Per- and polyfluoroalkyl substances and the gut microbiota in infants: A scoping review

Per-and polyfluoroalkyl substances (PFASs) are persistent environmental chemicals associated with adverse health effects. Emerging evidence suggests PFAS exposure may influence gut microbiota composition, which is a critical determinant of health particularly during infancy. A systematic search was conducted in PubMed to identify epidemiological studies investigating PFAS exposure and infant gut microbiota. Seven studies met the inclusion criteria, examining a range of PFASs derived from either breast milk, maternal blood, or umbilical cord blood and including from 30 to 789 subjects. These studies used either 16S rRNA sequencing or shotgun metagenomics to assess microbiota changes. Perfluorooctane sulfonic acid (PFOS) and perfluorooctanoic acid (PFOA) were the most frequently examined PFASs. Across studies, exposure to PFASs was associated with both increased and decreased α-diversity. β-diversity shifts were also observed in some studies, suggesting altered microbial structures. PFAS exposure was associated with changes in the abundance of specific taxa, such as increased Enterococcus and decreased Faecalibacterium and Phocaeicola vulgatus. Functional pathway alterations were also reported, including disrupted bile acid metabolism. Variation in study design, covariate adjustment, and methodological approaches likely contribute to the inconsistencies in the observed associations between PFAS exposure and the infant gut microbiota. In conclusion, current evidence suggests that PFAS exposure may influence infant gut microbiota, but more and larger longitudinal studies are needed to better understand whether PFAS exposure is associated with altered gut microbiota composition in infants. This review synthesizes existing evidence on associations between PFAS exposure and gut microbiota composition in infants.