Per- and polyfluoroalkyl substances (PFAS) and microRNA: An epigenome-wide association study in firefighters

The occupation of firefighting is classified as a Group 1 carcinogen. Increased cancer risk among firefighters may be partly attributable to increased occupational exposure to a range of chemicals, including per- and polyfluoroalkyl substances (PFAS). Some PFAS are known and suspect human carcinogens. Investigating epigenetic response to these PFAS exposures in firefighters may help to identify biological pathways of specific cancers, and previously unidentified health outcomes that are associated with PFAS. We therefore investigated the associations of serum PFAS concentrations with miRNA expression in firefighters. Serum samples collected from 303 firefighters from 6 sites across the USA were analyzed for 9 PFAS along with miRNA expression. Covariate-adjusted linear regression was used to estimate associations between log PFAS and miRNA expression, with false discovery rate (FDR) set to 0.05 for significance, and an exploratory cutoff of FDR q < 0.20. Gene set enrichment analysis (GSEA) was performed using miRTarBase's miRWalk pathways. Age, race-ethnicity, BMI, fire department, and sex were controlled for in all models. At FDR<0.05, the linear isomer of perfluorooctane sulfonic acid (PFOS) was inversely associated with miR-128-1-5p expression (Beta = -0.146, 95 % CI -0.216, -0.076). At a relaxed FDR of 0.20, we observed inverse associations for the sum of branched isomers of PFOS (Sm-PFOS) with 5 miRNAs (let-7d-5p, let-7a-5p, miR-423-5p, let-7b-5p, miR-629-5p). Several pathways were enriched for multiple PFAS, including those correlated with certain cancers, blood diseases, thyroid disorders, autoimmune disorders, and neurological outcomes. Some PFAS in firefighters were found to be associated with alteration of miRNA consistent with increased risk for a range of chronic diseases.