Date of Award

Fall 1-1-2025

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Chemical and Environmental Engineering (ENAS)

First Advisor

Peccia, Jordan

Abstract

The COVID-19 pandemic demonstrated the significance of understanding the airborne route of transmission for respiratory viruses and clarified the need to monitor and mitigate the presence of respiratory viral aerosols in indoor congregate settings. The goal of this dissertation is to evaluate the ability of emerging technologies to detect and reduce infectious viral aerosols within occupied indoor spaces. This work first explores the ability of a wearable passive sampler to collect viral aerosols for personal exposure assessments to SARS-CoV-2. The sampling material, polydimethylsiloxane (PDMS), efficiently collected enveloped viral aerosols, with a calculated uptake rate commensurate with previously developed passive aerosol samplers. These PDMS-based passive samplers were embedded in a wearable clip design and deployed on the shirt collars of community members to evaluate personal SARS-CoV-2 exposure. SARS-CoV-2 RNA was detected on 8% of analyzed samplers, with the greatest proportion of detection stemming from restaurant settings compared to healthcare and community-based congregate settings. This work demonstrates the utility of wearable PDMS-based passive samplers to serve as a broadly deployable personal assessment tool for airborne viral exposure among real-world environments, with the potential to identify high-risk settings. The identification of high-risk transmission environments within congregate settings exemplifies the need to deploy disinfection technologies that can interrupt disease transmission. With little practical validation in the peer-reviewed literature, bipolar ionization (BPI) recently emerged as a widely implemented technology that purports to reduce human exposure to airborne pathogens through inactivation and deposition mechanisms. Here, we characterized the effectiveness of BPI to promote reductions in enveloped viral aerosols as a function of relative humidity (RH). BPI dose-response relationships were developed for airborne SARS-CoV-2, demonstrating enhanced viral inactivation and deposition over background conditions, with BPI-mediated decay rate constants increasing with increasing RH. While BPI facilitates significant airborne viral inactivation and deposition at high concentrations (>105 ions cm-3), scaling bipolar ion concentration for realistically attainable in-room concentrations (103 ions cm-3) yields a total decay (inactivation plus deposition) equivalent air exchange rate of less than 0.1 hr-1, resulting in limited pathogen reduction under practical applications. Far-UVC irradiation, another emerging bulk-air disinfection technology, has been identified as a promising option to inactivate pathogens in occupied environments given its safer human exposure relative to conventional ultraviolet germicidal irradiation. Following the exposure of airborne SARS-CoV-2 to 222 nm irradiation in chamber experiments, significant far-UVC mediated viral aerosol inactivation was observed and a viral susceptibility was quantified, with far-UVC driven fluence rate-based Z value susceptibility constants of 4.4 and 6.8 cm2 mJ-1 for airborne SARS-CoV-2 under 40% and 65% relative humidity levels. Modeling of SARS-CoV-2 infection risk reduction corresponding to 25% of the maximum safe human exposure limit in a classroom scenario demonstrates the ability of far-UVC technology to promote SARS-CoV-2 aerosol disinfection in congregate settings. Overall, this work first provides the fundamental information and tools necessary to facilitate effective and broadly deployable monitoring of viral aerosols within indoor environments. This dissertation also quantifies the susceptibility of airborne SARS-CoV-2 to BPI and far-UVC irradiation, enabling the rational design of safe and low-cost systems to interrupt transmission in schools, public spaces, and other congregate settings during times of respiratory disease outbreaks.

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