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When Fresh Air Isn’t

By Katherine Bowers
April 9, 2012; 2:22 PM ET
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Right around the time when the days start getting longer and temps begin to rise, it's normal to want to ditch your spin class and liberate the road bike that's been sitting idle in your garage. What's not to love about filling your lungs with fresh spring air?

Actually, there is something. If your favorite bike path winds along a busy thoroughfare, or the tennis court you frequent is located near a traffic-clogged intersection, you may be loading your lungs with harmful pollutants in the form of ozone (the main component of smog) and microscopic bits of soot, dust, aerosol, metal, free radicals, and other airborne contaminants. Not only does this toxic assault on your lungs compromise the effectiveness of your workouts, but it can also take a toll on your health.

Running on Fumes

First, some good news. The air we breathe has become a lot cleaner in the past 30 years. Since 1980, emissions of the six worst pollutants have dropped by nearly 50 percent, thanks to stricter laws regulating air quality. But here's the thing: People who exercise outdoors may still breathe in up to 10 times more airborne nastiness than those who spend less time being active outside. Whether your workout of choice is running, cycling, or taking boot-camp classes on the beach, doing any kind of vigorous outdoor exercise that causes you to breathe hard means you are gulping more air than if you were standing still, says Sam Callan, USA Cycling's sport science and coaching education manager. Even moderate exercise, such as a brisk walk, can increase the amount of air you inhale. And along with all that extra muscle-fueling oxygen comes supersize portions of unhealthy pollution.

What's worse, as you huff and puff through your mouth, some of that contamination whooshes deep into your lungs, bypassing your nasal passages, the body's natural air filter. The result? An irritated and inflamed trachea and lungs. You may wind up with symptoms such as a pesky cough, chest tightness, or a scratchy throat.

Over time, regular exposure to pollution may trigger exercise-induced asthma (an attack of wheezing and airway constriction during a workout) and ups your risk for lung cancer by 20 percent, the same as a nonsmoker living with a smoker, says George D. Thurston, Sc.D., a professor of environmental medicine at New York University School of Medicine. Joggers who regularly run in high-ozone conditions may experience a thickening of the lining of their lungs (typically a smoker's affliction), which may prematurely age the lungs, although the exact health consequences are unknown, says Daniel Greenbaum, president of the Health Effects Institute, a Boston nonprofit organization that studies pollution's impact on health.

Yet these effects often go unnoticed. In fact, the fitter you are, the less likely you are to see signs. "Healthy people can be affected by air pollution without experiencing symptoms," says Norman Edelman, M.D., chief medical officer of the American Lung Association. So even if you feel fine, your lungs and workout still take a hit.

In a 2008 study, cyclists pedaled in polluted conditions. Three days later, the distance they could ride decreased by 5 percent. And women, who have smaller airways, are more affected by the irritation and swelling that restricts oxygen intake than men are. A 2010 study of marathon runners published in Medicine & Science in Sports & Exercise found that higher rates of pollution slowed women's race times, while men were unaffected.

Continue to to read more about how pollution can effect your body, and tips on how to avoid it.

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