Thesis of Mona Hamze

Abstract : Although it is now accepted that allergenic pollen grains are altered by air pollution, the role of these alterations on allergy is not yet clearly known. The (bio)chemical mechanisms involved are not completely elucidated, especially with regard to the exacerbation of symptoms by air pollution. The main objective of this thesis is to improve the knowledge on the exposure to allergenic pollen grains by taking into account their degree of alteration: pollution and pollen grain rupture.
A first laboratory study was carried out in order to explore the potential of several techniques for the characterization of the degree of alteration of the pollen grain. Pollen artificially polluted with ozone was analyzed by spectroscopic (Raman and infrared), microscopic and chromatographic techniques. Ozone uptake was also measured on a set of 22 pollen taxa with different bio-physical-chemical characteristics (grain size and mass, degree of allergenicity, lipid fraction...) to investigate possible determinants of ozone uptake.
The potential of pollen analysis by gas chromatography-mass spectrometry (GC-MS) was exploited and a new method of counting pollen grains was developed. This method required a study on the variability of the lipid fraction on different batches of birch pollen from different geographical origins and depending on the year of harvest. In order to test this counting method in real conditions, a sampling campaign was carried out on sedimented birch pollen in indoor and outdoor environments. The determination of chemical tracers of pollen grains by GC-MS has a great potential for the rapid counting of pollen grains, the determination of their state (broken or intact) and their degree of pollution. Keywords : air pollution, allergy, pollen