In chemical carcinogenesis metabolism, benzo[a]pyrene can be metabolized by CYP2C8, CYP2C9, CYP2C18, and CYP2C19, and then finally transformed into the DNA adduct (+)‐trans‐BPDE‐N2‐dG, which has been shown to promote cancers of the skin, lung, and stomach. Here, CYP2C9 is linked to cancer.