Study links PFAS chemicals to 50% higher MS risk in women

Researchers at the University of Miami have found that women carrying higher levels of PFAS chemicals in their blood face roughly 60% greater odds of developing multiple sclerosis, according to a study published in Environmental Research. The work examined blood samples from 439 U.S. participants and identified a particularly troubling pattern: among the three PFAS compounds measured, perfluorohexanesulfonic acid—known as PFHxS—emerged as the strongest predictor of MS risk.

PFHxS is a chemical found in firefighting foams, stain-resistant fabrics, and food packaging. For every incremental rise in PFHxS blood levels, the odds of MS increased by about 53% overall and 56% among women. Those with the highest PFHxS concentrations were more than 3.5 times as likely to have MS as those with the lowest levels. Perfluorooctanoic acid, or PFOA, showed a weaker but still significant association—people with the highest PFOA levels were about 2.6 times as likely to have MS. What struck the researchers most was the ubiquity of exposure: all three legacy PFAS chemicals were detectable in more than 99.5% of study participants.

The study's significance lies partly in what it revealed about specificity. Researchers compared blood samples from people with MS against those with two autoimmune diseases that can closely resemble it: myelin oligodendrocyte glycoprotein antibody-associated disease and neuromyelitis optica spectrum disorder. Women with MS showed consistently elevated PFHxS levels compared not only to healthy women but also to women with these lookalike conditions—a distinction that suggests these chemicals may operate through pathways unique to MS rather than triggering a generalized immune response. An outside expert from Oregon State University noted this finding strengthens the case that PFHxS and PFOA act through mechanisms specific to the disease itself.

Multiple sclerosis affects approximately 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, causing difficulty walking, cognitive changes, and vision problems. There is no known cure. The study's findings align with Swedish research published in 2025 that also linked PFAS exposure to MS in women, suggesting a pattern that extends beyond a single population.

The researchers acknowledged important limitations. The blood measurements captured exposure at a single point in time and were taken after participants had already developed MS, so the study cannot prove that PFAS exposure causes the disease. The study population was also limited to non-Hispanic white participants, restricting how broadly the results apply. However, because PFHxS persists in the human body for up to 35 years, a single blood test likely reflects years of accumulated exposure rather than a recent change tied to disease onset—evidence suggesting the chemicals contribute to MS rather than the reverse.

Nearly every American carries PFAS in their blood, largely because federal regulators have been slow to restrict these chemicals in consumer products and drinking water despite mounting evidence of harm. The current administration has moved to delay some PFAS water protections that were already in place. A researcher at Columbia University's Mailman School of Public Health described the findings as advancing a plausible and concerning hypothesis that a near-ubiquitous environmental exposure may be contributing to one of the most common serious neurological diseases in young adults—and one that disproportionately burdens already marginalized communities. Critics argue that families deserve full transparency about these exposures and resources to address them, rather than waiting on an industry and regulatory system that has historically prioritized production over disclosure.