A new study by researchers at UC Davis Health and Kaiser Permanente found that higher exposure to very small air pollution particles (PM2.5) over a 17-year span was associated with lower semantic memory. Semantic memory acts like the brain’s “encyclopedia” for things like facts, words and long-term general knowledge.

“Semantic memory is essential for communication, comprehension and navigating everyday life,” said senior author Kathryn Conlon, an associate professor in the UC 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.”

Two other measures of cognitive function — executive function and verbal episodic memory — did not show an impact related to the pollution.

The findings were published in Alzheimer’s & Dementia: Behavior & Socioeconomics of Aging.

Reducing air pollution may reduce dementia burden

The data for the research comes from the Kaiser Permanente Study of Healthy Aging in African Americans (STAR). Launched in 2017, the ongoing study aims to identify factors that impact healthy brain aging among Black adults.

Black adults in the United States experience 1.5 to 2 times higher rates of Alzheimer’s disease and other dementias compared with non-Hispanic White adults.

In the new study, the researchers focused on particulate matter (PM), a mixture of solid particles and liquid droplets found in the air. Particles less than 2.5 micrometers in diameter (about 1/30th of a human hair) are referred to as PM2.5_, or fine particulates.

Previous research has linked PM2.5 to cardiovascular disease and mortality; however, a growing area of study is focused on the role of fine particulate exposure in the progression of Alzheimer’s disease.