Air pollution influences childhood brain development, intelligence

Smog can debilitate the brain development in children, according to a recent study. Researchers from the University of Washington reveal air pollution can influence childhood behavioral problems and even their intelligence.

The study shows that children whose mothers experienced higher nitrogen dioxide exposure during pregnancy were more likely to have behavioral problems. Air pollution effects in children just didn’t stop in utero. Researchers also report that higher exposures to small-particle air pollution when children were 2 to 4 years old was associated with poorer behavioral functioning and cognitive performance.

“Even in cities like Seattle or San Francisco, which have a lot of traffic but where the pollution levels are still relatively low, we found that children with higher prenatal NO2 exposure had more behavioral problems, especially with NO2 exposure in the first and second trimester,” says lead author Yu Ni, a postdoctoral scholar in the Department of Environment and Occupational Health Sciences, in a statement.

Researchers analyzed data from 1,967 mothers recruited during pregnancy from six cities: Memphis, Tennessee; Minneapolis, Minnesota; Rochester, New York; San Francisco California; Seattle, Washington; and Yakima, Washington. The participants were enrolled as part of three separate studies which was combined under a major National Institutes of Health initiative called ECHO. The program brings together multiple pregnancy cohorts to address key child health concerns.

University researchers developed a state-of-the-art model to monitor air pollution levels in the U.S. over time and space. Using the participants’ addresses, researchers were able to estimate each mother and child’s exposure during pregnancy and early childhood.

“There are known biological mechanisms that can link a mother’s inhalation of these pollutants to effects on placenta and fetal brain development,” explains Li about why it’s important to understand the exposure effects of nitrogen dioxide and small-particle air pollution in early life.

Since the brain reaches 90% of its future adult size during a child’s first few years of life, pollutants that invade deep in the lung and enter the central nervous system can cause damage in areas relevant for behavioral and cognitive function.

“This study reinforces the unique vulnerability of children to air pollution — both in fetal life where major organ development and function occurs as well as into childhood when those processes continue,” says study senior author Dr. Catherine Karr, a professor in the UW School of Public Health and School of Medicine. “These early life perturbations can have lasting impacts on lifelong brain function. This study underscores the importance of air pollution as a preventable risk factor for healthy child neurodevelopment.”

The study found that exposure to small-particle air pollution was associated with more behavioral problems in girls rather than in boys, and that the adverse effect of small-particle air pollution in the second trimester on IQ was stronger in boys.

“We hope the evidence from this study will contribute to informed policymaking in the future,” says Ni. “In terms of reducing air pollution, the U.S. has gone a long way under the Clean Air Act, but there are threats to continued improvement in the nation’s air quality. The evidence suggests there is reason to bring the level of air pollution down even further as we better understand the vulnerability of pregnant women and children.”

The study is published in the journal Environmental Health Perspectives.

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