Aerobiologia 18: 185–193, 2002. © 2002 Kluwer Academic Publishers. Printed in the Netherlands. 185 Aerobiological behaviour of Platanus L. pollen in Catalonia (North-East Spain) Elena Gabarra 1 , Jordina Belmonte 1 & Miguel Canela 2 1 Unitat de Bot` anica. Universitat de Auton` oma de Barcelona, Cerdanyola del Vall` es, Spain; 2 Departament de Matem` atica Aplicada i An ` alisi, Universitat de Barcelona, Spain Received 7 March 2001; accepted 17 June 2002 Key words: aerobiology, allergy, Catalonia, main pollen season, Platanus, pollen dynamics, Spain Abstract The aim of this paper is to characterise the airborne behaviour of an allergenic and abundant pollen type, Platanus, in seven sites of the Aerobiological Network of Catalonia (Xarxa Aerobiològica de Catalunya, XAC). In Catalonia, the most extended Platanus species is Platanus × hybrida Brot., widely planted in forestry and as ornamental tree in streets and gardens. Naturalised specimens can also be found along river banks. The pollen records analysed are from different periods comprised between 1994 and 2000 in Barcelona, Bellaterra, Cambrils, Girona, Lleida, Manresa and Tarragona. All data were obtained using seven-day volumetric spore Hirst traps. Platanus pollination is concentrated in a few weeks, between March and April. Platanus pollen is present in all the atmospheric pollen spectra for the sites mentioned above. In Barcelona, Platanus pollen attained the highest concentrations, with an extreme annual index (sum of the mean daily concentrations) of 25790 in 1997, and a maximum daily concentration of 2567 P/m 3 on 15th March 2000. The lowest annual index (647) corresponds to Cambrils, 2000, and the lowest maximum daily concentration (74 P/m 3 ) was registered on 7th April 1996, in Manresa. The interannual variation of Platanus pollen values can be explained not only by meteorological parameters and the endogenous factors of the tree, but also by human activity such as elimination, pruning and watering. Introduction The genus Platanus L. comprises six species (Mabberley, 1987). In Catalonia, the most common species (Bolòs and Vigo, 1989) is Platanus × hybrida Brot. (= P. acerifolia (Aiton) Willd., = P. cuneata Willd., = P. hipanica Miller ex Münchh., = P. occi- dentalis × orientalis), flowering between April and June, and growing from 0 to 1500 m in altitude. Also present, but rare, are P. orientalis L. and P. occidentalis L. Platanus is mainly found in cities, planted as orna- mental tree, because of its quick growth and resistance to air pollution, however, it is also found as a forestry tree. It is not rare to find naturalised specimens near streams and river banks, particularly in wet regions. Its use as a roadside tree is decreasing. Many authors have considered that Platanus pollen has a moderate allergenic power (Lewis et al., 1983; Belmonte, 1988; Hernández de Rojas et al., 1991). Recent studies (Subiza et al., 1994; Varela et al., 1997) concluded that, in Madrid, Platanus pollen is an important cause of pollinosis. Yman (1982) points out that there is cross-reaction between Platanus × hybrida, P. orientalis and P. occidentalis pollen. Materials and methods The study was carried out in seven localities in the North-Eastern part of the Iberian Peninsula (Figure 1 and Table 1), where Hirst (1952) seven-day spore traps have been working for different years between 1994 and 2000, at an approximate height of 20–25 m