MONDAY, Aug. 25 (HealthDay News) -- More than 30 percent of U.S. public schools are within a quarter mile of major highways, which puts them in the "air pollution danger zone," says a University of Cincinnati study.

Previous research has shown that proximity to major highways and pollutants spewed by vehicles can increase school children's susceptibility to respiratory diseases later in life.

In this new study, the researchers examined data on more than 8,000 schools with 6 million students in Atlanta, Boston, Cincinnati, Denver, Philadelphia, Los Angeles, Memphis, Minneapolis and San Antonio.

"This is a major public health concern that should be given serious consideration in future urban development, transportation planning and environmental policies," principal investigator Sergey Grinshpun, a professor of environmental health, said in a new release from the university.

He noted that school-age children spend more than 30 percent of their day at school.

"For many years, our focus has been on homes when it comes to air pollution. School attendance may result in a large dose of inhaled traffic pollutants that -- until now -- have been completely overlooked," Grinshpun said.

New schools should be located well away from major highways, he suggested.

"Health risk can be mitigated through proper urban planning, but that doesn't erase the immediate risk to school-age children attending schools that are too close to highways right now," Grinshpun said. "Existing schools should be retrofitted with air filtration systems that will reduce students' exposure to traffic pollutants."

The study will be published in the September issue of the Journal of Environmental Planning and Management.

More information

The American Academy of Family Physicians has more about air pollution and health.