The closed mouth catches no fliesBenjamin Franklin, Poor Richard’s Almanac, 1742
We’re hopefully nearing the end of the COVID pandemic, with vaccines coming soon. Unfortunately, vaccines won’t be able to bail us out this winter. Neither will fancy designer pharmaceuticals. The main interventions necessary to keep us safe for now are basic public health stuff – like masking and social distancing.
There’s another extremely simple thing that might help reduce COVID transmission – quieting down. This is a bit of a sensitive topic, because we all talk. And sometimes we all talk too loudly. But hospitals are filling up so, well, it’s time to talk about talking.
Human beings are wind instrument that generate aerosols. Small particles are produced as exhaled gas rushes past vibrating vocal cords. As this gas passes further through the tongue, lips, and teeth, sounds from the vocal cords are modulated – generating additional particles.1 Aerosol generation is exacerbated by speaking at higher volumes and at higher pitches.2,3 Scientists have dissected this down to specific sounds which generate more particles than others.4
Studying aerosols is challenging, because we’re studying a surrogate measurement and attempting to predict the likelihood of disease transmission. Particles of different sizes may be more or less dangerous, with some falling rapidly to the ground and others remaining in the air for hours. Nonetheless, it seems fairly clear that loud talking or singing generate more aerosols than breathing or quiet talking.5 And the danger of such particles isn't difficult to infer. For example, singing indoors has been observed to trigger super-spreader events:
Wearing a mask reduces aerosol generation, so this is clearly an essential component for limiting the spread of COVID. However, masks aren’t 100% perfect. Depending on the mask, it may reduce particle generation by a factor of ~5-fold.6 Surgical masks seem to work better than many homemade, do-it-yourself masks.7 The combination of a mask plus being quiet may limit aerosolization more than either intervention alone.
There’s no solid, RCT-level evidence that being quiet reduces the spread of COVID. Nor will there ever be (some things are just too difficult to study with an RCT). But quieting down makes sense and it’s very easy and safe to do. There is literally zero cost or risk involved.
The most important interventions for avoiding aerosol spread are distancing, masking, and good ventilation. However, it’s not always possible to stay more than six feet away from everyone. In situations where all of these three interventions aren’t possible, being quiet could add a bit of safety.
- COVID-19 is spread by aerosols: an evidence review (First 10 in EM, by Justin Morgenstern)
- 1.Bax A, Bax C, Stadnytskyi V, Anfinrud P. SARS-CoV-2 transmission via speech-generated respiratory droplets. Lancet Infect Dis. Published online September 11, 2020. doi:10.1016/S1473-3099(20)30726-X
- 2.Asadi S, Wexler A, Cappa C, Barreda S, Bouvier N, Ristenpart W. Aerosol emission and superemission during human speech increase with voice loudness. Sci Rep. 2019;9(1):2348. doi:10.1038/s41598-019-38808-z
- 3.Echternach M, Gantner S, Peters G, et al. Impulse Dispersion of Aerosols During Singing and Speaking: A Potential COVID-19 Transmission Pathway. Am J Respir Crit Care Med. Published online October 16, 2020. doi:10.1164/rccm.202009-3438LE
- 4.Anfinrud P, Stadnytskyi V, Bax C, Bax A. Visualizing Speech-Generated Oral Fluid Droplets with Laser Light Scattering. N Engl J Med. 2020;382(21):2061-2063. doi:10.1056/NEJMc2007800
- 5.Bahl P, de S, Bhattacharjee S, et al. Droplets and Aerosols generated by singing and the risk of COVID-19 for choirs. Clin Infect Dis. Published online September 18, 2020. doi:10.1093/cid/ciaa1241
- 6.Alsved M, Matamis A, Bohlin R, et al. Exhaled respiratory particles during singing and talking. Aerosol Science and Technology. Published online September 17, 2020:1245-1248. doi:10.1080/02786826.2020.1812502
- 7.Asadi S, Cappa C, Barreda S, Wexler A, Bouvier N, Ristenpart W. Efficacy of masks and face coverings in controlling outward aerosol particle emission from expiratory activities. Sci Rep. 2020;10(1):15665. doi:10.1038/s41598-020-72798-7
- IBCC – Cardiac glycoside poisoning (including digoxin) - May 13, 2021
- IBCC – Approach to the poisoned patient - May 10, 2021
- IBCC – Thrombotic microangiopathies (TTP, HUS, et al.) - May 6, 2021