Traffic-related pollution near schools is linked to the development of asthma in kids according to a new study led by researchers at the Keck School of Medicine of the University of Southern California (USC).
Study's lead author Rob McConnell, professor of preventive medicine at the Keck School of Medicine of USC, and colleagues found that the risk of developing asthma due to exposure at school was comparable to that of children whose exposure occurred primarily at home, even though time spent at school only accounted for about one third of waking hours.
Children in schools located in high-traffic environments had a 45 percent increased risk of developing asthma.
The study drew upon data from the Children's Health Study (CHS), a longitudinal study of children in Southern California communities that was designed to investigate the chronic effects of air pollution on respiratory health.
Using a cohort of 2,497 kindergarten and first grade children who were asthma-free when they entered the CHS, researchers examined the relationship of local traffic around schools and homes to diagnosis of new onset asthma that occurred during three years of follow-up.
Traffic-related pollution exposure was assessed based on a model that took into account traffic volume, distance to major roadways from home and school and local weather conditions.
Regional ambient ozone, nitrogen dioxide and particulate matter were measured continuously at one central site in each of the 13 study communities.
The design allowed investigators to examine the joint effects of local traffic-related pollution exposure at school and at home and of regional pollution exposure affecting the entire community.
Researchers found 120 cases of new asthma. The risk associated with traffic-related pollution exposure at schools was almost as high as for residential exposure, and combined exposure accounting for time spent at home and at school had a slightly larger effect.
Although children spend less time at school than at home, physical education and other activities that take place at school may increase ventilation rates and the dose of pollutants getting into the lungs, McConnell noted.
Traffic-related pollutant levels may also be higher during the morning hours when children are arriving at school.
The study appears in the journal Environmental Health Perspectives.