Secondary contaminants from PCBs linked to higher MS risk in study
PFAS, or 'forever chemicals,' associated with lower risk of disability progression
A group of manufactured chemicals called hydroxylated polychlorinated biphenyls, or OH-PCBs, which persist in the environment despite a ban on production, are associated with an increased risk of developing multiple sclerosis (MS), according to a new study.
In turn, another family of compounds highly resistant to environmental breakdown, called per- and polyfluoroalkyl substances (PFAS) or more colloquially “forever chemicals,” was linked with a lower risk of disability worsening among MS patients.
Researchers suggest PFAS may suppress the immune system and associated inflammation, leading to a lower risk of disability worsening, but more studies are needed to understand how exposure to OH-PCBs impacts MS risk.
The study, “Associations of PFAS and OH-PCBs with risk of multiple sclerosis onset and disability worsening,” was published in Nature Communications.
Environmental and genetic factors have been associated with an increased risk of MS, an inflammatory disorder that affects certain parts of the brain and spinal cord. Such risk factors include female sex, low vitamin D levels, Epstein-Barr virus infection, smoking, adolescent obesity, and variations in genes called HLA.
Chronic PFAS exposure may adversely affect inflammation, immunity
PFAS are a family of manufactured compounds used in many industrial and commercial applications. Because they are highly resistant to environmental breakdown, they’ve been called “forever chemicals.” Growing evidence suggests, however, that chronic exposure to these compounds may adversely affect inflammation and immunity.
PCBs are another group of compounds that are associated with cancer, immunosuppression, and neurotoxicity. While many countries have restricted or banned their production since the 1970s, PCBs can persist in the environment. In humans, modified PCBs called OH-PCBs have additional toxic traits beyond those found in the original PCBs.
Given these concerns, scientists in Sweden sought to investigate whether blood levels of PFAS and OH-PCBs affect the risk of developing MS or if they influence the course of the disease.
The team analyzed blood samples collected from 907 people recently diagnosed with MS, of whom 801 had relapsing-remitting MS (RRMS) and 106 had a progressive form of MS. The researchers also examined samples from a group of 907 healthy individuals who were matched to MS patients by age, sex, and residential area.
Over an 18-year follow-up, 89 RRMS patients developed secondary progressive MS (SPMS).
In total, 24 PFAS compounds and seven OH-PCBs were assessed in blood samples, and data showed sex, age, whether a women had given birth, and geographic region were all factors that influenced the levels of certain PFAS and OH-PCBs.
Two OH-PCBs significantly associated with increased MS risk
In the risk analysis, two OH-PCBs — 4-OH-CB187 and 3-OH-CB153 — were significantly associated with increased odds of developing MS. Statistical models showed doubling the levels of 4-OH-CB187 in the blood boosted the likelihood of MS by 8.1%, while 3-OH-CB153 increased the odds by 5.5%. The results were similar regardless of sex or native-born/immigration status.
Conversely, across both sexes, three PFAS — PFOA, PFOS, and PFDA — were significantly associated with lower odds of confirmed disability worsening, as indicated by changes in the Expanded Disability Status Scale. In men, PFOA, PFOS, PFHpS, and PFNA were particularly linked to a lower risk of disability worsening, while in women, 4-OH-CB107 was linked to a lower risk of progression.
“The findings made herein suggest that PFAS may suppress the immune system in MS, resulting in a slower disease progression and lower risk of disability worsening,” the scientists wrote.
In other analyses, no association was found between disability worsening and the levels of albumin, the blood protein that carries PFAS. Concentrations of PFAS and OH-PCBs also did not affect the risk of transitioning from RRMS to SPMS.
Finally, the team investigated the relationship between PFAS, OH-PCBs, and vitamin D. While the levels of certain chemicals varied based on the levels of vitamin D, the impact of PFAS on disability progression could not be fully explained by vitamin D changes, the team found.
“We demonstrate a significant association between 4-OH-CB187 and 3-OH-CB153 exposure and increased risk of developing MS,” the scientists concluded. “We also demonstrated significant inverse associations between concentrations of PFOA, PFOS, and PFDA exposure and confirmed disability worsening.”
About the Author
