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Air Pollution May Diminish the Benefits of Exercise

You might want to rethink that walk along the smoggy roadway

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These days, walking is all the rage as an easy way to keep your cardiovascular system pumping and flowing with ease—particularly for older generations. But a new study suggests that for people over 60, where they walk might be just as important as how much they walk. Taking a stroll in an area with high air pollution doesn’t lead to the same benefits as a walk in the park, reports Sarah Boseley at The Guardian.

To study the rivaling effects of air pollution and exercise, researchers examined 119 volunteers over 60 years old who were either healthy or had stable coronary heart disease or chronic obstructive pulmonary disorder (COPD). The volunteers were randomly selected to either take two hour walk along Oxford Street—a bus and taxi-congested road in the heart of London—or through the quiet, green spaces of Hyde Park. During the walks, researchers measured the air quality, analyzing concentrations of black carbon, particulate and nitrogen dioxide—a highly reactive gas that primarily results from burning fuel.

The researchers compared blood pressure, lung volume and the elasticity of the volunteers' blood vessels before and after the stroll. All the volunteers received some benefit from walking, but those who walked in the green space away from the majority of the pollution received much more. An indicator of arterial stiffness, for instance, decreased by 24 percent for healthy and COPD patients and 19 percent for heart patients who walked in the park. Those who walked on Oxford street, saw fewer results. For example, for healthy patients there was no significant change the index for arterial stiffness (the largest measured difference was 4.6 percent), while COPD patients saw a 16 percent change and heart patients improved by 8.6 percent.

Overall walking significantly increased lung capacity, with the effects lasting 24 hours. But the effect was slightly magnified for park walkers compared to those strolling down Oxford Street. The research appears in the The Lancet.

“It is possible that studies such as this could support new air quality limits, it shows that we can’t really tolerate the levels of air pollution that we currently find on our busy streets,” Fan Chung, lead author of the study from the National Heart & Lung Institute at Imperial College London, says in a statement. “For people living in the inner city it may be difficult to find areas where they can go and walk, away from pollution. There may be a cost associated as they have to travel further away from where they live or work.”

Though the study only included people over the age of 60, Chung tells Boseley that it’s likely that air pollution has similar impacts on younger people as well. “I think it might well do. The only difference is that young people are much more resilient,” he says.

In fact, a report released earlier this year by the World Health Organization showed that cycling for 30 minutes in 15 of the world’s most heavily polluted cities was worse for the body than driving or staying indoors. That’s because at a certain point, inhaling fine particulates does so much damage that the benefits of exercise are not worth the effort. They calculated "tipping points" for dozens of cities, finding many in Africa and Asia where exercising two hours or less would be more harmful than beneficial.

None of these studies, however, are carte blanche to skip exercising. “The benefits of active travel outweighed the harm from air pollution in all but the most extreme air pollution concentrations,” Audrey de Nazelle, one of the authors of the WHO report told The Guardian's Nick Van Mead earlier this year. “It is not currently an issue for healthy adults in Europe in general.”

According to this earlier report, people exercising in New York, Paris and London never reach a point where the impact of pollution outweighs the benefit of exercise. So there’s no excuse. Next time you step out for a croissant, skip the boulangerie next door; head to the one 20 minutes down the road.

About Jason Daley

Jason Daley is a Madison, Wisconsin-based writer specializing in natural history, science, travel, and the environment. His work has appeared in Discover, Popular Science, Outside, Men’s Journal, and other magazines.

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