This health impact study on air pollution was conducted using the InVS methodological guide. Initially requested for the Metz-Thionville metropolitan area as part of the Trois Vallées Air Protection Plan (PPA), the study could only be applied to the Metz metropolitan area. Indeed, the presence of steep-sided valleys, combined with specific industrial activities, made it impossible to assume an average exposure for the population residing throughout the entire PPA zone. The results highlight that eliminating only the pollution peaks over the course of a year would have a short-term and long-term impact far less significant than reducing the daily average pollution level. However, the emission mapping conducted by Atmo-Lorraine Nord for this area as part of the PPA shows that a significant portion of pollutants is attributable to road transport. Based on these two findings, the recommendation is to implement policies to reduce emissions from this sector. (R.A.)