Thread by @HuffmanLabDU

New pre-print: “Respiratory aerosols and droplets in the transmission of infectious diseases”

Happy to contribute to this deeply detailed review paper by Mira Pöhlker et al. & colleagues at the Max Planck Institute for Chemistry.

Link: arxiv.org/abs/2103.01188…

A 🧵summary (1/x)

2/ Preprint review is very detailed: 50 pgs, 20 figures, 7 tables, >360 references.

☑️Reviews literature:
- Respiratory particle size distributions (rPSDs)
- Physical properties
- Emission & shrinkage mechanisms
☑️New multimodal parameterization of rPSDs
☑️Practical perspective

3/ The review ends by showing a parameterized size distribution of respiratory particles & the risks in different parts of a room using #masks, #ventilation, and #filtration. Broad application to SARS-CoV-2 other respiratory viruses.

Link: arxiv.org/abs/2103.01188…

4/ Reviews literature evidence & summarizes the relative concentrations (C) and emission rates (Q) of different particle sizes from breathing, speaking, coughing in both the near- and far-field of a room.

5/ Starts by considering the 'lifecycle' of respiratory droplets and aerosols, including emission; physics of transport and evaporation; exposure by deposition & inhalation.

6/ Presents a detailed overview of the physiological locations & physical mechanisms for each size range of respiratory particles emitted.

7/ Summarizes respiratory particle sedimentation and travel based on well-known physics.

8/ Reviews the processes and properties related to respiratory droplet shrinkage as a function of relative humidity, and provides links to long-standing experience with similar questions via atmospheric physics community.

9/ Takes all literature-available respiratory particle size distribution data, parameterizes to a multimodal fit algorithm, and also makes conceptual links to other particle generation mechanisms in the outdoor environment.

10/ Summarizing experimental evidence from literature, proposes that respiratory particle emissions from all standard activities (i.e. breathing, speaking, coughing) can be simplified into only five particle size modes: B1,B2 - bronchial; LT - larynx & trachea; ; O1,O2 - oral.

11/ Ultimately, the paper compares the newly parameterized distributions of respiratory particles w/ size distributions in which different respiratory viruses have been found - to suggest a physical basis for plausible physiological sources & emission mechanisms.

12/ Also calculates respiratory particle emission rates (aerosols & droplets) from speaking when using masks* and not.

Uses a combination of emission rates w/ published evidence of efficiency of different types of masks.

*Assuming perfect mask fit.
Also note log y-scale.

13/ Among the benefits for aerosol & respiratory disease researchers is the summarized literature evidence of various properties including -

A summary of experimentally determined decay rates by several respiratory viral pathogens.

14/ A summary of the main chemical constituents in saliva and epithelial lining fluid (both important for respiratory aerosol/droplet emissions).

15/ A summary of aerosol number size distributions reported in the literature from respiratory activities.

16/ *Preprint* manuscript "provides a critical review & synthesis of scientific knowledge" on emission, transport, & deposition of "Respiratory aerosols & droplets in the transmission of infectious disease".

Suggestions, omissions, edits welcome.

Link: arxiv.org/abs/2103.01188…