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High Ozone May Raise
Asthma Risk in Athletic Kids


NEW YORK (Reuters Health) - For children who live in areas with high ozone levels, playing several team sports may more than triple the risk of developing asthma, study findings suggest.

The results do not mean that children should stop playing sports, the study's lead author told Reuters Health. But parents may want to pay attention to ozone levels, according to Dr. Rob McConnell from the University of Southern California in Los Angeles.

"No one should stop exercising because of our study," McConnell said. But it would be a good idea to restrict outdoor activity on days when ozone levels are high, the California researcher noted.

"Here in southern California, predicted pollution levels are available in the daily paper, and schools are advised that children should not engage in vigorous, extended outdoor activity on those days," he said. McConnell advised parents to heed those warnings and consider contacting school officials to see whether they follow these recommendations.

In the long term, despite advances in reducing air pollution, "our research suggests that we and our government must do more to control pollution," McConnell said. He noted that besides affecting childhood asthma, air pollution has many other harmful effects, including increasing death rates among the elderly and impairing normal lung development in children.

Asthma is the most common chronic disease in children, and for reasons that are unknown, the number of asthma cases has been on the rise in the US and other developed countries.

Asthma is "almost certainly" caused by more than one factor, probably a combination of environmental exposures and an inherited predisposition to the illness, McConnell said.

Air pollution is known to exacerbate asthma in the short run, but there is little evidence showing whether ozone and other air pollutants can cause new cases of asthma, he explained.

"Our study provides evidence that ozone is involved in the development of new-onset asthma in children who exercise heavily," McConnell said. This high level of exercise increases the amount of ozone that enters the children's lungs, he said.

In the study, McConnell and his colleagues followed more than 3,500 children from 12 communities in southern California. At the start of the study, the children were 9 to 10, 12 to 13 or 15 to 16 years old.

None of the children had been diagnosed with asthma when they enrolled in the study, although some had a history of wheezing.

By the end of the 5-year study, 265 children had been diagnosed with asthma, the researchers report in the February 2nd issue of the medical journal The Lancet.

Overall, children living in communities with high ozone levels who played team sports were more likely to develop asthma. The risk of asthma increased with each additional sport played by a child in a high-ozone community.

In high-ozone areas, students who played three or more sports were more than three times as likely to develop asthma than schoolmates who did not play sports. But playing sports did not increase the asthma risk in children who lived in low-ozone areas.

Similarly, the time children spent outdoors affected the risk of asthma only in children living in high-ozone areas.

The study "is by no means conclusive proof that air pollution causes asthma, but it may be a piece of the complicated asthma puzzle that many investigators are trying to put together," McConnell said.

Unlike ozone, other air pollutants, such as nitrogen oxide, acid in the air, and particulate matter did not increase the risk of asthma among student athletes.

SOURCE: The Lancet 2002;359:386-391.

Reference Source 89



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