Exercising outdoors is certainly preferable to being cooped up in a stuffy gym, but if you live in an urban area, the pollution from cars and buses may give you pause. It shouldn’t. Zorana Andersen from the center for epidemiology and screening at the University of Copenhagen and her colleagues report in the journal Environmental Health Perspectives that being active trumps some of the negative health effects that breathing in polluted air might have.
In a study involving 52,061 people who were followed for around 13 years, Andersen found that those who were more active were less likely to die during the study than those who were more sedentary, regardless of the pollutant levels where they lived. The researchers asked the participants to detail their physical activities, including their leisure sports, how much they walked, whether they biked or walked to work, and whether they spent time gardening. They compared these responses to the levels of nitrogen dioxide near their homes; NO2 is a gas produced from the burning of fossil fuels in cars, and is an ingredient for other harmful pollutants such as ozone and particulate matter, which can cause respiratory illnesses. Previous studies found that walking along a busy London street, for example, caused a drop in lung function and that cycling or running near high traffic roadways also compromised people’s respiratory functions slightly.
In Andersen’s study, however, people who participated in sports showed a 22% lower risk of dying from any cause during the 13-year followup, while those who cycled regularly showed a 17% lower risk and people who spent time gardening showed a 16% lower risk compared to those who didn’t do either of those activities — and regardless of the pollution levels where they lived.
“We found an even more positive message around physical activity than we even hoped for,” says Andersen. “Physiologically it’s plausible that you inhale more particles [of pollution] when you exercise in polluted areas, and we thought maybe the accumulated lifetime effect of this would reduce the benefit of exercise. But we don’t see that.”
Essentially, the benefits of being active were strong enough to overcome some of the negative effects of breathing in pollutants. That makes sense, she says, because even if people aren’t exercising to avoid inhaling pollutants, they are still exposed to them, and Andersen’s study shows that even if exercises might be exposed to slightly higher levels of compounds like NO2, that still doesn’t negate the positive effects of physical activity on their heart, blood sugar levels and more. In fact, for specific conditions, the benefits of exercising remained quite high; active people even in highly polluted areas had a 66% lower chance of dying early from diabetes compared to those who didn’t exercise.
She notes, however, that some cities may have significantly higher pollution levels than Copenhagen, where the participants lived, and it’s not clear yet how greater concentrations can affect the exercise-pollution-mortality balance. So if you have a choice for working out, biking or walking in a less polluted area, however, such as a park or a quieter side street, that might be a good idea. But don’t worry too much if you don’t. “Being active prolongs life more than staying away from air pollution,” says Andersen. “So pollution shouldn’t be a barrier to exercise.”