Comparative study of air quality indices in the European Union towards adopting a common air quality index

This study aims to compare air quality indices applied in European Union countries towards adopting a common air quality index. The urban European cities Rome, Madrid, Paris, London, Berlin, Warsaw, Stockholm, and Oslo were selected. Using the EEA AirBase air quality database, time series data for the major atmospheric pollutants (CO, NO 2 , SO 2 , O 3 , PM 10 , and PM 2.5 ) were recovered for each city, for most recent years available. Daily averages, maximum hourly values and maximum 8-h averages were calculated for each pollutant. The air quality indices selected were BelAQI, DAQx, DAQI, AtmoIndex, AQIH, and CAQI. The daily value of each air quality indices and the corresponding dominant atmospheric pollutant were determined for each city. A two-stage normalization procedure was applied on air quality indices in a 0–1 range, to allow their direct comparison without altering their structure. All air quality indices exhibited air quality rates over 64% for all cities, thus below the European Union air quality standard. The dominant pollutant was NO 2 for both BelAQI and DAQx; O 3 for both DAQI and AQIH (with an exception for Warsaw where SO 2 was the dominant pollutant). For CAQI, NO 2 prevails in Berlin, London, Warsaw, Stockholm, and Oslo, while O 3 prevails in Rome, Madrid, and Paris. The dominant pollutant for AtmoIndex was NO 2 in Berlin, Warsaw, and Stockholm; O 3 in Madrid, Paris, London, and Oslo; PM 10 in Rome. A very strong positive statistical correlation ( p