A new analysis from researchers in Sweden links certain environmental pollutants and microplastics with higher odds of a multiple sclerosis diagnosis, using blood data and genetic information to explore how exposure and heredity might interact. The team examined PFAS and PCB-related compounds in roughly 1,800 blood samples, about half from people recently diagnosed with MS, and modeled both single chemicals and real-world mixtures. Their results point to potential risks tied to specific substances and combinations, highlight gene-environment interactions, and also acknowledge limits to what a single blood measurement can reveal.
Researchers published the work in the journal Environmental International after testing blood samples from 1,800 people, including around 900 with recent MS diagnoses. The study was designed to compare chemical levels in those diagnosed with MS to levels in others, looking for statistical links rather than proving direct cause. That makes the findings notable while still leaving open questions about timing and mechanism.
PFAS refers to per- and polyfluoroalkyl substances, often called forever chemicals because they persist in products and the environment and can accumulate in people. PCBs are polychlorinated biphenyls, older industrial compounds that were banned decades ago but still linger in ecosystems. Both groups are chemically stable and show up in the food chain and human blood, which is why scientists keep studying them.
The first phase of the analysis looked at 14 distinct PFAS compounds and three substances that appear when PCBs break down in the body, checking each for associations with MS diagnosis. The team also analyzed mixtures to capture how multiple exposures interact in real life. Modeling combinations is important because humans rarely face single toxins in isolation.
Overall, higher levels of certain chemicals were associated with greater odds of MS. “We saw that several individual substances, such as PFOS and two hydroxylated PCBs, were linked to increased odds for MS,” lead study author Kim Kultima said in a statement. “People with the highest concentrations of PFOS and PCBs had approximately twice the odds of being diagnosed with MS, compared to those with the lowest concentrations.”
When the researchers examined combined exposures, the chemical mixture also correlated with increased MS odds rather than just individual agents acting alone. That pattern supports the idea that small effects from multiple chemicals can add up in meaningful ways. Fellow researcher Aina Vaivade pointed out that risk assessments ought to account for mixtures because simultaneous exposures are the norm.
The genetic portion of the study added a surprising twist: a certain gene variant appeared to lower MS risk on its own, but its protective effect changed with chemical exposure. However, individuals who carried the gene and had higher exposure to PFOS had an “unexpected” increased risk of MS. “This indicates that there is a complex interaction between inheritance and environmental exposure linked to the odds of MS,” Kultima said.
“MS is a complex disease that is somewhat autoimmune and somewhat post-inflammatory,” said Siegel, who was not involved in the study. “Epstein-Barr virus infection” greatly increases the risk of MS. “There is every reason to believe that environmental triggers play a role, including microplastics, and this important study shows a correlation, but not causation — in other words, it doesn’t prove that the microplastics caused MS.”
The authors noted several limitations, including that chemical exposure was measured just once at the time of blood sampling and may not reflect past levels that mattered most for disease development. That single snapshot makes it harder to pin down when exposure occurred relative to MS onset. Future work with repeated measures or long-term monitoring would help clarify timing and causation.
Industry groups responded publicly, and one noted that “manufacturers and many users of today’s PFAS are implementing a variety of practices and technologies to help minimize environmental emissions.” Regulators have also moved: in April 2024 the EPA enacted a federal rule setting mandatory limits on certain PFAS chemicals in drinking water and pledged funding for testing and treatment. Those actions aim to reduce human exposure while research continues.
Multiple sclerosis damages the protective sheaths around nerve fibers and can cause numbness, weakness, difficulties with walking and movement, vision changes and other symptoms that may become permanent. There is currently no cure, but treatments exist to manage symptoms and slow disease progression for many patients. Studies like this one add pieces to a complicated puzzle about what triggers MS and how environment and genetics interact.
