VARIATION OF PARTICLE NUMBER AND MASS CONCENTRATION IN VARIOUS SIZE RANGES OF AMBIENT AEROSOLS IN EASTERN GERMANY

There is an ongoing debate on the question which size fraction of part icles in ambient air may be responsible for short-term responses of th e respiratory system as observed in several epidemiological studies. H owever, the available data on ambient particle concentrations in vario us size ranges are not sufficient to answer this question. Therefore, on 180 days during the winter 1991/92 daily mean size distributions of ambient particles were determined in Erfurt, a city in Eastern German y. In the range 0.01-0.3 mu m particles were classified by an electric al mobility analyzer and in the range 0.1-2.5 mu m by an optical parti cle counter. From the derived size distributions, number and mass conc entrations were calculated. The mean number concentration over this pe riod of time was governed by particles smaller than 0.1 mu m (72%), wh ereas the mean mass concentration was governed by particles in the siz e range 0.1-0.5 mu m (83%). The contribution of particles larger than 0.5 mu m to the overall number concentration was negligible and so was the contribution of particles smaller than 0.1 mu m to the overall ma ss concentration. Furthermore, total number and mass concentrations in the range 0.01-2.5 mu m were poorly correlated. The results suggest t hat particles larger than 2.5 mu m (or even larger than 0.5 mu m) are rare in the European urban environment so that the inhalation of these particles is probably not relevant for human health. Since particle n umber and mass concentrations can be considered poorly correlated vari ables, more insight into health-related aspects of particulate air pol lution will be obtained by correlating respiratory responses with mass and number concentrations of ambient particles below 0.5 mu m. (C) 19 97 Elsevier Science Ltd.