19th highest hourly mean NO2
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.
For the protection of human health from short-term NO2 peak concentrations, the European legislation imposes an hourly limit value of 200 μg/m³. This hourly limit is to be exceeded no more than 18 times (hours) per year. In Belgium, this hourly limit value is easily attained. Very locally, in busy traffic streets, the 200 μg/m³ limit may be exceeded a few times per year, but the 18-hour limit is never reached in any of the monitoring stations. Local exceedances are not visible due to the resolution of the RIO interpolation technique. The 19th highest hourly value in Belgium of each year is represented in the figure below (this corresponds to the 99.8th percentile of all hourly mean concentrations in one year). The maximum of the 19th highest hourly value in Belgium in 2015, representative at 4x4 km², is 107 μg/m³, which is well below the European limit of 200 μg/m³, and is measured in Brussels. The highest values occur only in large agglomerations such as Brussels and Antwerp. The WHO guideline value is also 200 μg/m³, but is not to be exceeded at any time. This value, too, is attained everywhere in Belgium.