NO2 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.
The European annual limit value for protection of human health is 40 μg/m³. This limit value applies as from 2010. Only the Port of Antwerp and Antwerp Agglomeration zones have been granted postponement until 2015 for compliance with this limit value. Until then, a limit value of 60 μg/m³, based on the limit value of 40 μg/m³ with a 50% margin of tolerance, applies in these two zones. To be granted this postponement, a detailed plan was drawn up showing that the limit value of 40 μg/m³ will be attained as from 2015.
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 NO2 concentrations in Belgium. The spatial average is represented by the blue circles.
Box plots of the annual mean NO2 concentrations (μg/m³) for the period 1990-2015. The spatial average is represented by the blue circles. All data were calculated using the RIO interpolation technique.
Click here for more information on how to interpret a boxplot.
Evolution of regional averages
The highest annual means are measured in the urban areas. This is not surprising due to the highly transport-related character of NO2. In 2015, annual mean concentrations above 40 μg/m³ were no longer measured in Belgium. No clear trend is visible in the annual mean NO2 concentrations at regional or Belgian level, although the mean concentrations slightly decline for all regions from 2007 on. The average annual mean concentration in 2015 across Flanders, Brussels and Wallonia is 14.3 μg/m³, 28.1 μg/m³ and 10.2 μg/m³ respectively. The average across Belgium, taking account of the number of inhabitants per grid cell (population-weighted average) is 19.1 μg/m³. This value clearly exceeds the non-population-weighted average across Belgium (12.1 μg/m³), which indicates that the grid cells with the highest population numbers are also those with higher NO2 annual mean concentrations, namely the urban areas.
Evolution of the NO2 annual mean in Belgium based on the RIO interpolation technique.
The decrease in the annual mean NO2 concentrations in Belgium over the period 1990-2015 is rather limited. The largest decreases - between 0.5 and 0.7 μg/m³/year - occur in the region roughly between Charleroi, Brussels and Liège.
Trend (μg/m³/year) of the annual mean NO2 concentrations in the period 1990-2015. All data were calculated using the RIO interpolation technique.