Particle Size Distribution and Seasonal Concentrations of Airborne Fungi in the Northeastern United States

NAOMICHI YAMAMOTO (1) (2), Jing Qian (1), Denina Hospodsky (1), Jordan Peccia (1)

(1) Yale University, (2) Japan Society for the Promotion of Science (JSPS)

     Abstract Number: 510
     Last modified: May 13, 2010

Abstract
Airborne fungi are ubiquitous in indoor and outdoor air and some fungi are important human pathogens or allergens. Accurate characterization of their particle size distribution and associated aerosol dynamics is crucial for understanding and reducing human exposures. Here we investigated the size distribution and seasonal trends of airborne fungi by molecular-based methodologies. In addition to culture based assays, quantitative polymerase chain reaction (qPCR) methods with primers and probes targeting the rRNA gene region were performed for seven fungi species and groups. Fall, winter, spring and summer sampling campaigns using multistage viable and nonviable impactors were conducted on the rooftop of a five-story building in New Haven, Connecticut, USA. Both the qPCR and culture-based assays demonstrated that airborne fungal concentrations were significantly decreased in winter. Aerodynamic diameters of each fungal species and groups were calculated based on the particle size distributions characterized by the qPCR assays. Aerodynamic diameters for species forming multicellular spores were relatively large, i.e., geometric mean diameters of >10.4 micro-meter (GSD = 1.4) and >10.5 micro-meter (GSD = 1.4) for Alternaria alternata and Epicoccum nigrum, respectively, while those for the species forming unicellular spores were small, 4.3 micro-meter (GSD = 1.6) and 5.2 micro-meter (GSD = 1.6) for Aspergillus fumigatus and Cladosporium cladosporioides, respectively. Aerodynamic diameter of total viable fungi was smaller than those characterized by the qPCR assays, i.e., 2.4 micro-meter (GSD = 1.7). Particle size distributions are important determinants for spore deposition in human airways and control the fate and transport in indoor and outdoor aerosols. Accurate molecular-based methodologies are essential to characterize this distribution as unculturability and agglomeration of microorganisms are potential artifacts and inaccuracies associated with traditional growth-based methods.