The transport of toxins moving from the blood stream into the ducts of the mammary glands is analyzed in this work. The model predictions are compared with experimental data from the literature. The utility of the model lies in its potential to improve our understanding of toxin transport as a pre-disposing factor to breast cancer. The model presented in Chapter I is based on a multi-layer transport model to analyze the toxins present in the breast milk. The breast milk in comparison with other sampling strategies allows us to understand the mass transport of toxins once inside the bloodstream of breastfeeding women. The multi-layer model presented describes the transport of caffeine, DDT and Cimetidine. The analysis done takes into account the unique transport mechanisms for each of the toxins. The model presented in Chapter II is based on a multi-layer transport model to analyze the concentration of toxins present in the breast ducts. The multi-layer model presented describes the transport of caffeine, cimetidine, aspirin and nicotine during the resting mammary gland period. Additionally, the dermal transport of drugs such as nicotine and aspirin into the resting mammary gland is analyzed. In a unique approach we also present the impact of introducing an external heat flux at the boundaries to increase the diffusion of these particles into the breast ducts. Our model predicts the movement of toxins and/or drugs within the resting mammary glands