By comparing quartiles, further examination of the candidate gene variants showed a significantly greater probability of CRC occurrence in women with the lowest (0.27–0.67 μg/L) blood-As levels carrying functional polymorphisms such as: CAT, rs1001179-nonCC (OR: 19.4 (95% CI 3.69–159.0); p = 0.001) (Table 3), ABCB1 rs2032582–CC (OR: 14.8 (95% CI 1.95–318); p = 0.024) (Table 4), GPX1 rs1050450-CC (OR: 11.6 (95% CI 2.74–60.9); p = 0.002) (Table 5), CRTC3 rs12915189-nonGG (OR: 10.3 (95% CI 2.42–52.8); p = 0.003) (Table 6). This evidence concerns the gene ABCB1 and colorectal carcinoma.