The European Environmental Agency (EEA) collects air pollution data from EU member states and makes it publicly available. These data contain information on the amount of air pollutants and dusts in the atmosphere from anthropogenic (man-made) and natural sources. The network of stations covers the whole of Europe.
daily
hourly to daily
5647 Stations 24406 Sensors
Data will be made available through search, display, and, where possible, download services that comply with current standards from ISO, OGC, INSPIRE, and other authoritative standards bodies. EEA will hold data where it deems necessary and will attempt to provide meta-information for all data. Unless otherwise specified, datasets will be distributed on the basis of an Open Standards License, such as an ODC By License or similar.
https://www.eea.europa.eu/de/legal/eua-datenpolitik#toc-5