Wind Tunnel Based Evaluation of Aerosol Control Technologies for Indoor Air and Characterization Methods for Workplace Aerosol Exposure, Aerosol Formation, and Aerosol Growth

Abstract

Aerosol exposure can have both short-term and long-term effects on human health. As examples, inhaled particle deposition within the human respiratory systems can affect blood cells as well as brain cells, increasing cardiovascular mortality and disability, respiratory tract infections, and incidence of cancer (Burnett, Pope III et al. 2014, Rajagopalan, Al-Kindi et al. 2018, Deepthi, Nagendra et al. 2019). For this reason, a large number of studies have been devoted to understanding particle sources in the environment, combustion source emission, and such particles’ impacts on the environment with underlying health effects in humans. However, the majority of aerosol exposure studies focus on outdoor pollution (PM 2.5) and its anthropogenic sources. Conversely, aerosol exposure research in indoor environments and assessment of control technologies to reduce exposure are underdeveloped. This is perhaps best highlighted by the SARS-CoV-2 pandemic of the past several years; the role of aerosol based disease transmission was ignored and not well understood in the early stages of the pandemic, and only after COVID-19 had spread worldwide was it clear how aerosol transport contributed to disease spread and how control technologies for indoor aerosol particles could help reduce disease spread. The studies in this dissertation are largely motivated by this issue, i.e. the need for improved characterization of aerosol exposure indoors and the need to develop and apply methods to assess the capabilities of control technologies design to collect and inactivate infectious, virus-laden aerosol particles. As these are very broad topics, this dissertation cannot completely cover all workplace exposure and assessment of all HVAC control technologies. Therefore specific focus is on: (1) Understanding the size distribution, mass, and morphology of aerosol particles from surgical smoke, which is an exposure risk to operating room workers and a unique health risk not studied in detail in prior research efforts; (2) Assessing the performance of control technologies designed to mitigate aerosol and bioaerosol exposure in indoor environments. Along with those two goals, I also carried out studies to (3) analyze nucleation and growth of particles from organometallic precursors at high temperature. While this topic is distinct from aerosol exposure characterization and control technology assessment it is also of fundamental importance in understanding the origin and growth rate of industrial aerosols. In total, I completed 6 distinct studies as part of my dissertation research. In the subsequent subsections of this introductory chapter, I provide a background and motivation each study. Studies are presented in chronological order in which they were performed during my dissertation, demonstrating the influence of the COVID-19 pandemic on my research, as I was a graduate student from 2018-2022, with the peak of the COVID-19 pandemic occurring in the middle of my graduate studies. While for this reason, the transition from chapter-to-chapter may appear abrupt, I believe it highlights how research in aerosol science was affected in this time period by the COVID-19 pandemic, and how studies related to developing technologies to reduce infection spread occurred alongside studies in fundamental aerosol science. The subsequent chapters after this are written as stand-alone works containing “Introduction”, “Methods”, “Results and Discussion”, and “Conclusion” sections. Finally, a conclusions chapter is provided, summarizing the key findings from all studies.