Study Links Smog, Sports to Asthma
Children who live in smoggy cities and play strenuous sports are three times more likely to develop asthma than kids breathing cleaner air, according to a new study of 3,500 children by USC and government researchers.
The study is the first to show smog can cause the sickness in otherwise healthy kids. About 5 million children suffer from asthma nationwide, and its prevalence has increased dramatically in recent years. Smog is one of several suspected causes of the problem, but a cause-and-effect link has proven elusive until now.
“We’ve known for some time that smog can trigger attacks in asthmatics. This study has shown that ozone [the main component of smog] can cause asthma as well,” said Alan C. Lloyd, chairman of the state Air Resources Board, which sponsored the study. “This illustrates the need not to retreat but to continue pushing forward in our efforts to strengthen air pollution regulations.”
Although the study focuses on 13 cities in California, the researchers say the results suggest young people in such ozone hot spots as Houston, Atlanta and Phoenix may face similar risks.
The findings are part of an $18-million, decade-long children’s health study at USC. Previous studies have found that smog causes bronchitis in children, increases school absenteeism and results in decreased lung function.
Results of the study will be published Saturday in Lancet, a British scientific journal. Researchers from USC, the state air board and the National Institute of Environmental Health Sciences participated in the research.
Even as health experts encourage children to exercise more to promote well-being, the scientists involved in the study found that increased exertion on smoggy days can lead to the onset of a long-term condition that sometimes proves life-threatening. Researchers emphasize that kids need to stay fit, but parents and coaches need to be more mindful of air pollution levels.
“Exercise is really healthy for children and children should be encouraged to play team sports, but on days when air pollution levels are expected to be high, children should limit prolonged outdoor exertion,” said Dr. Rob McConnell, the study’s lead author and associate professor of preventive medicine at the USC Keck School of Medicine.
Marie Ishida, executive director of the California Interscholastic Federation, said she will refer the study to the organization’s health and safety committee for review. The federation, which oversees athletic programs involving 661,000 high school students, routinely advises school districts to avoid games and practices during hot days, but not when it’s smoggy.
“It troubles me. If it is a health and safety issue for our athletes, we certainly need to look into it,” Ishida said.
Yet the study offers some assurance for parents and children. Only kids who participated in three or more strenuous sports, including football, swimming and basketball, were most at risk. They made up just 8% of the children in the study. Whites and Hispanics, boys, and youths of both sexes from middle- or upper-income families were most likely to play multiple sports.
Whereas the researchers found that the risk of illness is greater in smoggy cities in inland valleys downwind of city cars, trucks and factories, they saw little or no effect in towns with little or no air pollution.
Pollution levels across much of California have declined since the fieldwork for the study was completed four years ago.
Scientists tracked 3,535 fourth-, seventh- and 10th- graders in seven smoggy communities--Lake Arrowhead, Mira Loma, Riverside, Upland, Glendora, San Dimas and Alpine--and six with cleaner air--Atascadero, Santa Maria, Lompoc, Lancaster, Long Beach and Lake Elsinore--from 1993 to 1998. None of the children had a history of asthma, respiratory disease, wheezing, chest injuries or surgery. Scientists took into account each child’s socioeconomic status, history of allergies and family history of asthma. By the end of the study, researchers had identified 265 new cases of asthma, mainly in the smoggy cities. Across all communities, children who played three or more sports were 80% more likely to develop asthma, and children in the smoggy cities who participated in multiple sports were 330% more likely to develop the ailment.
Ozone, created in abundance when emissions mix with sunlight, was most clearly implicated as the cause. It scars lung tissue, leads to shortness of breath, and can cause permanent loss of lung function and trigger asthmatic attacks. California has higher concentrations of the pollutant spread over a wider area than any other state.
Though the study indicates ozone can cause asthma, scientists say other factors play a role as well. Other studies have blamed latex in tires, socioeconomic status and cockroach droppings as possible causes. About 15 million Americans suffer chronic inflammation of the airways, or asthma, 50% more than 20 years ago.
