Abstract View
High-Resolution Detection of Aerosols Produced During Breathing and Speech with an Electrical Low-Pressure Impactor
PAUL TUMMINELLO, Caleb Everett, Marva Seifert, Chantal Darquenne, Jonathan Slade, University of California San Diego
Abstract Number: 240
Working Group: Infectious Aerosols in the Age of COVID-19
Abstract
Aerosols produced from speech and breathing are thought to contribute to airborne pathogen transmission, which has become a focal point of the SARS-CoV-2 pandemic. Previous studies have measured aerosols produced during speech using laser-based detection and analysis with an aerodynamic particle sizer. These techniques have elucidated relationships between particular words and vocal amplitude in the production of aerosols. However, these measurements have been limited regarding the size (>0.5 µm) and timescales (1 s) of aerosol detection. In English, individual words and certain sounds may last only a fraction of a second. Here we utilize an electrical low-pressure impactor (ELPI) for detecting aerosols, one not previously applied to speech, which offers a greater range of detectable aerosol size (0.006 µm – 10 µm) and heightened temporal resolution (100 ms) compared to other methods. Participants in the study read stimuli while speaking and breathing with and without an N95 mask into an aluminum funnel connected to the ELPI. The results demonstrate significantly more aerosol production from human speech and breathing than previously thought, with a majority of the number of particles with diameters comparable to single viruses (between 0.07 µm and ~0.2 µm). Combined phonetic and aerosol analysis enabled detection of aerosols from some sound types lasting only ~100 ms. To simulate the aerosol concentrations one may be exposed to from speech in real conversation, participants read a paragraph for ~30 s, producing nearly 106 particles cm-3 cumulatively and volume concentrations ~105 µm3 cm-3. Nasal breathing alone produced about half the concentration of aerosols as speaking while wearing an N95 mask effectively removed nearly all particles generated from speaking and breathing. These results provide novel insights into aerosol production by human speech as well as the efficacy of masks in reducing aerosol transmission. Given the relatively greater buoyancy of fine aerosols and inordinate volumes of aerosol produced, these results can help inform transmission risks of airborne pathogens not accessible from previous methods.