Children in communities with high average ozone levels who compete in three or more team sports have a three-to-four-times higher risk of developing the respiratory illness than non-athletic kids, researchers report in the Feb. 2 issue of The Lancet. The more sports children participate in, the greater the effect.
"This research suggests that contrary to conventional wisdom, ozone is involved in the causation of asthma," says Rob McConnell, M.D., associate professor of preventive medicine at the Keck School and lead author of the study. Air pollution has been thought to worsen existing asthma, but not cause it.
Although asthma is the most common chronic disease of childhood, and the disease has been becoming more common for several decades, this is the first study to examine athletic activity, air pollution and the development of new-onset asthma.
"Identifying potential causes of asthma is very important because eliminating the causative factors can prevent this life-threatening disease," says John Peters, M.D., D.Sc., M.P.H., Hastings Professor of Preventive Medicine at the Keck School.
The research is part of the USC-led Childrens Health Study, an extensive investigation into pollution and kids respiratory health. Environmental health researchers have tracked levels of major pollutants and monitored the respiratory health of more than 6,000 children in a dozen Southern California communities since 1993.
For the Lancet study, researchers monitored about 3,500 of these children. Children with no history of asthma were recruited from the fourth grade (age 9 or 10), seventh grade (age 12 or 13) and tenth grade (age 15 or 16) and were tracked for up to five years.