Abstract View
Aerosol Phase Changes Relevant to the Airborne Survival of Pathogens
ERIK HUYNH, Anna Olinger, David Wooley, Josefina Hajek-Herrera, Ryan Davis, Trinity University
Abstract Number: 197
Working Group: Infectious Aerosols in the Age of COVID-19
Abstract
The phase state of respiratory aerosol particles and droplets has been linked to the humidity-dependent airborne and surface survival of pathogens. Thus, to understand and inform strategies to mitigate the spread of infectious disease, it is prudent to understand the potential phase changes occurring with the complex organic-inorganic media in which pathogens are suspended. Here, we study the phase changes of levitated aerosol particles composed of model respiratory compounds (salt, protein) and culture media (organic-inorganic mixtures commonly used as suspension media in studies of pathogen survival) with decreasing relative humidity (RH). Depending on composition, efflorescence was either not observed or occurred between ~30 and 45% RH (consistent with NaCl efflorescence). Further, we identify humidity-dependent amorphous phase changes at intermediate RH (45-80%). Specifically, we identify (semi-)solid gel and ultra-viscous states, where the organic fraction becomes more viscous with decreasing RH. A higher protein content causes aerosol particles to be (semi-)solid under a wider range of RH conditions. Diffusion, and thus disinfection kinetics, are expected to be inhibited in these observed amorphous (semi-)solid states. Thus, amorphous phase states are likely hindering virus inactivation at moderate to low RH, which may help explain the protective effect of proteins on virus survival. Comparisons of our observations to previous studies of viral survival suggest that formation of a (semi-)solid state can contribute to the recovery of virus viability at intermediate to low RH. We discuss the implications for amorphous phase states of respiratory aerosol for ambient transmission under, as well as a conceptual framework toward predicting the survival of pathogens in varying suspension media and ambient conditions.