Several genes studied here have been shown to be differentially expressed by PAH exposure in previous studies, and we investigated the effects of two PAH mixtures on these common biomarkers of PAH exposure including CYP1A1, CYP1B1, GSTA, and ALDH3A1 which have been demonstrated to mediate PAH metabolism and are biomarkers of PAH exposure [38,50,51,52,53,54,55]. This evidence concerns the gene CYP1B1 and pulmonary arterial hypertension.