In 2023, RIVM will take systematic measurements of ultrafine particles in the outside air for the first time. This is necessary because little is known at present about ultrafine particles and their potential health effects. Ultrafine particles must be measured with different equipment than that usually used for particulate matter. RIVM has examined how the existing National Air Quality Monitoring Network (LML) could be adapted for these measurements. The first instruments for this will be installed in 2023. The Netherlands is one of the first countries in Europe to start taking systematic measurements of ultrafine particles over a prolonged period of time.

Incorporating a new measurement and monitoring strategy 

RIVM examined which measurement and modelling strategy was needed to adapt the LML for the measurement of ultrafine particles. The researchers also asked Dutch health experts about their wishesregarding the measurement of ultrafine particles. Measurement experts from the Netherlands and abroad were consulted about the equipment needed to carry out the measurements.

The method for measuring ultrafine particles (smaller than 0.1 micrometre) is different from the method used for particulate matter (smaller than 2.5 or 10 micrometres). Particulate matter is measured based on its weight in the outside air. Ultrafine particles are so light that the number of particles in the outside air is measured instead.

RIVM will measure ultrafine particles at several fixed LML monitoring stations. In addition, three mobile monitoring stations will be added. These can be used to take targeted measurements in the vicinity of sources that emit large numbers of ultrafine particles. The first instruments will be installed after the summer of 2023.

Supplementing measurements with model calculations

At the international level, there is still little experience with measuring ultrafine particles. That is why it is currently too early for a large-scale monitoring network. Obtaining a national picture of the number of ultrafine particles in the outside air requires both measurements and model calculations. Calculation models are used to calculate the number of ultrafine particles in places where measurements are not taken. This national picture is necessary in order to determine the concentrations of ultrafine particles that the Dutch population is exposed to.

With these measurements, the Netherlands is leading the way in Europe

The Netherlands is the first country in Europe to include ultrafine particle measurements in a national monitoring network as standard. The Ministry of Infrastructure and Water Management made this decision based on the Health Council of the Netherlands’ advisory report Risks of ultrafine particles in the outside air from 2021. The Health Council recommended incorporating the measurement of ultrafine particles into the LML. This will enable greater insight into the nature and distribution of ultrafine particles in the Netherlands. By modelling for the whole of the Netherlands, the Dutch population’s exposure to concentrations of ultrafine particles can now be identified systematically as well.