Probing the particle size-viability relationship in bioaerosols through size-controlled measurements - Abstract Bioaerosols are small particles suspended in the air that contain living organisms such as bacteria, fungi, and viruses, and have caused some of the most severe and costly diseases, including the SARS-CoV-2 pandemic. Among the various factors, the bioaerosol particle size plays a crucial role in all stages of transmission, including the generation locations and mechanisms in the host's respiratory system, the suspension time and the traveling distance (short-range vs. long-range), and the final deposition efficiency and location into the recipient's respiratory system. Despite significant interest in this area over the past few years, current methods to generate bioaerosols cannot produce bioaerosols with uniform size and sufficient quantity to allow reliable measurement of pathogens that remain infectious over a long time period. Furthermore, no single method can cover the complete size range of bioaerosols from the human respiratory system. As a result, the field has suffered from the lack of capability to study important and basic questions, including how size in the entire respirable bioaerosol range and respiratory activities (coughing, speaking, sneezing, etc.) influences how infectious pathogens transmit under different environmental conditions (such as relative humidity, UV lights, ventilation). This proposed research aims to address these critical limitations. Our central hypothesis is that the bioaerosol size and size distribution due to respiratory activities have a significant impact on how the airborne pathogens stay infectious in the air as a function of environmental conditions, and a virtual impact design produces monodisperse pathogen-laden bioaerosols and in sufficient quantities to detect live pathogens to study the size-viability decay rate relationship. We will test respiratory syncytial virus (RSV), which disproportionally affects infants under 2 years old. It is critical to understand how RSV is transmitted while there is scarce data in the area of RSV transmission studies. The overall objective of this project is to design and build an easy-to-manufacture and easy-to-use bioaerosols generation system and investigate the crucial role of size in the bioaerosol viability decay under various environmental conditions. Our specific aims are (1) to determine the size-viability decay relationship for RSV with monodisperse bioaerosols and (2) to estimate the viability decay rate of different respiratory activities with a few well-characterized log-normal distributions. The success of this proposed work will provide a new scientific tool to generate monodispersed bioaerosols with sufficient quantity for viability assays and elucidate the key contribution of bioaerosol size on pathogen viability in different environmental conditions. Furthermore, our work will reveal how respiratory activities impact pathogen transmission. These tools and insights can lead to future studies on bioaerosol deposition in rodent and non-human primate lung models.
