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Play Ball! But Play Inside on Smoggy Days

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WebMD Health News

May 24, 2001 (San Francisco) -- Exercise is supposed to be good for you. But too much exercise in highly polluted areas may be a risky activity for children, according to a new study presented here at an annual meeting of lung specialists.

"Too much exercise in a high-pollution area might increase the risk of asthma," public health expert Talat S. Islam, MBBS, MSc, tells WebMD. Islam reported his findings at the 97th International Conference of the American Thoracic Society.

Previous studies have shown that air pollution triggers asthma attacks and breathing problems in people who already have asthma. And for some asthmatics, exercise can worsen asthma. Until now, however, no studies had investigated the effect of exercising outside in different levels of air pollution.

In the study, researchers followed about 3,500 children aged 8-14 in 12 Southern California communities for four years. Each of the communities had different levels of ozone, a key indicator of air pollution. The children were healthy with no history of asthma when they entered the study.

Over time, parents filled out questionnaires asking about the children's involvement in outdoor sports like soccer, tennis, football, and basketball. The youngsters were checked at school for symptoms of asthma.

During the study, 265 children reported a new diagnosis of asthma. After adjusting for other factors linked to asthma, like income status, race, and wheezing, the researchers correlated each child's asthma status with their participation in team sports and the ozone level of their community.

Researchers found that in communities with high ozone levels, children participating in three or more team sports were three times more likely to develop asthma than children participating in no sports. In contrast, sports participation in low-ozone communities had little effect on the risk for asthma.

The bottom line is that lots of sports activity where the pollution was worse spelled a much greater risk of asthma.

"When there is too much pollution, it is probably better to exercise indoors or in a controlled environment where you don't expose yourself to the pollution," Islam tells WebMD. "In the low-ozone communities, there is no effect. But all the signal is coming from the high-ozone communities."

In fact, researchers found that active children with the greatest risk of getting asthma in high ozone areas had no history of wheezing symptoms at the beginning of the study period.

While exercise is generally healthy, the new study suggests that environmental factors may turn a plus into a medical minus.

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