Figure 3.

Experimental exposure of cypress and birch pollen with nitrogen dioxide (NO₂). (a) Cypress (25–30 μm) or birch (20 μm) pollen grains, filed on filter (0.22 μm), were aerosolized into a synthetic industrial air flow of 100 mL/min (allowing the flight of smaller particles than pollen) and sent into an impactor equipped solely with a PM₁₀ stage. Particle size distributions were measured, during 10 min, at the outlet of the impactor with an aerosol particle sizer (APS) (0.5–20 μm). (b) Pollen samples were moistened and then dried with air during 10 min (blue curves) and control samples were realized with industrial air (green curves). Impaction tests were also done with pollen grains artificially polluted with NO₂ (0.5% for 10 min) (red curves). Particle size distributions were normalized to show an equal number of pollen grains at 17 μm.