New research finds that exposure to PFAS may weaken the immune system in adults, raising new concerns about the long-term health effects of these widely used chemicals.
Per- and polyfluoroalkyl substances, or PFAS, are a large class of human-made chemicals used in products ranging from nonstick cookware and stain-resistant fabrics to firefighting foams. Often called “forever chemicals,” they do not easily break down in the environment and can accumulate in the human body over time.
Some PFAS remain in the body for years. One compound highlighted in the study, perfluorohexanesulfonic acid, or PFHxS, can persist for nearly a decade, making it a particularly important marker of long-term exposure.
In a study of people previously exposed to PFAS through contaminated drinking water, researchers found that individuals with higher levels of the forever chemicals in their blood produced fewer protective antibodies when their immune systems encountered a new virus – a key measure of how effectively the body responds to infection.
“Antibodies act like tiny soldiers, helping the body recognize and fight off viruses,” said Courtney Carignan, senior author of the study and an environmental health researcher at Michigan State University.
When fewer of these “soldiers” are produced, the immune system may be less effective at fighting infection.
“These results raise important concerns about how long-term exposure to PFAS reduces the body’s ability to respond to infections, even in adulthood,” Carignan said.
The effect was strongest among older adults, men and people who were overweight – groups that often have higher PFAS levels in their bodies.
For some families, those effects are already a reality.
“When you find out your family has been exposed, it changes everything – especially how you think about your children’s health,” said Tobyn McNaughton, a Belmont, Michigan, mother whose family was affected by contaminated drinking water. “We’re poisoned people. We learned that some of my son’s childhood vaccines weren’t fully effective due to his compromised immune system, and that’s something no parent expects to face.”
McNaughton connected with Carignan in 2018 after high levels of PFAS were found in her family’s drinking water and has since become a clean water advocate with the Great Lakes PFAS Action Network, a group co-founded by her neighbor Sandy Wynn-Stelt that is centered and driven by people impacted by toxic PFAS pollution.
Carignan said McNaughton’s and others’ experiences reflect broader patterns seen in the data.
“Previous studies in adults have produced mixed results, in part because prior exposures and existing immunity can make responses difficult to isolate,” Carignan said. “The pandemic provided a rare opportunity to observe how the immune system responds to a new virus, allowing us to more clearly detect how PFAS exposure may influence antibody production and helping resolve long-standing uncertainty about its effects in adults. Our findings make clear that PFAS exposure can affect immune response in adults in addition to the known effects in children.”
The findings come as the United States continues to debate and implement new drinking water standards for PFAS. The U.S. Environmental Protection Agency finalized its first enforceable drinking water standards for certain PFAS chemicals in 2024, but implementation timelines and enforcement for some compounds have since shifted.
Carignan said the findings support efforts to reduce PFAS exposure – particularly through drinking water – and highlight the importance of continued monitoring and regulation.
“Exposure to PFAS is widespread, but it is also preventable,” Carignan said. “Reducing levels in drinking water is one of the most effective ways to lower exposure and protect public health.”
Reference: Bauer RA, Yang Z, Petriello M, et al. Associations of serum PFAS with COVID-19 antibody levels among fully vaccinated adults. Environ Res. 2026;298:124154. doi: 10.1016/j.envres.2026.124154
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