Chicago had the worst air quality in the world this past July. As extreme weather events become more common, researchers are exploring the long-term effects of poor air quality — including on dementia risk.
Recent studies have shown a link between dementia and very fine particulate matter in wildfire smoke. This matter is called PM2.5 because it measures 2.5 microns or less in diameter. Researchers also looked at PM2.5 from different emission sources and found an association between wildfire-related PM2.5 and dementia.
“There is emerging interest in this idea that not all PM2.5 is created equal,” says Holly Elser, MD, PhD, assistant professor of neurology at the University of Pennsylvania Perelman School of Medicine. Scientists are analyzing whether burning organic material and vegetation differs from man-made structures that might have higher concentrations of heavy metal particles, and whether the composition of those particles have health implications.
Elser studies how particulate matter affects the brain specifically. She worked on a study in 2025 that found higher PM2.5 exposure was associated with more severe Alzheimer’s-related brain changes and greater cognitive and functional impairment.
In analyzing brains of people who had died, Elser says there’s an association between long-term air pollution exposure and the extent of Alzheimer’s disease’s pathological changes in the brain. The results aligned with other studies that looked at living brains.
Elser says there’s more to learn about the connection between dementia and poor air quality, especially as wildfire smoke can travel long distances and expose people who live far from the fires.
“The question is why do we see such a strong association,” she says. Is the wildfire smoke itself accelerating dementia? Or does the stress of being near a wildfire, having disruptions in your daily routine, potentially being displaced or having to relocate play a role?
Research continues to reveal associations between PM2.5 exposure and brain health, a concern that may become increasingly important as climate conditions contribute to wildfire risk.
According to the National Oceanic and Atmospheric Administration (NOAA), July 2026 tied with 2024 as the hottest July on record.
“Climatologically, July is the warmest month of the year,” NOAA states in its monthly online report. July 2026 and 2024 are more likely than not the warmest months on record for the globe since 1850, when humans began burning significant amounts of fossil fuels.
U.S. space agency NASA, which has used satellites to track active wildfires for more than 20 years, has found that fire seasons are getting longer in some regions, while extreme wildfires are growing in frequency. In recent years, summer wildfire smoke drifting into Chicago has caused dangerous air quality on several occasions, including 2023. People can monitor air quality on the AirNow Air Quality Map or the IQAir map.
More immediately apparent than its impact on brain health, drifting wildfire smoke can irritate people’s throats and eyes. It’s especially dangerous for children and older adults or people with existing cardiovascular or respiratory illnesses, such as asthma.
And Chicagoans’ exposure to air pollution is not evenly distributed. In a 2022 air quality survey of the city, Microsoft installed more than 100 sensors on CTA bus shelters and found that areas along heavy-traffic corridors, including Little Village, and areas near industrial sites had higher pollution levels.
In 2025, the city installed 277 air sensors, which were more sophisticated than those used in 2022, to provide residents with neighborhood-level data on PM2.5 and nitrogen dioxide. The city developed the Open Air Chicago project in collaboration with community groups, including People for Community Recovery. The environmental justice organization was founded to combat environmental racism and pollution in Altgeld Gardens, a neighborhood on Chicago’s Far South Side surrounded by landfills and industrial facilities.
“We live in a toxic donut,” says Jermica Davis, health equity and outreach associate with People for Community Recovery. “We do have high cases of asthma in our neighborhood, so we want to try to get to the root.”
The organization is also installing air monitors inside some residents’ homes in the neighborhood and surrounding areas to measure indoor and outdoor air quality.
“This will allow us as well as the resident to monitor air quality throughout the year and collect data on air quality conditions in the community,” Davis says. “The older people are more concerned about the air quality because they have lived here for so long. They notice the change because the air quality used to be way worse than what it is now.”
People can take steps to protect themselves and their loved ones during wildfire smoke events. Individuals can use KN95 masks, indoor air filtration systems, or seek shelter in buildings with air conditioning and filtration. Elser, who has also studied population health and epidemiology, says healthcare systems need to prepare.
“Patients with neurologic diseases are vulnerable and may not be able to make adaptive changes to poor air quality because of cognitive impairment or mobility-related limitations,” Elser says. “Thinking about how to make sure patients with existing conditions are protected and as safe as possible is going to be extremely important as we have more and more people living with dementia.”
Rachel Duckett is a freelance health and science writer. A lifelong Midwesterner, she previously hosted All Things Considered at WVIK, Quad Cities NPR in Rock Island, Illinois. She has also worked at an environmental initiative out of Detroit Public Television called Great Lakes Now, covering environmental stories in the Great Lakes Basin, and as a copy editor for the Spartan Medical Research Journal in East Lansing, Michigan. She hopes to demystify research and medicine for a general audience with her writing.
