Cord-blood black carbon burden is associated with coordinated inflammatory and heme-metabolic transcriptional programs at birth in Bradford, United Kingdom

Prenatal exposure to ambient air pollution has been linked to adverse perinatal and childhood outcomes, yet the molecular consequences of fetal black carbon (BC) exposure remain poorly characterized. In this prospective study nested within the Born in Bradford's Better Start cohort and the wider Born in Bradford data linkage cohort, we examined the association between cord-blood BC burden and neonatal cord-blood gene expression at birth. BC particles were quantified in cord blood using label-free femtosecond pulsed-laser microscopy, and transcriptomic profiling was performed with the BioSpyder TempO-Seq whole-transcriptome platform. Of 109 mother-infant pairs with exposure measurements and metadata, 83 samples passed transcriptomic quality control and were included in the analysis. Gene-level associations with log10-transformed BC were evaluated using limma-voom models adjusted for library batch, infant sex, cohort source, and maternal age. Pathway-level analyses were performed using CAMERA, with fry as sensitivity analysis, and robustness of pathway-contributing genes was assessed using 100 repeated 20% holdout analyses. No individual genes remained significant after false discovery rate correction across 9941 tested genes. In contrast, CAMERA identified two enriched Hallmark pathways associated with higher cord-blood BC: negative enrichment of heme metabolism and positive enrichment of TNFα signaling via NF-κB. These two pathways showed concordant directions in fry analysis, although they did not reach statistical significance in that framework. Additional Hallmark, GO Biological Process, and Reactome signals were directionally consistent but did not survive multiple-testing correction. Of 233 directional genes extracted from the two significant Hallmark pathways, 184 remained stable across repeated holdout analyses. These exploratory findings suggest that fetal BC exposure may be associated with coordinated inflammatory activation and suppression of heme-metabolic transcriptional programs at birth, warranting replication in independent cohorts.