Apheis aims to provide European decision makers, environmental-health professionals and the general public with up-to-date and easy-to-use information on air pollution (AP) and public health (PH). In the Apheis-3 phase we quantified the PH impact of long-term exposure to PM2.5 (particulate matter < 2.5 μm) in terms of attributable number of deaths and the potential gain in life expectancy in 23 European cities.