Main findings
- Increased combined PFAS exposure, primarily caused by the chemical PFHxS, was associated with approximately 50% higher odds of MS overall and approximately 60% higher odds among women.
- PFHxS, which is used in antifouling textiles, food packaging, and firefighting foams, showed the strongest and most consistent association with MS. For each increase in PFHxS levels, the odds of MS increased by approximately 53% overall and by 56% in women.
- Women with MS had higher blood levels of the ‘eternal chemical’ perfluorohexane sulfonic acid (PFHxS) To a lesser extent, perfluorooctanoic acid (PFOA) was also higher in women without the disease and in women with two other unrelated autoimmune diseases.
Women with high blood levels of per- and polyfluoroalkyl substances, known as PFAS or “forever chemicals,” may be more likely to develop multiple sclerosis (MS), according to a new study.
PFAS are highly persistent chemicals used in common items such as nonstick cookware, food packaging, stain-resistant fabrics, and firefighting foam. Nearly all Americans are exposed through consumer products, food, and contaminated drinking water.
The survey results are environmental research Also, based on 439 US participants, PFAS exposure has not been proven to cause multiple sclerosis. But they add Concerns are growing that these widespread chemicals could contribute to autoimmune diseases, even as the Trump administration moves to roll back or delay some federal drinking water protections for PFAS.
“While the evidence is still in its early stages, PFAS are emerging as environmental chemicals that may contribute to the development of MS in some people,” said co-author Farren Briggs, a health scientist and associate professor at the University of Miami Miller School of Medicine.
PFHxS shows the strongest association with multiple sclerosis
The researchers measured three PFAS chemicals: perfluorohexane sulfonic acid (PFHxS), perfluorooctanoic acid (PFOA), and perfluorooctane sulfonate (PFOS). The strongest and most consistent association with MS involved PFHxS, which has an exceptionally long half-life of up to 35 years in humans.
Researchers found less consistent associations for PFOA, with PFOS showing the weakest association. Although PFOA and PFOS are not currently widely manufactured in the United States, they have been used for decades, meaning they persist in water, soil, wildlife, and humans.
Researchers found that people with higher overall PFAS exposure were about 50% more likely to develop MS. For women, it increased by about 63%.
PFHxS has emerged as the strongest and most consistent contributor to the association. Research shows that:
- For each increase in PFHxS levels, the odds of MS increased by approximately 53% overall and by 56% in women.
- Those with the highest PFHxS levels were more than 3.5 times more likely to develop MS than those with the lowest levels.
- Those with the highest PFOA levels were about 2.6 times more likely to develop MS.
“What was most surprising was that all three legacy PFASs studied were detectable in more than 99.5% of study participants, and that PFHxS in MS patients was consistently higher than in people with other autoimmune diseases such as MS,” Professor Briggs said.
Growing attention to multiple sclerosis and PFAS
Multiple sclerosis is a chronic disease in which the immune system mistakenly attacks the protective membrane (myelin) around nerve fibers in the brain and spinal cord. This impairs the nervous system’s ability to transmit signals to other parts of the body, which can cause symptoms such as difficulty walking, cognitive changes, and vision problems. There is no cure.
The disease affects approximately 2.8 million people worldwide, with women accounting for approximately two-thirds of those diagnosed. Risk factors include carrying certain genes, Epstein-Barr virus infection, smoking, childhood obesity, and vitamin D deficiency.
Scientists increasingly suspect that environmental exposures, especially early in life, may cause multiple sclerosis. PFAS are associated with immune and hormonal disruption, reproductive and developmental problems, childhood obesity, and an increased risk of some cancers. Recent clinical research also suggests that PFAS chemicals may interfere with normal placental function.
Higher PFAS levels found in women with MS
In a first-of-its-kind analysis, researchers compared blood samples from patients with MS and patients with two autoimmune diseases that can mimic MS: myelin oligodendrocyte glycoprotein antibody-associated disease (MOGAD) and neuromyelitis optica spectrum disorder (NMOSD).
Women with MS consistently had higher PFHxS levels compared to healthy women and women with MOGAD or NMOSD. PFOA showed a similar pattern, but with less consistency.
“This is an important point that emphasizes that PFHxS and possibly PFOA act through pathways that are specific to MS and are not general to the brain’s immune system or the brain as a whole,” said Dr. Jamie DeWitt, professor at Oregon State University and director of the Pacific Northwest Center for Translational Environmental Health Research.
Elevated PFOA levels in women with MS were also associated with changes in the compounds the body uses to process and regulate hormones (endocrine disruption). The same pattern was not seen in healthy women.
Growing evidence links PFAS and likely MS
The findings build on two Swedish studies (one published last year and the other earlier this year) that showed a link between PFAS exposure and MS, particularly in women. Together, these studies analyzed blood samples from more than 1,800 people, making this one of the most comprehensive investigations of environmental chemical exposure and MS to date.
They discovered:
- Higher combined exposure to PFAS mixed with PCB-related chemicals was associated with a higher probability of MS, suggesting that the mixture may play a larger role than the individual chemicals.
- Among people with genetic variants typically associated with a lower risk of MS, higher exposure to PFOS was found to be more than four times more likely to develop MS.
Another Chinese study in 2025 showed an association between high PFOS exposure and MS and identified four important genes that may help explain the association. It was also suggested that PFOS may disrupt the immune system, affecting biological pathways involved in inflammation and the removal of damaged cells.
Important questions remain about the role of PFAS
Among other limitations of the latest study, the authors note that the blood measurements captured exposure at a single time point. PFAS levels were also measured after participants had already developed MS.
PFHxS and PFOA remain in the body for years, so a single blood sample may reflect long-term exposure rather than recent disease activity or treatment. This makes it less likely that the disease itself caused elevated PFAS levels and is more consistent with the possibility that the chemicals play a role in the development of MS, the authors said.
Additionally, the study included only non-Hispanic white participants, which limits the generalizability of the findings. Some analyzes included relatively small numbers of participants, particularly men and people with MS-like neurological symptoms.
The researchers said future studies should include larger and more diverse populations, longer follow-up periods, and a broader range of PFAS chemicals and exposure routes.
This isolated study is not conclusive evidence that PFAS “forever chemicals” cause multiple sclerosis, said Haley Cavalier, a research scientist in environmental epidemiology at Columbia University’s Mailman School of Public Health.
“But it advances the plausible and concerning hypothesis that near-ubiquitous environmental exposures, which place a disproportionate burden on already marginalized communities, may be contributing to serious neurological diseases most common among young people,” she said.
reference
Briggs FBS, Montini F, Spurlock CF III, et al. Associations between perfluoroalkyl substances and multiple sclerosis in a US cohort compared with NMOSD, MOGAD, and healthy controls. environmental research. 2026;303:124763. doi:10.1016/j.envres.2026.124763
