Outdoor air pollution from power plants, fires and automobiles continues to degrade human, animal and environmental health around the world. New research shows that even pollution levels that are below government air quality standards are associated with differences in children’s brains.
A research team at the University of California, Davis, systematically analyzed 40 empirical studies, most of which had found that outdoor air pollution is associated with differences in children’s brains. These differences include volumes of white matter, which is associated with cognitive function, connections throughout the brain, and even early markers of Alzheimer’s.
The study, “Clean the Air: A Systematic Review of Studies on Air Pollution and Child Brain Outcomes to Mobilize Policy Change,” was published this month in Developmental cognitive neuroscience.
“We are seeing differences in brain outcomes between children with higher levels of pollution exposure versus lower levels of pollution exposure,” said Camelia Hostinar, associate professor of psychology and corresponding author of the study.
Children and teenagers are especially vulnerable to air pollution because their brains and bodies are still developing. They tend to spend more time outdoors and their bodies absorb more pollutants relative to their body weight than adults, the researchers said.
Outdoor air pollution and brain development
This study examined 40 published, peer-reviewed studies that included measures of outdoor air pollution and brain outcomes in children of varying ages, from newborns to adults aged 18 years. Most of the studies came from the United States, Mexico and Europe, one from Asia and one from Australia.
The studies varied in how they measured brain differences. Some used advanced scanning methods such as MRI or MRI. Others tested changes in chemical compounds that aid brain function and health. Some studies looked for tumors in the brain or central nervous system.
Studies conducted in Mexico City that compared children from high- and low-pollution areas found significant differences in brain structure.
Each study included air pollution measures related to the child’s address or neighborhood, showing that children’s brain differences were seen in places with high levels of air pollution, as well as in places that met local standards. of air pollution.
“Many of these studies include children in places with air pollutant levels that are well below the limits set by US or European regulations,” said Anna Parenteau, Ph.D. psychology student at UC Davis and co-first author of the study.
Outdoor air pollution
Sources of outdoor air pollution include coal-fired plants, wildfires, and many other sources close to where people live. This systematic review is unique because most others have focused on how air pollution affects adults or animals, the researchers said.
“We can’t necessarily apply the findings from adults and assume it will be the same for children,” said Johnna Swartz, associate professor of human ecology and co-author of the study. “We also need to look more at different windows of development because that could be really important in terms of how air pollution could affect these brain outcomes.”
To establish a causal link between outdoor air pollution and differences in the brain, the research team turned to experimental research in animals. That research showed that pollution produces many of the same outcomes identified in the studies in this review, including markers of Alzheimer’s disease.
“A lot of researchers working on brain development, whether it’s autism, Alzheimer’s or something else, really discounted environmental factors for a long time,” said Anthony Wexler, a UC Davis professor and director of its Air Quality Research Center. . “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.”
Reduce damage
This systematic review proposed measures for both parents and policymakers to protect their children from outdoor air pollution, for example by adding air filters to homes and schools near highways.
“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,” Hostinar said. “These can be quite effective.”
Researchers can also incorporate measures of air pollution into studies related to brain health or other health outcomes.
“Anyone collecting data from human participants on brain or cardiovascular outcomes or anything else could easily add questions to assess air pollution exposure, such as getting their addresses,” said Sally Hang, Ph.D. psychology student and first co-author of the study.