Recent research published in journals Alzheimer’s disease and dementia: the behavior and socio-economics of aging provide evidence that long-term exposure to particulate air pollution can negatively impact certain types of memory in older Black adults. This study suggests that breathing polluted air for more than a decade tends to negatively impact semantic memory, the brain’s ability to recall common knowledge and facts. These findings highlight the importance of environmental factors in brain health and point to potential reasons behind racial differences in dementia risk.
In the United States, black adults are 1.5 to 2.0 times more likely to develop Alzheimer’s disease and other dementias than white adults. Despite this increased risk, Black adults have historically been underrepresented in environmental health research.
Stacey Alekseef, a research scientist and biostatistician at Kaiser Permanente Research Division, explained the motivation behind the study. “Studies show that dementia rates among black adults are much higher than among white adults in the United States,” Alexev told Cypost. “Black adults are more likely than white adults to live in areas with higher levels of particulate air pollution.”
Alexeeff noted that focusing on these environmental factors could provide insight into broader public health patterns. “Thus, examining how air pollution affects cognitive function among Black adults may help understand these disparities,” Alekseef said. “The Kaiser Permanente Northern California Study of Healthy Aging in African Americans (STAR) aimed to identify factors that influence brain aging in Black adults, allowing us to examine air pollution over a 17-year period based on each person’s home address.”
To explore these questions, scientists analyzed data from the STAR project, focusing on 740 black adults between the ages of 53 and 94, primarily living in the San Francisco Bay Area. All participants had undergone a health check in the past and had not been diagnosed with dementia when they participated in this study from 2017 to 2020. The researchers collected each participant’s residential address and linked these locations to high-resolution daily estimates of particulate air pollution.
The scientists focused on fine particulate matter, which is made up of tiny particles less than 2.5 microns wide. “Air pollution in your neighborhood can affect your health,” Alexev said. “Small particles come from car exhaust, factories, and wildfires. When we breathe in those small particles, they can reach our bloodstream and brain.”
Alexev emphasized that while the respiratory and cardiovascular effects of pollution are well established, neurological effects are a new area of scientific attention. “We already know a lot about how air pollution affects the heart and lungs, including an increased risk of heart attacks and asthma,” Alexev said. “However, a growing body of research suggests that long-term exposure to air pollution also affects brain function.”
The researchers calculated the average amount of pollution each person was exposed to over three specific time periods: 5 years, 10 years, and 17 years. During the study, each participant completed a detailed assessment measuring three different areas of cognitive ability. These include semantic memory, verbal episodic memory, and executive function.
This data provides evidence that greater long-term exposure to particulate air pollution is associated with lower scores in semantic memory. Specifically, the authors found that a 5 micrograms per cubic meter increase in pollution exposure over a 17-year period was associated with a 0.61 standard deviation decrease in semantic memory performance. The 5-year and 10-year exposure averages showed similar trends, but the association was strongest over the 17-year period.
“Previous studies have shown that aging affects different aspects of our brain function in different ways,” Alexev says. “So we knew it would be important to look at each type of brain function separately, but we didn’t know what we would find. Interestingly, we found that long-term exposure to air pollution was associated with poorer semantic memory, but not with other types of brain function.”
To put this into perspective, researchers compared this pollution-related memory decline to the natural aging process. “In fact, people who lived in areas with high air pollution for 17 years had worse semantic memory than people who lived in cleaner areas, and the difference was larger than would be expected from aging by about 10 years,” Alexev said.
These long-term effects indicate that the environment shapes cognitive trajectories in ways that require sustained perspective. “This study is an important contribution to understanding the long-term effects of particulate air pollution on our health,” Alexev said. “Air pollution affects multiple systems in the body, and our findings suggest that exposure may continue to affect health even after a decade or more.”
Researchers say systemic change is needed because individual choices are often limited by socio-economic factors. “In our study, we looked at exposure to pollution over long periods of time: five, 10, and 17 years,” Alexev said. “If you live in an area with high levels of particulate pollution, most people cannot easily move to another area, so it is difficult to reduce exposure through individual behavior alone.”
“There are several steps people can take, such as using household air filters to reduce exposure to indoor particles,” Alekseef says. “But we need much larger-scale policy solutions to ensure everyone in every region has access to clean air.”
The authors acknowledge some potential misconceptions and limitations. Because this study included only Black participants, these results cannot be directly compared to other racial or ethnic groups within the same research framework. Although the findings highlight risk factors specific to black adults, they do not determine whether this population is uniquely vulnerable to contamination compared to other populations.
Another limitation involves tracking residential addresses over time. The researchers used addresses collected at specific ages. That is, we did not know the exact dates when participants may have moved from one home to another. There was also no information on how much time participants spent outdoors or away from home. This can actually impact your daily exposure to polluted air.
Future research should aim to track cognitive decline in individuals over time and distinguish between different sources of air pollution. “The next step is to find out whether particle pollution from fires, for example, causes more cognitive harm than particle pollution from car exhaust or factories,” Alexev said. Understanding exactly how certain types of dirty air affect brain function can help public health officials predict future medical needs and plan targeted interventions.
The study, “Particulate Air Pollution and Domain-Specific Cognition in Black Adults,” was authored by Stacey E. Alexeeff, Chinomnso N. Okorie, Paola Gilsanz, Joel Schwartz, Amanda J. Goodrich, Ai-Lin Tsai, Rachel A. Whitmer, Kelly M. Bakulski, Scarlet Cockell, and Kathryn C. Conlon.
