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By Pamela Ferdinand
Key findings
- Higher combined per- and polyfluoroalkyl substances (PFAS) exposure, largely driven by the chemical perfluorohexanesulfonic acid (PFHxS), was associated with roughly 50% greater odds of multiple sclerosis (MS) overall and about 60% greater odds among women.
- PFHxS, used in stain-resistant fabrics, food packaging and firefighting foams, showed the strongest and most consistent association with MS. For each increase in PFHxS levels, the odds of MS rose by about 53% overall and 56% in women.
- Women with MS had higher blood levels of the “forever chemical” PFHxS and, to a lesser extent, perfluorooctanoic acid (PFOA) than women without the disease and those with two other unrelated autoimmune diseases.
Women with higher blood levels of PFAS — or “forever chemicals” — may be more likely to have MS, according to a new study.
PFAS are highly persistent chemicals used in nonstick cookware, food packaging, stain-resistant fabrics and firefighting foams, among other common items. Nearly all Americans are exposed through consumer products, food and contaminated drinking water.
The findings, published in Environmental Research and based on 439 U.S. participants, do not prove that PFAS exposure causes multiple sclerosis.
But they add to growing concerns that these widespread chemicals may contribute to autoimmune disease, even as the Trump administration moves to undo or delay some federal PFAS drinking water protections.
“The evidence is still early, but PFAS are emerging as environmental chemicals that could be contributing to MS onset in some individuals,” said co-author Farren Briggs, an associate professor and health scientist at the University of Miami Miller School of Medicine.
PFHxS shows the strongest link to MS
The researchers measured three PFAS chemicals — PFHxS, PFOA and perfluorooctane sulfonate (PFOS). The strongest and most consistent associations 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, while PFOS showed the weakest links. PFOA and PFOS are no longer widely manufactured in the U.S., but decades of use mean they remain in water, soil, wildlife and people.
Researchers found people with higher overall PFAS exposure had about 50% higher odds of having MS. Among women, the increase was about 63%.
PFHxS emerged as the strongest and most consistent contributor to the association.
The study shows:
- For each increase in PFHxS levels, the odds of MS rose by about 53% overall and 56% among women.
- People with the highest PFHxS levels were more than 3.5 times as likely to have MS as those with the lowest levels.
- Those with the highest PFOA levels were about 2.6 times as likely to have MS.
“What was most surprising were that all three legacy PFAS under study were detectable in more than 99.5% of our study participants, and how PFHxS was consistently higher in people with MS — even compared with people who had other MS-like autoimmune diseases,” Briggs said.
MS and the growing focus on PFAS
MS is a chronic disease in which the immune system mistakenly attacks the protective coating (myelin) around nerve fibers in the brain and spinal cord.
This impairs the nervous system’s ability to communicate signals to the rest of the body, which can lead to difficulty walking, cognitive changes and vision problems, among other symptoms. It has no cure.
The disease affects about 2.8 million people worldwide, and women account for about two-thirds of diagnoses. Risk factors include having certain genes, Epstein-Barr virus infection, smoking, childhood obesity and vitamin D deficiency.
Scientists increasingly suspect environmental exposures may contribute to MS, especially early in life.
PFAS have been linked to immune and hormone disruption, reproductive and developmental problems, childhood obesity and increased risks of some cancers.
A recent laboratory study also suggested that PFAS chemicals may disrupt normal placental function.
Higher PFAS levels found in women with MS
In a first-of-its-kind analysis, researchers compared blood samples from people with MS and those with two autoimmune diseases that can resemble MS: myelin oligodendrocyte glycoprotein antibody-associated disease (MOGAD) and neuromyelitis optica spectrum disorder (NMOSD).
Women with MS consistently had higher levels of PFHxS compared to healthy women and women with MOGAD or NMOSD. PFOA showed a similar but less consistent pattern.
“This is important as it highlights that PFHxS and maybe PFOA act through pathways unique to MS and not general across the immune system in the brain or the brain in general,” said Dr. Jamie DeWitt, an Oregon State University professor and director of the Pacific Northwest Center for Translational Environmental Health Research.
Higher PFOA levels in women with MS were also linked to changes in compounds the body uses to process and regulate hormones (endocrine disruption). The same pattern was not seen in healthy women.
Growing evidence links PFAS to higher chance of MS
The findings build on two Swedish studies — one published last year and another earlier this year — that linked PFAS exposure to MS, particularly among women.
Together, those studies analyzed blood samples from more than 1,800 people and are among the most comprehensive investigations of environmental chemical exposures and MS to date.
They found:
- Higher combined exposure to PFAS mixed with PCB-related chemicals was linked to greater odds of MS, suggesting mixtures may play a larger role than individual chemicals.
- Among people with a gene variant usually associated with lower MS risk, higher PFOS exposure was linked to more than fourfold greater odds of having MS.
A separate 2025 Chinese study linked higher PFOS exposure to MS and identified four key genes that may help explain the connection. It also suggested PFOS may disrupt the immune system and influence biological pathways involved in inflammation and the clearance of damaged cells.
Key questions remain about the role of PFAS
Among other limitations of the most recent study, the authors note that blood measurements captured exposure at a single point in time. PFAS levels were also measured after participants had already developed MS.
Because PFHxS and PFOA remain in the body for years, a single blood sample may reflect long-term exposure rather than recent disease activity or treatment.
That makes it less likely that the disease itself caused the higher PFAS levels and more consistent with the possibility that the chemicals play a role in the development of MS, the authors say.
The study also included only non-Hispanic white participants, limiting how broadly the findings can be generalized. Some analyses involved relatively small numbers of participants, especially men and people with neurological conditions that resemble MS.
Researchers said future studies should include larger and more diverse populations, longer follow-up periods, and a wider range of PFAS chemicals and exposure pathways.
This individual study is not definitive proof that PFAS “forever chemicals” cause multiple sclerosis, notes Haleigh Cavalier, a research scientist in environmental epidemiology at Columbia University Mailman School of Public Health.
“However, it advances a plausible and concerning hypothesis that a near-ubiquitous environmental exposure, one that disproportionately burdens already marginalized communities, may be contributing to one of the most common serious neurological diseases in young adults,” she said.
Originally published by U.S. Right to Know.
Pamela Ferdinand is an award-winning journalist and former Massachusetts Institute of Technology Knight Science Journalism fellow who covers the commercial determinants of public health.
