There is evidence both ways, its very hard to measure independent of other variables...
And yet it says...
'Cochrane (
7) and the World Health Organization (
8) both point out that, for population health measures, we should not generally expect to be able to find controlled trials, due to logistical and ethical reasons, and should therefore instead seek a wider evidence base'
Also
'Overall, direct evidence of the efficacy of mask use is supportive, but inconclusive. Since there are no RCTs, only one observational trial, and unclear evidence from other respiratory illnesses, we will need to look at a wider body of evidence.'
The best controlled trial I've seen was this one.
'Unlike other studies looking at masks, the Danmask study was a randomised controlled trial –
making it the highest quality scientific evidence.'
Also...
The evidence isn't clear-cut.
www.channel4.com
There's a few types of thing to measure. If your a mask wearer that doesn't have covid and walk into room with tiny covid particles in the air, the air sucked in around or through your mask is going to be infected.
If you have covid then you will be breathing it out in tiny particles, which will escape the masks or go through it. The things it will stop more are coughs and sneezes etc, as they will be much bigger particles. But seeing as a cough is so infrequent compared to breathing, breathing is a bigger contributer. Speaking actually gets singled out as the bigger contributer.
I did find this interesting though from your link..
"The ability of masks to filter particles depends on the particle size and trajectory, with smaller floating aerosols more challenging to filter than larger particles with momentum (
66). Because speech produces more particles containing the SARS-CoV-2 virus, and because transmission of SARS-CoV-2 without symptoms is associated with URT shedding, where particles formed through vocalization are likely to contain the virus, we should be particularly cognizant of the role of speech particles in transmission (
59). Speech particles lose their momentum and become much smaller shortly after ejection, which is likely to make them easier to filter by source control (as egress at the wearer) than by PPE (at ingress to an susceptible person). We will look at source control and PPE efficacy in turn."
So masks best chance are stopping it at source, rather than once its in a room and you walk in with mask on, you will prob still get it. However as we learn the chances of stopping it at source can be slim with the sizes of particles.
It mentioned that a test conducted were based on particles being micrometers not nanometres. Hence the below.
Dr Colin Axon warned some cloth masks have gaps that are invisible to the naked eye, but are 5000 times the size of viral Covid particles
www.telegraph.co.uk
'He warned some
cloth masks have gaps which are invisible to the naked eye, but are 5,000 times the size of viral Covid particles.
"The small sizes are not easily understood but an imperfect analogy would be to imagine marbles fired at builders' scaffolding, some might hit a pole and rebound, but obviously most will fly through," he told The Telegraph.'
From another source...
"In addition to mechanistic information, researchers have also evaluated the size and content characteristics of the SARS-CoV-2 particles. Upon analysis of negative-stained SARS-CoV-2 articles by electron microscopy, different researchers have had varying results, but the diameter of the virus has been found to range between 50 nm to 140 nm.
In addition to measuring the spherical size of the virus particle, it has also been confirmed that the length of the size tumors surrounding the outermost surface of SARS-CoV-2 can vary in length from 9 to 12 nm."
From the study you posted again.
"There are currently no studies that measure the impact of any kind of mask on the amount of infectious SARS-CoV-2 particles from human actions. Other infections, however, have been studied. One of the most relevant papers (
67) is one that compares the efficacy of surgical masks for source control for seasonal coronaviruses (NL63, OC43, 229E, and HKU1), influenza, and rhinovirus. With 10 participants, the masks were effective at blocking coronavirus particles of all sizes for every subject.
However, masks were far less effective at blocking rhinovirus particles of any size, or of blocking small influenza particles. The results suggest that masks may have a significant role in source control for the current coronavirus outbreak. The study did not use COVID-19 patients, and it is not yet known whether SARS-CoV-2 behaves the same as these seasonal coronaviruses, which are of the same family."
Although it blocks coronavirus of the same family it didn't block the smaller influenza particles, given we know covid is so small its likely a similar result.
Surgical masks can limit the release of droplets larger them 5 um or 5000 nanometres. Cloth will be worse.
Hence the marbles fired at scaffolding analogy.
We also have the fact the Scotland and Wales used masks to no noticeable gain.
At the end of the day we are meant to be returning to normality not bringing out mask mandates etc each time there's a mutation.
The truth remains that the government have done it to be seen to be doing something to cover thier backs, just incase.
