Air quality alongside traffic routes in the Netherlands, 1990-2002
Concentrations of air pollutants alongside busy urban traffic routes fell in the last ten years. Nevertheless, the EU standards for the average annual concentrations of nitrogen dioxide and particulate matter were still being exceeded.
Air pollution alongside urban traffic routes falling
In recent years, there have been almost no more exceedances of the standards for benzene, benzo[a]pyrene (B[a]P) and carbon monoxide (CO) alongside traffic routes. However, there are still large-scale exceedances of the average annual concentrations of nitrogen dioxide (NO2) and particulate matter (PM10), particularly in areas with high traffic emissions, such as the Rhine estuary area (Rijnmondgebied), Amsterdam and the surrounding region, and motorways in urban areas.
Lead is no longer a problem. No more exceedances have been observed for this substance for a number of years now as a result of the introduction of low-lead and unleaded petrol.
Nitrogen dioxide
In 2002, the EU standard for the annual average nitrogen dioxide concentrations (40 µg/m3) was exceeded along approximately 1,700 km of road length, 70% of which is is located in the four large cities. While 65% of the exceedances of the standard are only 5 µg/m3 or less, some exceedances are as high as 20 µg/m3. The plan threshold for nitrogen dioxide (56 µg/m3) is exceeded on approximately 5 km of roads.
In 1990, the annual average nitrogen dioxide concentration on many busy roads was still above the current standard of 40 µg/m3. The concentrations have fallen in the last ten years.
Particulate matter
The road length in urban areas where the limit value (40 µg/m3) for particulate matter (PM10) was exceeded was approximately 1,600 km; for the plan threshold, this figure was approximately 200 km. In the case of particulate matter, the problem is not confined to the large towns; it is also a feature in smaller towns in the southern half of the country.
Road traffic is the principal polluter
Road traffic constitutes the main source of local air pollution in the urban environment. Of the total number of car kilometres in the Netherlands, approximately 30% are travelled in built-up areas. Passenger cars account for 95% of this figure.
The increase in the volume of road traffic is primarily concentrated on motorways. The rise in the number of car kilometres in urban areas can largely be explained by urban sprawl. Traffic intensity in town centres has been reasonably stable in recent years.
Local air quality alongside traffic routes benefits from the falling emissions per kilometre driven for the average car and the declining background concentrations.
Different standards for prolonged and brief exposure
The exceedances shown here are relative to the EU standards for the annual averages of nitrogen dioxide (NO2, 40 µg/m3), particulate matter (PM10, 40 µg/m3) and benzene (10 µg/m3). The 'old' Dutch standards apply to carbon monoxide (CO, 6000 µg/m3 for the 98-percentile of hourly values) and benzo[a]pyrene (1 ng/m3 as an annual average).
