Inflammation caused by air pollutants can damage brain structure, neural networks and influence adolescent behaviour
A new study conducted by researchers at the Keck School of Medicine of the University of Southern California has linked the incidence of teenage delinquency with the rise in air pollution levels.
“Studies are beginning to show exposure to various air pollutants causes inflammation in the brain. PM2.5 is particularly harmful to developing brains because it can damage brain structure and neural networks and, as our study suggests, influence adolescent behaviors,” said Diana Younan, a preventive medicine research associate and the lead author of the paper.
Published Wednesday in the Journal of Abnormal Psychology, the study was conducted through a test administered to nine to 18-years-old. A checklist was prepared to assess the children’s behaviours over the years. This checklist was distributed to the parents who filled these at various intervals.
"It is widely recognised that ambient air pollution is detrimental to the respiratory and cardiovascular health of young and old alike. But in recent years, scientists have come to acknowledge the negative impact of air pollution on human brains and behaviors," said Jiu-Chiuan Chen, an associate professor of preventive medicine at the Keck School of Medicine and senior author of the study.
The study tracked 682 children from Greater Los Angeles for nine years, beginning when they were aged nine. The parent’s responses were recorded four times at intervals through the checklist, which assessed if their child engaged in lying, cheating, truancy, stealing, vandalism, arson, or substance abuse among other rule-breaking behaviours.
“Previous studies have shown that early exposure to lead disrupts brain development and increases aggressive behavior and juvenile delinquency,” Younan said. “Both lead and PM2.5 are environmental factors that we can clean up through a concerted intervention effort and policy change,” she said. She further added that it is possible that growing up in places with unhealthy levels of small particles outdoors may have similar negative behavioral outcomes, although more research is needed to confirm this.
The study identified higher air pollution levels near freeways and in neighbourhoods with limited green space. “Poor people, unfortunately, are more likely to live in urban areas in less than ideal neighborhoods,” said Younan. She added that many affordable housing developments are built near freeways. This close proximity to freeways causes health problems, such as asthma and can perhaps alters teenagers' brain structures. This makes them more likely to engage in delinquent behaviour.
Underlining the shortcomings, the researchers said they were unable to explore early-life exposure effects because ambient PM 2.5 data was not collected until 1999, when subjects were already 9 to 10-years-old. Prenatal and early-childhood are critical exposure periods, which may impart much stronger neurotoxic effects. Although their analysis did not show an interaction between PM2.5 and age, the possibility of exposure effect on early-life trajectories before age nine cannot be ruled out.
Can parents protect their children?
Youhan said that a bad parent-child relationship causes a stressful family environment and if that carries on for too long, the teenager could be in a chronic state of stress. This chronic stress makes teens more vulnerable to the effects of exposure to small particles. “Many scientists suspect PM 2.5 causes inflammation in the brain or somehow travels directly into the brain and messes with neural network connections, resulting in the observed bad behaviors,” added Youhan.
Youhan suggests that if you live in an area with high air pollution, such as a freeway or in a neighbourhood with little greenery, try to avoid being outside so much and keep windows closed as much as possible, when the ambient PM2.5 levels are high. “Try to compensate for air pollution by having a good indoor environment and healthy family dynamics,” said Youhan.
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