Long-term exposure to air pollution from traffic, industry, and wildfires linked to to worse cognitive function and small but visible brain damage, with higher effects observed in women.

 

The study, published online in the journal Stroke on May 13, 2026, found that people living in areas with higher air pollution scored worse on tests of memory, understanding and mental speed. This finding was true for places where air pollution is considered low by international standards. 

Higher levels of traffic–related pollution were also linked to small but visible signs of damage to the brain seen on MRI scans, and more so in women. These relationships remained even after accounting for heart-health risk factors like high blood pressure, diabetes, and body adiposity, suggesting that air pollution may be directly affecting the brain. 

Unlike many previous studies conducted in regions with heavy pollution, this research focused on Canada, a country with some of the lowest average air pollution levels in the world. Researchers studied nearly 7,000 middle-aged adults across five Canadian provinces to see if long-term exposure to common air pollutants was linked to how well people think and remember.  

To do this, researchers compared people’s exposure over several years with their performance on cognitive tests. They focused on two pollutants: fine particles in the air known as fine particulate matter or PM2.5 and nitrogen dioxide. Both are common byproducts of vehicle exhaust, with PM2.5 particles also common within fumes from wildfires and industry.