Most people know that air pollution can make it harder to breathe. Many also know that it can increase the risk of heart disease and other serious medical problems.
What is less widely known is that the air around us may also influence how our brains age. A new study suggests that years of exposure to polluted air could quietly affect a person’s ability to remember facts, words, and general knowledge.
Researchers from UC Davis Health and Kaiser Permanente examined the effects of fine particle pollution, commonly known as PM2.5.
These microscopic particles come from sources such as vehicle exhaust, industrial activities, power plants, and wildfire smoke. Because they are extremely small, they can enter the body easily and may trigger harmful biological changes.
The study found that people exposed to higher levels of PM2.5 for many years showed poorer performance in semantic memory, an important form of memory that serves as the brain’s storehouse of knowledge.
Semantic memory allows people to remember information such as the meaning of words, names of places, historical facts, and other knowledge accumulated throughout life.
The findings were published in Alzheimer’s & Dementia: Behavior & Socioeconomics of Aging.
To conduct the study, researchers used data from the STAR project, a large investigation of healthy aging among African American adults. Understanding dementia risk factors in this population is especially important because Black Americans face higher rates of Alzheimer’s disease and related dementias than many other groups.
The study included 740 participants aged between 53 and 94 years. Researchers estimated each participant’s long-term exposure to PM2.5 by analyzing pollution levels at their home addresses over periods of up to seventeen years. Cognitive testing was then used to measure different aspects of brain function.
When the results were analyzed, the researchers found a consistent relationship between higher pollution exposure and poorer semantic memory performance. The effect remained significant even after accounting for social and economic factors that could influence cognitive health.
Not all forms of memory were affected equally. The researchers found no clear evidence that pollution influenced verbal episodic memory or executive function. This suggests that some parts of the brain may be more sensitive to pollution exposure than others.
Semantic memory plays a major role in everyday life. It helps people understand language, recognize objects, communicate effectively, and make sense of the world around them. A decline in this type of memory can reduce independence and make daily activities more difficult.
One of the most concerning findings was that the estimated effect of pollution on semantic memory appeared larger than the decline expected from ten years of normal aging. This suggests that air quality may have a substantial impact on cognitive health over time.
Scientists are still working to understand exactly how air pollution affects the brain. One possibility is that tiny particles trigger chronic inflammation throughout the body. Another theory is that particles or related chemicals may affect blood vessels that supply oxygen and nutrients to brain tissue. Both processes could contribute to gradual cognitive decline.
The study also draws attention to environmental inequality. Many communities with fewer resources experience higher exposure to air pollution. These same communities often face other health challenges, creating a combination of risks that can influence long-term wellbeing.
Although individuals cannot completely control the air they breathe, there are practical ways to reduce exposure. Monitoring local air quality reports, using indoor air filtration systems, avoiding outdoor exercise near busy roads, and staying indoors during wildfire smoke events can help lower personal exposure levels.
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Source: University of California, Davis.
