Common Chemical Exposure Linked to Multiple Sclerosis Risk
Long-term exposure to specific industrial chemicals may meaningfully increase the odds of developing multiple sclerosis
Topline
A large Swedish case-control study found that higher blood levels of certain PFAS and hydroxylated PCBs were associated with roughly a twofold increase in the odds of multiple sclerosis, with evidence that genetic susceptibility can amplify this risk.
Study Details
Multiple sclerosis is a chronic autoimmune disease affecting the central nervous system. While genetics play an important role, environmental exposures are increasingly recognized as contributors to disease onset. Among the strongest genetic links are variants in the human leukocyte antigen system, but genetics alone do not explain rising MS prevalence.
This new study focused on endocrine-disrupting chemicals, specifically polyfluoroalkyl substances and hydroxylated polychlorinated biphenyls. PFAS are often referred to as “forever chemicals” because they persist in the environment and the human body. They are commonly found in nonstick cookware, food packaging, stain-resistant fabrics, and firefighting foams. PCBs were banned decades ago but remain present in soil, water, and the food chain.
The research was published in December 2025 in Environment International and represents one of the largest population-based investigations to date examining these chemicals in relation to MS.
Methodology
Researchers analyzed blood samples from approximately 1,800 individuals in Sweden. This included 907 people recently diagnosed with MS and 907 matched controls of similar age, sex, and geographic location.
Serum samples were tested for 24 PFAS compounds and seven hydroxylated PCBs using high-precision laboratory techniques. Participants also completed questionnaires covering lifestyle and environmental factors. Statistical analyses adjusted for body mass index, smoking, genetic risk variants related to MS, and other known confounders.
The goal was to understand not only individual chemical exposures but also the combined effect of multiple chemicals acting together.
Key Findings
Higher blood levels of PFOS and specific hydroxylated PCBs were associated with increased odds of MS.
Individuals in the highest exposure group for one PCB metabolite had more than double the odds of MS compared with those in the lowest group.
Each increase in PFOS exposure was linked to a modest but statistically significant rise in MS risk.
A notable interaction was observed between chemical exposure and a specific HLA genetic variant that is usually considered protective. In carriers, higher PFOS exposure was linked to a much stronger increase in MS odds.
Implications for Practice
For individuals and families
These findings reinforce the idea that environmental exposures may matter for autoimmune disease risk. While causality is not proven, reducing unnecessary exposure to persistent industrial chemicals could be a reasonable precaution, especially for people with a family history of MS. Practical steps may include paying attention to drinking water quality, limiting consumption of contaminated fish, and being mindful of products known to contain PFAS.
For clinicians and healthcare providers
This study highlights the importance of considering environmental history alongside genetic risk in MS. It also suggests that gene-environment interactions may help explain why some patients develop MS despite having protective genetic markers. While these results are not ready to change clinical guidelines, they may inform future risk stratification, counseling, and research into prevention strategies.
The researchers emphasize that MS likely develops over many years, and single blood measurements cannot fully capture lifetime exposure. Still, the consistency of associations across multiple chemicals strengthens the signal that environmental contaminants may contribute to disease risk.