Effect of sampling height on the concentration of airborne fungal spores

Background: Spores of many fungal species have been documented as important aeroallergens. Airborne fungal spores are commonly collected from the outdoor air at the rooftop level of high buildings; however, human exposure usually occurs nearer to the ground. It is necessary to estimate the concentration of airborne fungal spores at the human breathing level to evaluate the actual human exposure to outdoor aeroallergens. Objective: To compare the concentration of airborne fungal spores at human respiration level (1.5 in above the ground) and at roof level (12 in height). Methods: Air samples were collected using 2 Burkard volumetric 7-day recording spore traps from July 1 to October 31, 2005. One sampler was located on the roof of a building at the University of Tulsa at 12 m above ground, and the second sampler was placed in the courtyard of the building at 1.5 m. Burkard slides were analyzed for fungal spores by light microscopy at a magnification of 1,000, and the results were statistically analyzed to compare the concentration of airborne fungal spores at the 2 levels. Results: The ground sampler had significantly higher concentration of basidiospores, Penicillium/Aspergillus-type spores, and smut spores than the roof sampler. By contrast, the rooftop sampler registered significantly higher concentration of Alternaria, ascospores, and other spores. Conclusions: Ground level had significantly higher concentration of some important fungal aeroallergens but lower concentrations of others, suggesting that sampling height is one of the many variables that influence bioaerosol levels.