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Women with higher levels of "forever chemicals" in their blood could be more likely to have multiple sclerosis (MS), a new study has found.
The research, published in the August 2026 issue of Environmental Research, found that levels of per- and polyfluoroalkyl substances (PFAS)—commonly known as "forever chemicals"—were consistently elevated in women with MS, a chronic disease that affects the central nervous system. The findings do not show that PFAS exposure causes MS, but they do suggest an association between higher levels of certain PFAS compounds and the disease.
An estimated 1 million Americans are living with MS, according to a 2017 study, and the prevalence of the disease has increased over the past five decades. PFAS chemicals, which have been linked to a range of health concerns, were first developed in the 1930s and remained largely unregulated until the early 2000s.
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Public concern over PFAS has also intensified as the Trump administration's Environmental Protection Agency (EPA) has revised certain federal drinking water protections related to the chemicals.
What the Study Found
Researchers identified the strongest association with perfluorohexanesulfonic acid (PFHxS), one of thousands of PFAS compounds. The link was observed only in women; among men, the researchers described the association as "imprecise." They also found a similar, though less consistent, pattern involving perfluorooctanoic acid (PFOA).
The study was based on a review of 439 U.S. participants, and levels of PFHxS, PFOA and perfluorooctane sulfonate (PFOS) were analyzed in each participant's blood. The association was found most strongly with PFHxS, less so with PFOA and weakly with PFOS.
Among the study's key findings was that higher PFHxS levels were associated with approximately 53 percent greater odds of MS overall and 56 percent greater odds among women.
Participants 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 approximately 2.6 times as likely to have the disease.
Dr. David Hafler, a professor of neurology and immunobiology at Yale University, who was not part of the study, told Newsweek that it is known MS is "caused by the interactions of now over 260 genetic variants interacting with the environment, including vitamin D, smoking, high BMI, high salt." He added that there is also "compelling evidence that the [Epstein-Barr virus (EBV)] triggers the disease in genetically susceptible individuals."
Hafler said this study is the second body of research showing an association of PFAS and MS risk, "thus adding more evidence that this is yet one more environmental factor." The professor added that this therefore does not mean PFAS chemicals are "causative" by themselves, but a risk factor.
"As with all epidemiological studies, more basic immunologic investigations will be important, as is pointed out in the study," Hafler said.
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What Are 'Forever Chemicals'?
PFAS chemicals are a group of thousands of different substances widely used across different industries and consumer products such as nonstick cookware, waterproof clothing, stain-resistant furniture, and many others—even smartwatch wristbands.
Growing research has raised concerns about the potential health effects of PFAS exposure. The International Agency for Research on Cancer (IARC), part of the World Health Organization (WHO), has classified certain PFAS compounds as Group 1 carcinogenic.
Studies have also linked PFAS exposure to thyroid disease, liver disease, immune system dysfunction and other health problems.
These chemicals are also able to get into drinking water supply. As they do not break down naturally in the environment, they can find their way into drinking water sources and wastewater. The chemicals can also pass through many traditional water filtering systems, as only advanced, and more expensive, measures can effectively remove them from water.
Analysis of American drinking water systems has continued to expose just how widespread PFAS contamination of the U.S. drinking water supply is.
What Is Multiple Sclerosis?
MS is a disease that affects the central nervous system, including the brain and spinal cord.
The condition disrupts communication between the brain and the rest of the body, leading to symptoms that can include fatigue, cognitive difficulties, mood changes, pain, numbness, tingling, vision problems, mobility challenges and impaired coordination.
MS can impact different areas of the body as a result, and symptoms can vary day-to-day and year-to-year, depending on the patient's internal inflammation.
The exact cause of MS remains unknown. Researchers believe the disease develops when people with certain genetic susceptibilities are exposed to environmental triggers, though the precise mechanisms involved are still being studied.
Researchers have identified several factors that may increase the likelihood of developing MS, though none are considered definitive.
Potential risk factors include smoking, obesity during adolescence, low vitamin D levels, geographic location, genetics, ethnic background and age. While MS is not directly inherited, researchers have identified around 200 genes that may contribute to overall risk. Most new diagnoses occur between the ages of 20 and 50, and the condition is most commonly diagnosed among white people of northern European ancestry.
Research has also suggested that infection with the EBV, which causes mononucleosis, may increase the risk of developing MS.
Sex also appears to play a role in MS risk. A 2017 study found that women accounted for nearly three-quarters of cases, with 74 percent of diagnoses occurring in women and 26 percent in men. Researchers also found that the condition was more prevalent in the Northwestern and Midwestern United States.
Contact Newsweek editors on this story: Daniel Orton and James Debens.
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