- Higher PFAS blood levels are linked to roughly 50% greater odds of multiple sclerosis, especially in women.
- PFHxS, a chemical in firefighting foams and stain-resistant products, showed the strongest and most consistent association with MS.
- People with the highest PFHxS levels were more than 3.5 times as likely to have MS as those with the lowest.
- The study is the first to differentiate PFAS effects between MS and similar autoimmune diseases, pointing to MS-specific pathways.
- Nearly all Americans carry PFAS in their blood, and critics say regulators have been too slow to restrict these chemicals despite growing evidence.
Women with higher blood levels of PFAS "forever chemicals" may face significantly greater odds of developing multiple sclerosis, according to a new study published in Environmental Research. Researchers led by the University of Miami examined blood samples from 439 U.S. participants and found that higher combined exposure to PFAS was associated with roughly 50% greater odds of multiple sclerosis (MS) overall, and about 60% greater odds among women.
The findings add to mounting evidence that these nearly ubiquitous chemicals, which linger in the environment and human bodies for decades, may contribute to autoimmune disease — the latest reminder that Americans are routinely exposed to industrial chemicals whose long-term health effects were never fully disclosed to the public.
PFHxS shows strongest link to multiple sclerosis
Researchers measured three PFAS chemicals in study participants: perfluorohexanesulfonic acid (PFHxS), perfluorooctanoic acid (PFOA), and perfluorooctane sulfonate (PFOS). PFHxS, a chemical 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. 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," said co-author Farren Briggs, an associate professor at the University of Miami Miller School of Medicine.
The study's findings echo Swedish research published in 2025 that also linked PFAS exposure to MS, particularly among women. That research, which analyzed blood samples from more than 1,800 people, found that participants with higher concentrations of PFOS — a related chemical — had approximately twice the odds of developing MS compared with those with the lowest concentrations. That research also suggested chemical mixtures may play a larger role than individual compounds.
Diseases resembling MS show a different chemical pattern
In a first-of-its-kind analysis, researchers compared blood samples from people with MS and those with two autoimmune diseases that can mimic MS: myelin oligodendrocyte glycoprotein antibody-associated disease (MOGAD) and neuromyelitis optica spectrum disorder (NMOSD). Women diagnosed with MS showed consistently elevated PFHxS levels relative to both healthy women and women with the two lookalike conditions, while PFOA followed a similar though weaker trend — a distinction outside expert Dr. Jamie DeWitt, an Oregon State University professor, said strengthens the case that these chemicals may act through pathways specific to MS.
"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," DeWitt said.
MS affects about 2.8 million people worldwide, with women accounting for roughly two-thirds of diagnoses. The disease occurs when the immune system attacks the protective coating around nerve fibers in the brain and spinal cord, leading to difficulty walking, cognitive changes and vision problems. It has no known cure.
Regulators have been slow to act despite mounting evidence
The study does not prove that PFAS exposure causes MS. Researchers noted limitations, including that blood measurements captured exposure at a single point in time and were taken after participants already had MS. The study population was also limited to non-Hispanic white participants, restricting how broadly the results apply.
Still, because PFHxS lingers in the body for up to 35 years, a single blood test likely reflects years of accumulated exposure rather than a recent change tied to the disease itself — evidence, researchers said, that points toward the chemicals contributing to MS rather than the reverse.
Haleigh Cavalier, a research scientist in environmental epidemiology at Columbia University Mailman School of Public Health, said the study 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."
Nearly every American carries these chemicals in their blood, largely because federal regulators have been slow to restrict them in consumer products and drinking water, even as the current administration has moved to delay some of the PFAS water protections that were already in place. Critics argue that families deserve full transparency about these exposures and the resources to address them, rather than waiting on an industry and regulatory system that has historically prioritized production over disclosure.
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