Each extra day spent in wildfire smoke and other forms of polluted air raises the likelihood of mental health issues in children, based on a new study from the University of Colorado Boulder involving 10,000 children aged 9 to 11.
Each extra day spent in wildfire smoke and other forms of polluted air raises the likelihood of mental health issues in children, based on a new study from the University of Colorado Boulder involving 10,000 children aged 9 to 11.
“Our research shows that an increase in days with fine particulate matter exceeding EPA standards correlates with more symptoms of mental illnesses, both during the exposure year and up to a year afterward,” stated Harry Smolker, the first author and research associate at CU’s Institute of Cognitive Science.
This study, published in Environmental Health Perspectives, coincides with smoke from fires in Southern California affecting large areas of the West, darkening skies as far as Las Vegas and parts of Colorado. Although air quality has generally improved over the decades due to regulations on emissions from combustion sources, more frequent fires have brought about a new challenge: more days with dangerously high levels of particulate matter in the air.
“We are entering a time where we face unprecedented levels of particulate exposure multiple times each year,” Smolker noted. “Understanding the effects of these extreme events on young people’s brains and behaviors is crucial.”
The connection between pollution and mental health
Researchers have long known that air pollution can harm respiratory and cardiovascular health, but only recently have they started investigating its effects on cognitive functions and behavior.
Some studies indicate that PM 2.5, a type of particulate matter smaller than 2.5 micrometers, could potentially cross the blood-brain barrier, causing inflammation, cell damage, and triggering an immune response that may lead to both immediate and long-term changes in the brain.
Adult hospitalizations for depression, suicide attempts, and psychotic episodes tend to increase on days when pollution levels are high. Additionally, studies suggest that children of pregnant individuals exposed to high particulate levels may experience developmental and cognitive challenges later in life.
This study by Smolker is one of the first to examine the potential impacts on adolescents, whose brains are still undergoing development.
The research team analyzed data from 10,000 pre-teens involved in the Adolescent Brain Cognitive Development (ABCD) Study, which is the largest long-term research project on brain development and child health ever conducted in the US. CU Boulder is part of the 21 research sites involved in the ABCD study.
They assessed participant addresses using historical air quality data to determine the number of days in 2016 that youth were subjected to PM2.5 levels exceeding 35 micrograms per cubic meter (35ug/m3), a threshold set by the Environmental Protection Agency as unsafe.
About a third of the children experienced at least one day over the EPA limit, with one individual exposed for a staggering 173 days. The highest exposure level recorded was 199 micrograms/m3, which is over five times the safe level.
By examining parent surveys collected over three years at four different intervals, researchers noted that exposure to unsafe air levels corresponded with an increased likelihood of youth showing symptoms of depression, anxiety, and other “internalizing symptoms” even up to a year later.
This finding remained significant even after considering various other influencing factors, including race, socioeconomic status, and parental mental health. Interestingly, children often reported symptoms even if their parents did not.
“This indicates that PM2.5 exposure could uniquely affect youth, separate from the impact on their parents,” Smolker explained.
Every single day matters
Continuous exposure to unsafe levels had a much stronger effect on risk than average annual levels or maximum levels, indicating that each additional day of poor air quality carries weight.
For each day exposed to unsafe air, the risk of developing symptoms increased by an average of .01 points on a scale ranging from 1 to 50.
“Though this increase is quite small, it shouldn’t be dismissed,” Smolker highlighted, reminding that PM2.5 is just one pollutant among many that make up the “exposome” – the collection of environmental exposures influencing children’s growth and development. “Together, these factors can accumulate significantly.”
Some young individuals might be genetically predisposed to be even more susceptible to the cognitive and behavioral effects of air pollution.
While particulate matter can originate from various sources like traffic and industries, study co-author Colleen Reid, a geographer with CU Boulder’s Institute for Behavioral Science, suspects that wildfire smoke was a major contributor to the exposures noted in this study.
“Wildfire smoke events are becoming increasingly frequent, and this study adds to the growing evidence that they can have serious health implications,” Reid commented.
