GSTZ1 and urinary bladder cancer: Associations between increasing quartiles of THMs and bladder cancer were stronger among subjects with GSTT1 +/+ or +/− versus −/−, GSTZ1 rs1046428 CT or TT versus CC, and CYP2E1 rs2031920 CC versus CT (no subjects had TT), with statistically significant interactions for each of the respective gene variants.