a new and common risk for deep vein thrombosis, the researchers said and "give further substance to the call for tighter standards and continued efforts aimed at reducing the impact of urban air pollutants on human health."
"This makes a very strong case that air pollution is connected to deep vein thrombosis," said Dr. Robert D. Brook, an assistant professor of internal medicine at the University of Michigan, who wrote an accompanying editorial in the journal.
"But it is a first study and a single study," he added, "and I would be cautious about making generalizations and drawing conclusions on the basis of one study."
Still, "the results are very positive," Brook said. "Even if they are overestimating the effect, the effect, which is relatively so robust, is there. But how strong it is requires further studies."
"If future studies corroborate their findings and address some of the limitations, it may be proven that the actual totality of the health burden posed by air pollution, already known to be tremendous, may be even greater than anticipated," Brook said.
Baccarelli agreed with Brook’s assessment, saying, clearly the finding needs to be confirmed in additional studies.
The findings are published in the May 12 issue of the Archives of Internal Medicine.
Learn more about the health risks of air pollution from the U.S. National Library of Medicine. Click here
SOURCES: Andrea Baccarelli, M.D., assistant professor, environmental health, University of Milan, Italy; Robert D. Brook, M.D., assistant professor, internal medicine, University of Michigan, Ann Arbor; May 12, 2008, Annals of Internal Medicine