All data below are the result of the RIO interpolation technique, in which the measurement observations are interpolated to a 4x4 km² grid resolution. Locally, concentrations can be higher or lower.
Evolution of the percentiles
The figure below uses box plots to show the evolution of the minimum, the 25th percentile (P25) , the 50th percentile (P50), the 75th percentile (P75) and the maximum annual mean PM2.5 concentrations in Belgium. The spatial average is represented by the blue circles. The spatially averaged PM2.5 concentrations as well as the lowest percentiles have shown a downward trend since 2006. However, this trend is not further observed in 2013, where a slight increase occurs. The maximum annual mean concentration has levelled out over the last few years, but is below the European limit value of 25 μg/m³. In 2013, annual mean PM2.5 concentrations above the WHO guideline value of 10 μg/m³ were, however, still recorded in over 75% of Belgium.
Box plot of annual mean PM2.5 concentrations (μg/m³) over the period 2005-2013. The spatial average is represented by the blue circles. All data were calculated using the RIO interpolation technique.
Click here for more information how to interpret a boxplot.
Evolution of regional trends
The spatially averaged annual concentrations for Flanders, Wallonia and Brussels were 15.3, 11.3 and 17.6 μg/m³ respectively in 2013.Since 2006, the PM2.5 concentrations have decreased in all Regions, although there is a light increase between 2012 and 2013.
Evolution of the spatially averaged annually mean PM2.5 concentrations for the three Regions and Belgium, and of the population-weighted annual mean concentration for Belgium. All data were calculated using the RIO interpolation technique.