Schools that are located near busy roads may be more dangerous than remote schools due to the increased levels of air pollution generated by passing cars, a new study finds.

Toxic chemicals found in the air pose a growing concern for scientists studying brain health, especially among adolescents. Experts call them neurotoxicants, and they’ve been linked with a higher risk of suicide, autism, and the myriad direct physical effects of breathing in harmful air, such as asthma and diseases of the lungs.

“From animal studies we know that ultrafine particles cross the blood brain barrier, interact with the microglial cells, which in turn affects neurons,” said Dr. Jordi Sunyer, lead author of the recent study from the University of Barcelona. This can result in chronic low-grade brain inflammation, he added, which delays brain maturation.

To better understand how air pollution could affect kids’ brain development, Sunyer and his colleagues from the Centre for Research in Environmental Epidemiology (CREAL) collected data on 2,715 children ages 7 to 10, who attended 39 schools in Spain. Every three months for a year, the researchers issued tests that were designed for the kids’ cognitive abilities in three domains: working memory, superior working memory, and attentiveness. In other words, they wanted to check how strong their brains were.

Comparing kids from heavily trafficked schools and those less bogged down by pollution, the CREAL team found an 11.5 percent increase in working memory at the clean-air schools, but only a 7.4 percent increase at the highly polluted schools. The findings suggest vast room for improvement, Sunyer says. Both parents and local governments can take steps to making sure an area stays pollutant-free and ensuring a child’s brain develops at a normal rate.

Choosing a more active form of transportation, such as walking or riding a bike, can go a long way toward increasing overall health and avoiding adding to the pollution. More on the technological side of things, school buses can install particle filters and stay conscious to turn the engine off at stoplights. Adds Sunyer, “if classrooms are oriented to the busy roads, they could capture indoor air from an opposite origin,” which would make the room cleaner.

Ideally, improvements would start higher up, the researchers claim. Parents and children can take certain precautions and make changes to their lifestyles, but ultimately, a cleaner neighborhood is the most sustainable solution. “Policy should set plans for improving the air quality in areas with high traffic related air pollution,” Sunyer said. “These plans necessarily require reduction of traffic.”

At stake could be a slew of behavioral, intellectual, and social problems spurred on by rising levels of nearby pollution. As the authors explain, this could have life-long effects that limit children’s achievement as they age. New schools should take these findings into account when deciding where to break ground.

Source: Sunyer J, Esnaola M, Alvarez-Pedrerol M, et al. Association between Traffic-Related Air Pollution in Schools and Cognitive Development in Primary School Children: A Prospective Cohort Study. PLOS Medicine. 2015.