Comtois and Gagnon. 1988. The
authors compared airborne pollen levels with patient symptom scores in Montreal over a two year period. Their goal was to establish
clinical thresholds for pollen concentrations which triggered symptoms. Their
data suggest that concentrations of 8-25 grains/m3 for tree pollen,
4-12 grains/m3 for grass pollen and 1-3 grains/m3 for
ragweed pollen were clinical thresholds.