AAAR 37th Annual Conference October 14 - October 18, 2019 Oregon Convention Center Portland, Oregon, USA
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Aerosol Particles from Human Speech as a Possible Vector for Airborne Infectious Disease Transmission
SIMA ASADI, Anthony S. Wexler, Christopher Cappa, Santiago Barreda, Nicole M. Bouvier, William D. Ristenpart, University of California, Davis
Abstract Number: 704 Working Group: The Air We Breathe: Indoor Aerosol Sources and Chemistry
Abstract Mechanistic hypotheses about airborne infectious disease transmission have traditionally emphasized the role of coughing and sneezing, which are dramatic expiratory events that yield both easily visible droplets and large quantities of aerosol particles too small to see by eye. Nonetheless, it has long been known that breathing and normal speech also yield large quantities of particles that are too small to see by eye, but are large enough to carry a variety of communicable respiratory pathogens. Here we show that the rate of particle emission during normal human speech is positively correlated with the loudness (amplitude) of vocalization, and that it varies significantly with manner of articulation and voicing. Our results indicate that certain ‘phones’ (the basic units of speech) associated with voiced plosives and nasals yield more aerosol particles than fricatives. We interpret these results in terms of the egressive airflow rate associated with the vocalization, which is known to vary significantly with both loudness and consonant type. Furthermore, the data reveals that a small fraction of individuals behaves as “speech superemitters,” consistently releasing an order of magnitude more particles than their peers. This observation potentially explains the existence of “superspreaders” who are disproportionately responsible for outbreaks of airborne infectious disease. We use the experimental data and the Wells-Riley model to estimate the potential impact of human speech on indoor airborne disease transmission.