Air pollution from high-traffic roads increases the risk of asthma in children who attend nearby schools, new research suggests.

In a study that looked at statistics on children's health in Southern California communities, researchers found that those who attend schools near high-traffic areas are 45 percent more likely to develop asthma, although the number of students in the study who developed asthma was small.

"Exposure to pollution at locations other than home, especially where children spend a large portion of their day and may engage in physical activity, appears to influence asthma risk," Dr. Rob McConnell, professor of preventive medicine at the Keck School of Medicine of the University of Southern California and lead author of a new study, said in a university news release.

The researchers examined a previous study of kindergartners and first-grade students who initially didn't have asthma. In that study, researchers followed-up with the children for three years and examined traffic around their schools and homes. The investigators also monitored air pollution levels around the 13 communities that were studied.

Of the 2,497 students, 120 developed asthma.

"It's important to understand how these micro-environments where children spent a lot of their time outside of the home are impacting their health," McConnell said. "Policies that reduce exposure to high-traffic environments may help to prevent this disease."