The claim-'The best available scientific evidence is that, when used correctly, wearing a face covering may reduce the spread of coronavirus droplets in certain circumstances, helping to protect others.’'
(https://www.gov.uk/government/publications/face-coverings-when-to-wear-one-and-how-to-make-your-own/face-coverings-when-to-wear-one-and-how-to-make-your-own
Basically the evidence does not exist as the data shows that ‘viral’ RNA mostly are in particles and mask only stop airdrops and not airborne transmission ie particles.Even the N95 ( respirator touted as best) gives warning that it does not eliminate transmission.
And my understanding is surgical mask( half mask) are not tested for particles/ viruses and are only tested for bacterial ( I presume droplets and not actual bacteria).
As apparently a doctor said quoted on radio , wearing a face-mask is as useful as carrying sand with a tennis racket
– 0.06-0.14 µm coronavirus– 0.3 µm -N95- (touted as the most efficient masks thus far)
leaving aside-the virus theory of disease and it’s transmission based on a belief system – impossible to prove that mask prevent transmission of anything but a theoretical assumption using physics and not biology or based on host health, immune system and resistance to diseaseProduction of infectious respiratory particles is dependent on the type and frequency of respiratory activity, type and site of infection and pathogen load. Further, relative humidity, particle aggregation and mucus properties influence expelled particle size and subsequent transmission. ( 2) Also incorrect mask wearing and how facial hair so prevents nothing.
Even when use Laboratory studies data government ‘official health advisors and fabricated science and facts-checkers ) shows clearly , that mask do not prevent ‘viral’ RNA particle transmission .
N95- (touted as the most efficient masks thus far) – only 85% filtration efficiency for particles smaller than 0.3 µm- ( 1)Also they have not tested or proved that is stops biological transmission so comes with a warning.Eg. N95- 3M respiratorWarning – This respirator helps protect against certain particulate contaminants but does not eliminate exposure to or the risk of contracting any disease or infection.(4)
Majority of ‘viral ‘ RNA are in small particles for which masks do not work.So masks are mainly designed to prevent droplets and not airborne transmission so do little to prevent spread of ‘coronavirus ’, let alone fabric masks.
Aerosol transmission routes of respiratory viruses have been classified by the WHO on the basis of equilibrium particle size. Droplet transmission is associated with particles sized >5 µm in diameter and airborne transmission is associated with particles sized ≤5 µm in diameter. Current infection control measures for respiratory viruses are directed at preventing droplet transmission, although epidemiological evidence suggests concurrent airborne transmission also occurs.(3)
Droplets and particles carry RNA, small particles carry more viral load than droplets.‘expelled particles carrying pathogens do not exclusively disperse by airborne or droplet transmission but avail of both methods simultaneously’(2)
Particle size (3)Droplet transmission ->5 µmParticle sized ≤5 µm
‘Coronavirus ‘size-coronaviruses 0.06-0.14 µm – (ref 1)
N-95 respiratorshave a tight-fitting design and are engineered to protect the wearer by removing 95 percent of particles, at least 0.3 µm and greater, from the air moving through it.
This study demonstrates that individuals with symptomatic respiratory viral infections produce both large and small particles carrying viral RNA on coughing and breathing.
On breathing –-58% of participants produced large particles (>5 µm) containing viral RNA– 80% produced small particles (≤5 µm) carrying viral RNA. ( 3)
On coughing,– 57% of participants produced large particles containing viral RNA and– 82% produced small particles containing viral RNA. ( 3 )
This indicates that expelled particles carrying pathogens do not exclusively disperse by airborne or droplet transmission but avail of both methods simultaneously and current dichotomous infection control precautions should be updated to include measures to contain both modes of aerosolised transmission.(2)
-healthy individuals generate particles between 0.01 and 500 μm-individuals with infections produce particles between 0.05 and 500 μm( 2)
Face masks.I do not know how the testing is done but definitely does not prove anything conclusive as applied to biology.It in as impossible to test in vivo ( can sort of interpret epidemiological data and those only interpretation through correlation and that data that have come out show mask make no difference or people who wear mask are more likely to have ‘covid’ ).
Production of infectious respiratory particles is dependent on the type and frequency of respiratory activity, type and site of infection and pathogen load. Further, relative humidity, particle aggregation and mucus properties influence expelled particle size and subsequent transmission. ( 2)
Masks are of specific interest in reducing the respiratory transmittance and exposure to viral particles. Although touted as the most efficient masks thus far, N95s have only an 85% filtration efficiency for particles smaller than 300 nm.36The COVID‐19 virus, however, has been shown to have a diameter range of 60‐140 nm, illustrating an unmet need for more efficient filtration masks.( 1)(Micron, also called micrometer, is symbolised as ‘μm’ and is equal to 0.001 mm or about 0.000039 inch.)
Should I Wear a Face Mask. by Cathy A. Spigarelli June 8, 2020
(https://thenewamerican.com/print/should-i-wear-a-face-mask/)‘ As an environmental, health, and safety manager responsible for respiratory protection, I understand that face masks can play a supportive role in protecting the wearer from airborne hazards if the proper mask is chosen under the right circumstances. I also know that face masks can be ineffective, can create new hazards, and should not be the first or only line of defense. Face masks should be relegated to those in an industrial, emergency services, or healthcare work setting where proper mask selection, training, fit testing, and mask inadequacies can be addressed. The general public, in community settings, should not be wearing face masks to lessen viral transmission, as the data and potential drawbacks do not support their use. Instead, the focus should be on the more-effective ways you can protect yourself and those around you.’
And made up guidelines on mask wearing for a ‘virus ‘ that only has never been isolated or proven to exist but for mask that are tested for bacterial filtration capacity and cannot find a study that shows that stops ‘viral’transmission
What’s the difference between Type I and Type II Masks?
Type I, and Type I R face masks have a BFE (bacterial filtration efficiency) of 95%, whereas Type II and Type II R face masks have a BFE of 98%. The breathing resistance, and splash resistance for Type I R and Type II R masks, are exactly the same.
( https://nhsprocurement.org.uk/covid-19-a-guide-to-face-masks/)
1-Potential nanoparticle applications for prevention, diagnosis, and treatment of COVID‐19- :25 September 2020https://onlinelibrary.wiley.com/doi/10.1002/VIW.20200105
2-The role of particle size in aerosolised pathogen transmission: a review- 2010(https://pubmed.ncbi.nlm.nih.gov/21094184/ )
3-Respiratory virus RNA is detectable in airborne and droplet particles) – Dec 2013(https://pubmed.ncbi.nlm.nih.gov/23959825/
4 – N95 respirator- 3 M makehttps://multimedia.3m.com/mws/media/175119O/1860-1860s-particulate-respirator-and-surgical-mask.pdf?&2EVuQEcuZgVs6EVs6E666666–
5-Respirator Trusted-Source Information -Updated November 3, 2020Surgical N95 Respiratorshttps://www.cdc.gov/niosh/npptl/topics/respirators/disp_part/respsource3surgicaln95.html
Face-masks ( no-one walks around in respirators) as in Europe certification only specify bacterial
https://www.irema.com/wp-content/uploads/2017/12/EN_14683-2005.pdf
Than mixed information on mask .
Eg. N95- 3M respiratorWarning – This respirator helps protect against certain particulate contaminants but does not eliminate exposure to or the risk of contracting any disease or infection.
( ( a EN14683 Type II/ASTM level 1 mask will need to meet the following specifications:Bacteria Filtration Efficiency (BFE): >98% (Size of typical bacteria at 3-5 microns)Particulate Filtration Efficiency (PFE): >99% 0.1 micron particle size)
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