Pollution May Hasten Hardening of Arteries

Long-term exposure tied to early development of condition

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SUNDAY, Nov. 7, 2004 (HealthDayNews) -- Long-term exposure to air pollution maycontribute to early hardening of the arteries, a new study says.

"If this can be confirmed, it would have huge implications," said Dr. Nino Kuenzli, lead author of the study, which was presented Sunday at the American Heart Association's scientific sessions in New Orleans. "Atherosclerosis is a major underlying disease process for so much morbidity and mortality in the United States. Some 50 percent of diseases and death have some underlying atherosclerosis."

Air pollution is, of course, something virtually everybody is exposed to at one level or another.

"If the findings can be confirmed, this really turns a new page on the story of chronic effects of air pollution," added Kuenzli, an associate professor of environmental health at the University of Southern California's Keck School of Medicine.

Confirmation of these findings, which are observational, is not a sure thing. "In some ways it confirms something that seems intuitively obvious -- that toxins inhaled into the body do have effects," said Dr. Stephen Siegel, a cardiologist and clinical assistant professor of medicine at New York University School of Medicine. "It supports previous notions, but still there could be other confounding factors."

Noted observational studies had found a significant reduction in heart disease in women taking hormones. A controlled study, the Women's Health Initiative, found the reverse was true, though.

In the case of air pollution, researchers had previously noted associations between bad air and cardiovascular death and heart attacks, but it hasn't been clear what the effect is early on in the process.

According to the authors, these results are the first evidence of an association between atherosclerosis and ambient air pollution.

Kuenzli and his colleagues looked at data from two clinical trials involving 798 people age 40 or older living in the Los Angeles area. They used ultrasound to measure the thickness of the inner lining of the neck arteries (known as carotid artery intima-media thickness, or CIMT).

Participants were then divided based on their geographic location, with each ZIP code given a different value based on the estimated concentration of PM2.5 particles. PM2.5 particles are air pollutants with a diameter of 2.5 micrometers or less, small enough to invade even the smallest airways. These particles generally come from activities that burn fossil fuels, such as traffic, smelting, and metal processing.

PM2.5 particles were measured in micrograms per cubic meter. For every 10 micrograms per cubic meter increase of PM2.5, CIMT increased by 5.9 percent. After adjusting for various factors, including smoking, the researchers found that CIMT increased by 3.9 to 4.3 percent for every 10 micrograms per cubic meter increase in PM2.5. There were greater increases in people over 60, women, and people taking cholesterol-lowering medication. The greatest increases were seen in women 60 or older: a 15.7 percent rise in CIMT for every 10 micrograms per cubic meter.

The changes observed were similar to those that occur in people living with smokers, Kuenzli said.

According to Kuenzli, air pollution can cause inflammatory responses both in the body's respiratory tract and in the blood vessels. In the case of the circulatory system, this can eventually lead to thickening of the artery wall and its attendant problems.

Rabbit studies had shown that exposure to airborne particles produced all the signs of atherosclerosis, while human studies have shown that inhaling these particles resulted in systemic inflammation. "We think it's plausible," Kuenzli said.

Although the findings do need to be confirmed, maybe this information is enough to spur some action. "This really tells us that air pollution chronically contributes to theunderlying process toward cardiovascular morbidity and death, not justyesterday's pollution or pollution during last two or three years of yourlife," he said. "This is really something that starts at birth."

"We are not policymakers, but it's obvious what you do. It's just not right to support an environment that is clearly unhealthy for a large mass of the population," Kuenzli added. "We know where air pollution is coming from, thus it's absolutely clear that we should clean up the air with more stringent policies."

"It is nice to have these things quantified so they can be used as a basis for public policy," Siegel said. "That's what the government needs sometimes, to have things put in terms of numbers. Whether it's generating any real new science, I couldn't tell."

More information

The Environmental Protection Agency has tips on what you can do to reduce air pollution.

SOURCES: Nino Kuenzli, M.D., Ph.D., associate professor, environmental health, Keck School of Medicine, University of Southern California, Los Angeles; Stephen Siegel, M.D., clinical assistant professor, medicine, New York University School of Medicine, New York City; Nov. 7, 2004, presentation, American Heart Association's scientific sessions, New Orleans

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