Environmental Pollution Can Increase Your Alzheimer’s Risk, Say BrightFocus-Funded Scientists

The environment is woven into the fabric of our daily lives—shaping the air we breathe, the water we drink, and the places we call home. Often, its impact goes unnoticed, but beneath its surface lies a truth we can no longer ignore: what sustains us can also shape our health in profound ways. 

Previously underrecognized, environmental pollutants are now regarded as significant risk factors for dementia, including Alzheimer’s disease, by global health experts. Their effects extend beyond biology, disproportionately affecting vulnerable and underserved communities, and quietly influence our ability to age healthfully.

As we uncover the connections between our environment and our brain health, a vital question emerges: what can we do to protect ourselves and promote healthier futures—for everyone, everywhere? 

Traffic Pollution Can Place Brain Health at Risk 

Living in a big city comes at a cost—one measured not just in time spent in traffic but in invisible particles that fill the air. While you sit bumper-to-bumper, microscopic pollutants quietly enter your lungs and move into your bloodstream, carrying risks that extend far beyond your commute. 

These fine particles, called PM2.5, are emitted into the air by fossil fuels, wildfires, agricultural burning, and other sources. One pilot study found that brain donors from the Atlanta metro area tended to have higher levels of amyloid plaques in their brains —a biological hallmark of Alzheimer’s—compared to donors from outside the city. Further, research from the National Institutes of Health examining over 4,000 adults found that those who developed dementia tended to live in areas with higher levels of PM2.5—like major cities.

What happens when we widen the lens beyond Atlanta or even the U.S.? Take India, a country grappling with some of the worst air quality in the world. Nine out of the ten most polluted cities globally, ranked by the 2023 World Air Quality Report, are in India, where millions live under a constant haze of air pollution. 

For Dr. Jinkook Lee, an Alzheimer’s Disease Research grant recipient, this presents a unique opportunity. As the lead investigator of the Harmonized Diagnostic Assessment of Dementia for the Longitudinal Aging Study in India, Dr. Lee turned to India’s urban and rural landscapes to explore how chronic exposure to outdoor and household pollutants impacts brain health.

“Low and middle-income settings, such as India, offer an important opportunity to study [the effect of] air pollution—particularly PM2.5 from different sources—on the brain,” said Dr. Lee. “They share many common sources with high-income countries like traffic, energy production, and windblown dust.”

Dr. Lee and colleagues found that high long-term exposure to both outdoor and household air pollutants are associated with poorer cognition and faster cognitive decline. Countries like India often experience some of the highest PM2.5 concentrations due to a reliance on biomass fuel use and fewer emission controls compared to countries with higher income, explained Dr. Lee. 

Stateside, similar inequities emerge. Communities of color and low-income populations are more likely to live near highways, power plants, or industrial facilities, exposing them to disproportionate levels of PM2.5. Some scientists believe this may contribute to racial disparities in Alzheimer’s disease, especially for Black women in the U.S.   

Findings from Dr. Lee’s work have the potential to affect global change. By building scientific evidence for the impact of air pollution on brain health, her work can “inform interventions and policy changes aimed at reducing exposures to certain pollutants to reduce or delay the onset of cognitive decline and dementia,” she said. 

Wildfires Impact Long-Term Health in Rural Communities 

Those living in more rural areas are not necessarily protected from air pollution, as prolonged exposure to wildfires still poses a risk. The same National Institutes of Health study mentioned previously also evaluated the impact of different sources of air pollution. It found that pollution from wildfires and agriculture has the strongest link with dementia.  

Wildfires affect “a lot of rural communities, particularly here in the Northwest and throughout Canada and other parts of the continent where there’s dense woodland and high wildfire risk,” said Dr. Justin Miller, an Alzheimer’s Disease Research grant recipient at the University of Washington Medical— the primary academic institution providing medical education in the 5-state region including Washington, Wyoming, Alaska, Montana, and Idaho, supporting over 11 million rural residents.

“If you live in an area that is prone to wildfires, there’s definitely going to be a possible exposure. The thing is that these are prolonged periods and it’s not just in the immediate area where the fire is actively burning,” Dr. Miller said. 

Wind patterns coupled with the increasing size and frequency of wildfires from climate change create widespread exposure to wildfire smoke, explained Dr. Miller. This may place rural residents at greater risk of adverse health consequences from prolonged PM2.5 exposure. 

According to the Environmental Protection Agency, wildfires generate a significant amount of PM2.5 as their main air pollutant. One of the most devastating fires in U.S. history—the 2018 Camp Fire in California—burned over 150,000 acres and emitted an estimated 32,000 metric tons of PM2.5. That means the daily average of PM2.5 emissions in cities like Sacramento and San Francisco rose to over five times the standard limit and rural cities like Paradise were nearly destroyed.   

Rural residents may lack access to air filtration systems or cleaner indoor environments, placing them at greater vulnerability to the impacts of elevated PM2.5 levels from the wildfire. They also faced greater difficulty accessing medical care than those residing within urban areas. 

California continues to struggle with devastating wildfires, the latest of which have greatly impacted Los Angeles and surrounding areas. It remains unclear what impact wildfires like the Camp Fire have had on rural health long-term—especially brain health. But scientists are working to better understand rural aging and the factors that can place these residents at greater risk for age-related diseases like Alzheimer’s.  

“There hasn’t been a tremendous amount of research done prospectively following people who choose to age in a community outside of a major metropolitan area,” said Dr. Miller. “And yet, what we do know from things like public claims data, for example, is that the individuals who age in rural communities faced increased risk of morbidity and mortality from Alzheimer’s disease.”

With early funding from Alzheimer’s Disease Research, Dr. Miller is leading the Rural Brain Health Initiative—the largest, most comprehensive longitudinal study of rural cognitive aging ever done.

Establishing a research hub for rural brain health fills a significant gap for this underrepresented community. Rural residents tend to experience delays in getting their dementia diagnosis and have shorter survival than those who age in urban areas, explained Dr. Miller.

He hopes to improve access to critical health care for older adults and establish a better understanding of brain aging and dementia in rural America. Collecting key health information, biological samples, and lifetime residential history will give Dr. Miller the foundation he needs to begin studying specific risk factors for this community, like environmental toxins.  

Looking Beyond Air Pollution 

Environmental toxins extend far beyond the air we breathe. Water quality, agricultural practices, and groundwater contaminants are emerging areas of concern for long-term aging.  

“There have been decades of research on the association with organophosphates and fertilizers, for example, and pesticides and overall health. I think what may be less known are the specific influences on Alzheimer’s disease risk,” Dr. Miller explained. 

In many rural areas, reliance on well water can create an opportunity for exposure to agricultural chemicals. Well water doesn’t necessarily go through a treatment facility or municipal supply chain. This means farming chemicals like pesticides can end up in groundwater and may go unchecked, leaving questions as to the potential impacts on long-term health and aging.   

Water quality in major cities may also pose a risk, especially for lower-income areas. Mounting concerns surrounding chemical pollutants like PFAS—known as forever chemicals—in drinking water has spurred more recent exploration into possible ties to dementia risk. However, Dr. Lee cautions that the research in this area is very early days.  

How to Protect Your Health Today 

Dr. Miller shared his suggestions to manage your overall health and collective exposure to environmental toxins and pollutants.

1. Pay attention to the air quality index. Consider limiting your activity outdoors if the air quality is poor—especially important if you live in a big city or an area that is prone to wildfires. 
2. Make sure you have a high-quality air filter. Using good filters in your home’s heating and cooling system, or getting dedicated room air-filters, can help you maximize the air quality in your home for everyday health. 
3. Know where your food supply comes from. Shopping local, when possible, can help limit your exposure to potential chemical pollutants from large-scale production plants.  
4. Ask for water quality reports and get your water well tested. Whether you are on a municipal water supply or a well, know what is in your drinking water to help mitigate potential health risks.  

Summary 

Where and how we live can profoundly shape the trajectory of our cognitive aging. From bustling cities blanketed in smog to rural towns shrouded in wildfire smoke, exposure to PM2.5 and other pollutants has the potential to erode not just the air we breathe but the memories we hold dear. 

The path forward is one we all share. We can take steps to protect ourselves and our families and advocate for healthier environments to support our global community. A healthier environment means healthier aging—for everyone, everywhere. 

BrightFocus Foundation is committed to supporting research and raising awareness for risk factors of Alzheimer’s disease. Learn more about our Alzheimer’s Disease Research program here.