A study was made of the total pollen production per individual tree in ten anemophilous arboreal species (including wild, cultivated and ornamental species) of considerable aerobiological importance: Pinus pinaster, Ulniirs minor, Juglam regia, Platanics liispaniea, Quercus rotundiJolia, Salix atrveinerea, Populus nigra. Aeer negundo, Olea eiiropaea and Fraximts angustijolia.For each species three isolated well-shaped specimens of medium height were chosen, and the number of flowers per indibidual tree and the number of pollen grains per anther was estimated.The values of total pollen production varied between a little over 1000 million grains in Jiiglans regia and more than 500,000 million in one single tree in Quercus rotitiidifolia. For the production of pollen grains per anther, the values oscillated betneen 3000 grains in Jiigluiis regia and 100,000 in Olea europaea. There is an exponential correlation betaeen the size of the anthers and the number of pollen grains they contain. A linear correlation is also evident between the volume of the tree crown and the total production of inflorescences, floners, anthers and pollen grains per individual tree. Based on this, a mean coefficient of the number of grains/meter of diameter of the tree cronn is obtained which varies between 3.4 x 10' for Juglaiis regia and 550.9 x lo* for Qrtercus rotriridifolia. The ratio between the number of anthers per inflorescence and the number of pollen grains per anther carries out a hyperbolic function; thus, the inflorescences nith the most anthers have the anthers with the least pollen and vicewrsa. This ratio is also manifest between the number of grains per flower and the number of floaers per tree, as nell as the number of grains per inflorescence and the number of inflorescences per tree.

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No operational forecasting model for allergenic fungal spore exposure exists in Europe.• Potential exposure in Europe was assessed and predicted for 2 major allergenic fungi. • Random forest modelling was applied to N7000 daily time series. • Air temperature and vapour pressure were the most significant variables. • Classification models showed higher capacity for large-scale spore predictions.

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