Airborne microorganisms, such as bacteria, viruses and fungi, are abundant in the natural and built environments. This research encompasses two studies on virus aerosolization and transport in the built environment and the subsequent implications for human health. In the first study, we quantified the impact of a barrier on the spatial distribution of different-sized particles released by speaking in a poorly ventilated room. The room was outfitted with 108 passive sampling sites. The barrier resulted in an increase in 0.5 µm particles deposited on the source-side of the barrier and an increase in 0.5 µm particles at other locations 4-6 m from the source. The barrier had minor impacts on the distribution of 1, 6, 10 and 20 µm particles. The results from this study indicated that barriers may not serve as adequate protection to others in the room, depending on their locations relative to the barrier and the timescale of exposure. In the second study, we reviewed the applications of next-generation sequencing for viruses in water environments. We also characterized the occurrence of two viruses (crAssphage and SARS-CoV-2) from a local wastewater treatment plant (WWTP) in both water and air samples at two locations within the WWTP (influent and aeration basin). We found that crAssphage, a fecal indicator, was quantifiable in most air and water samples, but was not detected in control samples. SARS-CoV-2 N2 RNA was detected in a fraction of the water and air samples but was present in the control water samples, so results for this virus are confounded by laboratory contamination. We also found that there was no correlation between airborne and waterborne SARS-CoV-2 concentrations at the WWTP. A quantitative microbial risk assessment model was constructed to determine inhalation risks associated with airborne SARS-CoV-2 for WWTP operators. The probability of infection ranged from about 2.4 x 10-4 to 5.6 x 10-8 and was heavily dependent on exposure time, airborne concentration and other parameters. / Doctor of Philosophy / Airborne microorganisms, such as bacteria, viruses and fungi, are abundant in the natural and built environments. This research encompassed two studies that evaluated the impact of viruses in the built environment on public health. The first study investigated whether a barrier, like Plexiglas, could protect people from another person's exhaled particles in a poorly ventilated room. The barrier resulted in an increase in the smallest particles (0.5 µm) on the same side of the barrier as the source and an increase in these particles at other locations 4-6 m from the source, indicating that individual exposure depends on their location relative to the barrier. The barrier had minor impacts on larger particles (1, 6, 10, and 20 µm). The second study focused on viruses at wastewater treatment plants (WWTPs). As part of this study, we reviewed how one can use knowledge about the DNA and RNA of viruses in water and wastewater. We also measured the amount of two viruses (crAssphage and SARS-CoV-2) in wastewater and in air surrounding the WWTP. We detected crAssphage, a virus that infects bacteria and a marker for human activity, in most wastewater and air samples. We also detected SARS-CoV-2 in some wastewater and air samples, but this virus was also present in some control samples, so laboratory contamination was an issue. Using the concentrations of airborne SARS-CoV-2, we constructed a computational model to estimate the risk of infection for SARS-CoV-2 inhalation for WWTP employees. Our calculations indicated that the risk of infection ranged from 2.4 x 10-4 to 5.6 x 10-8 and heavily depended on parameters such as exposure time and airborne SARS-CoV-2 concentrations.
| Identifer | oai:union.ndltd.org:VTETD/oai:vtechworks.lib.vt.edu:10919/113989 |
| Date | 27 February 2023 |
| Creators | Gnegy-Spencer, Mariah Ann |
| Contributors | Civil and Environmental Engineering, Marr, Linsey C., Pruden, Amy, Hamilton, Kerry, Wigginton, Krista Rule, Vikesland, Peter J. |
| Publisher | Virginia Tech |
| Source Sets | Virginia Tech Theses and Dissertation |
| Language | English |
| Detected Language | English |
| Type | Dissertation |
| Format | ETD, application/pdf |
| Rights | In Copyright, http://rightsstatements.org/vocab/InC/1.0/ |
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