Meteorological variability in NO2 and PM10 concentrations in the Netherlands and its relation with EU limit values

An analysis of model calculations and measurements yields variations (1 sigma) in the annual average concentration of about 5% for NO₂ and 9% for PM₁₀, due to meteorological fluctuations. These deviations from long-term average concentrations affect assessments of future levels, set against limit values. For instance, an NO₂ concentration of 39 µg/m³, estimated for a given year with long-term average meteorology, indicates that it is likely (chance >66%) that the limit value of 40 µg/m³ will not be exceeded in that particular year.

At the same time, the estimation also indicates, for example, that this situation is unlikely (change <33%) to continue for three years in a row. However, with an estimated concentration of 38 µg/m³, it is likely that the limit value will not be exceeded for three years in a row. The limit value for the daily average PM₁₀ concentration is equivalent to an annual average of about 32 µg/m³. This threshold is unlikely to be exceeded for three years in a row, when an annual average concentration of 29 µg/m³ is estimated. Interannual variations in concentrations of NO₂ and PM₁₀ are linked to large-scale meteorological fluctuations. Therefore, similar results can be expected for other European countries.