L’aérobiologie du pollen de bouleau (Betula spp.) : synergie avec les facteurs environnementaux et impacts sur les maladies respiratoires

Several studies published around the world have shown an association between health issues related to respiratory diseases and the following environmental factors: aeroallergens, air pollution and weather conditions. However, much less attention has been attributed to the combined impact or synergy between these different families of co-stressors. Thus, the notion of synergy between environmental factors and airborne pollen represents the main motivation underlying this thesis. Furthermore, numerical simulations of one of the most allergenic pollen (Betula spp.) are necessary to protect and inform citizens of the risks to respiratory health, but also to understand in a regional context (using mapping) the spatial variability of both environmental factors and airborne pollen. In this thesis, the developed simulation system allows the combined analysis of medium and long-distance transport and dispersion (TDMLD) of both anemophilic pollen and atmospheric pollutants. Subjected to multiple environmental stresses the pollen grain may undergo an increase in the fractures of its external envelope (exine) which can lead to a release of allergenic intracytoplasmic granules and a modification of the allergens exacerbating impacts on atopic patients. According to several researchers, these allergenic proteins present within pollen grains when inhaled cause attack of asthma in susceptible humans. Although the thesis discusses many aspects related to aerobiology, it does not yet allow to completely model all the facets of the problem. However, it opens the door to several avenues of multidisciplinary research. Five major research questions or methodological challenges are addressed in this thesis : 1. Given the scarcity or absence of phenological observations, how do we construct a phenology module that is suitable as an input to a pollen emission model for Betula pollen simulation (Chapter 3) ? 2. How to simulate and integrate pollen emissions and adequately reproduce airborne pollen dispersion in an existing coupled meteorology / air quality model developed in Canada, recognizing that this model is not originally designed to simulate airborne pollen (Chapter 4) ? 3. What is the origin of the Betula pollen affecting the Montreal area and what is the best way to establish its provenance, considering that traditional methods (back-trajectories, inverse methods, two-dimensional models, etc.) present their own difficulties (Chapter 4) ? 4. What are the synergistic links between exposure to allergenic pollen, pollution and weather conditions and what impacts are apparent on the respiratory health of atopic patients given the presence of confounding factors (i.e. meteorological, geographical, socio-economic, etc.) in the analysis of Betula pollen data in relation to respiratory diseases in Montreal and the province of Quebec (Chapters 5 and 6)? 5. What is the spatio-temporal variability of respiratory diseases in Quebec in relation to factors of the atmospheric environment (Chapter 6) ?

Keyphrases: Betula, fronts, Betula, Fronts, Asthma, Air pollution, Synergy, Phenology, Air quality index, TDMLD (Transport/Dispersion at the Medium and Long-Distance)