The assignment has to aim to evaluate time trends in PM10 in Flanders. This evaluation is needed to underpin the government on PM10 in Flanders the science policy. The study will be based on the available measurement data from the VMM. PM10 measurements were started by the VMM 1996. Over the years, the monitoring network was expanded. To answer the question of present trends, it seems necessary to filter the influence of meteorological conditions in the different years of the concentrations. This may indeed vary greatly from year to year. Also, the goal is to get a methodology available that will allow annually to perform trend analysis VMM.