Aerobiologia 16: 453–454, 2000. © 2000 Kluwer Academic Publishers. Printed in the Netherlands. 453 Short communication Airborne allergenic pollens in Padua: 1991–1996 Marina Giorato 1 , Francesca Lorenzoni 1 , Anna Bordin 2 , Giuseppe De Biasi 2 , Carla Gemignani 2 , Michele Schiappoli 2 & Guido Marcer 2* 1 Department of Biology, University of Padua, Italy; 2 Department of Occupational Health, University of Padua, Italy ( * Author for correspondence, e-mail: guimar47@ux1.unipd.it; fax: +39 498212542) Received 11 February 1999; accepted in final form 15 May 2000 Key words: aerobiological monitoring, allergenic flora, pollen Abstract Graminaceae, Urticaceae, Compositae, Betulaceae, Corylaceae and Oleaceae are the most representative allergenic taxa in Italy. In this paper the airborne pollen counts of the main allergenic families collected for a six-year period (1991–1996) in Padua’s area were analysed. We observed a significant variability for all allergenic pollen types considered. 1. Introduction The aim of this study was to analyse the annual variations of cumulative pollen counts and pollina- tion periods of the main allergenic families (Corsico et al., 1999) in order to ascertain whether length and intensity of allergic symptoms season could be predicted. 2. Materials and methods The airborne pollen counts of Graminaceae, Urticaceae, Compositae, Betulaceae, Corylaceae and Oleaceae recorded during the years 1991–1996 have been analysed. Pollen counts were carried out using a volumet- ric trap (VPPS 2000 Lanzoni, Bologna) placed about 25 m above ground level, on the roof of the St. Antonio Hospital in Padua, a city located in north-eastern Italy in the Po Valley. Samples were collected daily on slides. Sampling method, slide preparation and data interpretation have been performed according to the standard method of the Italian Network for the Aerobiological Monitoring (Mandrioli, 1990) and were expressed as pollen grains per cubic meter (p/m 3 ). The analysis of the pollen concentration trend from 1991 to 1996 has been performed using the annual sum (AS) of the daily values. The “effective” pollen season (EPS), defined as the period in which the daily pollen count exceeded 30 p/m 3 for Graminaceae and Urticaceae and 20 p/m 3 for the other families (Viander et al., 1978; Saia et al., 1983; Tariq et al., 1996; D’Amato et al., 1998), was calculated to better compare the year trends of the pollen concentration. 3. Results In the years examined, AS of Graminaceae showed relatively constant values, even in 1993 when an exceptional pollination occurred and in 1996 a marked decrease was recorded. AS of Urticaceae showed a constant increase of pollen concentration until 1995 and a slight drop in 1996. Compositae pollination pattern in 1991 and 1992 were similar, in 1993 a pollen peak was reached; AS in 1994 and mainly in 1995 and 1996 was significantly lower. Betulaceae