| Title | Nickname | My summary | Citation and date | Links | |
| Performance of fabrics for home-made masks against the spread of COVID-19 through droplets: A quantitative mechanistic study | Aydin 2020 | Did not read Investigated filtration of large, high-velocity droplets by 11 common household fabrics. Used commercial medical mask as a benchmark. Assessed the breathability (air permeability), texture, fiber composition, and water absorption properties of the fabrics. We found that most fabrics have substantial blocking efficiency (median values >70%). In particular, two layers of highly permeable fabric, such as T-shirt cloth, blocks droplets with an efficiency (>94%) similar to that of medical masks, while being approximately twice as breathable. The first layer allows about 17% of the droplet volume to transmit, but it significantly reduces their velocity. This allows the second layer to trap the transmitted droplets resulting in high blocking efficacy. | Onur Aydin, Bashar Emon, Shyuan Cheng, Liu Hong, Leonardo P.Chamorro, M. Taher A.Saif
Extreme Mechanics Letters, Volume 40, October 2020, 100924 doi.org/10.1016/j.eml.2020.100924 |
Elsevier
doi |
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| A Performance Evaluation and Inter-laboratory Comparison of Community Face Coverings Media in the Context of COVID-19 Pandemic | Bourrous 2021 | Need summary | Bourrous, S., Barrault, M., Mocho, V., Poirier, S., Bardin-Monnier, N., Charvet, A., Thomas, D., Bescond, A., Fouqueau, A., Mace, T., Gaie-Levrel, F., Ouf, F. (2021). A Performance Evaluation and Inter-laboratory Comparison of Community Face Coverings Media in the Context of COVID-19 Pandemic. Aerosol Air Qual. Res. 21, 200615. https://doi.org/10.4209/aaqr.200615 | aaqr | |
| Surgical Mask Partition Reduces the Risk of Noncontact Transmission in a Golden Syrian Hamster Model for Coronavirus Disease 2019 (COVID-19) | Chan | Surgical mask barrier placed between hamster cages reduced
both COVID transmission and severity of transmitted disease.
Masks did not stop transmission, however.
Noncontact transmission was found in 66.7% (10/15) of exposed naive hamsters. Surgical mask partition for challenged index or naive hamsters significantly reduced transmission to 25% (6/24, P = .018). Surgical mask partition for challenged index hamsters significantly reduced transmission to only 16.7% (2/12, P = .019) of exposed naive hamsters. Unlike the severe manifestations of challenged hamsters, infected naive hamsters had lower clinical scores, milder histopathological changes, and lower viral nucleocapsid antigen expression in respiratory tract tissues. Some hamsters were inoculated with Covid and placed in cages adjacent to healthy hamsters (the naive group). When there was no barrier, more naive hamsters got sick, and they got very sick. With a surgical mask as a barrier, fewer naive hamsters got sick and their illness was mild. |
Surgical Mask Partition Reduces the Risk of Noncontact Transmission in a Golden Syrian Hamster Model for Coronavirus Disease 2019 (COVID-19)
Jasper Fuk-Woo Chan, Shuofeng Yuan, Anna Jinxia Zhang, Vincent Kwok-Man Poon, Chris Chung-Sing Chan, Andrew Chak-Yiu Lee, Zhimeng Fan, Can Li, Ronghui Liang, Jianli Cao Clinical Infectious Diseases, Volume 71, Issue 16, 15 October 2020, Pages 2139-2149 https://doi.org/10.1093/cid/ciaa644 Published: 30 May 2020 |
Full | |
| Evaluation of Cloth Masks and Modified Procedure Masks as Personal Protective Equipment for the Public During the COVID-19 Pandemic | Clapp | Tested filtration of 0.05um NaCl particles by masks worn by a volunteer. Tested 7 cloth masks, plus a medical procedure mask in 6 configurations to modify fit. | JAMA Intern Med.
doi:10.1001/jamainternmed.2020.8168 Published online December 10, 2020. |
Links | |
| Forgotten Technology in the COVID-19 Pandemic: Filtration Properties of Cloth and Cloth MasksdA Narrative Review | Clase | Need summary | Citation | Full | |
| Testing the efficacy of homemade masks: would they protect in an influenza pandemic? | Davies | Filtration efficiency of two different aerosolized microorganisms
(a bacterium and a virus)
was tested across 10 different fabrics, with both filtration and
pressure drop across the fabric reported. A surgical mask filtered
about 96%, with "Cotton mix" fabric at 74% and cotton t-shirt at
69%. (See Table 1 for all results.)
Participants also made home-made masks, whose fit and filtration of coughs was tested. I don't really understand the results in Table 2 and Table 3. |
Testing the efficacy of homemade masks: would they protect in an influenza pandemic?
Anna Davies, Katy-Anne Thompson, Karthika Giri, George Kafatos, Jimmy Walker, Allan Bennett PMID: 24229526 PMCID: PMC7108646 DOI: 10.1017/dmp.2013.43 Published online 2013 May 22 |
Short
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| Uniting Infectious Disease and Physical Science Principles on the Importance of Face Masks for COVID-19 | Ghandi-Marr | Need summary | Citation | ||
| Method for Evaluating Effectiveness of Surgical Masks | Greene 1962 | Need summary | V. W. Greene and D. Vesley. "Method for Evaluating Effectiveness of Surgical Masks" J Bacteriol. 1962 Mar; 83(3): 663–667. | PMC | |
| Comparing the Respirable Aerosol Concentrations and Particle Size Distributions Generated by Singing, Speaking and Breathing | Gregson | Need summary | Gregson, Watson, Orton, Haddrell, McCarthy, Finnie, Nick Gent, Donaldson, Shah, Calder, Bzdek, Costello, Jonathan Reid.
Preprint submitted 19.08.2020, posted 20.08.2020. |
Full | |
| Recharging and rejuvenation of decontaminated N95 masks | Hossain | Paper focuses on a technique for recharging discharged masks. As a side effect, provides tables of filtration by new masks, discharged masks, and recharged masks. New surgical masks filtered 65% ,79%, 98%. N95 masks filtered >95% when new, 75% after washing in washing machine. | Emroj Hossain, Satyanu Bhadra, Harsh Jain, Soumen Das, Arnab Bhattacharya, Shankar Ghosh, Dov Levine.
"Recharging and rejuvenation of decontaminated N95 masks".
Physics of Fluids 32, 093304 (2020);
https://doi.org/10.1063/5.0023940
Published Online: 08 September 2020 |
Full | |
| Evaluation of Filtration Performance Efficiency of Commercial Cloth Masks | Jang | Evaluated five cloth masks and one respirator. All masks were synthetic
(A: 50% nylon, 40% polypropylene, 10% polyurethane;
B: 84% nylon, 12% polyester, 4% spandex;
C: 100% polyester (cool comfort);
D: 100% polyester (microfibre);
E: 100% polyester (microfibre);
R: Respirator). Used NaCl particles (neutralized polydisperse) with
US NIOSH test method (42 CFR 84). Flow rate 30 LPM, equivalent to
normal breathing.
One layer masks did poorly, with roughly 40% filtration at 1um.
Two layers were better. Four layers filtered about 70% to 80%.
Washing of single layer masks significantly decreased their
effectiveness, by factors of 2 or 3.
The pressure drop of a respirator was slightly more than a
2 layer version of Mask A, and about half that of a 4 layer
Mask A.
Overall: 3 layers seems like best option, probably. Note none of the fabrics were cotton, which seems like the present mainstream choice. |
Evaluation of Filtration Performance Efficiency of Commercial Cloth Masks
Jang, Ji Young (Department of Public Health, Keimyung University) ; Kim, Seung Won (Department of Public Health, Keimyung University) Received: 2015.05.13 Accepted: 2015.06.19 Published: 2015.06.28 doi.org/10.5668/JEHS.2015.41.3.203 |
doi
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| Aerosol Filtration Efficiency of Common Fabrics Used in Respiratory Cloth Masks | Konda | Encourages incorporating electrostatic filtration in masks.
Two layers of chiffon are effective.
Study uses NaCl aerosol, which is a standard technique, but
does not address how the materials tested would do in high
humidity. Nicely shows raw data with error bars.
See "Konda correction" below. |
Aerosol Filtration Efficiency of Common Fabrics Used in Respiratory Cloth Masks
Abhiteja Konda, Abhinav Prakash, Gregory A. Moss, Michael Schmoldt, Gregory D. Grant, and Supratik Guha Cite this: ACS Nano 2020, 14, 5, 6339-6347 https://doi.org/10.1021/acsnano.0c03252 Copyright 2020 American Chemical Society Publication Date:April 24, 2020 |
Boston Globe
phys.org summary Full Local PDF |
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| Correction to Aerosol Filtration Efficiency of Common Fabrics Used in Respiratory Cloth Masks | Konda correction | Oops! Big oops! They didn't recognize that airflow is significantly reduced by the fabric. They didn't monitor the air flow rate during testing, only when there was no sample inserted. The flow rates are about an order of magnitude lower than intended and not known. | Abhiteja KondaAbhiteja Konda, Abhinav Prakash, Gregory Moss, Mike Schmoldt, Gregory Grant, and Supratik Guha.
ACS Nano 2020, 14, 8, 10742-10743 Publication Date:June 18, 2020 https://doi.org/10.1021/acsnano.0c04676 |
ACS | |
| Efficacy of face masks, neck gaiters and face shields for reducing the expulsion of simulated cough-generated aerosols | Lindsley | Tested filtration of 0 to 7um particles by various masks worn by a manequin. The air flow was an emulated cough, with a single rapid expulsion of air and aerosol (KCl and sodium fluorescein) expelled at a rate similar to a cough. | Citation | HTML
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| Measurement of filtration efficiencies of healthcare and consumer materials using modified respirator fit tester setup | Long | This study developed a test setup that approximates NIOSH testing standards with standard hospital fit-testing equipment plus <$300 of additional equipment. The particle sizes used were slightly smaller than NIOSH. The study tested various fabrics and fabric combinations, demonstrating that alternative mask materials can be used to achieve filtration efficiencies approaching those of N95 respirators. The best performers were non-woven polypropylenes, including: Halyard H100 and H500, Pellon 915 (“interfacing”), and SmartFab. Table S2 in the supplemental materials is worth viewing. | Long KD, Woodburn EV, Berg IC, Chen V, Scott WS
Measurement of filtration efficiencies of healthcare and consumer materials using modified respirator fit tester setup.
PLoS ONE 15(10): e0240499.
(October 13, 2020) doi.org/10.1371/journal.pone.0240499 |
Pone DOI | |
| Effectiveness of Common Fabrics to Block Aqueous Aerosols of Virus-like Nanoparticles | Lustig | A very useful paper overall, but with some holes. Generated aerosols containing fluorescent virus-like nanoparticles (PLGA), prepared PLGA pellets with ethyl acetate, rhodamine 6G, and eicosane. Results include a table of fractional transmission, comparing a number of fabrics used in cloth masks with N95 mask material. Some funny things in the data include (1) listing "Pellon #SF101 fusible polyester" though this is a cotton interfacing, (2) failure to note whether the fusible Pellon midweight #931TD was fused or not (if neither fused nor washed, this is not a typical usage and the glue droplets could affect the results, and (3) funny results where "Kona cotton (x2)" filters better than "Kona cotton/white 12 oz denim/Kona cotton" -- no discussion why adding a denim layer would make filtration worse. Also missing is measurement of pressure across each fabric, which is essential along with filtration efficiency to optimizing mask fabric selection. | Effectiveness of Common Fabrics to Block Aqueous Aerosols of Virus-like Nanoparticles
Steven R. Lustig, John J. H. Biswakarma, Devyesh Rana, Susan H. Tilford, Weike Hu, Ming Su, and Michael S. Rosenblatt Cite this: ACS Nano 2020, 14, 6, 7651-7658 https://doi.org/10.1021/acsnano.0c03972 Publication Date: May 21, 2020 |
Full
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| Mechanistic insights into the effect of humidity on airborne influenza virus survival, transmission and incidence | Marr 2020 | "Mechanisms" section describes evaporation of particles from some initial diameter to some equilibrium diameter. Mentions that NaCl and proteins are usually part of the viral droplet, but does not say what overall equilibrium droplet sizes are to be expected. | Linsey C Marr, Julian W Tang, Jennifer Van Mullekom, Seema S Lakdawala | PubMed | |
| Influenza Virus Aerosols in Human Exhaled Breath: Particle Size, Culturability, and Effect of Surgical Masks | Milton 2013 | Collected samples of exhaled particles, with or without mask, in ≤5μm or >5 μm bins. Fine particles contained 8.8 fold more viral copies than coarse particles. Surgical masks reduced viral copy numbers by 25-fold for droplets larger than 5 μm but only 2.8-fold for fine droplets smaller than 5 μm.
Copy numbers declined rapidly with day after onset of illness.
[Read abstract only] |
D.K. Milton, M.P. Fabian, B.J. Cowling, M.L. Grantham, J.J. McDevitt, Influenza virus aerosols in human exhaled breath: particle size, culturability, and effect of surgical masks, PLoS Pathog. 9 (3) (2013), e1003205 | doi | |
| Droplet fate in indoor environments, or can we prevent the spread of infection? | Morawska 2006 | Discussion of droplet fate in relationship to disease transmission.
Smaller droplets undergo more rapid acceleration or deceleration than larger droplets.
Early studies in 1920s and 1940s concluded that most droplets generated through expiratory human activities are >1um due to lack of better methods. More recent studies suggest that most particles are <1um.
Papieni and Rosenthal 1997 concluded that 80-90% of particles
are <1um; relationship between original droplet size and size
measured was not addressed. Droplets <100um will evaporate
before reaching the ground. Plotted evaporation rate of
droplets at various humidities in Figure 1; a 10um
droplet evaporates in about 0.1 seconds.
Droplets produced from body secretions have a significant amount
of residue, affecting the final droplet size.
Ferrets (1941) and mice (1962) can transmit influenza through
aerosolized droplets, through ducts too curvy for large droplets.
Droplets do not remain in the air for any considerable period of
time as they evaporate very quickly, with the solid airborne
residue remaining suspended in air for prolonged periods.
Around 50% of low submicron particles deposit in respiratory
tract.
Viruses with lipid envelope are more stable in dry air, while viruses without are more stable in moist air. Viruses with lipid envelope include influenza, parainfluenza, respiratory syncytial and corona viruses. |
L. Morawska.
Indoor Air 2006; 16: 335-347. doi.org/10.1111/j.1600-0668.2006.00432.x |
DOI | |
| Size distribution and sites of origin of droplets expelled from the human respiratory tract during expiratory activities | Morawska 2009 | Seminal plots of count vs particle size. | https://doi.org/10.1016/j.jaerosci.2008.11.002 | doi | |
| Size characteristics of particles generated by people | Morawska ??? | slides | Citation | slides | |
| It Is Time to Address Airborne Transmission of Coronavirus Disease 2019 (COVID-19) | Morawska 2020 | summary | Lidia Morawska, Donald K Milton
Clinical Infectious Diseases, Volume 71, Issue 9, 1 November 2020, Pages 2311–2313, https://doi.org/10.1093/cid/ciaa939 Published: 06 July 2020 |
Full | |
| Quantitative Protection Factors for Common Masks and Face Coverings | Leith 2021 | Methods describes how CSU does their mask testing. | David Leith, Christian L’Orange, and John Volckens
Environ. Sci. Technol. 2021, 55, 5, 3136–3143 Publication Date:February 18, 2021 https://doi.org/10.1021/acs.est.0c07291 |
doi | |
| Inward and outward effectiveness of cloth masks, a surgical mask, and a face shield | Pan | Evaluated 11 masks for material filtration efficiency, inward protection efficiency, and outward protection efficiency. Evaluated effect of particle size, with much better filtration at larger (2um to 5um) sizes than 0.3um. Fabric descriptions are inadequate to replicate. Carefully described methods. | Jin Pan, Charbel Harb, Weinan Leng, Linsey C. Marr.
Inward and outward effectiveness of cloth masks, a surgical mask, and a face shield doi: https://doi.org/10.1101/2020.11.18.20233353 |
medRxiv
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| Ability of fabric face mask materials to filter ultrafine particles at coughing velocity | OKelly | Looked at filtration at air flow corresponding to
coughing. Dry and damp fabrics. Aerosolized NaCl.
2.5cm diameter tube. measured particles 0.02um to 0.1um.
results for N95 mask were ~53% filtration, so fast air
flow rate may affect results. Authors claim unusually
low efficiencies for fabrics are due to single wash of
material before testing, but that sounds like magical
thinking given their N95 results are also unusually low.
Very rough assessment of pressure drop, subjective rating
of 0 to 3 by two experimenters.
Read references 2-4 (Davies, Konda, Rengasamy). Read references 13: Fennelly "transmission through small particle aerosols, rather than through large droplets, is the rule rather than the exception." |
Eugenia O'Kelly, Sophia Pirog, James Ward, P John Clarkson
BMJ Open 2020;10:e039424. doi:10.1136/bmjopen-2020-039424 Received 15 April 2020 Revised 19 August 2020 Accepted 04 September 2020 |
PopSci
BMJ |
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| Assessing the quality of nontraditional N95 filtering face-piece respirators available during the COVID-19 pandemic | Plana | Tested KN95 masks. About half the masks tested do not filter >95%, though most filtered >60%. | Citation | medRxiv | |
| SARS-CoV-2 disease severity and transmission efficiency is increased for airborne but not fomite exposure in Syrian hamsters. | Port 2020 | Hamsters were inoculated either intranasally, by
aerosol, or by fomite exposure.
Airborne transmission is more efficient than fomite
transmission.
Only the aerosol-exposed hamsters showed SARS-CoV-2
in the lungs or trachea.
All animals had SARS-CoV-2 in the nasal epithelium.
Day 1: Nasal turbinate pathology in some hamsters regardless
of inoculation route, primarily in ciliated
epithelial cells.
Day 4: Virus in lungs of all animals, regardless of
inoculation route.
Fomite-exposed hamsters had least severe outcomes in
all regards.
Aerosol exposure lead to most virus in the lungs and
correspondingly most severe illness.
No SARS-CoV-2 antigen was detected in the esophagus or brain. |
Port et al.,
"SARS-CoV-2 disease severity and transmission efficiency is increased for airborne but not fomite exposure in Syrian hamsters",
Preprint: 28 Dec 2020 doi: 10.1101/2020.12.28.424565 |
NIH | |
| Simple respiratory protection-- evaluation of the filtration performance of cloth masks and common fabric materials against 20-1000 nm size particles. | Rengasamy | Tested filtration of very small particles, 20nm to 1um, through single layer fabric samples, mostly cotton and polyester. NaCl aerosol. Measured both filtering and pressure drop. Two air flow rates (5.5 cm/s and 16.5 cm/s). Showed plots of penetration vs particle diameter, and weirdly penetration *increases* with particle size. | Rengasamy S, Eimer B, Shaffer RE. Simple respiratory protection-- evaluation of the filtration performance of cloth masks and common fabric materials against 20-1000 nm size particles. Ann Occup Hyg 2010;54:789–98. | PubMed | |
| Properties of materials considered for improvised masks | Rogak | Nice introduction discussing some of the multi-disciplinary nuances missed by many 2020 studies. (Missing is the observation that smaller particles originate deep in the respiratory system where Covid attacks, while large droplets come from the oral cavity.) Measured filtration of large number of single-layer materials for 2.75um NaCl, and a few for 0.5um to 4.0um. Also pressure drop. Created model for combining layers, unfortunately with significant (up to 20%) residual error. | "Properties of materials considered for improvised masks"
Steven N. Rogak, Timothy A. Sipkens, Mark Guan, Hamed Nikookar, Daniela Vargas Figueroa and Jing Wang 28 December 2020, Aerosol Science and Technology. DOI: 10.1080/02786826.2020.1855321 Received: 11 Aug 2020 Accepted: 12 Nov 2020 Published online: 28 Dec 2020 |
News
Full Tool MaskProject |
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| FreeMaskProjectVancouver | FreeMaskProjectVancouver | Free Mask Project Vancouver, Collaboration with "UBC Aerosol Lab" which is Rogak's lab. Evaluated filtration of
some washed and unwashed fabrics, including
2 layers cotton, and 2 layers cotton plus Halyard H400.
Listed breathability, with much higher pressure drop
for their best choice than for cotton masks or
medical masks, and slightly worse than for an N95.
I Washed My Mask in the Laundry: is it Still Protective? Should I Use a Filter in My Mask | Citation | Links | |
| Tim Sipkens | Nickname | From post-doc in Rogak lab. | Citation | fmvis | |
| Reinventing Cloth Masks in the Face of Pandemics | Salter 2020 | summary | 24 September 2020
https://doi.org/10.1111/risa.13602 |
doi | |
| Recognition of aerosol transmission of infectious agents: a commentary | Tellier | A publication predating Covid-19 discussing how science and medicine arrive at conclusions about airborne spread of several diseases. Scientific conclusions often arise from how many studies reach the same consensus. Some diseases may be spread through different routes predominating depending on the specific situation, leading to mixed results in the scientific literature. For SARS and MERS, the airborne transmission seems likely to underlie at least some cases. Likelihood and severity of disease can depend on mode of transmission. For example, aerosolized influenza viruses are infectious at a dose much lower than by nasal instillation. Also, the severity of anthrax, plague, tularemia, and smallpox depend on mode of transmission. | Tellier, R., Li, Y., Cowling, B.J. et al.
Recognition of aerosol transmission of infectious agents: a commentary BMC Infectious Diseases (2019) 19, 101 (2019) https://doi.org/10.1186/s12879-019-3707-y Received: 29 August 2017 Accepted: 10 January 2019 Published: 31 January 2019 |
Links | |
| Association Between Universal Masking in a Health Care System and SARS-CoV-2 Positivity Among Health Care Workers | Wang-MGH | Universal wearing of surgical masks in March-April 2020 reduced SARS-CoV-2 positivity rate among MGH employees from 14.65% to 11.46%, while positivity rates in the community rose. | Xiaowen Wang, Enrico G. Ferro, Guohai Zhou, Dean Hashimoto, Deepak L. Bhatt.
JAMA. 2020;324(7):703-704. doi:10.1001/jama.2020.12897 |
JAMA | |
| Airborne transmission of respiratory viruses | Wang 2021 | summary | Chia C. Wang*, Kimberly A. Prather*, Josué Sznitman, Jose L. Jimenez, Seema S. Lakdawala, Zeynep Tufekci, Linsey C. Marr,
Wang et al., Science 373, 981 (2021) 27 August 2021 https://doi.org/10.1126/science.abd9149 |
doi | |
| The quest of the virosols_final_090821 | Virosols | Cartoon version of Wang 2021 | Citation | slides | |
| Factors influencing the filtration performance of homemade face masks | Hao | Need summary | Weixing Hao , Guang Xu & Yang Wang (2021): Factors influencing the filtration performance of homemade face masks, Journal of Occupational and Environmental Hygiene, DOI: 10.1080/15459624.2020.1868482 | full | |
| Filtration Efficiencies of Nanoscale Aerosol by Cloth Mask Materials Used to Slow the Spread of SARS-CoV‐2 | Zangmeister | Tested materials with 50 to 825nm NaCl aerosol particles, in accordance to standard established filter testing protocols (Parts 3 and 5 of EN 1822 and ISO 29463). Materials included an N95 respirator, N95 base fabric, surgical mask, cotton twill, lightweight cotton flannel. Data is consistent with electrostatic deposition as not being significant in filtration by cloth materials. Plots of filtration vs particle size showed the expected curve with a low around 200nm, and better filtration of larger particles. Plots of filtration by the cotton flannel versus number of layers showed roughly linear behavior, with an offset if we extrapolate towards zero (similar to Zhao's plot of polypropylene filtration vs number of layers) consistent with the first layer providing more filtration than each subsequent layer. Also tested a large number of materials, including some polypropylenes (HEPA Filter, medical wrap, N95, surgical masks). Used nearly a page to discuss inability to replicate Konda's results (the ones with a big methodological oops). | Christopher D. Zangmeister, James G. Radney, Edward P. Vicenzi, and Jamie L. Weaver
"Filtration Efficiencies of Nanoscale Aerosol by Cloth Mask Materials Used to Slow the Spread of SARS-CoV-2" ACS Nano 2020, 14, 7, 9188-9200 June 25, 2020 doi.org/10.1021/acsnano.0c05025 |
acs | |
| Household Materials Selection for Homemade Cloth Face Coverings and Their Filtration Efficiency Enhancement with Triboelectric Charging | Zhao | Tested fabric samples with modified NIOSH procedure, modified to use 32 L/min instead of 85 L/min (NaCl, 0.075 +/-0.2 um count median diameter, 0.26 μm mass mean diameter) Tested: N95 meltblown polypropylene, medical mask meltblown polypropylene, spunbond polypropylene interfacing, 3 cotton fabrics, polyester, silk, nylon, 3 paper products. Measured filtration and pressure drop. N95 had best Q, polypro was 2nd. Electron microscope photos of fabrics. Tried charging fabrics; only polypro held electrostatic charge for hours/overnight. Supplemental materials include test of 1 to 5 layers of polypro (multi-layer). | Mervin Zhao, Lei Liao, Wang Xiao, Xuanze Yu, Haotian Wang, Qiqi Wang, Ying Ling Lin, F. Selcen Kilinc-Balci, Amy Price, Larry Chu, May C. Chu, Steven Chu, and Yi Cui
Nano Lett. 2020, 20, 5544-5552 June 2, 2020 doi.org/10.1021/acs.nanolett.0c02211 | NanoLetters | |
| Efficacy of masks and face coverings in controlling outward aerosol particle emission from expiratory activities | Asadi | Need summary | 24 September 2020 | Nature | |
| Professional and home-made face masks reduce exposure to respiratory infections among the general population | Sande | Need summary | van der Sande M., Teunis P., Sabel, R., 2008, PLoS One (doi: 10.1371/journal.pone.0002618) | NIH
PlosOne |
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| Aerosol emission and superemission during human speech increase with voice loudness | Asadi 2019 | Need summary | Sima Asadi, Anthony S. Wexler, Christopher D. Cappa, Santiago Barreda, Nicole M. Bouvier, William D. Ristenpart.
Sci Rep. 2019; 9: 2348. Published online 2019 Feb 20. doi: 10.1038/s41598-019-38808-z |
Full | |
| Visualizing Speeck-Generated Oral Fluid Droplets with Laser Light Scattering | Anfinrud | Need summary | Anfinrud P, Stadnytskyi V, Bax CE, Bax A. 2020. "Visualizing Speeck-Generated Oral Fluid Droplets with Laser Light Scattering". New England Journal of Medicine (doi: 10.1056/NEJMc2007800) | NEJM | |
| Comprehensive characterization of protective face coverings made from household fabrics | Guha | Need summary | Citation | Full |
| The Astounding Physics of N95 Masks | N95 video | Nice explanation and visualization of how N95 masks rely on electrostatics (6:07 video). | Jun 18, 2020 | YouTube |
| Linsey Marr's Tweet of my data | Marr Tweet | summary | 4 March 2021 | Tweet |
| Mask Design 101: A Bootcamp for Masks during Covid-19 | Volckens video | 1.5 hour video. First half hour is Volckens discussing particle physics. Second half hour is L'Orange discussing mask construction recommendations (notably omitting specific fabrics and omitting high-Q fabrics). Third half hour is Q&A. | 21 Sept 2020 | YouTube |
| FAQs on Protecting Yourself from COVID-19 Aerosol Transmission | FAQ-aerosols | summary | https://tinyurl.com/FAQ-aerosols | Links |
| High-Performance COVID-19 Masks | N95DECON | Explains why we might want to use KF94s and KN95s, fit, filtration. Mentions where to buy KF94s and how they performed in filtration tests. | Citation | Link |
| Advice on the use of masks in the context of COVID-19 | WHO guidance | Advice on construction and use of masks from the WHO, though lacking in data to back the WHO's specific recommendations for the specific 3 layer stack-up. | Advice on the use of masks in the context of COVID-19
WHO Reference Number: WHO/2019-nCov/IPC_Masks/2020.4 Publication date: 5 June 2020 |
WHO on masks
ArsTechnica Local PDF |
| "Evidence-informed Cloth Masks" | ClothMasks.ca | summary | https://www.clothmasks.ca/guidance
https://www.clothmasks.ca/plain-language-summary-of-evidence Cite some studies, but I don't think they understood them well. For one, they mention Konda as if they didn't recognize the oops. For another, they don't seem to make a trade-off with breathability. Link to Clase et al. as "our study". |
Links |
| Mask adherence and rate of COVID-19 across the United States | Fischer 2021 | summary | Citation | pone |
| Moving Personal Protective Equipment Into the Community: Face Shields and Containment of COVID-19 | Perencevich | Compares rates of spread of COVID-19 to other diseases
(measles, flu, chicken pox) and concludes that
the community attack rates are consistent with droplet and
contact spread.
Relies on a study done early in the epidemic which looked at 445 contacts of the first 10 travel-related COVID-19 patients in the U.S. Those 10 patients had 19 associated household members. Of those 19, 2 developed COVID-19, 5 tested negative for COVID-19, and the article does not comment directly on the other 12 but based on the methods those 12 were asymptomatic and not tested. While 10% of household contacts developed COVID-19, we do not know how many contracted asymptomatic SARS-CoV-2 since those 12 (63%) household contacts were not tested. The study assumes that asymptomatic illness is rare, which may have seemed sensible on March 6, 2020 when the study was published, but has turned out not to be the case. If 40% of all infected people are asymptomatic, then for every 6 symptomatic people, there are 4 others in the population who are asymptomatic. So if the study tested only symptomatic individuals, and if the study found 2 infected friends/partners, then likely there were 1.5 (1 or 2) others who were asymptomatic but infected. Then, overall, we have 2 known tested infected persons, plus 1.5 others who were infected but asymptomatic and thus not tested, for an overall household transmission rate of 3.5/19=18%, somewhere between flu and measles, suggesting both aerosols and droplets are involved in transmision. 3 Jun 2020 estimate that 40% to 45% are asymptomatic: https://www.acpjournals.org/doi/10.7326/M20-3012 |
Perencevich, E., Diekema, D., Edmond, M.
JAMA, Volume 323, Number 22, p.2252-2253 June 9, 2020 |
Local PDF |
| July 16, 2020 UCSF School of Medicine Grand Rounds | July 16 Grand Rounds | Middle third of presentation is on masks. First third discusses whether the aerosols vs droplets distinction makes sense, pointing out that the difference is size and size is a contiuum. Last third is on face shields. | YouTube | YouTube |
| What the Data Say About Wearing Face Masks | Nature | Nice summary of exisitng studies on efficacy of masks.
Bibliography is a good reading list. |
Nature, Vol 586, 8 October 2020, p. 186-189 | Nature |
| Loretta Fernandez and Amy Mueller preliminary data | Nickname | Nice preliminary data. For the cloth masks, descriptions of what materials were used are sorely lacking. Compelling case that fit is very important. But still shy of answering how to make a good cloth mask. | Loretta Fernandez and Amy Mueller | |
| Colorado State data plots | Nickname | summary | http://jv.colostate.edu/masktesting/ | Links |
| Filtration performance of common household materials for manufacturing homemade masks | Yang Wang spreadsheet | summary | Citation | SS |
| Rebecca's "Comparing Filtration Lab Results" | Nickname | Comparisont of NIOSH, Nelson Labs, CTT, UBC, CSU | Rebecca Lau spreadsheet | ss |
| Master Mask Testing Data Set | Collins data | Aaron Collins adult mask test data | Citation | ss |
| Kid's Mask Summary[WIP] | Collins data | Aaron Collins kid mask test data | Citation | ss |
(Mostly from open tabs in my browser... to read later.)
| Title | Nickname | My summary | Citation and date | Links |
| Selection of homemade mask materials for preventing transmission of COVID-19: A laboratory study | Wang 2020 | summary | Published: October 15, 2020https://doi.org/10.1371/journal.pone.0240285 | doi-pone |
| Identifying airborne transmission as the dominant route for the spread of COVID-19 | Zhang 2020 | summary | Renyi Zhang, Yixin Li, Annie L. Zhang, Yuan Wang, and Mario J. Molina
"Identifying airborne transmission as the dominant route for the spread of COVID-19" PNAS June 30, 2020 117 (26) 14857-14863; published June 11, 2020; https://doi.org/10.1073/pnas.2009637117 Submitted May 16, 2020 |
PNAS |
| Influence of particle size on regional lung deposition – What evidence is there? | Carvalho 2011 | summary | Thiago C. Carvalho, Jay I. Peters, Robert O. Williams III
"Influence of particle size on regional lung deposition – What evidence is there?" International Journal of Pharmaceutics, Volume 406, Issues 1–2, 15 March 2011, Pages 1-10 |
doi |
| Face Masks Against COVID-19: An Evidence Review | Howard 2020 | summary | Citation | preprint
PNAS |
| Exhaled aerosol increases with COVID-19 infection, age, and obesity | Edwards 2021 | summary | David A. Edwards, Dennis Ausiello, Jonathan Salzman, Tom Devlin, Robert Langer, Brandon J. Beddingfield, Alyssa C. Fears, Lara A. Doyle-Meyers, Rachel K. Redmann, Stephanie Z. Killeen, Nicholas J. Maness, and Chad J. Roye
Proc Natl Acad Sci U S A. 2021 Feb 23; 118(8): e2021830118. Published online 2021 Feb 9. doi: 10.1073/pnas.2021830118 |
doi |
| "NOVEL APPROACHES TO ENHANCE PULMONARY DELIVERY OF PROTEINS AND PEPTIDES" | Scheuch | Has plot of deposition rates in lungs | Citation | full |
| Mask adherence and rate of COVID-19 across the United States | Fischer 2021 | summary | Charlie B. Fischer ,Nedghie Adrien ,Jeremiah J. Silguero,Julianne J. Hopper,Abir I. Chowdhury,Martha M. Werler
"Mask adherence and rate of COVID-19 across the United States" Published: April 14, 2021https://doi.org/10.1371/journal.pone.0249891 |
doi-pone |
| Viral Load of Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) in Respiratory Aerosols Emitted by Patients With Coronavirus Disease 2019 (COVID-19) While Breathing, Talking, and Singing | Coleman 2021 | 85% of Covid viral load is in particles ≤5 um. |
https://doi.org/10.1093/cid/ciab691
Published: 06 August 2021 |
doi |
| Measurements and Simulations of Aerosol Released while Singing and Playing Wind Instruments | Stockman 2021 | Evaluating emissions through clarinet keyholes, they found that particles did not escape but CO2 did escape due to how clarinet keys are constructed: "This keyhole is always slightly obstructed by a small key of cork and metal on which moisture collects over time, and so while CO2 escaped the keyhole, respiratory aerosol did not." | Consistent with my recorder experiment (wherein most of the air exits the window, not the bell), the flute emits very little at its bell. Indoor CFD simulation assumes 4m box (2m of space from singer to edge). For mask, used surgical mask (not cloth). Majority of aerosol number were particles <2.5μm diameter (so... not well filtered by fabrics).Tehya Stockman, Shengwei Zhu, Abhishek Kumar, Lingzhe Wang, Sameer Patel, James Weaver, Mark Spede, Donald K. Milton, Jean Hertzberg, Darin Toohey, Marina Vance, Jelena Srebric, and Shelly L. Miller
https://doi.org/10.1021/acsenvironau.1c00007 |
doi |
| Evidence of Long-Distance Droplet Transmission of SARS-CoV-2 by Direct Air Flow in a Restaurant in Korea | Kwon 2020 | Analysis of June 17, 2020 COVID-19 transmission, with 3 cases identified. One person was infected at a distance of 6.5m from the infector in a 5 minute exposure. Another was infected with a 21 minute exposure at 4.8m. | Kwon, Park, Park, Jung, Ryu, Lee.
J Korean Med Sci. 2020 Nov 30;35(46):e415. English. Published online Nov 23, 2020. https://doi.org/10.3346/jkms.2020.35.e415 |
doi |
| Implementation and Evolution of Mitigation Measures, Testing, and Contact Tracing in the National Football League, August 9-November 21, 2020 | CDC NBA 2020 | CDC report on COVID transmission in the NBA, showing multiple transmissions in <15 minutes. | Citation | html |
| Inhaled aerosols: Their role in COVID-19 transmission, including biophysical interactions in the lungs | Sosnowski 2021 | Need summary | Citation | doi |
| Short-range airborne route dominates exposure of respiratory infection during close contact | Chen | Probably the first study in which the large droplet route, traditionally believed to be dominant, has been shown to be negligible compared with the short-range airborne route. Large droplet route only dominates when subjects are within 0.2 m while talking or 0.5 m while coughing. Large droplet route contributes less than 10% of exposure when the droplets are smaller than 50 µm at 0.3 m apart. The large droplet route only dominates when the droplets are larger than 100 µm and when the subjects are within 0.2 m while talking or 0.5 m while coughing. | Wenzhao Chen, Nan Zhang, Jianjian Wei, Hui-Ling Yen, Yuguo Li
Building and Environment, Volume 176, June 2020, 106859 https://doi.org/10.1016/j.buildenv.2020.106859 |
Full |
| Transmission of airborne virus through sneezed and coughed droplets | Das 2020 | Has nice figure on distance traveled vs ejection speed for 200um droplets. | S. Das, J.-e. Alam, S. Plumari und V. Greco,
"Transmission of airborne virus through sneezed and coughed droplets“ Phys. Fluids 32, 097102 (2020); https://doi.org/10.1063/5.0022859 Submitted: 25 July 2020 . Accepted: 15 August 2020 . Published Online: 03 September 2020 | doi |
| COVID-19 Data Dives: Why Arguments Against SARS-CoV-2 Aerosol Transmission Don't Hold Water | Jimenez July 2020 | Article providing compelling explanations of why aerosol transmission
dominates SARS-CoV-2 spread, including debunking arguments made
by proponets of droplets.
A review of evidence behind airborne transmission of Covid-19, presenting data behind airborne transmission being more significant than droplet or fomite transmission in the ongoing pandemic. |
Jose-Luis Jimenez | Medscape |
| Summary of the Evidence For and Against the Routes of Transmission of SARS-CoV-2 | Jimenez slides | Slides. Some nice visualizations in the back. | - | Slides |
| Measurements of Airborne Influenza Virus in Aerosol Particles from Human Coughs | Lindsley 2010 | summary | William G. Lindsley ,Francoise M. Blachere,Robert E. Thewlis,Abhishek Vishnu,Kristina A. Davis,Gang Cao,Jan E. Palmer,Karen E. Clark,Melanie A. Fisher,Rashida Khakoo,Donald H. Beezhold
Published: November 30, 2010 https://doi.org/10.1371/journal.pone.0015100 |
doi |
| COVID-19 patients in earlier stages exhaled millions of SARS-CoV-2 per hour | Ma | Measured SARS-CoV-2 RNA in exhaled breath condensate (EBC),
air samples, and surface swabs from and near COVID-19 patients in
Beijing.
Results are consistent with aerosol transmission: most virus
in EBC, also some in places inaccessible to patient such as air
duct under the bed.
Emissions are sporadic; samples from same patient on different
dates returned very differnt results.
Reference 11 (Xu et al.: "peak of biological particles at around 1um in exhaled breath from healthy subjects" |
Jianxin Ma, Xiao Qi, Haoxuan Chen, Xinyue Li, Zheng Zhang, Haibin Wang, Lingli Sun, Lu Zhang, Jiazhen Guo, Lidia Morawska, Sergey A. Grinshpun, Pratim Biswas, Richard C. Flagan, Maosheng Yao | Links |
| SARS-CoV-2 disease severity and transmission efficiency is increased for airborne but not fomite exposure in Syrian hamsters. | Port | Hamsters are susceptible to SARS-CoV-2 infection through intranasal, aerosol and fomite exposure. Airborne transmission was more efficient than fomite transmission. Intranasal and aerosol inoculation caused more severe respiratory pathology, higher virus loads and increased weight loss. Fomite exposure led to milder disease manifestation characterized by an anti-inflammatory immune state and delayed shedding pattern. Magnitude of shedding not related to severity, but timing is: early shedding linked to increased disease severity. | Port et al.,
"SARS-CoV-2 disease severity and transmission efficiency is increased for airborne but not fomite exposure in Syrian hamsters." Version 1. bioRxiv. Preprint. 2020 Dec 28. doi: 10.1101/2020.12.28.424565 |
DOI |
| Defining the sizes of airborne particles that mediate influenza transmission in ferrets | Zhou 2018 | Separated ferrets with influenza from healthy
ferrets with barriers that blocked particles greater
than certain sizes (1um, 2.5um, 5.3um, 9.9um)
to determine particle sizes mediating
airborne influenza transmission. Ferret-to-ferret
transmission was mediated by airborne particles
larger than 1.5 μm.
Approximately 76.8% of total airborne particles released from the donor ferrets were fine droplet nuclei with aerodynamic diameters of 0.52-1.54um; however, virus-laden particles were predominantly enriched in particles at >4μm. Ferrets exposed to <1.5um particles from other ferrets didn't get sick. Ferrets could be infected with nebulized 1um aerosols. Overall, ferret-to-ferret influenza transmission occured with particles 1.5um to 15.3um. Also, viral RNA was detected in >4μm particles but not smaller particles. They detected influenza virus RNA in air at 1, 3, and 5 dpi despite gradually decreasing infectivity. Infectivity was highest at 1dpi and decreased at 3dpi and decreased further at 5dpi, while viral gene counts peaked at 3dpi and were higher at 5dpi vs 1dpi... which is to say infectivity is not directly related to gene counts or droplet count. Virus-laden particles continue to shed in air despite decreasing infectivity. |
Zhou et al.
"Defining the sizes of airborne particles that mediate influenza transmission in ferrets" PNAS March 6, 2018 115 (10) E2386-E2392; Published February 20, 2018; https://doi.org/10.1073/pnas.1716771115 |
doi |
| Fluorescent bioaerosol particles resulting from human occupancy with and without respirators. | Xu | summary | Xu C, Wu C, Yao M. Fluorescent bioaerosol particles resulting from human occupancy with and without respirators. Aerosol Air Qual Res, 2017; 17: 198-208. | AAQR |
| The Infectious Nature of Patient-Generated SARS-CoV-2 Aerosol | Santarpia | Collected aerosol samples around 6 Covid patients and assessed virus in particles of <1um, 1-4um, and >4.1um. Found infectious, replicating virions in three <1um samples. Found less/no viable virus in larger samples, but methodology of collection may have damaged virions in the larger bins. | doi: https://doi.org/10.1101/2020.07.13.20041632
Posted July 21, 2020 |
medRxiv |
| The airborne lifetime of small speech droplets and their potential importance in SARS-CoV-2 transmission | Stadnytskyi | Laser light scattering observations have revealed that loud speech can emit thousands of oral fluid droplets per second. In a closed, stagnant air environment, they disappear from the window of view with time constants in the range of 8 to 14 min, which corresponds to droplet nuclei of ca. 4 um diameter, or 12- to 21um droplets prior to dehydration. Probability that speech droplets pass on an infection: how long droplet nuclei remain airborne (proportional to d-2) and the probability that droplets encapsulate at least one virion (proportional to d3), the product of which is proportional to d. Probability that a 50-μm-diameter droplet, prior to dehydration, contains at least one virion is ~37%. For a 10-μm droplet, this probability drops to 0.37%. At saliva viral load of 7 × 106 per milliliter, the probability that a 1μm droplet nucleus (scaled back to its originally hydrated 3μm size) contains a virion is only 0.01%. | Valentyn Stadnytskyi, Christina E. Bax, Adriaan Bax, and Philip Anfinrud
"The airborne lifetime of small speech droplets and their potential importance in SARS-CoV-2 transmission" PNAS June 2, 2020 117 (22) 11875-11877; first published May 13, 2020; https://doi.org/10.1073/pnas.2006874117 |
PNAS |
| Relationship of George Floyd protests to increases in COVID-19 cases using event study methodology | Valentine | The George Floyd protests led to increases in Covid. In the eight cities analyzed, all had positive abnormal growth in infection rate. In six of the eight cities, infection rate growth was positive and significant. This advocates strongly for continued social distancing, as the protests did not follow social distancing guidelines. Also, since the protests were held outdoors, merely being outdoors is not sufficient to stop spread. | Randall Valentine, Dawn Valentine, and Jimmie L Valentine
J Public Health (Oxf). 2020 Aug 5 : fdaa127. Published online 2020 Aug 5. doi: 10.1093/pubmed/fdaa127 | NIH |
| Infectious virus in exhaled breath of symptomatic seasonal influenza cases from a college community | Yan 2018 | smaller droplets have higher virus concentrations than larger droplets | J. Yan, M. Grantham, J. Pantelic, P.J.B. de Mesquita, B. Albert, et al., Infectious virus in exhaled breath of symptomatic seasonal influenza cases from a college community, Proc. Natl. Acad. Sci. U.S.A. 115 (5) (2018) 1081–1086. | doi |
| Title | 50um video | Video evidence of 50 micron droplets wafting in lab | Citation |