Could Gut Bacteria Be a Weapon Against ‘Forever Chemical’ Brain Damage?

Per- and polyfluoroalkyl substances, the so-called "forever chemicals" found in nonstick cookware, firefighting foam, food packaging, and water supplies worldwide, do not break down in the environment or the body. A new review in Trends in Pharmacological Sciences, led by Dhirendra Pratap Singh and colleagues at APC Microbiome Ireland, University College Cork, lays out a case that some of PFAS's effects on the brain may run through an unexpected middleman: the trillions of bacteria living in the human gut. The same review points to an emerging, early-stage countermeasure: specific gut bacteria that can trap PFAS inside their own cells before it gets fully absorbed.

PFAS Chemicals Now Number Over 13,000 Compounds

PFAS is not one chemical but a family of more than 13,000 industrial compounds, according to the review, all sharing an extremely stable carbon-fluorine bond that makes them resistant to breakdown. That stability is exactly why they persist in water, food chains, and human tissue for so long. The review notes that oral absorption of legacy PFAS compounds ranges from about 50 percent (for PFHxS) to 95 percent (for PFOA and PFNA), and that plasma half-lives for some PFAS can stretch from 5 to 15 years. These chemicals accumulate in blood, liver, and kidney tissue, and are able to cross both the blood-placenta barrier and the blood-brain barrier.

Regulatory limits have tightened sharply as the science on PFAS toxicity has accumulated. The US Environmental Protection Agency set an initial health advisory of 70 parts per trillion for PFOA and PFOS combined back in 2016; it has since finalized enforceable drinking water limits of 4 parts per trillion for PFOA and PFOS individually, and 10 parts per trillion for PFHxS, PFNA, and the GenX replacement chemical HFPO-DA, with a stated long-term goal of zero.

Gut Bacteria Disruption Links PFAS to Neurobehavioral Effects

The review's central argument is that PFAS does not just act directly on brain tissue, it also remodels the gut microbiome in ways that ripple outward through the gut-brain axis, the bidirectional communication network linking gut bacteria to brain function via metabolites, immune signaling, and the vagus nerve. According to the authors, chronic PFAS exposure triggers gut inflammation and weakens the intestinal barrier, a condition sometimes called "leaky gut." That shift in immune signaling favors the overgrowth of harmful bacteria over beneficial ones. Because PFAS molecules structurally resemble fatty acids, they also bind receptors that regulate how the liver produces bile acids, which are themselves powerful antimicrobial signals in the gut, giving PFAS another indirect route to reshaping the microbial community.

The review cites a mother-child cohort study in which prenatal exposure to PFHxS was associated with conduct and externalizing behavior problems in children during their first two years of life. That exposure correlated with an increase in Enterobacter bacteria and a drop in several bacteria that produce short-chain fatty acids, beneficial metabolites tied to gut and brain health, including Dorea, Collinsella, Faecalibacterium, and Alistipes species. Separately, the review cites a mouse study in which an environmentally relevant PFAS mixture accumulated in brain tissue and altered electrical brain wave patterns, alongside disruption of signaling pathways involved in mood and cognition and changes to tryptophan and other metabolic pathways.

Newly Discovered Bacteria That Bind and Trap PFAS

The most striking piece of evidence the review highlights comes from outside its own research group: a 2025 study in Nature Microbiology by Anna Lindell and colleagues, also covered by the University of Cambridge, which screened human gut bacteria and identified at least 38 strains capable of bioaccumulating PFAS at physiologically relevant concentrations without harming their own growth. Bacteroides uniformis and E. coli were standouts, forming dense clusters of PFAS inside their own cells, effectively acting as a biological sink. In the Cambridge-led study, colonizing mice with these PFAS-accumulating bacteria measurably increased how much PFAS the mice excreted in feces. The review also cites a rat study in which a diet rich in soluble fiber increased fecal excretion of PFOS, hinting that diet alone might nudge the same mechanism.

Building on those bacterial discoveries, the review notes that "efforts are being made to develop precision-formulated probiotics for naturally cleansing PFAS exposure," pointing toward a therapeutic strategy built around cultivating or supplementing PFAS-sequestering microbes rather than only trying to avoid exposure in the first place.

A Review, Not a New Trial, With Real Limits

It is worth being clear about what this paper is and is not. It is a review and synthesis of existing research, published in the "Science & Society" section of Trends in Pharmacological Sciences, not a new clinical trial or a single definitive experiment. The authors themselves acknowledge that the evidence linking PFAS exposure to specific neurobehavioral outcomes in humans remains inconsistent across cohorts, and that much of the animal-model work uses environmentally unrealistic doses or single-compound exposures rather than the complex mixtures people actually encounter. The bacterial bioaccumulation findings, while striking, come from lab and mouse-model conditions, not human trials, and the authors are careful to note that microbiome-based interventions could increase resilience to PFAS's effects without eliminating the underlying exposure, meaning they would complement rather than replace efforts to reduce PFAS contamination at the source.

What Comes Next for Microbiome-Based PFAS Defenses

The review calls for future studies to fold microbiome profiling, metabolomics, and immune signaling into PFAS research as a matter of course, and it points to longitudinal birth cohorts with banked biological samples as a key tool for untangling cause from correlation in humans. On the applied side, it flags early efforts to formulate precision probiotics designed specifically to bind and clear PFAS, alongside interest in fiber-rich, plant-diverse diets as a lower-tech way to support the same PFAS-sequestering bacteria. None of that is available as a validated treatment yet. For now, the review's authors frame the goal as building resilience to a class of chemicals that, given how widespread and persistent they already are in water and food supplies, people are likely to keep encountering for decades regardless of how quickly manufacturing is curtailed.

References

1. Dhirendra Pratap Singh, Eileen Ryan, Gerard Clarke, John F. Cryan (2026). Forever chemicals, the microbiome, and brain health: towards therapeutics. Trends in Pharmacological Sciences. https://doi.org/10.1016/j.tips.2026.06.010
2. Per- and Polyfluoroalkyl Substances (PFAS) | US EPA. epa.gov. https://www.epa.gov/sdwa/and-polyfluoroalkyl-substances-pfas
3. Anna E. Lindell, Anne Grießhammer, Lena Michaelis, et al. (2025). Human gut bacteria bioaccumulate per- and polyfluoroalkyl substances. Nature Microbiology. https://doi.org/10.1038/s41564-025-02032-5