Children exposed to high amounts of air pollution were more likely to end up in the emergency room for a mental health problem a couple days later than children with lower exposure, according to a new study.
The study, published today in Environmental Health Perspectives, is the first to examine short-term exposure to small particulate matter pollution and mental health effects in children, and found that pollution was linked to worsening mental health disorders just days after exposure.
It adds to growing evidence that dirty air may be causing and worsening depression, anxiety and other mental health issues in children and teenagers. Nearly 1 in 7 children and teens in the U.S. have a mental health condition, according to a 2018 study.
Researchers from the Cincinnati Children's Hospital Medical Center and the University of Cincinnati examined 13,176 emergency room visit to the Medical Center by 6,812 children from 2011 to 2015 for psychiatric disorders, including anxiety, depression, bipolar disorder, suicidality, personality disorders and schizophrenia.
They then estimated the kids' exposure to small particulate matter pollution (PM2.5) from the three days prior to their visit to the emergency room.
They found every 10 micrograms per cubic meter of increase in PM2.5 exposure was linked to a large jump in emergency room visits. "Notably, all daily exposures within our study domain were below the National Ambient Air Quality Standards set by the U.S. Environmental Protection Agency," the authors wrote.
They saw an even stronger association between air pollution and emergency room visits from children living in poorer, high poverty neighborhoods.
"The fact that children living in high poverty neighborhoods experienced greater health effects of air pollution could mean that pollutant and neighborhood stressors can have synergistic effects on psychiatric symptom severity and frequency," said lead author Cole Brokamp, a researcher and assistant professor in the University of Cincinnati Department of Pediatrics, in a statement.
Poverty causes stress, inflammation and harms normal brain and immune system development, the authors wrote, which could add to any potential air pollution impacts on mental health.
Growing evidence
Credit: CDC
The study doesn't prove air pollution causes or exacerbates mental health problems in children, but it is the latest research to suggest the association exists.
In August a large study of Danish and Americans found people exposed to high levels of air pollution have much greater odds of suffering from a psychiatric illness such as depression, schizophrenia or bipolar disorder. In the Danish population, people with the highest exposures had 148 percent and 162 percent higher rates of schizophrenia and personality disorder, respectively.
In addition, two other recent Cincinnati children studies reported similar links: In May researchers found traffic-related air pollution was linked to higher anxiety in children, by measuring markers of the kids' brain neuroinflammatory responses. And, in a companion study, they found traffic pollution was associated with more self-reported depression and anxiety in children.
"Collectively, these studies contribute to the growing body of evidence that exposure to air pollution during early life and childhood may contribute to depression, anxiety, and other mental health problems in adolescence," said coauthor Patrick Ryan, a professor and researcher in the University of Cincinnati Department of Pediatrics, in a statement.
Instigating inflammation
It's not entirely clear how air pollution could spur mental health issues, however, prior research in rodents shows exposure to pollution can cause inflammation and cell death in brain tissues—such changes can potentially lead to and worsen psychiatric disorders.
PM2.5—fine particles less than 2.5 microns in diameter and comprised of particles, gases, metals and other toxic chemicals —comes from traffic, power plants, fires and other sources. Given its small size it is good at infiltrating our bodies and is known to cause oxidative stress and inflammation, which is why it would make sense for it to cause inflammation in cells crucial for the brain and mental health.
Ryan and Brokamp compared the idea of PM2.5 worsening mental health to asthma, "wherein an individual with an underlying inflammatory disorder is prone to acute exacerbations after experiencing acute increases in air pollution exposure."
The study was limited in that it relied on medical records for emergency room visits, so there could have been impacts on children that didn't result in a hospital visit.
"These findings need to be confirmed in other populations, but they strongly support the need for further research on the potential influence of ambient air pollution on child and adolescent mental health," the authors wrote.
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