For millions of Americans, the air they breathe and the water they drink are quietly shaping their health in ways that only now are coming into sharper focus. Two new streams of research and reporting, published on November 12, 2025, reveal a mounting body of evidence linking environmental pollutants—both in the air and water—to serious neurological and other health risks. The findings, drawn from major studies and local investigations, not only underscore the complexity of these threats but also highlight the patchwork response from government agencies and local officials.
At the heart of the air pollution story is the Penn Memory Center at the University of Pennsylvania, where researchers have spent decades tracking cognitive decline in older adults. Their latest study, the largest autopsy-based investigation to date, involved more than 600 donated brains collected over twenty years. According to KFF Health News, the study found a clear association between long-term exposure to fine particulate matter—known as PM2.5—and the severity of Alzheimer’s disease pathology in the brain. PM2.5 refers to microscopic particles less than 2.5 micrometers in diameter, which are small enough to be inhaled deep into the lungs and even enter the bloodstream.
The researchers’ approach was as meticulous as it was personal. Among the donors were a man and a woman who had both been followed for years at the Penn Memory Center. The man, who died at age 83 with dementia, had lived near Interstate 676 in Philadelphia and was exposed to high levels of PM2.5. His brain, upon autopsy, showed extensive amyloid plaques and tau tangles—the biological hallmarks of Alzheimer’s disease—as well as signs of multiple small strokes. In contrast, the woman, who died at 84 of brain cancer but showed no signs of cognitive decline, had lived in the leafy suburb of Gladwyne, Pennsylvania, where her exposure to PM2.5 was less than half that of the man. Her brain revealed almost no Alzheimer’s pathology.
“The quality of the air you live in affects your cognition,” Dr. Edward Lee, the neuropathologist overseeing the study, told KFF Health News. “The higher the exposure to PM2.5, the greater the extent of Alzheimer’s disease.” The odds of severe Alzheimer’s pathology were nearly 20% higher among those who had lived in areas with high PM2.5, the study concluded.
But the story doesn’t stop with Alzheimer’s. A separate, massive epidemiological study led by researchers at Columbia University’s Mailman School of Public Health analyzed records from more than 56 million Medicare beneficiaries between 2000 and 2014. Their findings, as reported by KFF Health News, showed that chronic exposure to PM2.5 was linked to a 12% higher rate of hospitalizations for Lewy body dementia—a form of dementia related to Parkinson’s disease and considered the second most common type after Alzheimer’s.
To further validate these epidemiological findings, scientists at Johns Hopkins School of Medicine exposed laboratory mice to PM2.5 for ten months. The results were striking: the mice developed “clear dementia-like deficits,” including getting lost in mazes they previously navigated with ease and building sloppy, disorganized nests. Their brains, upon examination, showed atrophy and accumulations of alpha-synuclein, the protein associated with Lewy bodies in humans.
These studies are part of a growing consensus. A third analysis, published in The Lancet this summer, reviewed 32 studies from Europe, North America, Asia, and Australia, and also found that long-term exposure to PM2.5 and other pollutants is significantly associated with dementia diagnoses. The mechanism—whether it’s inflammation or another physiological process—remains under investigation, but the pattern is clear: the air we breathe is shaping our brains in profound ways.
Despite these findings, the policy response has been uneven. The Environmental Protection Agency (EPA) set tougher annual standards for PM2.5 in 2024, recognizing that existing limits might not adequately protect public health. But by March 2025, the new EPA chairman announced that those standards would be “revisited.” Meanwhile, the Trump administration has reversed several key environmental policies, including rescinding tax incentives for solar power and electric vehicles, halting new offshore wind farms, and moving to stop California’s plan to phase out gasoline-powered cars by 2035. “Drill, baby, drill is totally the wrong approach,” Dr. John Balmes, an American Lung Association spokesperson and air pollution researcher, told KFF Health News. “All these actions are going to decrease air quality and lead to increasing mortality and illness, dementia being one of those outcomes.”
While the air pollution crisis is unfolding, a parallel story is developing in Oregon, where water contamination by PFAS—so-called “forever chemicals”—has put public health at risk. According to Oregon Public Broadcasting, officials discovered PFAS contamination in the water supply of Hermiston, the largest city in eastern Oregon, in 2023. PFAS are a wide-ranging group of chemicals used in everything from nonstick cookware to waterproof clothing, and their persistence in the environment and the human body has earned them their ominous nickname.
Despite exceeding the federal maximum containment level for at least one PFAS chemical, Hermiston officials have adopted a “wait-and-see” approach, citing uncertainty over the source and a desire to be efficient with costs. “Hermiston’s water is safe to drink,” Assistant City Manager Mark Morgan told OPB, even as state and federal guidelines warn of health risks. The Oregon Health Authority, meanwhile, is waiting for a final ruling from the EPA before mandating further action.
The stakes are high. PFAS have been detected in the blood of 97% of Americans, according to the Centers for Disease Control and Prevention. Exposure to certain PFAS has been linked to thyroid disease, infertility, high cholesterol, higher risks of asthma, and some cancers. Cleaning up PFAS is notoriously difficult and expensive, as these chemicals resist filtration and linger in both water and the human body.
With regulatory action lagging, nonprofits and local governments are stepping in. Oregon Rural Action is advocating for cleaner groundwater, and projects are underway to connect homes to municipal water systems that are more strictly regulated. The state plans to have every water system tested for PFAS by the end of 2027, according to OPB.
As communities across the country grapple with these invisible threats, experts warn that the cost of inaction could be staggering. “People argue that air quality is expensive,” Dr. Lee said. “So is dementia care.” The same could be said for water safety. While the research continues and policymakers debate, the evidence is mounting: the environment is not just a backdrop to our lives—it’s a key player in our long-term health and well-being.
