Exposure to green space and pollen allergy symptom severity: A case-crossover study in Belgium

The prevalence of pollen allergy has increased due to urbanization, climate change and air pollution. effects green space pollution on respiratory health patients are complex best studied in spatio-temporal detail. We tracked 144 adults sensitized Betulaceae during the tree season (January–May) 2017 2018 assessed their exposure space, allergenic trees, pollutants birch pollen. Participants reported daily symptom severity scores. extracted 404 case days with high scores matched these control days. data were analyzed using conditional logistic regression a 1:1 case-crossover design. Case associated concentration (100 grains/m3) [adjusted odds ratio 1.045 95% confidence interval (1.014–1.078)], O3 (10 ?g/m3) [1.504 (1.281–1.766)] PM10 [1.255 (1.007–1.565)] day severe event cumulative one two before. Exposure grass cover (10% area fraction) [0.655 (0.446–0.960)], forest [0.543 (0.303–0.973)] density Alnus (10%) [0.622 (0.411–0.942)] protective for allergy, but only event. Increased densities Betula trees risk factor [unadjusted OR: 2.014 (1.162–3.490)]. may mitigate when is low. Air contribute more symptoms. Spatio-temporal tracking allows realistic assessment.