Preprocessed EEA Air Quality eReporting dataset over Europe. This dataset contains the hourly, daily 24-hour mean, daily 1-hour maximum and daily 8-hour maximum concentrations of O3, NO2, SO2, CO, PM10 and PM2.5, with and without Quality-Assurance (QA) filtering using the QA flags available through GHOST (Globally Harmonised Observational Surface Treatment). GHOST is project developed at the Earth Sciences Department of the Barcelona Supercomputing Center that harmonises the global surface atmospheric observations and metadata, in order to facilitate quality-assured use of observations (for instance for comparisons with models within the atmospheric chemistry community).