Exercise Is Good for You, Even in Polluted Cities

Even in cities with badly polluted air, the health benefits of walking or bicycling outweigh the risks of breathing dirty air, a new study contends.

Researchers used computer simulations to compare the risks and benefits of walking or cycling in a range of air pollution levels. In most cities worldwide, the risks from air pollution do not cancel out the positive effects of cycling and walking, the study found.

Only 1 percent of cities have air
pollution levels high enough to negate the benefits of cycling 30 minutes every day, the researchers said.

"Our model indicates that in London health benefits
of active travel always outweigh the risk from pollution. Even in Delhi, one of the most polluted cities in the world -- with pollution levels 10 times those in London -- people would need to cycle over five hours per week before the pollution risks outweigh the health benefits," said study leader Dr. Marko Tainiio, of the University of Cambridge in England.

"We should remember, though, that a small minority of workers in the most polluted cities, such as bike messengers, may be exposed to levels of air pollution high enough to cancel out the health benefits of physical activity," Tainiio added in a university news release.

Study senior author James Woodcock said: "Whilst this research demonstrates the benefits of physical activity in spite of air quality, it is not an argument for inaction in combating pollution. It provides further support for investment in infrastructure to get people out of their cars and onto their feet or their bikes -- which can itself reduce pollution levels at the same time as supporting physical activity."

Regular exercise reduces the risk of heart disease, diabetes and several cancers, and one way for people to boost their physical activity levels is through "active travel" such as walking and cycling, the study authors said.

The study appears May 5 in the journal Preventive Medicine.