Current evidence suggests that chemical exposure alters gut microbiota composition, with higher exposure to environmental chemicals being associated with reduced microbiome diversity. However, not much is known about the impact of per- and polyfluoroalkyl substances (PFAS) on gut bacteria. Here we set out to identify the gut bacterial species that associate with chemical exposure before (maternal) and after (maternal, infant) birth in a mother-infant series. Paired blood and stool samples were collected from mother-infant dyads (n = 30) in a longitudinal setting. PFAS were quantified in maternal blood to examine their associations with the microbial compositions (determined by shotgun metagenomic sequencing) in mothers and infants. High maternal exposure to PFAS was persistently associated with increased abundance of Methanobrevibacter smithii in maternal stool. Among individual PFAS compounds, PFOS and PFHpS showed the strongest connection with M. smithii. However, maternal PFAS exposure associated only weakly with the infant microbiome. Our findings suggest that PFAS exposure contributes to the modulation of the adult gut microbiome composition.

The authors have declared no competing interest.

NCT01735123

This study was supported by the Swedish Research Council (grant no. 2016-05176 to T.H and M.O), Formas (grant no. 2019-00869 to T.H and M.O), and the Novo Nordisk Foundation (Grant no. NNF20OC0063971 to T.H. and M.O.). The EDIA study was supported by the National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK), National Institutes of Health (No. 1DP3DK094338-01 to M.K.), the Academy of Finland Centre of Excellence in Molecular Systems Immunology and Physiology Research 2012-17, No. 250114 to M.K. and M.O.). Further support was received by the Academy of Finland postdoctoral grant (No. 323171 to S.L.) and the Medical Research Funds, Tampere and Helsinki University Hospitals (to M.K.).

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The details of the IRB/oversight body that provided approval or exemption for the research described are given below:

The study followed the guidelines of the Declaration of Helsinki for research on human participants. The study was carried out according to good clinical practice. The study protocol was approved by the Joint Municipal Authority of the Pirkanmaa Hospital District, Finland (no. R11166). The parents gave their written informed consent, which was overseen by the Ethical Committee of the Joint Municipal Authority of the Pirkanmaa Hospital District. The study is registered under Clinicaltrials.gov Identifier NCT01735123.

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Metagenomic sequencing data for all subjects have been deposited to the SRA database under BioProject ID PRJNA475246.The metabolomics datasets and the clinical metadata generated in this study were submitted to MetaboLights (Haug et al., 2020), under accession number MTBLS875.