In recent years there has been a decline in the average concentrations of fine particulates and nitrogen dioxide. In most parts of The Netherlands these are now below their respective limit values. Nevertheless, at some sites, these values for both types of pollutant are persistently exceeded in a limited number of cases. These findings were reported in the yearly monitoring report of the National Air Quality Collaboration Programme (NSL). This cooperation programme provides a platform where government bodies combine forces to improve air quality.

At a local level, the limit values for fine particulates are exceeded at livestock farms and along roads passing through areas characterized by intensive livestock farming or by industry. As a result, in 2012 The Netherlands did not comply with the fine particulate limit value everywhere in the country. It should be noted that this was the first full year in which this limit value applied.

Nitrogen dioxide

European agreements require The Netherlands to comply with the limit values for nitrogen dioxide in 2015. Current calculations indicate that, in 2015, the annual average limit value will be exceeded at several locations. These will mainly be in the Randstad area, along urban roads that carry heavy traffic. The fact that the limit value is still being exceeded in some places is partly due to the fact that there has been less of a decline in the actual emissions of nitrogen oxides by traffic than was expected based on the Euro standards for passenger cars and trucks.

A report entitled “The Euro emission standards for passenger cars and trucks in relation to NO2 limit value exceedances in the Netherlands“ published by the National Institute for Public Health and the Environment (RIVM National Institute for Public Health and the Environment ), the Netherlands Environmental Assessment Agency (PBL) and the Netherlands Organization for Applied Scientific Research (TNO) shows that, in 2015, there would be almost no exceedances of the limit values if actual emissions from passenger cars and trucks were to decline to the same extent as was expected based on the Euro standards.

Based on anticipated total nitrogen-oxide emissions, road traffic in the Netherlands is expected to emit around 50 million kilograms in 2015. Using actual emissions, however, the estimated value is 50 percent higher, at about 74 million kilograms.

Uncertainties and risks

Another reason for the high degree of uncertainty regarding the expected number of occasions in which the limit values will be exceeded is that the calculated concentrations at many locations lie just below the limit values. Consequently, there will be a large increase in the number of exceedances should one or more of the working assumptions become less favourable.
This introduces a degree of uncertainty into the calculations with regard to the number of locations where the limit values will be exceeded, and it also produces a slight increase in the concentrations. If these uncertainties are factored into the calculations, the number of  points at which the nitrogen dioxide limit value will be exceeded in 2015 could be up to ten times higher than the value produced by calculations based on current assumptions.

Soot - an extra index

To date, efforts to identify the health effects of air pollution have focused primarily on the levels of fine particulates and nitrogen dioxide, as standards have already been established for these pollutants. Soot (or elemental carbon) is an extra index for the health effects produced by traffic. For several years now, at the request of the ministry of transportation and the environment, RIVM has been publishing maps showing large-scale soot concentrations. RIVM and DCMR have produced the very first map of soot concentrations throughout the Netherlands. In doing so, they used measurement data collected over the past few years, together with continually improving data on emissions, plus the detailed input that is now available within the NSL.

This analysis of air quality based on soot concentration delivers a clearer image of the resultant health effects than was possible by monitoring fine particulates and nitrogen dioxide alone. For each additional 0.5 micrograms of soot per cubic metre of air to which they are exposed for extended periods of time, people’s life expectancy will be reduced by an average of three months. Information about soot concentrations could, therefore, help to guide decisions on measures (including traffic measures) to improve local air quality, even in situations where all of the European standards have been met. The newly published soot map can be of great use in this context.