CYP1A1 and cancer: While CYP1A1 activity trends to be highest for the m4 variant in benzo[a]pyrene metabolism (Schwarz et al., 2001), the m4 variant exhibits the greatest catalytic efficiency for producing diol species and significantly increases formation of diol epoxide-2 (BPDE2)—the potent mutagenic species associated with increased cancer risk (Schwarz et al., 2001; Rubin, 2001).