10th International Aerosol Conference September 2 - September 7, 2018 America's Center Convention Complex St. Louis, Missouri, USA
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Bioaerosol Sampling in Field surveys
TIINA REPONEN, University of Cincinnati
Abstract Number: 779 Working Group: Bioaerosols
Abstract The choice of a bioaerosol sampling method depends on the purpose of the sampling: is sampling conducted for verification of the presence of microbial problems, identification of the source, monitoring the efficiency of control methods or assessment of the human exposure. When choosing a sampling method, one also has to consider which analysis method would give most relevant measures for the question asked. This, in turn, may limit the choice of sampling methods available. A wide variety of sampling methods are available for assessing microorganisms in indoor environments. These can be categorized into four main groups: air sampling, dust sampling, surface sampling and building material sampling. This presentation will review the traditional and modern sampling techniques available with a focus on air sampling and will discuss the advantages and disadvantages of the choices available.
Air samplers are based on well established aerosol collection mechanisms, such as impaction, interception, diffusion, electrostatic attraction, and gravitational settling. The same physical principles that are applied to non-biological particles can be applied to bioaerosol sampling in terms of sampling efficiency of a given particle size range. An additional consideration for sampling microorganisms is the ability to maintain the biological property that is used in the analysis, e.g., culturability of cells or integrity of genetic material. Also, particle bounce can be a pronounced problem in impaction sampling of spores. Although air sampling should be the most representative of respiratory exposure, traditional air sampling methods have several limitations. Most methods cannot be used for assessing long-term exposure to bioaerosols. The sampling period of most commonly used commercially available instruments (e.g., Burkard, Andersen, Air-O-Cell) is limited to 5-20 min while the bioaerosol concentrations have wide temporal variation, particularly if an active source is present, such as in mold-problem homes. Therefore, short-term sampling often fails to detect certain species, which are present in low concentration but may be important for the subsequent health effects. Several new samplers have recently been developed specifically for the collection of bioaerosol particles, e.g., Viable Virus Aerosol Sampler (VIVAS) and Rutgers Electrostatic Passive Sampler (REPS). There are also a few direct-reading instruments, most of which are based on laser-induced autofluorescence of biological material, but these have limitations in identifying the specific microbial types.
For building investigations, direct source evaluation techniques (bulk, surface, and dust sampling) may be preferred as these allow the investigators to collect extensive information about the source. The disadvantages of dust sampling, especially from the floor, are that the sample may not adequately reflect human inhalation exposure and that the age of floor dust is often not known. An alternative is a long-term collection of settled dust by placing dust sampling platforms at a certain height in the indoor environment. Another approach is to use a specially-designed aerosolization chamber that releases biological particles from contaminated surfaces by air currents and vibration (e.g., Fungal Spore Source Strength Tester, FSSST, and Particle-Field and Laboratory Emission Cell, P-FLEC). This approach can give the worst-case scenario for the possible airborne concentration of biological particles that can be released or resuspended from the surface under investigation.
As each technique has unique advantages and disadvantages, it is often beneficial to use multiple techniques in each investigation. Also, it should be kept in mind that results between different studies could be compared only if same sampling and analysis methods were used.