Health impact studies of air pollution, including wildfire smoke, have mostly focused on the lungs. But toxicologist Matthew Campen of the University of New Mexico in Albuquerque is looking at the brain.

In a study of the inflammatory effects of smoke PM2.5 on the brains of mice, Campen and colleagues found that inflammation in the lungs was modest compared with the “profound” inflammation in the brain, Campen says. Given what’s known about how damaging smoke can be in the lungs, to find even greater effects on the brain is troubling, he says.

The inflammatory effect on the mice’s brains was almost immediate, within 24 hours of exposure, the researchers reported in the March Toxicological Sciences. The particulates enter the body through the respiratory system, get in the blood, and are small enough to cross the blood-brain barrier and start affecting the brain. Inflammation has been linked with dementia in older people and neurodevelopmental issues in younger people, plus mood disorders like anxiety and depression, Campen says.

“I’m hoping that our study with mice spurs… epidemiologists to take a look,” he says. “The effects we see are much stronger and more worrisome than what we see in the lungs,” he says, but we don’t know yet at what PM2.5 levels the danger begins. “We need to explore this more rigorously.”

— Megan Sever