The concept of care pathway contributes to a better organization of health services in a local area, in particular for chronic diseases such as nowadays breast cancer. A thorough cost analysis of these pathways (direct vs. indirect, supported by the patient vs. the institution...) is essential for public health policies to weigh in the trade-offs between health efficiency and financial viability. This work proposes a method based on impact pathway approach and recommended pollution cost values to integrate the environmental costs of air pollution due to transportation to the total costs of the pathway. This pollution depends on the means of transportation (public transportation vs. private car or cab, fuel type...), the distance, the urban density and the frequency of travels. The recommended pollution cost values are taken from French public investments guidelines and reflect the impact of local air pollution as well as global greenhouse gases emissions. We apply this original analysis to healthcare pathways of breast cancer patients in the Western Île-de-France area (France) thanks to an original database derived from an auto-reporting protocol involving more than 600 patients. We shed some light on the order of magnitude of these environmental costs linked to transportation as well as on the key parameters that must be taken into consideration for this evaluation. In order to contribute to the debate on the spatial allocation of medical resources, we carry out a simulated redirection of the flux of patients towards the most specialized health center. Further study on environmental impacts of care pathways, beyond the ones induced by transportation, are needed to assess their weight of environmental costs in the global cost.