By VERONICA SIKKA, M.D.

Eat healthy. Exercise. Don't smoke.

These are all tips we've heard on ways to reduce the risk of heart attacks and blood clots. But most people would never think air pollution can increase their risk.

A study, published today in the Journal of the American Medical Association, found that a drop in air pollution levels during the 2008 Beijing Olympics was linked to decreased risk factors for heart problems, stroke and blood clots there.

Authors of the research attributed the improved air in China's capital to a decreased amount of traffic in normally congested areas during this time. Two weeks after the Olympics, the air pollution returned to its normally high levels - and so did the risk factors in Beijing's inhabitants.

While previous research has suggested such a link, "this study is different because it is the first study to show how air pollution affects young and healthy hearts," said Junfeng Zhang, professor of environmental and global health at the University of Southern California and one of the authors. "It also shows how our body responds rapidly to changes in pollution."

In separate research, Dr. Tim Nawrot, associate professor at Hasselt University in Belgium, led a 50-year review of the literature on the relationship between heart attacks and air pollution. His findings also supported the link between air pollution and heart disease - and he believes the impact can even be quantified.

"On a population level, our study found that air pollution is comparable to other triggers for heart attacks such as using cocaine, stress, physical exertion, and excess coffee or alcohol," Nawrot said. "Actually, we can say that at a population level, 5 percent of heart attacks are triggered by air pollution."

In light of the growing body of research, major organizations such as the American Heart Association are taking notice.

"Previously we thought that air pollution affects only the lungs but there is a huge body of evidence that suggests air pollution synergizes with other risk factors such as diabetes, high cholesterol, smoking, obesity, and hypertension to increase the risk of having a heart attack," said  Dr. Sanjay Rajagopalan, professor of cardiovascular medicine at Ohio State University and a member of the heart association's  Scientific Statement Committee. "In and of itself, air pollution is a weak factor, but in conjunction with other risk factors, it can amplify the risk for heart attacks."

So what can be done in light of today's study? Zhang suggests greater use of public transportation and not going outdoors when levels of air pollution are high.

Rajagopalan said people should focus on the things they can control, such as blood pressure, cholesterol, diabetes, and smoking.  He also suggests avoiding nonessential travel to areas that are heavy in air pollution.

Internationally, this would include India, which was found to have the worst air pollution in the entire world, followed by Bangladesh, Pakistan and China. The figures come from the 2012 Yale and Columbia Universities Environmental Performance Index.

According to the American Lung Association, the top 10 polluted U.S. cities in 2012 include:

1.            Bakersfield-Delano, Calif.

2.            Hanford-Corcoran, Calif.

3.            Los Angeles-Long Beach-Riverside, Calif.

4.            Visalia-Porterville, Calif.

5.            Fresno-Madera, Calif.

6.            Pittsburgh-New Castle, Pa.

7.            Phoenix-Mesa-Glendale, Ariz.

8.            Cincinnati-Middletown-Wilmington, Ohio/Ky./Ind.

9.            Louisville-Jefferson County-Elizabethtown-Scottsburg, Ky./Ind.

10.          Philadelphia-Camden-Vineland, Pa./N.J./Del./Md.