Air pollution from traffic may slow cognitive development in children: study

Children studying in schools exposed to high levels of traffic-related air pollution are at an increased risk of having impaired cognitive development, a Spanish study said Tuesday.

The study, published in the U.S. journal PLOS Medicine, measured three cognitive outcomes -- working memory, superior working memory, and attentiveness -- every three months over a 12- month period in 2,715 kids aged seven to 10 from 39 schools in Barcelona, Spain.

Traffic-related air pollutants including nitrogen dioxide were measured twice weekly both in school playgrounds and indoor environments.

Researchers then compared the development of these cognitive outcomes in the children attending schools where exposure to air pollution was high to those attending a school with a similar socio-economic index where exposure to pollution was low.

They found that the increase in cognitive development over time among children attending highly polluted schools was less than among those attending paired lowly polluted schools, even after adjusting for additional factors that affect cognitive development.

For example, there was an 11.5 percent 12-month increase in working memory at the lowly polluted schools but only a 7.4 percent 12-month increase in this regard at the highly polluted schools.

"We found here an association between traffic-related air pollution exposure at school and cognitive development during primary school age, independent of residential air pollution and beyond the effects related to home exposures in early life found by previous studies," said the study led by Jordi Sunyer of the Center for Research in Environmental Epidemiology in Spain.

"This higher exposure level at school could be attributed to peaks of pollution occurring during school time, and higher inhaled dose during school time due to exercise and physical activity at schools," it explained.

Previously, exposure to the air pollutants produced by the combustion of fossil fuels by vehicles during pregnancy or infancy has been associated with delays in cognitive development.

Moreover, experiments in animals suggested that traffic-related air pollution is a developmental neurotoxicant, a factor that disrupts brain development.

The new findings "do not prove that traffic-related air pollution causes impairment of cognitive development," an editors' summary of the research said. "Rather, they suggest that the developing brain may be vulnerable to traffic-related air pollution well into middle childhood, a conclusion that has implications for the design of air pollution regulations and for the location of new schools."