Higher childhood exposure to the PAH cluster was associated with significant hypomethylation at two CpG sites (cg09219877, DNASE1L2; cg09938479), with cg09938479 along with two additional CpG sites (cg01076459, RAP1GAP2; cg11152384), also showing significant hypomethylation with cumulative PAH exposure at the Bonferroni threshold (P < 2.02 × 10; (Figure 2, Supplementary Table 3). This evidence concerns the gene RAP1GAP2 and pulmonary arterial hypertension.