Naked Science Forum

Life Sciences => Physiology & Medicine => COVID-19 => Topic started by: chris on 10/03/2020 07:47:35

Title: Are face masks effective against Covid-19 transmission?
Post by: chris on 10/03/2020 07:47:35
Aaron has been in touch to say

Quote
Dear Chris,

I am a regular listener of the Naked Scientists. I have listened to all of your shows from the beginning. I know that Chris has a pet hate for the wearing of surgical masks as a preventative measure during this awful viral outbreak. I am living in China.

There is one major benefit of wearing these masks that I feel Chris may have overlooked. The masks stop an individual from touching their mouth or nose. As Chris has mentioned many times in various podcasts the most important thing a person can do is wash their hands regularly..So a physical barrier acting as a constant reminder to avoid touching your face must be a positive thing. I feel to state that the masks do nothing to prevent catching the virus is therefore not entirely true.

As a doctor I think Chris has a valid point in citing various studies that indicate wearing surgical masks has little or no effect on flu prevention. I would be interested to hear his opinion on the masks acting as a psychological reminder to avoid touching ones face.

Thank you all for your wonderful podcasts (https://www.thenakedscientists.com/podcasts).


What does everyone think?
Title: Re: Are face masks effective against Covid-19 transmission?
Post by: chris on 10/03/2020 07:51:59
Thank you for your kind feedback and for passing on your thoughts.

You are quite right: these masks do have a psychological effect in terms of reminding people about infection risks, but I'm not sure there's any evidence that people wearing these things touch their faces - or the masks - any less frequently.

In fact, by definition, mask wearers need to touch their faces more frequently: to put on and take off the mask - for instance to eat and drink; o blow their noses; adjust the mask etc. This matters, because contact between the mask and potentially contaminated fingers can apply viruses to the mask surface; the particles can then make their way through the mask and be inhaled.

I would advise that, for medical staff and certain patients, wearing masks is highly effective at defending against disease spread, so long as they are used correctly.

But for the average - uninfected - person, using low-grade or non-medical standard masks, there is no benefit whatsoever and risk might increase for the reason outlined above. I would therefore forego using them.
Title: Re: Are face masks effective against Covid-19 transmission?
Post by: Petrochemicals on 11/03/2020 01:19:10
Thank you for your kind feedback and for passing on your thoughts.
Is that sarcasm Dr Chris ? Anyhoo I save to suggest your approximation of masks is wayward

My own theory is that facemasks are brilliant for anyone who is sneezing coughing or dribbling in anyway, to help not spread the virus. As for protection against catching viruses and pollution they are not very effective exept for incidental passing threats direct to the face. There is a reason that modern respirator equipment is deemed ineffective unless "face fit". Stopping airborn water droplets is more desirable !

https://www.hse.gov.uk/respiratory-protective-equipment/fit-testing-basics.htm
Title: Re: Are face masks effective against Covid-19 transmission?
Post by: Colin2B on 11/03/2020 08:30:04
Thank you for your kind feedback and for passing on your thoughts.
Is that sarcasm Dr Chris ?
I donít think so. My experience is that Chris welcomes any opinion within the rules, feedback is always useful.

To add my opinion (and this is opinion, not based on knowledge) surgical masks are there to prevent infections from doctor to patient. Although they might stop some airborne droplets they also raise the humidity a person is breathing which could change the survival rate of any virus. I think the points Chris makes about contamination of the mask is valid.
Title: Re: Are face masks effective against Covid-19 transmission?
Post by: Petrochemicals on 13/03/2020 20:24:09
Thank you for your kind feedback and for passing on your thoughts.
Is that sarcasm Dr Chris ?
I don’t think so. My experience is that Chris welcomes any opinion within the rules, feedback is always useful.

To add my opinion (and this is opinion, not based on knowledge) surgical masks are there to prevent infections from doctor to patient. Although they might stop some airborne droplets they also raise the humidity a person is breathing which could change the survival rate of any virus. I think the points Chris makes about contamination of the mask is valid.
It does make a wonderful evapouration medium, this will surely take water droplets with it. Given that C19 survives for 3 days in outdoor conditions(so I have been informed), this makes a wonderful contamination device. Perhaps mask disposal after 15 minutes for those who are forced to wear them ?

I do not think the humidity the person is breathing will alter, if you have ever used a propper sealed respitator from the atmosphere, not gas tank, you will notice the difference in effort to draw breath.  Face masks with the elastic draw of breath  just goes up the sides !
Title: Re: Are face masks effective against Covid-19 transmission?
Post by: Bored chemist on 13/03/2020 23:46:39
It does make a wonderful evapouration medium, this will surely take water droplets with it.
You might be "sure" of that, I'm not.
I know that water evaporates, but leaves things like salt behind.
Perhaps mask disposal after 15 minutes for those who are forced to wear them ?
What orifice did you get that number from?

Having said that there's some truth to this
  Face masks with the elastic draw of breath  just goes up the sides !

Unless the mask fits properly (and there's a fairly involved testing method to see if it does) then all it does is stop you picking your nose.
Title: Re: Are face masks effective against Covid-19 transmission?
Post by: id2000 on 14/03/2020 12:41:11
I struggle trying to make sense of the conflicting information about face masks. The Guardian mentions that some studies indicate masks can reduce the risk of infection by a factor of 5.

I have noticed that if I spend time talking to a friend who is coughing or spluttering then it is not unusual to notice tiny droplets on my spectacles when I remove them. Presumably these are the droplets that can carry infectious material? In which case, if spectacles form an effective barrier for the eyes, why not face masks for the nose & mouth?

I appreciate that walking in the street I am unlikely to encounter the virus so there is no point wearing one, but what about on a flight or long distance bus journey where one could be a few seats away from an infected person?

I am due to make two coach trips; one in and one out of Oxford (which seems to be a bit of a hot spot for Corona). I am in an at-risk group and so wonder if I should wear a mask on the coach or perhaps it would be better to cancel the trip.
Title: Re: Are face masks effective against Covid-19 transmission?
Post by: Bored chemist on 14/03/2020 13:21:42
In which case, if spectacles form an effective barrier for the eyes, why not face masks for the nose & mouth?
Spectacles don't have holes in them to let air through.
Also the tiny droplets can be swept round masks or glasses by air currents- notably those due to breathing.

If the mask isn't properly fitted and sealed it's really not much use.

There's a pessimistic estimate that there are about 10,000 undiagnosed cases in the UK at the moment.
And we have a population of about 70 million.
So there's a roughly 1 in 7000 chance of any particular person having it.
Are there 7000 people on the coach?
If not, it's likely that nobody on that coach has the virus.

Can we please leave the masks for those who actually need them?
Title: Re: Are face masks effective against Covid-19 transmission?
Post by: id2000 on 14/03/2020 15:00:17
Spectacles don't have holes in them to let air through.

I had assumed that a droplet that is visible to the naked eye would not penetrate say an FFP2 mask?

Also the tiny droplets can be swept round masks or glasses by air currents- notably those due to breathing.

But presumably the exposure would be reduced?


There's a pessimistic estimate that there are about 10,000 undiagnosed cases in the UK at the moment.
And we have a population of about 70 million.
So there's a roughly 1 in 7000 chance of any particular person having it.
Are there 7000 people on the coach?
If not, it's likely that nobody on that coach has the virus.

Yes, this was my original thinking - the risks seem vanishingly small - but after thinking about it some more I am less sure.

Firstly, I am travelling through Oxfordshire so I could use the Oxfordshire stats (not all the passengers will originate from Oxfordshire but I am erring on the side of caution). Up to 12th March there were 22 cases recorded in Oxfordshire - when I travel I assume there will be 44 recorded cases (assuming cases double every 4 days).

When the 10,0000 figure for the UK was estimated it was approximately 15 times the recorded number at that time. So applying the same rule to the Oxfordshire number gives 15x 44 = 660 actual cases when I travel.

The Oxfordshire population is 687,524 so 660/687,524 = 0.00096. So that I think is the chances of someone in the local population being infected. Unfortunately I have to change buses in Oxford - so two buses on the outward trip and two on the return - say 30 passengers in each = 120 in total. So I think the probability of a passenger being free from infection is 1 - 0.00096 =  0.99904 and the probability of all 120 being free of it = 0.99904^120 = 0.89 - so actually an 11% risk of encountering an infected person- no longer vanishingly small. I am not sure if I have calculated the probabilities correctly - 40 years since I did them in the classroom.



Can we please leave the masks for those who actually need them?

I have a half used pack of 3M FP2 masks acquired long before Corona for DIY work so would not be depriving others.
Title: Re: Are face masks effective against Covid-19 transmission?
Post by: Bored chemist on 14/03/2020 15:14:39
I had assumed that a droplet that is visible to the naked eye would not penetrate say an FFP2 mask?
True, but the droplets that are small enough to get inhaled may be small enough to get through (or round).
A droplet doesn't need to be visible to be infectious.
Title: Re: Are face masks effective against Covid-19 transmission?
Post by: Bored chemist on 14/03/2020 15:24:30
This may help
https://www.hse.gov.uk/research/rrpdf/rr619.pdf
Title: Re: Are face masks effective against Covid-19 transmission?
Post by: Colin2B on 15/03/2020 09:14:13
I do not think the humidity the person is breathing will alter, if you have ever used a propper sealed respitator from the atmosphere, not gas tank, you will notice the difference in effort to draw breath.  Face masks with the elastic draw of breath  just goes up the sides !
Whenever Iíve used them in cold air Iíve noticed condensation on the outlets and sometimes on inside.
I decided to try testing humidity yesterday. I used a 3M disposable dust mask P2. Relative humidity was 48%, after 2min I put the probe inside the mask and recorded 95%. Not surprising as we breath out a lot of moisture.

This may help
https://www.hse.gov.uk/research/rrpdf/rr619.pdf
Also, this one might, backs up much of what you are saying:

 https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5058571/
Title: Re: Are face masks effective against Covid-19 transmission?
Post by: Petrochemicals on 15/03/2020 21:04:08
I do not think the humidity the person is breathing will alter, if you have ever used a propper sealed respitator from the atmosphere, not gas tank, you will notice the difference in effort to draw breath.  Face masks with the elastic draw of breath  just goes up the sides !
Whenever I’ve used them in cold air I’ve noticed condensation on the outlets and sometimes on inside.
I decided to try testing humidity yesterday. I used a 3M disposable dust mask P2. Relative humidity was 48%, after 2min I put the probe inside the mask and recorded 95%. Not surprising as we breath out a lot of moisture.

Did your earlier comment mean the humidity of the mask and the breeding ground for bacteria on the wearers intake of breath, rather than infecting anyone else, so possibly infecting the wearer? I was thinking more about leaks.
Title: Re: Are face masks effective against Covid-19 transmission?
Post by: Colin2B on 16/03/2020 05:52:04
Did your earlier comment mean the humidity of the mask and the breeding ground for bacteria on the wearers intake of breath, rather than infecting anyone else, so possibly infecting the wearer?
Context was supporting @chris in his comment about contamination, when fitting, adding to infection of wearer. Extra humidity can increase risk of viruses in droplet or infected material surviving.
Title: Re: Are face masks effective against Covid-19 transmission?
Post by: set fair on 21/03/2020 00:31:27
Taking what the government and health authories say as true ie masks won't offer any protection to the wearer but they will reduce infections passed on by the wearer.

Consider the first 100 people to be infected in the UK and let us say they went on to infect 250 more people. Then the question is :- would tthey have infected less than 250 people had all 100 of them been wearing face masks from the moment of their being infected? I don't think the answer can be anything but yes. Conclusion, everbody should be wearing masks.
Title: Re: Are face masks effective against Covid-19 transmission?
Post by: Petrochemicals on 26/03/2020 23:04:54
I know that someone was ridiculed by the wider stage for suggesting medical staff could use military cbn respiration devices, but given that medical staff are dying at 12 percent of covid dead, surely its a good idea, as face masks OBVIOUSLY DO NOT WORK.
Title: Re: Are face masks effective against Covid-19 transmission?
Post by: set fair on 27/03/2020 14:56:57
I know that someone was ridiculed by the wider stage for suggesting medical staff could use military cbn respiration devices, but given that medical staff are dying at 12 percent of covid dead, surely its a good idea, as face masks OBVIOUSLY DO NOT WORK.

Clearly the masks don't prevent medical staff from being infected, but that doesn't mean that they don't reduce the spread. The medical staff wash their hands and still get infected that doesn't mean that OBVIOUSLY HAND WASHING DOES NOT WORK. For a look at the difference between counties using masks and those not, see the chart at 19:20 in this video We should all be wearing masks, even home made cotton ones washed and reworn slow the rate of spread. I wouldn't argue with your comment on military cbn respiration devices.
Title: Re: Are face masks effective against Covid-19 transmission?
Post by: Petrochemicals on 30/03/2020 01:34:45
You have to ask of our motives really, during Ebola, we thought they where adequate(https://www.thenakedscientists.com/forum/proxy.php?request=http%3A%2F%2Fanimalnewyork.com%2Fwp-content%2Fuploads%2Fgetty-ebola.jpg&hash=001eb1fb1321abd9b37ae871ae681973)

http://animalnewyork.com/2014/picture-ebola-inside-west-african-isolation-ward/
Title: Re: Are face masks effective against Covid-19 transmission?
Post by: Petrochemicals on 30/03/2020 01:48:57
I know that someone was ridiculed by the wider stage for suggesting medical staff could use military cbn respiration devices, but given that medical staff are dying at 12 percent of covid dead, surely its a good idea, as face masks OBVIOUSLY DO NOT WORK.

Clearly the masks don't prevent medical staff from being infected, but that doesn't mean that they don't reduce the spread. The medical staff wash their hands and still get infected that doesn't mean that OBVIOUSLY HAND WASHING DOES NOT WORK. For a look at the difference between counties using masks and those not, see the chart at 19:20 in this video .
yep surgical masks prevent infection to some degree but dont protect the surgeon. As for the medical staff, what precautions are they not taking that they could other than better facial protection. There is a hole in the system, what is it? You can be sure that all hospital patients are treated inline with the standards of korean public apparel, and then some, so even surgical masks worn by patients are not very effective.

I doubt very much that medical staff are doing the wearing vinyl gloves and then having a fag with them on that I have seen. Or the licking of things in the way children have a tendancy too.
Title: Re: Are face masks effective against Covid-19 transmission?
Post by: alancalverd on 30/03/2020 08:57:49
The primary purpose of ordinary surgical kit is to prevent reasonably fit staff infecting the patient with common bugs like streptococcus. The positive pressure incoming air to theaters and critical wards is highly filtered and thus fit to breathe. But where the patient is known to carry a highly infective and novel virus, the problem is inverted and you need to step up the protection substantially, hence the full body, helmet and respirator kit worn by ebola nurses and now required for COVID.

As far as the general public is concerned, the probability and intensity of exposure are lower and can be further reduced (but not eliminated) in both directions with a simple mask.
Title: Re: Are face masks effective against Covid-19 transmission?
Post by: vhfpmr on 30/03/2020 23:12:56
This is interesting:
Title: Re: Are face masks effective against Covid-19 transmission?
Post by: Petrochemicals on 31/03/2020 18:15:07
A
This is interesting:

And  yet on that grapg italy and south Korea are closer than japan and singapore. 85 percent of statistics are made up !
Title: Re: Are face masks effective against Covid-19 transmission?
Post by: vhfpmr on 03/04/2020 11:53:36
A
This is interesting:

And  yet on that grapg italy and south Korea are closer than japan and singapore. 85 percent of statistics are made up !
They aren't made up, they're the stats from the Johns Hopkins University database that seems to be everyone's go to reference. That was a tweet from a virologist at Columbia University.

Here's a review published in Nature this morning, drawing attention to a study published a few years ago finding that surgical masks do reduce transmission of coronaviruses. To quote Dr Beale, in charge of the Cell Biology of Infection lab at the Crick Institute, "As far as I am concerned the mask 'debate' is over. They work.".
https://www.nature.com/articles/s41591-020-0843-2
Title: Re: Are face masks effective against Covid-19 transmission?
Post by: Petrochemicals on 03/04/2020 23:08:56
A
This is interesting:

And  yet on that grapg italy and south Korea are closer than japan and singapore. 85 percent of statistics are made up !
They aren't made up, they're the stats from the Johns Hopkins University database that seems to be everyone's go to reference. That was a tweet from a virologist at Columbia University.

Here's a review published in Nature this morning, drawing attention to a study published a few years ago finding that surgical masks do reduce transmission of coronaviruses. To quote Dr Beale, in charge of the Cell Biology of Infection lab at the Crick Institute, "As far as I am concerned the mask 'debate' is over. They work.".
https://www.nature.com/articles/s41591-020-0843-2



But i didnt say to mug grannies and club puppies to death
Title: Re: Are face masks effective against Covid-19 transmission?
Post by: set fair on 04/04/2020 00:45:09
Important note on masks. If yours has a valve, then you need to wear a bandana or scarf over it. The valve points down (usually) but you don't want to breath virus out if your infected but have no symptoms.

ps or glue it shut even better
Title: Re: Are face masks effective against Covid-19 transmission?
Post by: Petrochemicals on 10/04/2020 01:20:09
I do not think the humidity the person is breathing will alter, if you have ever used a propper sealed respitator from the atmosphere, not gas tank, you will notice the difference in effort to draw breath.  Face masks with the elastic draw of breath  just goes up the sides !
Whenever Iíve used them in cold air Iíve noticed condensation on the outlets and sometimes on inside.
I decided to try testing humidity yesterday. I used a 3M disposable dust mask P2. Relative humidity was 48%, after 2min I put the probe inside the mask and recorded 95%. Not surprising as we breath out a lot of moisture.

This may help
https://www.hse.gov.uk/research/rrpdf/rr619.pdf
Also, this one might, backs up much of what you are saying:

 https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5058571/

Ive just held a surcical mask tight on my face and breathed through it, it it very much hard work even at that low protection factor,  how easy is this with a p2 mask ?
Title: Re: Are face masks effective against Covid-19 transmission?
Post by: Colin2B on 10/04/2020 09:07:25
Ive just held a surcical mask tight on my face and breathed through it, it it very much hard work even at that low protection factor,  how easy is this with a p2 mask ?
I use P2 and P3 and find them very easy, but then I donít find a surgical mask offers any real resistance.
When working with irritating dusts eg hardwoods I use a forced air headset, just because the dust clogs the mask filters, so if you are in an area of high particle/droplet concentration itís worth changing regularly.
Title: Re: Are face masks effective against Covid-19 transmission?
Post by: RD on 10/04/2020 10:51:25
When working with irritating dusts eg hardwoods ...

Wood-dust can do more than irritate ...
Quote
An increased risk of adenocarcinoma of the sinonasal cavity is an important and serious problem associated with occupational exposure to wood dust. Adenocarcinoma constitutes about half of the total number of cancers induced by wood dust. An increased incidence of the squamous cell cancers can also be observed.
https://www.ncbi.nlm.nih.gov/pubmed/8231799
Title: Re: Are face masks effective against Covid-19 transmission?
Post by: Colin2B on 10/04/2020 15:52:55
Wood-dust can do more than irritate ...
Quote
An increased risk of adenocarcinoma of the sinonasal cavity is an important and serious problem associated with occupational exposure to wood dust. Adenocarcinoma constitutes about half of the total number of cancers induced by wood dust. An increased incidence of the squamous cell cancers can also be observed.
https://www.ncbi.nlm.nih.gov/pubmed/8231799
I know, yet another reason I take precautions, not to mention the effects on the lungs.
Title: Re: Are face masks effective against Covid-19 transmission?
Post by: set fair on 18/04/2020 16:31:52
Early to be certain but it looks like the Czechs have reduced R0 below 1... by wearing masks. Time one of the experts to break ranks and tell the truth. Homemade masks will work to slow the spread, if we all wear them. Be brave Chris, you don't want to be remembered for saying no to masks.

OK pretty please then  :D
Title: Re: Are face masks effective against Covid-19 transmission?
Post by: alancalverd on 19/04/2020 14:15:20
ve just held a surcical mask tight on my face and breathed through it, it it very much hard work even at that low protection factor,  how easy is this with a p2 mask ?
A surgical mask is not designed for inhaling - you inhale through the lack of fitting at the edges. A builder's dust mask is a lot more effective at trapping incoming aerosol (because it is a full fit) whilst providing enough total area  to allow relatively easy inhalation. If you use a HEPA-quality full-fit mask, you are doing as well as possible short of a Noddy suit. A one-way valve will stop your goggles steaming up.
Title: Re: Are face masks effective against Covid-19 transmission?
Post by: alancalverd on 19/04/2020 14:25:33
As far as statistics are concerned, most people will accept a 1 in 10,000 risk for a substantial reward, but would avoid anything above 1 in 100,000 if the reward is purely pleasure. My bands all cancelled gigs as soon as the probability of anyone present being infectious exceeded about 1 in 50,000.   
Title: Re: Are face masks effective against Covid-19 transmission?
Post by: Petrochemicals on 19/04/2020 15:32:34
ve just held a surcical mask tight on my face and breathed through it, it it very much hard work even at that low protection factor,  how easy is this with a p2 mask ?
A surgical mask is not designed for inhaling - you inhale through the lack of fitting at the edges. A builder's dust mask is a lot more effective at trapping incoming aerosol (because it is a full fit) whilst providing enough total area  to allow relatively easy inhalation. If you use a HEPA-quality full-fit mask, you are doing as well as possible short of a Noddy suit. A one-way valve will stop your goggles steaming up.
I agree whole heartedly.Point is that the air takes the least resistance, which is round the leaky edges. I think you would be surprised at the difference between a propper face fit mask, with its extravagent gussets and the pressure that has to be applied, and the paper single use dust mask that you describe, which are only good for stuff that falls to the ground fairly quickly. Amazon search for aerosol filter mask, they do not make them for nothing.

https://www.amazon.co.uk/spray-paint-masks/s?k=spray+paint+masks
Title: Re: Are face masks effective against Covid-19 transmission?
Post by: Petrochemicals on 13/01/2021 22:35:40
A bit late now.

https://www.bbc.co.uk/news/health-55537624
Title: Re: Are face masks effective against Covid-19 transmission?
Post by: alancalverd on 14/01/2021 01:03:27
Let's go back to the HSE's actual findings mentioned by BC several months ago

[quote[Using separate tests to measure levels of inert particles and live aerosolised influenza virus, our findings show that surgical masks provide around a 6-fold reduction in exposure. Live viruses could be detected in the air behind all surgical masks tested. By contrast, properly fitted respirators could provide at least a 100-fold reduction.[/quote]

So: simple surgical masks, as they are intended to do and have done for umpteen years, reduce the probability of you infecting anyone else because they intercept projected aerosol in your exhalate. If everybody wears them properly, they are more effective than not in reducing new infections in public places. But if you have to work in a known infective environment, you need a fitted HEPA respirator and scrupulous hand hygiene.