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Face coverings and respiratory tract droplet dispersion.
R Soc Open Sci. 2020 Dec; 7(12):201663.RS

Abstract

Respiratory droplets are the primary transmission route for SARS-CoV-2, a principle which drives social distancing guidelines. Evidence suggests that virus transmission can be reduced by face coverings, but robust evidence for how mask usage might affect safe distancing parameters is lacking. Accordingly, we set out to quantify the effects of face coverings on respiratory tract droplet deposition. We tested an anatomically realistic manikin head which ejected fluorescent droplets of water and human volunteers, in speaking and coughing conditions without a face covering, or with a surgical mask or a single-layer cotton face covering. We quantified the number of droplets in flight using laser sheet illumination and UV-light for those that had landed at table height at up to 2 m. For human volunteers, expiratory droplets were caught on a microscope slide 5 cm from the mouth. Whether manikin or human, wearing a face covering decreased the number of projected droplets by less than 1000-fold. We estimated that a person standing 2 m from someone coughing without a mask is exposed to over 10 000 times more respiratory droplets than from someone standing 0.5 m away wearing a basic single-layer mask. Our results indicate that face coverings show consistent efficacy at blocking respiratory droplets and thus provide an opportunity to moderate social distancing policies. However, the methodologies we employed mostly detect larger (non-aerosol) sized droplets. If the aerosol transmission is later determined to be a significant driver of infection, then our findings may overestimate the effectiveness of face coverings.

Authors+Show Affiliations

School of Engineering, University of Edinburgh, The King's Buildings, Edinburgh EH9 3FB, UK.School of Engineering, University of Edinburgh, The King's Buildings, Edinburgh EH9 3FB, UK.School of Engineering, University of Edinburgh, The King's Buildings, Edinburgh EH9 3FB, UK.School of Engineering, University of Edinburgh, The King's Buildings, Edinburgh EH9 3FB, UK.School of Engineering, University of Edinburgh, The King's Buildings, Edinburgh EH9 3FB, UK.Queen's Medical Research Institute, University of Edinburgh, The King's Buildings, Edinburgh EH9 3FB, UK.The Roslin Institute, University of Edinburgh, The King's Buildings, Edinburgh EH9 3FB, UK.School of Informatics, University of Edinburgh, The King's Buildings, Edinburgh EH9 3FB, UK.School of Engineering, University of Edinburgh, The King's Buildings, Edinburgh EH9 3FB, UK.School of Engineering, University of Edinburgh, The King's Buildings, Edinburgh EH9 3FB, UK.

Pub Type(s)

Journal Article

Language

eng

PubMed ID

33489292

Citation

Bandiera, Lucia, et al. "Face Coverings and Respiratory Tract Droplet Dispersion." Royal Society Open Science, vol. 7, no. 12, 2020, p. 201663.
Bandiera L, Pavar G, Pisetta G, et al. Face coverings and respiratory tract droplet dispersion. R Soc Open Sci. 2020;7(12):201663.
Bandiera, L., Pavar, G., Pisetta, G., Otomo, S., Mangano, E., Seckl, J. R., Digard, P., Molinari, E., Menolascina, F., & Viola, I. M. (2020). Face coverings and respiratory tract droplet dispersion. Royal Society Open Science, 7(12), 201663. https://doi.org/10.1098/rsos.201663
Bandiera L, et al. Face Coverings and Respiratory Tract Droplet Dispersion. R Soc Open Sci. 2020;7(12):201663. PubMed PMID: 33489292.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - Face coverings and respiratory tract droplet dispersion. AU - Bandiera,Lucia, AU - Pavar,Geethanjali, AU - Pisetta,Gabriele, AU - Otomo,Shuji, AU - Mangano,Enzo, AU - Seckl,Jonathan R, AU - Digard,Paul, AU - Molinari,Emanuela, AU - Menolascina,Filippo, AU - Viola,Ignazio Maria, Y1 - 2020/12/23/ PY - 2020/09/16/received PY - 2020/12/11/accepted PY - 2021/1/25/entrez PY - 2021/1/26/pubmed PY - 2021/1/26/medline KW - COVID-19 KW - face covering KW - handmade mask KW - respiratory droplets KW - social distancing KW - surgical mask SP - 201663 EP - 201663 JF - Royal Society open science JO - R Soc Open Sci VL - 7 IS - 12 N2 - Respiratory droplets are the primary transmission route for SARS-CoV-2, a principle which drives social distancing guidelines. Evidence suggests that virus transmission can be reduced by face coverings, but robust evidence for how mask usage might affect safe distancing parameters is lacking. Accordingly, we set out to quantify the effects of face coverings on respiratory tract droplet deposition. We tested an anatomically realistic manikin head which ejected fluorescent droplets of water and human volunteers, in speaking and coughing conditions without a face covering, or with a surgical mask or a single-layer cotton face covering. We quantified the number of droplets in flight using laser sheet illumination and UV-light for those that had landed at table height at up to 2 m. For human volunteers, expiratory droplets were caught on a microscope slide 5 cm from the mouth. Whether manikin or human, wearing a face covering decreased the number of projected droplets by less than 1000-fold. We estimated that a person standing 2 m from someone coughing without a mask is exposed to over 10 000 times more respiratory droplets than from someone standing 0.5 m away wearing a basic single-layer mask. Our results indicate that face coverings show consistent efficacy at blocking respiratory droplets and thus provide an opportunity to moderate social distancing policies. However, the methodologies we employed mostly detect larger (non-aerosol) sized droplets. If the aerosol transmission is later determined to be a significant driver of infection, then our findings may overestimate the effectiveness of face coverings. SN - 2054-5703 UR - https://www.unboundmedicine.com/medline/citation/33489292/Face_coverings_and_respiratory_tract_droplet_dispersion_ L2 - https://royalsocietypublishing.org/doi/10.1098/rsos.201663?url_ver=Z39.88-2003&rfr_id=ori:rid:crossref.org&rfr_dat=cr_pub=pubmed DB - PRIME DP - Unbound Medicine ER -
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