Living near a freeway may increase child's risk of asthma

• Living near a freeway may mean more than the annoying rumble of cars and trucks: For children, it brings an increased risk of asthma, according to researchers at the Keck School of Medicine of the University of Southern California.
• Scientists studying air pollution levels in 10 Southern California cities found that the closer children live to a freeway, the greater their chance of having been diagnosed with asthma.
• They report their findings in the November issue of the journal Epidemiology.
• Researchers also found that children who had higher levels of nitrogen dioxide, or NO2, in the air around their homes were more likely to have developed asthma.
• "These results suggest that tailpipe pollutants from freeway traffic are a significant risk factor for asthma," says lead author James Gauderman, Ph.D., associate professor of preventive medicine at the Keck School.
• "These results have both scientific and public health implications," says David A. Schwartz, M.D., director of the National Institute of Environmental Health Sciences, the federal agency that funded the study.
• The investigators placed air samplers outside the home of each student to measure NO2 levels.
• In addition, they determined the distance of each child's home from local freeways, as well as how many vehicles traveled within 150 meters (about 164 yards) of the child's home.
• Finally, they estimated traffic-related air pollution levels at each child's home using models that take weather conditions, vehicle counts and other important factors into account.
• It was not surprising, then, when they found that the closer the students lived to a freeway, the higher the students' asthma prevalence.
• For every 1.2 kilometers (about three-quarters of a mile) the students lived closer to the freeway, asthma risk increased by 89 percent.
• For example, students who lived 400 meters from the freeway had an 89 percent higher risk of asthma than students living 1,600 meters away from the freeway.