Can forever chemicals affect the brain? TXST researcher studies firefighters to find out

Dr. Xi Pan has studied risk factors that can lead to dementia and other neurodegenerative conditions since her postdoctoral fellowship in public health at Clemson University over a decade ago.

Researching caregivers at a public hospital in South Carolina, she observed that a significant number of older patients had some form of dementia and that the people who took care of them, typically family members, struggled with intense stress and social isolation. She wanted to find a way to prevent the dementia that was making life difficult for so many people.

“If we can identify the modifiable risk factors for people to develop dementia in the future, we can intervene and stop it in the early stages,” says Pan, an associate professor in Texas State University’s Department of Sociology and faculty member in the Dementia and Aging Studies master’s program. “That’s going to eventually help the highest number of people.”

Since she joined Texas State University in 2016, Pan’s research has focused on various non-medical contributors to disease, such as behavioral choices and social factors. A few years ago, she turned her attention specifically to the environmental risks for cognitive aging and impairment, including the cognitive health of firefighters and the impact of PFAS, or per- and polyfluoroalkyl substances.

Widely used in products like frozen food packaging, pizza boxes, and waterproof clothing, PFAS are often called “forever chemicals” because they break down slowly and can accumulate in the environment and possibly in the human body.

Pan became interested in studying the impact of PFAS after meeting Dr. Sangchul Hwang, professor of civil and environmental engineering, through TXST’s Alliance of Researchers in Aging. Hwang’s research includes environmental contaminants in water, such as PFAS. Having learned from Hwang that some firefighting foam contains PFAS, she decided to study whether exposure to the chemicals was associated with cognitive performance in firefighters.

In July, the Journal of Exposure Science & Environmental Epidemiology published Pan’s article “Association of per- and polyfluoroalkyl substances (PFAS) exposure with cognitive function in firefighters,” coauthored with colleagues at the Yale School of Public Health and two TXST students, Felipe Armstrong, a 2025 sociology graduate, and Bonny Amin, a 2025 agricultural sciences master’s graduate.

Partnering with fire departments in Kyle, San Marcos, New Braunfels, and San Antonio, Pan’s team collected blood samples from 65 firefighters and analyzed them for the presence of 24 PFAS analytes. Each subject also took a seven-part cognitive assessment including tests of executive function, processing speed, and working memory.

Pan’s study showed that firefighters with higher concentrations of one type of PFAS—known as PFOS (perfluorooctane sulfonic acid)—in their blood scored worse on processing speed, which might signal the early onset of cognitive decline if cumulative. While the results of the study are preliminary and do not demonstrate that exposure causes impaired processing speed, the article is one of the first epidemiological studies on the impact of PFAS in the context of cognitive health, and it sets the stage for future studies to determine causality by testing a much larger and more diverse group of people.

Expanding the Study to a Broader Population 

To demonstrate causality, Pan says, researchers would need to test more people and understand the mechanism through which the chemical impacts the brain. Pan’s next step is to work with collaborators to expand the study to a general population and test whether her findings hold true even among people with less PFAS exposure than firefighters.

Firefighters were a good population to test, Pan says, because they had known PFAS exposure; if they showed cognitive impairment, further research on the general population would be warranted. Pan learned that firefighters are regularly screened for cancer but not for cognitive problems associated with chemical exposure.

“I was so surprised,” she says. “I assumed this population’s cognitive health would have been studied a long time ago because of the high risk—but, unfortunately, no.”

The chemical associated with decreased processing speed in Pan’s firefighter study, PFOS, is considered a “legacy,” or long-chain, PFAS. Legacy PFAS have been phased out of use since 2000 because they were linked with health problems, but they may still be present in some firefighting equipment and foam.

New Braunfels Assistant Fire Chief Mike Wehman says he was happy for his department to participate in Pan’s study and to contribute to better understanding the risks firefighters face. The department conducts numerous annual physical and mental health screenings for firefighters but has not previously offered cognitive health tests.

“We have to make firefighting a career that people can come into and feel safe about their future and their children and their spouses when they go home — whether that be mental health, physical health or, now, cognitive health,” Wehman says.

Prevention vs. Treatment 

Pan’s study is also notable because it focuses on middle-aged adults. Clinicians often assess children’s neurocognitive development and older patients’ cognitive health. But Pan says middle-aged adults, who are not commonly screened, deserve far more study.

“Because of many social, familial, and professional stresses, this is actually a very critical life stage when people start to have some risk for future illness,” she says.

Pan’s latest research expands upon her previous studies of modifiable risk factors for dementia, including Alzheimer’s disease, mild cognitive impairment, and vascular dementia. These include behavioral factors, such as diet, exercise, smoking, and alcohol consumption; and social factors, such as a person’s social support network, socioeconomic status, frequency of volunteering, and access to healthcare and healthcare information.

She has also examined environmental influences, such as air pollution, noise, drinking-water quality, and exposure to chemicals, as well as whether people have access to social infrastructure such as parks, libraries, and community or senior centers.

As Pan and other researchers learn more about the various factors that could impact cognitive decline, she wants to see neurocognitive health checkups become as common as annual physical exams.

“Preventive health should be a focus to eventually reduce the burden on healthcare, nationally and globally,” she says. “We cannot wait until people get too sick and then start to spend a lot of money to address the issue when it may be too late. We need to focus on prevention.”