Air pollution may accelerate brain aging, a new study has found.

The findings, by researchers at the University of Southern California, are based on an analysis of 1,403 women without dementia who were tracked from 1996 to 2006, when the women were 71 to 89 years old, The New York Times reports.

Using residential histories and air pollution data, they estimated the women’s exposure to air pollution from 1999 to 2006. The results showed that the women exposed to higher levels of pollutants had a greater decrease in white matter in the brain — a key measurement of brain aging.

Past studies have shown that air pollution can cause inflammation and damage to the vascular system, but the new research, published in The Annals of Neurology, is the first to show damage to the brain itself.

“This tells us that the damage air pollution can impart goes beyond the circulatory system,” said lead researcher Jiu-Chiuan Chen, M.D., an associate professor of preventive medicine at the Keck School of Medicine at USC. “Particles in the ambient air are an environmental neurotoxin to the aging brain.”