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:: Section 9 of 10

Bioaerosol Sampling

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Due to the health and welfare effects of bioaerosols, obtaining exposure limits is crucial to public safety. Therefore, any sampling method for bioaerosols must do well in three categories. Firstly, the sampler must have high inlet efficiency, meaning that the sampler takes in a representative number of aerosols. Secondly, the sampler must have a good physical collection efficiency. The physical collection efficiency describes the sampler's ability to remove the bioaerosols from the air stream; it depends on size, shape, and aerodynamic behavior of the particles13. Lastly, the sampler must have a high biological collection efficiency. The biological collection efficiency describes the sampler's ability to maintain the true viability and then quantify the viable count. While inlet efficiency and physical collection efficiency are standards for any aerosol sampling method, the biological collection efficiency is unique to bioaerosol samplers.

In bioaerosol sampling, there are multiple things that ought to be measured for health purposes depending on the type of bioaerosol. For instance, for non-viable bioaerosols, mass or number may be the most important. A person may experience an allergic reaction to pollen or fungi once exposed to a threshold mass of the allergen. For viable bioaerosols, the number of viable microorganism is critical because the infectivity of viruses is measured as a minimum threshold. To determine the viable count, the bioaerosols must be physically captured and then cultured in appropriate conditions. Viable bacteria and fungal spores will form colonies, while viable viruses will form plaques on their host cells.

To maintain high biological collection efficiency, special consideration must be given to preserving the viable count. Otherwise, the results will not be representative of actual levels of exposure to the pathogen. Therefore, the microorganisms should not encounter any harsh conditions, including disinfectants, such as chlorine or alcohol, or high-speed impaction onto sampler walls. The viability is also time-dependent, so immediate care must be taken when sampling. To physically collect bioaerosols, they must be collected into or onto some form of collection medium which will not harm them.

13Chapter 24: Biological Particle Sampling, Aerosol Measurement, Baron and Willeke, 2001