The influence of sampler height and orientation on airborneAmbrosiapollen counts in Montreal

Abstract

Airborne pollen concentrations are normally estimated by sampling 10 liters of air a minute at a height of 15-20 meters, e.g. on top of a university or hospital building. It is generally believed that at this height a homogeneous cloud of pollen is sampled, and that the results obtained will be representative of a large area. However, this protocol still leaves some doubts about the actual concentration found at breathing level (1.5 m). Since pollen counts are often used to forecast risk of allergies using threshold values, the height difference in concentrations can have important implications. Many previous studies have tackled this problem, but contradictory results were obtained. In our protocol, personal volumetric Burkard samplers were used at 0, 5, 10 and 15 m and at two different orientation (NW and NE) of a single building in Montreal, Canada. Results from 320 samples show that exposure and sampling hours were non-significant factors of Ambrosia pollen variation, but that height was a factor more significant than daily variations (the usual factor investigated in Aerobiology). An interaction was also found between the influences of height and orientation.