AAAR 32nd Annual Conference
September 30 - October 4, 2013
Oregon Convention Center
Portland, Oregon, USA
Abstract View
Indoor and Outdoor Size-Resolved Airborne Microorganism to Particle Number Ratios
DENINA HOSPODSKY, Naomichi Yamamoto, William Nazaroff, Jordan Peccia, Yale University
Abstract Number: 514 Working Group: Bioaerosols: Characterization and Environmental Impact
Abstract Accumulation of sufficient airborne material for DNA-based species enumeration and identification methods is a reoccurring challenge in field studies that use low volume aerosol samplers. A better understanding of the ratios of microbial aerosols to total aerosols would aid in decision-making on sampler type and sampling times for DNA based downstream bioaerosol analyses. Previously documented mass fractions of biological particles range from less than 1% to 80% depending on location, measured particle size, as well as height and type of measurement, and little consensus exists on the common proportions for indoor and ambient air.
We present number based bacteria to total aerosol particle and fungi to total aerosol particle ratios in indoor and outdoor air in five size bins. These ratios were calculated from optical particle counter (OPC) data and quantitative DNA-based bacteria and fungi estimates on size fractionating particle impactors from ten environments in four countries (U.S., Germany, Denmark, and China). Particle number concentrations in the size range from 0.4 to larger than 10 micrometers were quantified during occupied and vacant scenarios in school classrooms in parallel to fungal and bacterial collection and enumeration on filters of multistage impactors using quantitative PCR targeting universal fungal and bacterial genes. OPC data was converted to time averaged particle number concentrations for comparison purposes. The overall outcomes were fungal cell to particle number as well as bacterial cell to particle number ratios for each size bin.
Results indicate the low abundance of bioaerosols in size bins smaller than 2.5 micrometers and higher microorganism to aerosol particle number ratios in the indoor air of occupied buildings. Ratios increase with increasing particle size. The higher abundance of bacteria in occupied indoor air compared to outdoor air or unoccupied indoor air indicates and confirms indoor sources for bacteria.