Epigenome-wide association analysis of prenatal organophosphate ester flame retardant exposure in maternal blood implicates maternal immune and neuronal epigenetic alterations

Background Organophosphate esters (OPEs) are widely used flame retardants and plasticizers prevalent in indoor air, dust, and water. Studies suggest prenatal OPE exposure is linked to adverse maternal and infant outcomes, but the biological mechanisms remain unclear. Methods We examined associations between nine urinary OPE metabolites measured in the third trimester and DNA methylation in maternal blood from 175 pregnant women in the MADRES cohort. 837,856 CpGs were profiled using the Illumina EPIC array. We assessed the effect of each OPE (in tertile or detection status) and the joint effect of OPE mixtures using quantile g-computation models on DNA methylation sites, regions, and epigenetic age acceleration (EAA). Functional enrichment analyses were performed for suggestive CpGs and DMRs. Results We identified cg09294299 (P = 2.33 × 10 −8 ) and cg13756168 (P = 3.94 × 10 −8 ; ALS2 ) as epigenome-wide significant CpGs associated with BCEP and BDCIPP, respectively. Mixtures of OPEs also had joint effects on these two CpGs and three additional CpGs near PPP1R12A, AZI1 and ZDHHC11 (P < 0.05) . We identified six differentially methylated regions (DMRs) associated with OPEs: BBOEP and BMPP were both associated with a DMR near RP11-661A12.5 , BBOEP with a DMR near NNAT/BLCAP (P = 4.80 × 10 −28 ), BDCIPP with DMRs near SLFN12 (P = 4.63 × 10 −14 ) and ZDHHC11 (P = 1.42 × 10 −12 ), and BEHP with DMRs near POU5F1 (P = 2.74 × 10 −20 ) and PLA2G1B (P = 4.26 × 10 −14 ). OPE mixtures showed a suggestive association with one DMR near POU5F1 (P adj = 0.1193). Functional enrichment analyses implicated neurogenesis, immune signaling, and stress response pathways at the CpG site level, with shared transcription factor enrichment at DMRs across multiple OPEs, including EZH2 , EHMT2 , and POLR2A . Higher BCEP levels were associated with accelerated aging by DunedinPACE, whereas higher BMPP and BEHP were associated with epigenetic age deceleration by Horvath and Levine clocks, respectively; no significant association with epigenetic age acceleration was found for the OPE mixture. Conclusions Prenatal OPE exposure is associated with altered maternal DNA methylation and epigenetic aging, highlighting immune, inflammatory, and neurodevelopmental pathways