Air pollution, even at ‘safe' levels, harmful to teen brain development

LOS ANGELES —  Do you live in a city with a lot of air pollution? If you've got children or plan to start a family, you may want to consider moving to cleaner pastures. Researchers at the Keck School of Medicine USC say everyday air pollution can have a significant impact on the brain development of teenagers. The study, funded by the National Institutes of Health and the Environmental Protection Agency (EPA), sheds light on the potential risks posed by pollution levels previously considered safe by regulatory standards.

Using data from the largest-ever nationwide study of youth brain health, the Adolescent Brain Cognitive Development (ABCD) study, researchers analyzed brain scan data from over 9,000 participants. The findings reveal that exposure to certain pollutants is associated with brain connectivity changes, leading to excessive and inadequate connections between various brain regions.

“A deviation in any direction from a normal trajectory of brain development—whether brain networks are too connected or not connected enough—could be harmful down the line,” emphasized Doctorial candidate Devyn L. Cotter, MSc, in a media release.

The study utilized functional MRI scans collected from children aged 9 to 10, with follow-up scans taken two years later to observe changes in brain connectivity over time. The researchers focused on key brain networks and regions, such as the salience, frontoparietal, default-mode networks, as well as the amygdala and hippocampus, which are involved in emotion, learning, and memory.

By mapping air quality data, including fine particulate matter (PM2.5), nitrogen dioxide (NO2), and ground-level ozone (O3), at each child's residence, the researchers established links between air pollution levels and changes in brain connectivity. Exposure to PM2.5 was associated with increased functional connectivity, while exposure to NO2 predicted decreased connectedness. Higher levels of O3 were linked to increased connections within the cortex but decreased connections with other regions.

“Air quality across America, even though ‘safe' by EPA standards, is contributing to changes in brain networks during this critical time, which may reflect an early biomarker for increased risk for cognitive and emotional problems later in life,” says Megan M. Herting, PhD, associate professor of population and public health sciences at the Keck School of Medicine and senior author of the study.

The study's findings may have implications for air quality regulations. Policymakers could consider the impact of air pollution on brain health when setting or adjusting recommendations. The researchers also emphasize the need for further investigation into the chemical composition of pollutants to refine regulations and gain a deeper understanding of the mechanisms through which air pollution harms the brain.

“On average, air pollution levels are fairly low in the U.S., but we're still seeing significant effects on the brain. That's something policymakers should take into account when they're thinking about whether to tighten the current standards,” Cotter adds.

Moving forward, the researchers plan to continue analyzing brain health over time using data from the ABCD study, and further explore the long-term consequences of air pollution on mental health during adolescence.

The study is published in the journal Environment International.