CYP1A1 and lung cancer: Notably, the CYP1A1 gene is believed to encode an enzyme specifically involved in the activation of PAH carcinogenic intermediates36,39; the gene’s activity has consequently been associated with lung cancer risk after PAH exposure.39,40,41 Evidence suggests that the EWAS-identified CYP1A1 probes are located within a CYP1A1 gene-enhancer region.42 Thus, differential expression of the CYP1A1 gene may represent a pathway linking the childhood neighborhood environment to risk of disease in adulthood.