Prediction of the start of the grass pollen season for the southern part of the Netherlands

Abstract

To determine the best date for patients in the southern part of the Netherlands to begin treatment for pollinosis, an attempt was made to predict the start of the grass pollen season at Helmond as accurately as possible, as was previously done at Leiden. The start of the grass pollen season was defined as the date when at a given location the accumulated total (from 1 Jan.) of 24 h average grass pollen concentrations (No./m³) reaches 100 (the so-called Σ100-method). Using the phenological method over the years 1981 through 1985, with the birch (Σ125=x) as the indicator plant, the start of the grass pollen period (Σ100=z) could be predicted much more accurately than would have been possible solely on the basis of the mean starting dates in the preceding years. The predicted starting date (z) can be calculated with the equation z=0.44x+95.46 (x and z as day-of-year numbers), SD=3.6 days, r=0.83, n=5). The SD of the Σ100-method of grasses being 5.6 days, the effectivity of the prediction is 35.7%. The difference in results between Helmond and Leiden is discussed.