Insights into the evaporation characteristics of saliva droplets and aerosols: Levitation experiments and numerical modeling

Lieber, Christian; Melekidis, Stefanos; Koch, Rainer; Bauer, Hans‐Jörg

doi:10.1016/j.jaerosci.2021.105760

Cited by 76 publications

(91 citation statements)

References 61 publications

(67 reference statements)

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“…The same is true for surface deposits, particularly as it is not known why viral viability is enhanced in that form 16,25 . The drying of aerosols when emitted into ambient air has been quite extensively studied [27][28][29] and modelled 27,28,30,31 , often with the aim of predicting when droplets, initially large enough to sediment in still air, will shrink enough to remain suspended. In the biomedical literature, a droplet that has dried to equilibrium with the ambient air is called a droplet nucleus 1 .…”

Section: Introductionmentioning

confidence: 99%

“…Much of the published experimentation on droplet drying (cited by 27 ) has made use of simplified analogues of the respiratory fluids in which viruses are emitted by breathing, speaking, singing, coughing or sneezing. Sometimes just NaCl solutions have been used.…”

Section: Introductionmentioning

confidence: 99%

“…Metzger et al 34 give an accessible description of the underlying physics (Kohler theory) as an appendix: their nomenclature is adopted here. In respiratory droplets, proteins and glycoproteins have been recognised to contribute volume to the dried droplet nuclei, but little attention has been paid to other ways in which these polymers might influence the drying process 27,35 .…”

Section: Introductionmentioning

confidence: 99%

“…Because of the very high salt and polymer concentrations that can be reached when biological aerosols dry at low RH, classical colligative relationships like Raoult’s Law become increasingly unsatisfactory approximations and the relevant physical chemistry becomes necessarily more empirical. In these circumstances direct experimental measurements using real biological fluids may be more informative than theoretical prediction 27 . However, experimentation on aerosols is technically challenging 27,36,37 and during the pandemic time is short.…”

Section: Introductionmentioning

confidence: 99%

“…In these circumstances direct experimental measurements using real biological fluids may be more informative than theoretical prediction 27 . However, experimentation on aerosols is technically challenging 27,36,37 and during the pandemic time is short.…”

Section: Introductionmentioning

confidence: 99%

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Drying of virus-containing aerosol particles: Modelling effects of droplet origin and composition

Jarvis

2021

Preprint

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Virus-containing aerosol droplets emitted by breathing, speech or coughing dry rapidly to equilibrium with ambient relative humidity (RH), increasing in solute concentration with effects on virus survival and decreasing in diameter with effects on sedimentation and respiratory uptake. In simulations starting from drying data on mixed NaCl/KCl aerosols, the supersaturated salt concentrations were shown to reach 20-25M at the efflorescence RH of 40-55%, depending on the K:Na ratio. These salt concentrations may inactivate some viruses. The dependence on K:Na ratio implies that the evaporation curves differ between aerosols derived from saliva and from airway surfaces. Differences in drying behaviour are consequently predicted between breathing, speech and coughing emissions and between droplet size fractions within these. The direct effect of liquid droplet size through the Kelvin term was shown to be smaller and restricted to breath emissions. Comparative simulations starting from osmotic pressure measurements on airway surface liquid showed that salts are the primary determinants of drying equilibria down to the efflorescence RH, and macromolecules at lower RH.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Drying of virus-containing aerosol particles: Modelling effects of droplet origin and composition

Jarvis

2021

Preprint

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Droplets and aerosols: An artificial dichotomy in respiratory virus transmission

Drossinos

Weber

Stilianakis

2021

Health Science Reports

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In the medical literature, three mutually non‐exclusive modes of pathogen transmission associated with respiratory droplets are usually identified: contact, droplet, and airborne (or aerosol) transmission. The demarcation between droplet and airborne transmission is often based on a cut‐off droplet diameter, most commonly 5 μm. We argue here that the infectivity of a droplet, and consequently the transmissivity of the virus, as a function of droplet size is a continuum, depending on numerous factors (gravitational settling rate, transport, and dispersion in a turbulent air jet, viral load and viral shedding, virus inactivation) that cannot be adequately characterized by a single droplet diameter. We propose instead that droplet and aerosol transmission should be replaced by a unique airborne transmission mode, to be distinguished from contact transmission.

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Exhaled aerosols and saliva droplets measured in time and 3D space: Quantification of pathogens flow rate applied to SARS‐CoV‐2

et al. 2023

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SARS‐CoV‐2 and its ever‐emerging variants are spread from host‐to‐host via expelled respiratory aerosols and saliva droplets. Knowing the number of virions which are exhaled by a person requires precise measurements of the size, count, velocity and trajectory of the virus‐laden particles that are ejected directly from the mouth. These measurements are achieved in 3D, at 15,000 images/s, and are applied when speaking, yelling and coughing. In this study, 33 events have been analysed by post‐processing ∼500,000 images. Using these data, the flow rates of SARS‐CoV‐2 virions have been evaluated. At high concentrations, 107 virions/mL, it is found that 136–231 virions are ejected during a single cough, where the virion flow rate peak is capable of reaching 32 virions within a millisecond. This peak can reach tens of virions/ms when yelling but reduced to only a few virions/ms when speaking. At medium concentrations, ∼105 virions/mL, those results are hundreds of times lower. The total number of virions that are ejected when yelling at 110 dB, instead of speaking at 85 dB, increases by two‐ to threefold. From the measured data analysed in this article, the flow rate of other diseases, such as influenza, tuberculosis or measles, can also be estimated. As these data are openly accessible, they can be used by modellers for the simulation of saliva droplet transport and evaporation, allowing to further advance our understanding of airborne pathogen transmission.Key points Advanced, optimized and combined laser‐based imaging techniques for temporally sizing and tracking respiratory droplets and aerosols. Understanding how pathogens are being ejected from the mouth when speaking, yelling and coughing. Quantifying and analysing the variation of SARS‐CoV‐2 flow rates emission during exhalation.

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Insights into the evaporation characteristics of saliva droplets and aerosols: Levitation experiments and numerical modeling

Cited by 76 publications

References 61 publications

Drying of virus-containing aerosol particles: Modelling effects of droplet origin and composition

Drying of virus-containing aerosol particles: Modelling effects of droplet origin and composition

Droplets and aerosols: An artificial dichotomy in respiratory virus transmission

Exhaled aerosols and saliva droplets measured in time and 3D space: Quantification of pathogens flow rate applied to SARS‐CoV‐2

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