When wildfires started raging through southern California this month, Diana Younan warned her family members living in the path of the smoke to stay inside, as much as possible. Fires send air pollution levels soaring, filling the air with tiny particles. Younan, who studies environmental health at the Keck School of Medicine at the University of Southern California, knows the damage those tiny particles can do.
“It’s very well known that air pollution can affect respiratory function or health. But it’s not as well known that it can also affect the brain,” says Younan. Over the past decade, scientists started to note mounting evidence that suggests inhaling polluted air is toxic to the brain. That is slowly being linked to behavior, particularly for children and adolescents.
It’s similar, Younan says, to the way childhood exposure to lead—which used to be used in paint and gas—was eventually connected to behavioral problems. Some scientists even suspect that the decline in crime seen in the U.S. (and many nations) since the 1990s can be connected to the removal of lead from gasoline. “Lead is what pioneered the whole research on environmental risk factors,” she says.
In an analysis of data from nearly 700 children, Younan and her team found that kids in Los Angeles who were exposed to more air pollution over the course of adolescence were more likely to engage in delinquent behavior. The research was published today in the Journal of Abnormal Psychology. It also found that the same amount of pollution exposure had a stronger effect on behavior when kids had bad relationships with their parents, or when their mothers exhibited signs of depression.
Deborah Cory-Slechta, a professor of environmental medicine at the University of Rochester who wasn't involved in the new study, started her career by looking at lead exposure. But in the past few years, she’s moved towards research on air pollution. At the beginning, she was skeptical that pollution could impact the brain. “But it was amazing what we started to find,” Cory-Slechta says. “Everyone has been surprised, to say the least, at how dramatic some of these effects can be.”
Cory-Slechta studies the effect of air pollution on animal models, and says that the behavioral changes she sees in those studies seem to match onto the type of delinquent behavior observed in Younan’s longitudinal study. “Even at relatively low levels of exposure [in animals], we see changes in behavior,” Cory-Slechta says. “Things like impulsivity, which can relate to delinquent behavior.”