June 17, 2026
With higher summer temperatures come rising levels of air pollution and smog. And that may spell bad news for your brain.
A new study found that the tiny particles of air pollutants known as PM2.5 are linked to lower levels of semantic memory, the type of memory used for words, facts and general knowledge. The findings add to growing evidence that air pollution is not just bad for the lungs and respiratory health. Pollutants may also impair the brain, raising the risk of Alzheimer’s disease down the road.
“Semantic memory is essential for communication, comprehension and navigating everyday life,” said Kathryn Conlon, the study’s senior author and an associate professor in the University of California, Davis, Department of Public Health Sciences. “Our findings suggest that long-term exposure to air pollution doesn’t just affect physical health, it may also shape how the brain ages, particularly in ways that matter for independence and quality of life.”
For the study, researchers at UC Davis Health and Kaiser Permanente looked at 740 men and women who were part of an ongoing investigation called the Study of Healthy Aging in African Americans, or STAR. Launched in 2017, the study is examining factors that impact healthy brain aging among Black adults. Study participants ranged in age from 53 to 94.
The researchers focused on PM2.5 particulates, which previous studies have shown may be especially damaging to health. The tiny particles, less than 1/30th the width of a human hair, are easily inhaled into the lungs, where they enter the bloodstream and spread throughout the body, including the brain. High levels of PM2.5 pollutants have been linked to asthma and other respiratory disorders, as well as heart disease, strokes, Parkinson’s disease and other ailments.
These miniscule particles come from many sources, including car exhaust, wildfire smoke, power plants, construction site debris, and combustion from factories. Researchers estimated longtime exposure to these tiny pollutants by averaging daily measures of PM2.5 levels at the participants’ residential addresses using data from local air monitors. Participants also underwent regular tests of thinking and memory skills.
The researchers found that people who were exposed to higher levels of PM2.5 pollution over many years scored noticeably lower on semantic memory tests than those exposed to lower levels of pollution. Semantic memory acts like the brain’s “encyclopedia” for things like facts, words and long-term general knowledge.
The researchers considered other risk factors for brain and overall health, including age, education, and income levels. Long-term exposure to the air pollutants was independently linked to lower semantic memory scores over a 10-year period, greater than what would be expected from normal aging. The findings were published in Alzheimer’s & Dementia: Behavior & Socioeconomics of Aging.
In this study, air pollution did not have a notable effect on two other measures of cognitive function: executive function, which allows you to plan and solve problems, and verbal episodic memory, which allows you to recall and narrate experiences. But other studies have found that air pollution may impair a range of memory and thinking skills and raise the risk of developing Alzheimer’s disease.
Several studies have shown, for example, that people who live in areas with elevated levels of air pollutants had higher levels of toxic proteins characteristic of Alzheimer’s in their brains compared to their peers who lived in areas with cleaner air. Breathing in polluted air may also speed up the progression of Alzheimer’s in people who already have the disease.
Experts say there are several measures you can take to reduce exposure to air pollution.
- Check daily air quality forecasts on the AirNow.gov website. The Environmental Protection Agency’s website lets you enter your ZIP code to find out about air quality in your area.
- Limit outdoor activity when pollution levels are high, especially during wildfire smoke events. If you must be outdoors, wear a high-quality face mask.
- Move workouts indoors, to a gym, for example, or walk in a shopping mall.
- Purify indoor air with high-efficiency (HEPA) air filter. Keep windows closed on poor air quality days. Don’t smoke, especially in the home.
- Avoid exercising near busy roads or heavily trafficked areas, where vehicle exhaust fumes concentrate.
- Use recirculated air settings in vehicles during heavy traffic or smoky situations.
- Keep fuel-burning appliances and fireplaces in the home well maintained to minimize potentially dangerous emissions, and use exhaust fans in the kitchen when cooking. Ventilate your home regularly by opening windows when outdoor air quality is good.
By ALZinfo.org, The Alzheimer’s Information Site. Reviewed by Eric Schmidt, PhD, of The Fisher Center lab at The Rockefeller University.
Source: Stacey E. Alexeeff, Chinomnso N. Okorie, Paola Gilsanz, et al: “Particulate air pollution and domain-specific cognition among Black adults.” Alzheimer s & Dementia Behavior & Socioeconomics of Aging, May 18, 2026
