# PM2.5 annual mean

## PM10 annual mean | PM10 daily mean | PM2.5 annual mean

*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 seems to flatten out in the last few years, with similar values observed in 2014 and 2015. 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 2015, annual mean PM2.5 concentrations above the WHO guideline value of 10 μg/m³ were, however, still recorded in over 50% of Belgium.

*Box plot of annual mean PM2.5 concentrations (μg/m³) over the period 2005-2015. 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 12.0, 8.9 and 13.6 μg/m³ respectively in 2015. Since 2006, the PM2.5 concentrations have decreased in all regions, although this tendency seems to be levelling out in the last years, as mentioned before

*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.*