A new study suggests people who have been exposed to both PFAS and PCBs are more likely to be diagnosed with multiple sclerosis. The findings are based on blood samples analyses from more than 1,800 individuals in Sweden. This is one of the most comprehensive studies to date on the influence of chemical environmental exposure on the development of MS.

MS is an autoimmune disease in which both genetic and environmental factors can contribute to the risk of the disease. In the current study, researchers at Uppsala University, in Sweden, analyzed blood from individuals who had recently been diagnosed with MS to investigate concentrations of the common environmental contaminants PFAS and PCBs. PFAS and PCBs are collective names for a range of subsidiary groups of environmental toxins. 

In a first phase, the researchers studied the incidence of 14 different PFAS contaminants and three different substances that arise when PCBs are broken down in the body, called hydroxylated PCB metabolites. For each substance, the link between concentration and the odds of being diagnosed with MS was investigated.

The study included approximately 900 individuals who had recently been diagnosed with MS. They were compared with a control group consisting of an equal number of people without MS. The individuals with and without MS were drawn from the EIMS cohort, a nationwide collection of samples and data designed to investigate the reasons why people are affected by MS. The researchers then measured the concentrations of environmental toxins in the blood and used statistical methods to study the link between them and the odds of being diagnosed with MS.

To better reflect the actual exposure that people experience, the researchers also investigated how the odds were affected when the substances occurred together as a mixture of chemicals.

The researchers found an increase in total exposure was linked to higher odds of MS, even after adjusting for previously known lifestyle and genetic risk factors. The results show that when attempting to understand the effects of PFAS and other chemicals on human beings, mixtures of chemicals need to be taken into account, not just individual substances, as people are generally exposed to several substances at the same time.

In a final phase, the researchers also studied the relationship between inheritance, chemical exposure, and the odds of being diagnosed with MS. Individuals who carry a certain gene variant have a reduced risk of MS. In individuals in the study who carried this gene variant, an unexpected increased odds of getting MS was observed in the case of higher PFOS exposure.

The study’s authors note that this indicates there is a complex interaction between inheritance and environmental exposure linked to the odds of MS. Therefore, it is important to understand how environmental contaminants interact with hereditary factors, as this can provide new knowledge about the genesis of MS and could also be relevant for other diseases.

The findings were published in the journal Environment International.