To calculate the number of avoidable deaths, the study uses city-specific natural-cause mortality data for 2015 from the Eurostat database and applies the most recent and robust scientific evidence on the relationship between air pollution levels and mortality. The study follows a comparative risk assessment approach by comparing current air pollution levels in cities to two theoretical air-pollution reduction scenarios (WHO recommendations and lowest measured levels). The number of preventable deaths is estimated as a function of these reductions and the scientific evidence on the relationship between air pollution and mortality.