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"Face masks: what the data say" Topic


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Asteroid X31 Oct 2020 3:47 p.m. PST

Did you actually read what you posted above?

I know I did.

The key words being "a mask" followed by "especially" then "or other tightly fitting mask".

All cloth masks are tightly fitting. Even disposable surgical types have a metal band to pinch above the nose which then make them tightly fitting.

Personal logo McKinstry Supporting Member of TMP Fezian31 Oct 2020 9:54 p.m. PST

"or other tightly fitting mask".

As has been covered extensively and mentioned specifically in virtually everything posted, the 'tight' fit refers only to N-95 or similar. Anyone who has worn simple cloth or paper versus a true N-95 knows the difference.

Asteroid X31 Oct 2020 10:03 p.m. PST

the 'tight' fit refers only to N-95

Anecdotal evidence isn't.

Personal logo McKinstry Supporting Member of TMP Fezian31 Oct 2020 11:57 p.m. PST

especially an N95 mask or other tightly fitting mask

Direct quote from your last unsourced unattributed post. Don't want to be called on it, don't use an article using it. Do you really claim all commonly used masks are tight?

You also might look up the proper use of anecdotal.

Asteroid X01 Nov 2020 8:23 a.m. PST

Are you really claiming commonly used cloth masks are not tight fitting?

If you keep making unsourced unattributed claims about what is or is not tight fitting and do not want to be called on it don't keep saying it.


Are you asking me to have to define anecdotal for you?

Just highlight the word and right click on "define". If you do it for yourself you will have a higher chance of remembering it instead of just getting someone to do it for you.

rjones6901 Nov 2020 8:35 a.m. PST

N95 masks are tight-fitting. Commonly-used cloth masks, including even surgical masks, are loose-fitting, NOT tight-fitting.

Source with attribution:

PDF link

(Centers for Disease Control and Prevention (CDC), "Understanding the Difference")

Asteroid X01 Nov 2020 10:19 a.m. PST

Yes, those are surgical masks. McKinistry was making the assertion all cloth masks are loose fitting, as well.

The real question is what, exactly, defines "loose" and "tight"? Airflow? If so, how much and in what ways.

Like he said, "Anecdotal evidence isn't."

Personal logo McKinstry Supporting Member of TMP Fezian01 Nov 2020 12:35 p.m. PST

You have to have an anecdote for something to be anecdotal. Please identify the anecdote.

McKinistry was making the assertion all cloth masks are loose fitting, as well.

Most are and I don't believe I've used the word 'all'.

Facts are per AMA, CDC, NIH, WHO and virtually every competent government health entity on the planet, masks work in limiting the spread of Covid.

Given the US is running at 500,000+ cases per week, the worst showing ever in the pandemic, with the inevitable lagging hospitalizations and deaths. That 80% of ICU beds nationally are full and that deaths are closing in on a steady 1,000 per day, arguing against masks is the equivalent of refusing to move to higher ground in a flood.

Asteroid X01 Nov 2020 12:46 p.m. PST

masks work in limiting the spread of Covid.

That statement alone is an anecdote.

There is no evidence to support this given comparisons to regions that have not implemented mask usage and studies indicating mask users who have tested positive.

link

PDF link

TMP link

rjones6901 Nov 2020 1:31 p.m. PST

Yes, those are surgical masks. McKinistry was making the assertion all cloth masks are loose fitting, as well.

All cloth masks ARE loose-fitting.

The differences between surgical masks and commonly-used cloth or paper masks – for example, homemade masks or the masks commonly sold at a target or CVS – are the following:

Surgical masks are regulated by the FDA, and provide protection to both other people and to the mask wearer himself/herself: "provide the wearer protection against large droplets, splashes, or sprays of bodily or other hazardous fluids".

Non-FDA-regulated masks, e.g., homemade cloth masks, provide protection to other people but do not protect the mask wearer: "Protects other people by reducing the amount of respiratory droplets expelled by a person who may be infected but not showing signs of illness", "do not protect the wearer".

Source with attribution:
PDF link
(Minnesota Department of Health, "The Difference Between Alternative Masks and Surgical Masks for COVID-19")


But regardless of whether it's a surgical mask or a non-surgical cloth/paper mask, masks are loose-fitting, as contrasted for example with a respirator like an N95:

"Masks are loose fitting and may not provide full protection from breathing in airborne pathogens, such as viruses.
• Face masks (non-surgical masks) may not provide protection from fluids or may not filter particles, needed to protect against pathogens, such as viruses. They are not for surgical use and are not considered personal protective equipment.
• Surgical masks are fluid-resistant, disposable, and loose-fitting devices that create a physical barrier between the mouth and nose of the wearer and the immediate environment. They are for use in surgical settings and do not provide full protection from inhalation of airborne pathogens, such as viruses."

Source with attribution:
link
(U.S. Food & Drug Administration (FDA), "Face Masks and Surgical Masks for COVID-19")

Personal logo McKinstry Supporting Member of TMP Fezian01 Nov 2020 2:14 p.m. PST

That statement alone is an anecdote.

Here is the definition.

anecdote
[ˈanəkˌdōt]
NOUN
a short amusing or interesting story about a real incident or person.
"told anecdotes about his job" · [more]

Here is the statement.

"masks work in limiting the spread of Covid"

Not an anecdote. It is a declarative statement.

There is no evidence

I'm sure the CDC, NIH, WHO and the FDA along with the Doctors Fauci and Brix of White House Corona Virus Task Force will be shocked, shocked I tell you, to find out that random politically biased pseudo-science on the internet as opposed to the overwhelming majority of doctors and public health officials supersedes their education and experience.

As will the University of Washington.
link

or the Cleveland Clinic
link

and of course the CDC
link

rjones6901 Nov 2020 2:54 p.m. PST

The real question is what, exactly, defines "loose" and "tight"? Airflow? If so, how much and in what ways.
Like he said, "Anecdotal evidence isn't."

The difference between loose-fitting and tight-fitting is very simple to understand.

A tight-fitting respirator like an N95 is ~95% efficient at filtering out COVID-19 viruses free-floating in air (diameters of 0.06 to 0.140 microns, with an average diameter of ~0.1 microns). A loose-fitting mask, on the other hand, filters out respiratory droplets, which have dimensions of 5-10 microns.

So a loose-fitting mask can protect the wearer against respiratory droplets (5 to 10 microns) that contain COVID-19 viruses, but not against free-floating virus particles themselves (0.06 to 0.140 microns). A respirator like an N95, on the other hand, will stop a very high percentage (~95% or more) of COVID-19 virus particles free-floating in air.

Sources with attribution:

Filtration efficiency of N95 masks:
link
("Performance of N95 respirators: filtration efficiency for airborne microbial and inert particles", Y Qian, K Willeke, S A Grinshpun, J Donnelly, C C Coffey)


COVID-19 viruses have diameters ranging from 0.06 to 0.140 microns, and thus have an average diameter of ~0.1 microns. Respiratory droplets have a diameter of 5 to 10 microns:

link
("SARS-CoV-2 (COVID-19) by the numbers",
Yinon M Bar-On, Avi Flamholz, Rob Phillips, and Ron Milo)

link
("The Size of SARS-CoV-2 Compared to Other Things", Benedette Cuffari)

Asteroid X02 Nov 2020 9:29 p.m. PST

A tight-fitting respirator like an N95 is ~95% efficient at filtering out COVID-19 viruses free-floating in air (diameters of 0.06 to 0.140 microns, with an average diameter of ~0.1 microns). A loose-fitting mask, on the other hand, filters out respiratory droplets, which have dimensions of 5-10 microns.

That's not fitting, that is filtering.

Asteroid X02 Nov 2020 10:38 p.m. PST

A "tight fitting" mask will limit air passage (leakage) around the edges.

The porosity of the material will determine the filtration. Some cloth masks have several layers and a removable charcoal filter.

rjones6904 Nov 2020 10:30 a.m. PST

That's not fitting, that is filtering.

The effectiveness of an N95 respirator depends on BOTH filtering AND fitting.

The N95 respirator has to filter out particles from passing THROUGH the respirator, and also fit tightly enough to prevent those particles from BYPASSING the filter by going AROUND the edge of the respirator, via a gap between the respirator and the wearer's skin.

This is clearly stated by the CDC:

"Three key criteria are required for a respirator to be effective:
1.The respirator filter needs to be highly effective at capturing particles that pass through it,
2.The respirator must fit the user's face snugly (i.e., create a seal) to minimize the number of particles that bypass the filter through gaps between the user's skin and the respirator seal; and
3.The respirator must be put on (donned) and taken off (doffed) correctly before and worn throughout the exposure."

Source with attribution:
link
(Centers for Disease Control and Prevention (CDC), "Proper N95 Respirator Use for Respiratory Protection Preparedness")


Filtering and fit are both key criteria in providing respiratory protection, i.e., in reducing the number of particles breathed in by the wearer. It's obviously a requirement that an N95 filter out 95% or more of particles from passing through the respirator. It's also a requirement, as clearly stated by the CDC, that the respirator fit the wearer's face so that he/she doesn't breathe in particles that bypassed the filter because of gaps between the respirator and the wearer's skin.

As the CDC clearly states:

"To be effective, respiratory protection requires three main things: (1) the respirator has to be put on correctly and worn during the exposure; (2) the respirator needs to capture 95% or more of the particles that pass through the filter (where the 95 in N95 comes from); and (3) the respirator must fit the user's face to minimize the risk that particles will simply bypass the filter and get into the breathing zone through gaps between the user's skin and the respirator seal. If any one of these falls short, the wearer could be in store for bigger problems than an annoying wobble."

Source with attribution:
link
(Centers for Disease Control and Prevention (CDC), "N95 Day 2016: Proper Use, Filtration, and Fit – The Three-Legged Stool of Respiratory Protection")

rjones6904 Nov 2020 12:11 p.m. PST

A "tight fitting" mask will limit air passage (leakage) around the edges.

A device like an N95 will provide an adequate seal to prevent air leakage around the edges. A surgical mask or a non-FDA-regulated, commonly used mask will not do that.

As the CDC clearly states:

"Surgical masks are designed to provide barrier protection against droplets, however they are not regulated for particulate filtration efficiency and they do not form an adequate seal to the wearer's face to be relied upon for respiratory protection. Without an adequate seal, air and small particles leak around the edges of the respirator and into the wearer's breathing zone.

When properly fitted and worn, minimal leakage occurs around the edges of an N95 respirator when the user inhales, ensuring that the user's breathing air is being directed through the filter material."

Source with attribution:
link
(Centers for Disease Control and Prevention (CDC), "Proper N95 Respirator Use for Respiratory Protection Preparedness")

So a surgical mask does "not form an adequate seal to the wearer's face to be relied upon for respiratory protection" and thus "air and small particles leak around the edges of the respirator and into the wearer's breathing zone".

And surgical masks are regulated and cleared by the FDA. Commonly-used cloth or paper masks – for example, homemade masks or the masks commonly sold at a target or CVS – are not even regulated or cleared by the FDA, and thus are even less effective than a surgical mask.

Thus masks – whether surgical masks or non-FDA-regulated, commonly used masks – do not provide adequate protection against air and small particles leaking around the edges of the mask and being breathed in by the mask wearer.

Asteroid X04 Nov 2020 7:07 p.m. PST

It's possibly all a moot point anyway. Continued evidence seems to show how useless the masks are.

Canada has quietly revised its guidelines on how COVID-19 spreads to include the risk of aerosol transmission, weeks after other countries and international health organizations acknowledged the airborne threat of the coronavirus.

"This is pretty major," said Linsey Marr, one of the top aerosol scientists in the world and an expert on the airborne transmission of viruses at Virginia Tech. "The big difference now is that ventilation is important — distancing alone is not enough."

SECOND OPINIONCanada still downplays risk of airborne spread of coronavirus despite WHO, CDC guidance

CBC News pressed the federal agency last month on why it still made no mention about the risk of aerosols despite other international agencies doing so.

The U.S. Centers for Disease Control and Prevention (CDC) updated its guidelines in early October to include that COVID-19 can sometimes be spread by airborne transmission, after mistakenly posting and later removing a draft version of guidelines in late September.

The World Health Organization also came under fire in July after 239 scientists from 32 countries wrote an open letter calling on the United Nations agency to update its messaging on the risk of airborne transmission of the coronavirus.

The WHO amended its guidelines days after the letter and acknowledged the possibility that aerosols can lead to outbreaks of COVID-19 in places like choir practices, restaurants and fitness classes.

link

rjones6905 Nov 2020 5:16 a.m. PST

It's possibly all a moot point anyway. Continued evidence seems to show how useless the masks are.

The link you posted does not say or even imply that masks are useless. In fact, it says exactly the opposite. It states that virtually any mask, almost any single layer of fabric, will work against large droplets.

And multilayer masks will work against large droplets AND aerosols.

As Dr. Linsey Marr, who is "one of the top aerosol scientists in the world", clearly states:

"If we were only concerned about large droplets, then pretty much almost any piece of single layer of fabric would work," she said.

"But because we are concerned about aerosols, then we do need to think about the quality and fit of our masks and we know that having multiple layers improves the filtering performance of masks."

So, according to the very link you posted, masks work: single-layer masks work against large droplets, and multilayer masks provide additional protection against aerosols.

And that additional protection against aerosols, by wearing multilayer masks and by good ventilation of interior spaces, is the major point of the article:

"This is pretty major," said Linsey Marr, one of the top aerosol scientists in the world and an expert on the airborne transmission of viruses at Virginia Tech. "The big difference now is that ventilation is important — distancing alone is not enough."


That concern about indoor aerosol transmission is why Dr. Theresa Tam, Canada's Chief Public Health Officer, stated – in the very link you posted – that people should wear masks: multilayer masks.

Canada's Chief Public Health Officer Dr. Theresa Tam recommended the use of three-layer non-medical masks Tuesday to prevent the spread of COVID-19 ahead of winter weather that could bring more people together indoors.


The United States Centers for Disease Control and Prevention also recommends that people wear multilayer masks:

Wear masks with two or more layers to stop the spread of COVID-19

Source with attribution:
link
(Centers for Disease Control and Prevention (CDC), " How to Select, Wear, and Clean Your Mask")


So, the link you posted clearly states:

(a) Masks are useful against both large droplets and aerosols;
(b) A single-layer mask, made of almost any piece of fabric, will work against large droplets;
(c) A multilayer mask will provide additional protection against aerosols;
(d) Therefore, it is recommended that people wear multilayer masks to protect against both large droplets and aerosols.


For those who wish to go to the link wmyers posted and from which I quote in my post:

link

Asteroid X05 Nov 2020 6:41 a.m. PST

I really don't think most care anymore.

The filtration effectiveness on cloth masks is extremely low, the negative side effects very high and the virus itself is not filtered by the mask when aerosolized.

People are terrified by the media (rightly or wrongly) and will grasp onto whatever method they think will prevent what they fear without regard for valid effectiveness.

Au pas de Charge10 Nov 2020 7:55 p.m. PST

Hmm, seems like the truth is finally out

link

rjones6911 Nov 2020 12:36 p.m. PST

the virus itself is not filtered by the mask when aerosolized.

Your comment confuses an aerosol particle, which can contain hundreds of thousands to millions of virus particles, with the virus particle itself.

Aerosol particles are small droplets with diameters less than 10 microns. As was clearly stated by one of the world's top aerosol scientists, and by Canada's Chief Public Health Officer, and by the United States Centers for Disease Control and Prevention (CDC), a multilayer mask provides protection against aerosols.

This was clearly stated, wmeyers, in a link you yourself posted; see my previous post in this thread from 05 Nov 2020 4:16 a.m. PST.


The CDC has quantified how effective a multilayer mask is at filtering out aerosols, in the CDC link that MiniPigs posted:

"Multi-layer cloth masks block release of exhaled respiratory particles into the environment, along with the microorganisms these particles carry. Cloth masks not only effectively block most large droplets (i.e., 20-30 microns and larger) but they can also block the exhalation of fine droplets and particles (also often referred to as aerosols) smaller than 10 microns; which increase in number with the volume of speech and specific types of phonation. Multi-layer cloth masks can both block up to 50-70% of these fine droplets and particles and limit the forward spread of those that are not captured. Upwards of 80% blockage has been achieved in human experiments that have measured blocking of all respiratory droplets, with cloth masks in some studies performing on par with surgical masks as barriers for source control."

Source with attribution:
link
(Centers for Disease Control and Prevention (CDC), "Scientific Brief: Community Use of Cloth Masks to Control the Spread of SARS-CoV-2")


So, a multilayer mask blocks 50-70% of aerosol particles (diameter < 10 microns) from being released into the environment when the mask wearer exhales.

Your comment about "the virus itself is not filtered by the mask when aerosolized" confuses these aerosol particles (< 10 microns), that contain virus particles, with the virus particles themselves (~0.1 microns).

Since a virus particle has a diameter of ~0.1 microns, a 10 micron aerosol droplet will contain ~100,000 to 1,000,000 virus particles (this is simple geometry).

While it is true that a mask won't filter out individual virus particles free-floating in the air, a multilayer mask (which is the type of mask recommended by Canada's Chief Public Health Officer and by the US CDC) will filter out 50-70% of aerosol particles.

And each aerosol particle blocked is equivalent to blocking 100,000 to 1,000,000 individual virus particles from being exhaled into the environment.

Thus it is recommended that people wear multilayer masks to protect against aerosols and large droplets.

Martin From Canada11 Nov 2020 1:34 p.m. PST

I've been busy successfully defending my thesis, doesn't seem like I missed much.

USAFpilot14 Nov 2020 5:38 p.m. PST

These 12 graphs show that mask mandates do nothing to stop the spread of Covid

link

Personal logo McKinstry Supporting Member of TMP Fezian15 Nov 2020 2:02 p.m. PST

link

CDC Guidelines

Asteroid X15 Nov 2020 6:50 p.m. PST

Guidelines that don't acknowledge masks are not the answer (and those demanding their usage are not following their own demands). Apparently not social distancing either.

One law for them and another one for us.

Or is it they just know the true score.

YouTube link

link

Asteroid X19 Nov 2020 9:48 p.m. PST

More

link

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