Rs4986894 is located in the promoter of CYP2C19, and may modulate the transcriptional activity of CYP2C19. For rs1048943 in CYP1A1, exposure to 4-t-OP in both genotype groups was associated with significantly increased odds of male infertility compared with the non-exposure group. Here, CYP1A1 is linked to male infertility.