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Children with severe asthma develop shortness of breath and need emergency medications when exposed to ozone even at relatively low levels, according to a new report.
At the same time, children with asthma who do not require daily medication don't get much worse when ozone levels rise.
"These results suggest that even at low levels of ambient ozone, children with severe asthma are at a significantly increased risk of experiencing respiratory symptoms," said Janneane Gent, a researcher at the Yale University School of Medicine and lead author of the study. It was published Wednesday in the Journal of the American Medical Association.
The study included 271 children under 12 who lived in southern New England and were diagnosed with asthma. There were 130 children who used maintenance medications; the rest did not.
Exposure to ozone and fine particulate matter was assessed using air-quality readings from monitors around the region for each day between April 1 and Sept. 30, 2001. Respiratory symptoms and the use of rescue medications were recorded each day by the patients' mothers.
Among the children using maintenance medications, a 50 parts-per- billion (ppb) rise in ozone in one hour increased the likelihood that they would suffer wheezing by 35 percent and chest tightness by 47 percent. But there were no such effects on the asthmatic children who were not taking medications regularly.
Gent said the study's definition of severe asthma between children using maintenance drugs or not "strongly suggests there are two levels of vulnerability to air pollution."
"This study and others like it indicate that the increasing numbers of children with asthma represent an expanding pool of children at risk for respiratory symptom aggravation caused by air pollution, and by ozone in particular," said George Thurston, a professor of environmental medicine at New York University, and Dr. David Bates, an asthma specialist at the University of British Columbia.
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