Every day, people drink water believing it is clean and safe. Yet growing evidence suggests that invisible chemical leftovers from plastics and industrial products may still be present in drinking water and inside the human body.
A new study published in Nature Communications raises a troubling question: could these long-lasting chemicals push the immune system to attack the body’s own nervous system and increase the risk of multiple sclerosis?
Multiple sclerosis, often called MS, is a serious disease that affects the brain and spinal cord. It is the most common autoimmune disease of the nervous system in young adults. Around 2.9 million people worldwide live with MS. The disease happens when the immune system mistakenly attacks the protective covering around nerve fibers.
This causes inflammation and damage that disrupts communication between the brain and the rest of the body. Over time, MS can lead to muscle weakness, vision problems, numbness, poor balance, bladder issues, and extreme fatigue. Most people are diagnosed between the ages of 20 and 40, and women are affected more often than men.
Despite decades of research, there is no single known cause of MS and no cure. Scientists believe it develops from a mix of genetic risk and environmental triggers. Known risk factors include smoking, obesity during teenage years, low vitamin D levels, and certain viral infections. Now, researchers are adding environmental chemicals to the list of possible contributors.
The Swedish study focused on two groups of chemicals: per- and polyfluoroalkyl substances, known as PFAS, and polychlorinated biphenyls, known as PCBs.
These chemicals are sometimes called “forever chemicals” because they break down extremely slowly. Once released into the environment, they can remain for decades and build up in soil, water, animals, and human bodies.
PCBs were widely used in electrical equipment, paints, and building materials before being banned in many countries decades ago.
PFAS have been used in non-stick cookware, waterproof clothing, food packaging, firefighting foam, and many other everyday products. Even though some uses are now restricted, these chemicals continue to circulate through water systems and food chains.
In the Swedish study, researchers examined blood samples from 907 people who had recently been diagnosed with MS and compared them with samples from 907 healthy individuals.
They tested for 24 types of PFAS and seven byproducts formed when PCBs break down in the body. The results showed a clear pattern. People with higher levels of several PFAS and PCB byproducts were more likely to be in the MS group.
In particular, one PFAS compound called PFOS and two PCB byproducts stood out. Individuals with the highest levels of these substances had about twice the chance of being diagnosed with MS compared to those with the lowest levels.
Many of the people with high chemical levels also had multiple compounds present at the same time, suggesting combined exposure may be especially harmful.
The researchers published their findings in 2025 in the journal Nature Communications. The study does not prove that PFAS or PCBs directly cause MS, but it strongly suggests they may play a role in increasing risk. These chemicals are known to interfere with the immune system.
Previous research has linked PFAS to weakened vaccine response, higher cholesterol, high blood pressure, hormone disruption, and some cancers. PCBs have been linked to cancer, liver damage, skin disorders, and problems with immune, reproductive, and nervous systems.
One concerning aspect of the findings is that exposure can happen quietly and without warning. Even though PCBs were banned decades ago, they remain in the environment. PFAS are still detected in drinking water in many regions.
In some U.S. states, testing has found PFAS in public water supplies, and private well owners may not even know their water contains these chemicals unless they test it themselves.
While treatments for MS exist, such as steroid medications that reduce inflammation and help manage flare-ups, they do not stop the disease entirely. This makes prevention and early risk reduction especially important.
If environmental chemicals are contributing to immune system confusion, reducing exposure could become an important public health strategy.
In reviewing and analyzing the study, its strength lies in the large number of participants and the careful measurement of many chemical types at once. The clear difference in chemical levels between MS patients and healthy individuals adds weight to the findings. However, the study cannot prove cause and effect.
It also cannot determine whether exposure earlier in life or long-term buildup matters most. More studies are needed to confirm the results and explore how these chemicals might trigger immune attacks on nerve tissue.
Even so, the research highlights an important warning. Substances once considered harmless or already banned may still influence human health decades later. The findings suggest that protecting drinking water, monitoring chemical exposure, and reducing pollution are not only environmental issues but also neurological and immune health issues.
As scientists continue to explore the link between chemical exposure and autoimmune disease, this study serves as a reminder that what enters our bodies from the environment may shape health outcomes in ways we are only beginning to understand.
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