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
"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
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
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