Air quality is primordially affected by anthropogenic emissions and has a tremendous impact on human health with more than 6 million premature deaths worldwide in 2015 (Landrigan et al. in The Lancet Commission on pollution and health, 2017) . Biogenic emissions of aerosols such as pollen also impact the human wellbeing. The industrialized world suffers from a global increase in the burden of allergic respiratory diseases. Air pollution can influence both allergens and allergic subjects by increasing the immune reaction, and/or by an intensified biogenic emissions. In Europe, a quarter of the population suffers from pollinosis, whereas in some countries the prevalence is over 40%. To date, pollen of various trees and grasses in Belgium are monitored by the Belgian Scientific Institute for Public Health (Sciensano) at five stations on a daily basis. This sparse sampling cannot cover the spatial representativeness of the airborne pollen. Chemistry Transport Models (CTM’s) are therefore an interesting tool to both quantify and forecast its spatial and temporal distribution. Here we show the results of the spatio-temporal modelled birch pollen over Belgium using the CTM SILAM. This model is driven by 2008 ECMWF meteorological data and a MACC-III birch tree fraction map showing the spatial distribution of potential pollen sources. Pollen modelling is based on the temperature degree days approach.