Health Risks in relation to air quality, especially particulate matter. Interim report

One of the questions not answered yet is if smaller particles (PM_2.5) are more toxic than PM₁₀. According to the particle dosimetry models developed for the project, the local dose in the lungs of groups with a less than optimal health status may differ substantially when compared to healthy adults; this may partly explain differences in susceptibility. Modelling the Dutch and European emissions of PM and precursor gasses with an air pollution dispersion model has indicated that part (nearly half) of the Dutch yearly PM₁₀ averages are still unaccounted for.

A monitoring programme has been started to determine the composition of the missing PM₁₀ and its sources. An extensive programme of experimental inhalation toxicology using a mobile particle concentrator has also been developed to conform to epidemiological associations and more specifically to the discovery of causative fractions (and their sources). In vitro tests with lung tissue taken from a variety of individuals demonstrated great variability between these individuals in their susceptibility to collected ambient PM of different-sized fractions at the different locations. A scientific workshop, envisaged for mid-2001, will allow a wider application of the results, with answers to the questions of the Ministry of Housing, Spatial Planning and Environment possibly expected by the beginning of 2002.