This work is part of the development of the Franche-Comté Regional Air Quality Plan (PRQA). In its guidelines, the plan reaffirms the need to improve our understanding of air pollutant emissions and their effects on health. In particular, it calls for conducting health impact assessments (HIA) of air pollution in major cities in Franche-Comté. These studies were commissioned to the Franche-Comté Regional Directorate of Health and Social Affairs (DRASS), in partnership with the Center-East Interregional Epidemiology Unit (CIRE). The HIA conducted on the Besançon metropolitan area is based on the methodology of the French Institute for Public Health Surveillance (InVS), which aims to estimate the impact of air pollution on: total mortality (short- and long-term), cardiovascular and respiratory mortality (short-term); hospital admissions for respiratory, cardiovascular, and cardiac causes (short-term impact). According to InVS recommendations, the assessment of health risks associated with air pollution is based on a standardized four-step approach: selection of substances and identification of hazards; selection of exposure-risk relationships; estimation of population exposure; characterization and quantification of risk. In the context of a health risk assessment of urban air pollution, it is assumed that all individuals within a defined study area are exposed to the same level of pollution. Thus, before undertaking an HRA, it is necessary to ensure that the selected urban area meets certain criteria outlined in the InVS guide urbanization must be continuous within the study area (no significant discontinuities should be observed between the city center, neighborhoods, and any neighboring municipalities); the population living in the study area must be exposed to urban pollution for the majority of their time (place of residence and workplace within the study area); exposure to ambient pollution within the urban area must be homogeneous (the main sources of pollution must be identified and quantified; there must be no major point sources of pollution); the metropolitan area must have an air quality monitoring network that reliably measures, at background stations, certain pollutants necessary for calculating exposure. First, we will verify that the Besançon metropolitan area meets the feasibility criteria for an EIS. If so, we will then proceed to carry out the four steps of the health risk assessment in order to calculate the health impact associated with air pollution. (R.A.)