A comparison of respiratory particle emission rates at rest and while speaking or exercising

Christopher M Orton; Henry E Symons; Benjamin Moseley; Justice Archer; Natalie A Watson; Keir E J Philip; Sadiyah Sheikh; Brian Saccente-Kennedy; Declan Costello; William J Browne; James D Calder; Bryan R Bzdek; James H Hull; Jonathan P Reid; Pallav L Shah

doi:10.1038/s43856-022-00103-w

A comparison of respiratory particle emission rates at rest and while speaking or exercising

Commun Med (Lond). 2022 Apr 19:2:44. doi: 10.1038/s43856-022-00103-w. eCollection 2022.

Authors

Christopher M Orton^#^{1

2

3}, Henry E Symons^#⁴, Benjamin Moseley¹, Justice Archer⁴, Natalie A Watson⁵, Keir E J Philip^{1

3}, Sadiyah Sheikh⁴, Brian Saccente-Kennedy⁶, Declan Costello⁷, William J Browne⁸, James D Calder^{9

10}, Bryan R Bzdek⁴, James H Hull^{1

11}, Jonathan P Reid⁴, Pallav L Shah^{1

2

3}

Affiliations

¹ Department of Respiratory Medicine, Royal Brompton Hospital, London, UK.
² Department of Respiratory Medicine, Chelsea & Westminster Hospital, London, UK.
³ National Heart and Lung Institute, Guy Scadding Building, Imperial College London, Dovehouse Street, London, UK.
⁴ School of Chemistry, University of Bristol, Bristol, UK.
⁵ Department of Ear, Nose and Throat Surgery, Guys & St. Thomas NHS Foundation Trust, London, UK.
⁶ Speech and Language Therapy Department, Royal National Ear Nose and Throat Hospital, London, UK.
⁷ Ear, Nose and Throat Department, Wexham Park Hospital, Slough, UK.
⁸ School of Education, University of Bristol, Bristol, UK.
⁹ Department of Bioengineering, Imperial College London, London, UK.
¹⁰ Fortius Clinic, Fitzhardinge St, London, UK.
¹¹ Institute of Sport, Exercise and Health (ISEH), UCL, London, UK.

^# Contributed equally.

Abstract

Background: The coronavirus disease-19 (COVID-19) pandemic led to the prohibition of group-based exercise and the cancellation of sporting events. Evaluation of respiratory aerosol emissions is necessary to quantify exercise-related transmission risk and inform mitigation strategies.

Methods: Aerosol mass emission rates are calculated from concurrent aerosol and ventilation data, enabling absolute comparison. An aerodynamic particle sizer (0.54-20 μm diameter) samples exhalate from within a cardiopulmonary exercise testing mask, at rest, while speaking and during cycle ergometer-based exercise. Exercise challenge testing is performed to replicate typical gym-based exercise and very vigorous exercise, as determined by a preceding maximally exhaustive exercise test.

Results: We present data from 25 healthy participants (13 males, 12 females; 36.4 years). The size of aerosol particles generated at rest and during exercise is similar (unimodal ~0.57-0.71 µm), whereas vocalization also generated aerosol particles of larger size (i.e. was bimodal ~0.69 and ~1.74 µm). The aerosol mass emission rate during speaking (0.092 ng s^-1; minute ventilation (VE) 15.1 L min^-1) and vigorous exercise (0.207 ng s^-1, p = 0.726; VE 62.6 L min^-1) is similar, but lower than during very vigorous exercise (0.682 ng s^-1, p < 0.001; VE 113.6 L min^-1).

Conclusions: Vocalisation drives greater aerosol mass emission rates, compared to breathing at rest. Aerosol mass emission rates in exercise rise with intensity. Aerosol mass emission rates during vigorous exercise are no different from speaking at a conversational level. Mitigation strategies for airborne pathogens for non-exercise-based social interactions incorporating vocalisation, may be suitable for the majority of exercise settings. However, the use of facemasks when exercising may be less effective, given the smaller size of particles produced.

Keywords: Medical research; Physiology.