NQO1 and leukemia: The presence of someone in the house who ever smoked (second-hand smoking) in children with EAL with NQO1 wild-type/RASmut (OR, 3.06, 95% CI, 1.03-9.07); the association of second-hand smoking during pregnancy and children with NQO1 rs1800566 (C609T) polymorphism increased 2.97 folds the risk of developing leukaemia (95% CI, 1.16-7.60); RASmut and the presence of at least one variant allele of NQO1 rs1800566 (C609T) showed an increased risk developing leukaemia (OR, 4.24, 95% CI, 1.24-14.50).