This directory contains the (interpolated) daily mean air pollutant concentrations (PM10, PM2.5, NO2, O3 and BC) for every Belgian city/municipality. Concentrations are in µg/m3. For PM10, PM2.5, NO2 and O3 data are available for the period 2008-2020. For BC 2011-2020 data till 2019 are available in folder 2019 calculations based on not (yes) validated data for 2021 are available in folder 2021_notval. Please be aware that this data will change in 2022. Concentrations are calculated using the 4x4 km2 RIO ( https://www.irceline.be/en/documentation/models/models?set_language=en) interpolated concentrations based on an area weighted average: for every RIO 4x4 km2 grid, the area of a municipality that overlaps with that grid is calculated. The average concentration for a municipality is then calculated using the gridcel concentrations and the overlapping area. used RIO-version: v50_V2020 update: 09 November 2021