Many who exercise outdoors prefer to do so for the fresh air, but in areas with high air pollution, many worry that that quality of air and exercise can be an unhealthy combination. Recent studies have demonstrated evidence that the long-term benefits of exercise outweighs the potentials risks of exercising in polluted areas.
Air pollution is a concern, because during aerobic activity, people tend to inhale more air and breathe it in more deeply, taking in 10 to 20 times as much air as sedentary people. In addition, they are also more likely to mostly breathe through the mouth, bypassing the nasal passages that would normally filter airborne pollution particles. This means that more pollutant particles would enter the lungs and settle there, causing irritation/inflammation, or continue into the bloodstream.
A 2004 review of pollution studies found that during exercise, even low concentrations of pollutants caused lung damage to a similar degree that higher concentrations affects those not exercising. A study from the University of Edinburgh also found that blood and oxygen could not flow easily to the muscles of subjects who rode their bikes along a city highway during rush hour. They also found lower levels of a protein, tPA, which dissolves blood clots. This is important, because if clots are not dissolved, arteries can be left blocked and the heart damaged. Adverse effects of exposure like reduced lung function have also been observed in runners and cyclists who exercise along heavy traffic routes during rush hour.
According to the Mayo Clinic, the exposure could lead to damage of airways and increased risk of asthma, heart attacks and strokes, and death from lung cancer or cardiovascular disease.
Despite these risks, experts are not saying people should give up on exercise completely, and some studies show that the exercise might be worth it.
The results of a study revealed that over the long-term, the beneficial effects of exercise on mortality risk was not reduced by exposure to air pollution. In fact, even with high exposure to air pollution, mortality risk was reduced up to 25% with exercise. The results of this study is complemented by another study, which provided evidence that habitual exercise may help reduce the risk of premature death attributed to air pollution.
Evidence from the University of British Columbia also seemed to contradict the above claims that working out harder means taking in more pollutants. Rather, they found that higher-intensity exercise was associated with weaker effects from pollution.
Still, despite the results of these studies, the amount of exposure to air pollution should be cut down. The pollution is no excuse to not exercise, because there will still be exposure whether it is by running outside or driving a car. The Mayo Clinic advises people to monitor pollution levels in order to avoid working out when pollution levels tend to be highest (midday, afternoon, and during rush hour) and near high-pollution areas. Those who have conditions more sensitive to pollution exposure, such as those with asthma, diabetes, heart or lung conditions, or lower respiratory disease, should check with their doctors before exercising outdoors.