Pollen count variability

Abstract

Rationale Daily pollen counts provide a snapshot of the atmosphere for a given area and typically represent the average daily concentration from a single sampler. However, a great deal of variability exists within the atmosphere due to the diurnal rhythms of pollen discharge, fluctuations related to weather events, spatial effects, sampler function, and methods of analysis. Methods This study examined temporal and spatial variability of pollen from two Burkard spore traps placed approximately 2.0 m apart on a roof approximately 12 m above ground level. Methods of analysis were also examined. Samples were analyzed for the ragweed season from Aug 15, 1997 to Oct 26, 1997. Spore trap flow rates were maintained at 10 L/min. Results Analysis showed a significant correlation between the daily concentrations (r=0.97, p<0.05) from two samplers, however the seasonal means were significantly different. Sampler B showed higher daily concentrations 60 of the 74 days in the season. In addition, there was a significant correlation between the daily concentrations (r=0.91, p<0.05) for the two methods of analysis with seasonal means for both methods being significantly different. Analysis of the diurnal rhythm showed an average peak concentration to occur at noon, which was almost two times greater than the average daily concentration for the season. Conclusion Pollen counts represent an estimate of the atmospheric pollen levels rather than absolute numbers. Although it is not possible to routinely analyze multiple samples or to use multiple methods, the clinical significance of the atmospheric variability should always be considered.