It comes as no surprise that many experts have found evidence that air pollution could be damaging to our lungs and heart health. However, new research indicates that it also might be polluting our brains.

Researchers from Lancaster University in the U.K. set out to study the effects of pollution using the brains of 37 people from either Manchester, England, or Mexico City — known for its high rates of air pollution.

What they found, according to the researchers themselves, was “dreadfully shocking.”

The brain tissue contained high amounts of magnetite, a form of iron oxide particles “that are abundant in the airborne pollution found in urban settings, especially next to busy roads, and which are formed by combustion or frictional heating from vehicle engines or brakes,” said a co-author of the study, Barbara Maher of the Lancaster Environment Center.

In other words, the pollution from the air might be directly infiltrating our brains. According to co-author David Allsop, a researcher at Lancaster University Faculty of Health and Medicine, those magnetite particles might be related to Alzheimer’s or other neurodegenerative diseases.

“These particles are made out of iron and iron is very reactive so it’s almost certainly going to do some damage to the brain,” Allsop said. “It’s involved in producing very reactive molecules called reaction oxygen species which produce oxidative damage and that’s very well defined.

“We already know oxidative damage contributes to brain damage in Alzheimer’s patients so if you’ve got iron in the brain it’s very likely to do some damage,” he continued. “It can’t be benign.”

However, the link between air pollution and Alzheimer’s remains extremely tentative, and the researchers readily admit that further studies are needed.

“It’s a discovery finding,” said Maher. “It’s a whole new area to investigate to understand if these magnetite particles are causing or accelerating neurodegenerative disease.”

In the meantime, you can hedge your bets by living outside of high-pollution urban areas, which many young people are already looking to do. About 66% of Millennials look for homes in suburban locations, and 24% in rural areas. Only 10% prefer metro locations, which can be higher in air pollution. Experts also recommend regular exercise, a healthy diet, and avoiding smoking to prevent conditions like Alzheimer’s.