Globally, breast cancer is the primary cause of cancer-related death, and rising incidence rates are anticipated. Improving illness prevention and treatment strategies requires a better understanding of the interactions occurring between genetic variables, environmental exposures, and disease pathogenesis. This study investigated the impact of residence on the association between benzo[ a ]pyrene-DNA adduct levels and CYP1B1 gene polymorphisms in breast cancer patients. In brief, 58 female breast cancer patients in Babylon, Iraq were recruited as subjects of this cross-sectional study. We gathered clinical information (including residency, age, age at diagnosis, and haematological markers), and by using molecular and biochemical methods, the CYP1B1 polymorphisms and the benzo[ a ]pyrene-DNA adduct levels were assessed. Among the different types of breast cancer, there was no apparent association between the residence and CYP1B1 polymorphisms. However, the amounts of benzo[ a ]pyrene-DNA adduct varied according to where a patient lived, with urban residents showing higher concentrations than rural residents. Benzo[ a ]pyrene-DNA adduct levels were shown to be correlated with specific polymorphisms in the CYP1B1 gene. Our study highlights the intricate connections between environmental exposures, genetic variables, and place of residency in the aetiology of breast cancer. Variations in quantities of benzo[ a ]pyrene-DNA adducts imply possible functions for environmental carcinogens, although no substantial correlation was found between genetic polymorphisms and the place of residence.