Even Low Air Pollution Levels Can Harm Child Brain Development: Study

Federal guidelines for some types of air pollution levels have not changed for over 50 years, researchers noted.

New research suggests side effects of air pollution nationwide, even at low levels that are generally deemed safe by federal regulators, pose a serious risk of damage to children’s cognitive development and long-term mental health.

In a study published in the July 2023 issue of the medical journal Environmental International, researchers from the University of Southern California Los Angeles (UCLA) link relatively low air pollution exposure during childhood to abnormal brain region connections.

The researchers found that some types of pollution cause more brain connections than normal, while others cause fewer than average brain connections. These changes occur during a crucial cognitive development period, and can increase risks of mental and emotional issues later in life, they warn.

Air quality standards are set and enforced by the Environmental Protection Agency (EPA), including emission limits on six main types of air pollutants. Those pollutants are carbon monoxide, lead, nitrogen dioxide, ozone, and particulate matter, which is microscopic pollution particles made of dust, dirt, soot, and water particles that are 2.5 or 10 micrometers in size.

Air Pollution Linked to Abnormal Brain Development

In this latest study, researchers from UCLA assessed brain scans from 9,497 nationwide participants between the ages of 9 and 10 years old from the Adolescent Brain Cognitive Development (ABCD) databank. They then selected some participants for follow-up brain scans two years later, to assess brain connectivity changes over time.

They primarily focused on the salience, frontoparietal, and default-mode brain networks, and the amygdala and the hippocampus brain regions. These brain areas are known as critical in child cognitive development and for determining lifelong emotional, learning, and memory abilities.

After the follow up brain scans, researchers used EPA and other data to map air pollution at each participant’s residence. These measurements included levels of fine particulate matter (PM_2.5), nitrogen dioxide (NO₂), and ground-level ozone (O₃). They used this data to determine how pollution levels impact brain connectivity changes over time.

According to the findings, greater particulate matter exposure corresponded to abnormally high functional connectivity between different brain areas. Also, increased nitrogen dioxide exposure was linked to atypical decreases in brain connectivity.

Researchers also associated ground level ozone exposure with above average connections inside the brain’s cortex. However, they noted relatively fewer connections between the cortex and other areas, such as the hippocampus and amygdala.

The study concluded that air pollution levels considered “safe” by the EPA may still significantly alter brain structures during crucial periods of child development, and called for the EPA to review current air quality standards to determine if adjustments are warranted.

Air Pollution Guidelines Need Updating

These new findings aligns with prior research associating childhood air pollution exposure to various cognitive problems, including anxiety and reduced cognitive ability. Data suggests children born and raised in urban environments are twice as likely to develop psychosis in adulthood due to higher air pollution exposure levels compared to rural settings.

Research indicates prenatal air pollution exposure also negatively affects child brain health. A 2018 study found children of mothers living in areas with high particulate matter pollution were significantly more likely to receive an autism diagnosis by age five.

The researchers in this most recent study stressed that some air pollution guidelines, including those for nitrogen dioxide emissions, have not been updated since the EPA’s creation over 50 years ago. Since then, data on air pollution chemical structures and how they affect brain development has increased in quality. They concluded that EPA regulators should consider updated research when making air standard adjustments.

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