The data included in this report is all generated from ground-based monitoring stations, with a focus on measured PM2.5.
The majority of data presented here has been aggregated in real-time (on an hourly basis) from reports published by various governmental agencies as public data, from networks of continuous monitoring stations.
In addition, the real-time aggregated data from government sources within Europe has been combined with historical data records made available by the European Environment Agency (EEA) and some other government sources, to provide a fuller dataset where there may have been delays in some areas' real-time reporting.
In addition to these, PM2.5 data is also included from a selection of crowdsourced, public and validated outdoor IQAir AirVisual PM2.5 monitoring stations, many of which provide the only public, real-time air quality readings within their communities.