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| Smog may cause childhood
asthma Pollution does more than bring on attacks, USC study finds Jane Kay, Chronicle Environment Writer |
Friday, February 1, 2002
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In areas of smoggy air, children playing sports are three times more likely to develop asthma than those who don't actively exercise, while in regions of cleaner air, there is no such link between asthma and exercise, according to a study released yesterday. The findings by researchers at the University of Southern California are the strongest evidence yet that smog doesn't only bring on asthma attacks among those who already have it, but also may cause asthma in youngsters. Asthma is the most common childhood disease, and has increased in the last 20 years to some 9 million children. Earlier findings showed that air pollution contributed to school absenteeism and also impaired a child's growing lungs. The study found that children who participated in three or more sports such as basketball, football, soccer and softball in communities with high concentrations of ground-level ozone, the main ingredient in smog, were found to have asthma at a rate more than three times higher than children who weren't exercising in the bad air. Sports had no effect on new diagnoses of asthma in areas of relatively clean air. The results will be published tomorrow in the Lancet, a British medical journal. The findings are the latest to be released in a 10-year study financed mainly by the California Air Resources Board to examine links between air pollution and children's health. The air board, part of the state Environmental Protection Agency, regulates air quality. "We've known for some time that smog can trigger attacks in asthmatics. This study has shown that ozone can cause asthma as well," said Alan C. Lloyd, chairman of the state Air Resources Board. Between 1993 and 1998, researchers followed 3,535 children from schools in 12 Southern California towns -- six with higher than average ozone levels and and six with lower than average levels. They looked at children without histories of asthma from the fourth, seventh and 10th grades, and monitored their activities, including sports. Once a year they asked whether a doctor had given them any new diagnoses for disease. The researchers also measured air pollution, which was produced mainly by vehicles, and tracked the hourly levels of ozone, particles of dust and smoke, nitrogen dioxide and acid. Over five years, they found that asthma had been diagnosed in 264 children. Overall, children playing active sports in areas of the highest ozone were most likely to develop the disease. Asthma increased with the amount of team sports that the children played. Researchers said their analysis ruled out the possibility that the children had asthma all along but just hadn't been diagnosed until their intense participation in team sports. "Somewhat to our surprise, in low-ozone communities, we found no increased risk of asthma in children who played team sports," said Dr. Rob McConnell, associate professor of preventive medicine at the Keck School of Medicine of the University of Southern California and lead author of the study. "Exercise-induced asthma is well known. So it's not surprising to see an increase in asthma among children who play lots of team sports. But people haven't looked at the combination of sports and air pollution. The air pollution piece is interesting because we see no effect of sports in the low- ozone communities." Also, the researchers couldn't explain the increase in asthma by other factors such as socioeconomic status, family history of asthma or allergy, or housing conditions, McConnell said. The study is significant nationally because other regions -- Houston, Denver, Phoenix and Chicago -- have ozone levels that would probably produce the same health results, said Alan Lloyd, chairman of the state Air Resources Board. Although the Bay Area has violated ozone standards seven times over the past three years, its average concentrations don't place it among the nation's worst regions. "We've made significant progress in reducing air pollution, but we haven't attained health-based air quality standards," Lloyd said of the state's air. "We have to continue more stringently to make sure we attain those standards." Despite the findings, parents should encourage children to exercise because of the great health benefits, he said. "But you want to keep attuned to the health advisories, and modify outdoor activity. If there's a high pollution level, it would be unwise to go out and exercise vigorously." E-mail Jane Kay at jkay@sfchronicle.com. |
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