Research links outdoor air pollution to differences in children’s brains

Outdoor air pollution, even at levels below government standards, is associated with differences in children’s brain development, according to a new systematic review of research conducted across four continents. The study, led by researchers at the University of California, Davis, analyzed 40 empirical studies examining the relationship between air pollution exposure and brain outcomes in children and adolescents.

Summary: A UC Davis-led review of 40 studies finds that outdoor air pollution, even at levels below current standards, is linked to differences in children’s brain development across multiple continents. The research highlights the need for stricter air quality regulations to protect vulnerable young minds.

Estimated reading time: 5 minutes

The research team, led by Camelia Hostinar, an associate professor of psychology at UC Davis, found that exposure to outdoor air pollution was associated with various differences in children’s brains. These differences included changes in white matter volume, which is linked to cognitive function, alterations in brain connectivity, and even early markers for Alzheimer’s disease.

“We’re seeing differences in brain outcomes between children with higher levels of pollution exposure versus lower levels of pollution exposure,” said Hostinar, the study’s corresponding author.

Children’s Unique Vulnerability to Air Pollution

Children and teenagers are particularly susceptible to the effects of air pollution due to several factors:

Their brains and bodies are still developing
They tend to spend more time outdoors
Their bodies absorb more contaminants relative to their bodyweight than adults

The study, titled “Clearing the Air: A systematic review of studies on air pollution and childhood brain outcomes to mobilize policy change,” was published in the journal Developmental Cognitive Neuroscience. It surveyed research from the United States, Mexico, Europe, Asia, and Australia, encompassing children from newborns to 18-year-olds.

Diverse Methods Reveal Consistent Concerns

The reviewed studies employed various methods to measure brain differences, including:

Advanced scanning techniques like magnetic resonance imaging (MRI)
Testing changes in chemical compounds that aid brain function and health
Examining tumors in the brain or central nervous system

Notably, studies from Mexico City comparing children from high- and low-pollution areas found significant differences in brain structure. These differences were observed not only in areas with high levels of air pollution but also in places that met local air pollution standards.

“A lot of these studies include children in places with air pollutant levels that are well below limits set by U.S. or European regulations,” said Anna Parenteau, a Ph.D. student in psychology at UC Davis and the study’s co-first author.

Sources of Outdoor Air Pollution

The research highlighted various sources of outdoor air pollution, including:

Coal-fired power plants
Wildfires
Vehicle emissions
Industrial activities

Establishing Causality Through Animal Research

To strengthen the causal link between outdoor air pollution and brain differences, the research team also examined experimental research on animals. This animal research demonstrated that pollution leads to many of the same outcomes identified in the human studies, including markers for Alzheimer’s disease.

Anthony Wexler, a professor at UC Davis and director of its Air Quality Research Center, noted a shift in scientific thinking: “A lot of researchers working on brain development, whether it’s autism, Alzheimer’s or something else, really discounted for a long time the environmental factors. They argued that it’s genetic or some other factor other than exposure to air pollution. That’s changed a lot recently because of all this research literature.”

Steps to Reduce Harm

The systematic review proposed several steps for both parents and policymakers to protect children from outdoor air pollution:

Adding air filters to homes and schools near freeways
Providing subsidized air purifiers in schools and other places where children spend significant time
Incorporating measures of air pollution into studies related to brain health and other health outcomes

“We listed air purifiers as one of the policy recommendations, and that is something that could be subsidized or provided in schools and other places where children spend a lot of time,” said Hostinar. “These can be quite effective.”

Sally Hang, a Ph.D. student in psychology and the study’s first co-author, suggested that researchers could easily add questions to assess air pollution exposure in their studies, such as obtaining participants’ addresses.

Implications for Public Health and Policy

This comprehensive review of research from multiple continents underscores the urgent need for stricter air quality regulations and more proactive measures to protect children’s developing brains. As climate change and urbanization continue to impact air quality worldwide, policymakers and public health officials must prioritize reducing air pollution to safeguard the cognitive potential of future generations.

Quiz:

What is one reason children are especially vulnerable to air pollution?
Name one method researchers used to measure brain differences in the reviewed studies.
According to the study, are brain differences only observed in areas with high levels of air pollution?

Answer Key:

Children’s brains and bodies are still developing.
Magnetic resonance imaging (MRI).
No, brain differences were observed in places that met local air pollution standards as well.