Even ‘safe’ pollution levels can cause changes in child brain development: study

Levels of certain air pollutants previously considered safe can potentially harm a child’s developing brain, a new study has found.

The study, published this week in Environment International, involved the largest-ever nationwide survey of youth brain health — and ultimately concluded that kids exposed to more pollutants showed changes in connectivity between brain regions.

In some regions, the children had more connections than normal, while in other areas, they had fewer, according to the findings.

“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,” first author Devyn Cotter, a doctoral candidate at the University of Southern California’s Keck School of Medicine, said in a statement.

Because airborne contaminants have long been known contributors to many diseases, regulators such as the Environmental Protection Agency (EPA) have set limits on emissions of various pollutants.

But Cotter and her colleagues observed that even levels of some pollutants considered safe from a regulatory perspective could contribute to changes in brain function over time.

“Air quality across America, even though ‘safe’ by EPA standards, is contributing to changes in brain networks during this critical time,” senior author Megan Herting, an associate professor at the Keck School of Medicine, said in a statement.

Such changes, Herting continued, could be an early indicator “for increased risk for cognitive and emotional problems later in life.”

To draw their conclusions, the researchers analyzed MRI brain scans from 9,497 participants in the Adolescent Brain Cognitive Development Study — a collaboration among researchers across the country funded by the National Institutes of Health.

The researchers had access to baseline brain scans from the children, ages 9 to 10, as well as to follow-up scans taken two years later for a subset of the participants. This information then enabled the scientists to observe how brain connectivity evolved over time.

Cotter, Herting and their colleagues — from USC, Columbia, Harvard and Children’s Hospital of Los Angeles — focused on key regions of the brain that are involved in emotion, learning, memory and other complex functions.

The researchers also used data from the EPA and elsewhere to identify the levels of fine particulate matter (PM 2.5), nitrogen dioxide and ground-level ozone pollution at each child’s residence. Using statistical analyses, they uncovered how these levels related to brain connectivity changes over time.

To rule out other potential contributing factors, the authors said they controlled for sex, race and ethnicity, parental education level, household income, urban versus rural location and seasonality.

Cotter and her colleagues found that greater exposure to fine particulate matter was linked to relative increases in functional connectivity between regions, while heightened exposure to nitrogen dioxide was associated with declines in connectivity.

Exposure to higher concentrations of ozone was related to increased connections within the brain’s cortex, but to fewer connections between the cortex and other regions, such as the amygdala and the hippocampus, according to the study.

The cortex is responsible for complex processes, such as thought, memory, consciousness and emotion. The amygdala is associated with emotional processing, including the “fight or flight” response, while the hippocampus plays a key role in long-term memory.

The researchers said they hope that their findings could inspire regulators to consider brain health when setting future air quality standards. They also outlined plans to take a closer look at the chemical makeup of pollutants, to figure out how and why they cause harm in the brain.

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

For the latest news, weather, sports, and streaming video, head to The Hill.