Certain kinds of gut microbes absorb toxic Pfas “forever chemicals” and help expel them from the body via feces, new first-of-its-kind University of Cambridge research shows.
The findings are welcome news as the only options that exist for reducing the level of dangerous Pfas compounds from the body are bloodletting and a cholesterol drug that induces unpleasant side effects.
The microbes were found to remove up to 75% of some Pfas from the gut of mice. Several of the study’s authors plan to develop probiotic dietary supplements that boost levels of helpful microbes in the human gut, which would likely reduce Pfas levels.
“If this could be used in humans to create probiotics that can help remove Pfas from the body then this would be a nicer solution in that it wouldn’t have so many side effects,” said Anna Lindell, Cambridge doctoral student and a co-author of the study.
Pfas are a class of about 15,000 compounds most frequently used to make products water-, stain- and grease-resistant. They have been linked to cancer, birth defects, decreased immunity, high cholesterol, kidney disease and a range of other serious health problems. They are dubbed “forever chemicals” because they do not naturally break down in the environment.
The US Environmental Protection Agency has found no level of exposure to Pfos or Pfoa, two of the most common Pfas compounds, in drinking water is safe. They have a half-life in human blood of anywhere from two to five years, by most estimates. That means the body expels half the amount of the chemical that is in blood during that period. Depending on blood levels, it can take decades to fully expel Pfas naturally.
Though the findings represent the first time gut microbes have been found to remove Pfas, they have been found to alleviate the impacts of other contaminants, such as microplastics.
The researchers didn’t set out to determine if the gut bacteria expelled Pfas specifically, but instead looked at a suite of 42 common food contaminants. No Pfas limits for food exist in the US, but there is broad consensus that it is among the main exposure routes.
Some microbes performed well in expelling Pfas, so the study’s authors zoomed in on those.
The authors introduced nine of a family of bacterial species into the guts of mice to humanize the mouse microbiome – the bacteria rapidly accumulated to absorb Pfas eaten by the mice, and the chemicals were then excreted in feces.
The bacteria seem to absorb the chemical, then use a “pump” mechanism that pushes toxins from the cells and aids in excretion, the authors wrote. The mechanism by which the chemicals are pulled into the cell is not yet understood, Lindell said, but she suspects there may be a similar pump. These are developed by microbes to expel other contaminants, drugs or antibiotics, Lindell added.
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The microbes largely addressed “long-chain” Pfas, which are larger compounds and more dangerous than smaller “short chains” because they stay in the body longer. The body more efficiently discharges short-chain Pfas through urine because the compounds are generally water-soluble.
Among the most common and dangerous long chains are Pfoa and Pfna, which the microbes expelled at rates of up to 58% and 74%, respectively.
Lindell and other study leaders have started a company, Cambiotics, that will develop a probiotic based on their findings. They are planning to follow up the research with a human study.
However, Lindell stressed that the probiotic would not solve the broader Pfas crisis: “This should not be used as an excuse to downplay other sustainable solutions or to not address the bigger Pfas problem.”