A research team has thoroughly examined 40 empirical studies, most of which found that outdoor air pollution is linked to changes in children’s brain development. These changes include variations in white matter volume, which can affect cognitive abilities, as well as brain connectivity and early indicators of Alzheimer’s disease.
Outdoor air pollution from sources such as power plants, wildfires, and vehicles continues to harm human, animal, and environmental health worldwide. Recent findings suggest that even pollution levels lower than government air-quality standards can still impact children’s brain development.
A research team from the University of California, Davis systematically reviewed 40 empirical studies, most of which indicated a connection between outdoor air pollution and changes in children’s brains. These changes encompass white matter volumes linked to cognitive abilities, network connections across the brain, and even early signs of Alzheimer’s.
The study, titled “Clearing the Air: A systematic review of studies on air pollution and childhood brain outcomes to mobilize policy change,” was published this month in Developmental Cognitive Neuroscience.
“We’re observing differences in brain development between youngsters exposed to higher levels of pollution compared to those with lower exposure,” stated Camelia Hostinar, an associate professor of psychology and the corresponding author of the study.
Kids and adolescents are particularly at risk from air pollution since their brains and bodies are still maturing. They usually spend more time outdoors, and their bodies take in more pollutants in relation to their weight than adults do, according to the researchers.
Impact of outdoor air pollution on brain development
This review assessed 40 published, peer-reviewed studies that examined the relationship between outdoor air pollution and brain outcomes in children ranging from newborns to those 18 years old. Most of the studies originated from the U.S., Mexico, and Europe, with one each from Asia and Australia.
The methodologies varied in how they assessed brain differences. Some utilized advanced imaging techniques like magnetic resonance imaging (MRI), while others focused on changes in specific chemical compounds essential for brain health. Some investigations also searched for tumors in the brain or central nervous system.
Findings from studies in Mexico City indicated significant brain structure differences in children from high-pollution areas compared to those from low-pollution regions.
All the studies tracked air pollution based on the child’s home address or neighborhood, demonstrating that brain differences were evident even in areas with respectable air quality and within places that met local pollution guidelines.
“Many of these studies examined children living in environments where pollution levels were significantly below the limits established by U.S. and European regulations,” added Anna Parenteau, a UC Davis Ph.D. student and co-first author of the study.
Sources of outdoor air pollution
Outdoor air pollution stems from various sources, including coal-fired power plants and wildfires. This comprehensive review distinguishes itself by focusing on how air pollution affects children rather than adults or animals, which has been the focus of most previous research.
“It’s not necessarily valid to assume that findings applicable to adults will translate the same way for children,” remarked Johnna Swartz, an associate professor of human ecology and co-author of the study. “We must also consider different periods of development, as they may significantly influence how air pollution affects brain health.”
To establish a direct relationship between outdoor air pollution and brain differences, researchers referred to experimental animal studies. These studies indicated that pollution exposure leads to many outcomes consistent with the changes observed in this review, such as signs of Alzheimer’s disease.
“For a long time, many researchers focused strictly on genetics or other causes, overlooking environmental factors, including air pollution,” said Anthony Wexler, a UC Davis professor and director of its Air Quality Research Center. “However, this perspective has shifted significantly as a result of extensive research.”
Strategies to mitigate harm
This comprehensive review offers recommendations for both parents and policymakers on how to shield children from outdoor air pollution. Suggestions include installing air filters in homes and schools located near heavily trafficked roads.
“We suggested air purifiers as part of our policy recommendations since they can be subsidized or provided in schools and other areas where children spend a lot of their time,” Hostinar explained. “These can be remarkably effective.”
Researchers are also encouraged to include air pollution measurements in studies that assess brain health or other health-related outcomes.
“Anyone gathering data from human participants about brain or cardiovascular health can easily add questions regarding their air pollution exposure, such as through their address,” stated Sally Hang, a UC Davis Ph.D. student and the study’s first co-author.
