As we continue to navigate these unprecedented times, KCBS Radio is getting the answers to your questions about the coronavirus pandemic. Every morning at 9:20 a.m. Monday-Friday we're doing an "Ask An Expert" segment with a focus on a different aspect of this situation each day.
Today we're diving back into the debate and research around face masks with Jeremy Howard, data scientist and researcher in residence at the University of San Francisco.
We did this about 10 days ago, and one would think everything would have settled down, the questions would have been resolved and we'd have moved on, but that certainly is not what has happened here. What's what's your experience over these last few weeks, as you've been pushing a message regarding masks?
Well, it's been interesting to see what's been happening. As I was concerned would happen, things in the southern states of the US, particularly Texas and Arizona, are looking really scary. They opened up in an unsafe way, they didn't require masks in those states, they opened up places where there's a lot of talking and socializing like bars. And so we've been seeing a really concerning rise in cases and hospital capacity now being reached in Houston, for example.
And so what we're now seeing is people perhaps, well definitely far too late, more and more states are now finally requiring masks. And we're now at the point where about 2/3 of the US population lives in regions that have mask requirements. So masks are kind of an old thing for some parts of the country, had them for a month or two now, and some parts of the country, it's something they're just getting the hang of again.
Will you walk us through the data you've been able to gather? This is, of course, a real time experiment, as we're all learning in many ways as to the efficacy of masks. And we're not talking necessarily about some high grade, medical grade mask. We're talking about a plain old piece of cloth.
So the best way I think to look at that is to look at the difference between regions that have masks and use them, require them and time periods that do versus those that don't. There's been three really great papers on this. One of them looks at 193 countries around the world and found that countries that have widespread masks usage or mask requirements have a 10 times lower transmission rate than countries that don't have widespread mask usage or requirements. We've seen a similar thing in a study of U.S. states. U.S. states that have a mask requirement have dramatically lower transmission rates. And a paper that just came out from Goldman Sachs yesterday found that based on these studies, they estimate if the remaining states add a mask requirement now, it will save the U. S economy about $1 trillion.
Is there any way to know, in these places that have mask requirements, what the level of compliance is?
It's not easy to know, but you can make a pretty good guess. And the way that compliance is tested is through two things. One, through surveys, which is asking people, and another is through just observing folks on the street. And it appears that in the U.S., in states that have a mask requirement, masks compliance is about 30% higher than in places that don't have a requirement. And so the difference between, say, 40% compliance and 70% compliance could be the difference between the virus spreading dramatically quickly versus it being largely controlled.
There remains confusion because people heard early on and are still hearing that some masks protect you, some masks don't, that there's no absolute protection. So what is the truth about the protective value of a mask both in terms of emitting virus and of ingesting it?
Yeah, it is confusing and it's particularly confusing because healthcare authorities lied to us in the early days of the pandemic and told us that masks definitely don't work in order to try to protect supplies for healthcare workers. And so when healthcare authorities don't tell us the truth, obviously we're going to get pretty distrustful when they try to change it later.
The truth is that nearly any kind of face covering does a great job of protecting others from you. And about half of people who get infected, get infected from people who don't even know they're sick, so that's really important. On the other hand, the ability of a mask to protect you from others varies a lot, depending on the material that's used and fit. So definitely a mask is better than no mask because it could stop you from potentially killing somebody without even knowing it. But to keep yourself safe as well, you want to be careful to get the best kind of mask you can.
Let's get to questions then, which have been sent in to askus@kcbsradio.com. First one: since many are still not wearing masks, I think it's time for us masks wearers to be more proactive to protect ourselves. Is there something we can do to make our masks not only protect others from us, but also protect us from others?
Yes, there is. And we've got an increasing amount of scientific research around this now. The two things we look at is material and fit. So on the material of your mask, it's good to have two layers of a tight weave cotton. So say, 600 threads per inch such as you might find in a high quality bed sheet, and then between those two layers of cotton, leave room for a pocket where you can insert a piece of paper towel. Paper towel is an amazing material because it doesn't have the same kind of regular weave that most fabrics do, and therefore there aren't holes for droplets or particles to get through. It actually looks very similar under an electron microscope to what surgical mask material looks like. So for material, either a combination of cotton and paper towel - and obviously the paper towel you would remove after each trip outside and replace with a new piece of paper towel, that's what I do.
Another good one is a combination of two layers of cotton and one layer of chiffon or two layers of cotton and one layer of silk. It actually turns out that having two different materials works a lot better than just one material because they would filter more different types of particles. So that's the material.
And then for fit, you want a good tight fit around the nose. And the best way to do that is to get a mask where there's room to insert - if it doesn't already have one - something like a paper clip or a pipe cleaner or a tightly rolled little piece of aluminum foil. And that gives you a moldable nose piece that you can kind of mold to the contours of your nose and get rid of those gaps. And then the second thing is to avoid the gap under the chin, so make sure the mask goes all the way around the bottom of the chin, and then avoid the gaps on the sides of the mask by getting one that ties all the way around the head rather than one with just ear loops.
Okay, well, that gets a pretty good landscape of architecture for the right kind of mask. Let's go on to the next one: I see people using the same masks going on for months now. They have to be filling up with bacteria, don't they? Isn't this a problem?
No more than your socks or your t-shirt or your underpants. These are all pieces of clothing which touch your skin and therefore you should wash them regularly in soap. And soap actually destroys the lipid layer that protects the virus and destroys the virus. So as long as you wash your mask just as carefully as you wash any other pieces of clothing that are in direct contact with your skin, then you should be good to go.
How could it be safe to wear a mask when they reduce the amount of oxygen getting to the lungs and concentrate carbon dioxide right where you breathe?
Sure, so when you breathe you're breathing about a pint of air, or about half a liter of air on each breath. Where's that air coming from? Well, it's not largely coming from the area between your mouth and the mask, where as you say oxygen is lower and carbon dioxide is higher, because there's not much room for air there. There certainly isn't room for a pint of air, there's room for maybe a few milliliters.
So I've actually done some experiments and I found that in practice, wearing a mask, the vast, vast majority of the air you breath in is not coming from inside the mouth but it's coming from the air around the mask, just like you would normally breathe. And in practice, the amount of oxygen you breathe in is only reduced by about 0.1%, which is not at all significant from a health point of view.
And what of carbon dioxide? Because this is one that's continually popping up everywhere you go on social media, you see this concern.
Yeah, it's the same thing. So that 0.1% of oxygen decrease gets replaced with carbon dioxide, largely, instead. So there's a tiny, tiny difference in the amount of carbon dioxide and oxygen in practice. And again, the reason is because when you're breathing in, nearly all of the air that you breathe - when you actually do an experiment, you'll find that it comes from the area that is outside of the mask because there's very, very little room for retained atmosphere inside the mask. There is just no space really, between the mask and your mouth to actually hold much gas.
I have an N95, which has a small black band on one side and then a filter inserted on the inside of the mask, changed every month per manufacturers regulations. I wear this mask whenever I'm outdoors, also inside any building, stores, et cetera. Two stores only: Trader Joe's and Costco. When they saw my mask they immediately handed me a circular piece of Scotch tape to put over the outside ventilation circle that's about the size of a quarter. The person at the store said it was a state law that this small ventilation circle had to be covered. Why is this? Does this cover up the outside vent of my mask/compromise it?
So the reason for that law - I think it's a local law, not a state law, but the same thing. The reason for the law is that most of those valves allow largely unfiltered exhalation, so they're not protecting others from you in case you're sick. Some of them do have a filter on the inside, but that's pretty rare. So when people see that valve, they immediately will get concerned and they will ask you to cover it up. Covering up that valve certainly does not make the mask less effective. It actually makes it more effective. The reason for that valve is to make it a little easier for you to exhale, easier for you to breathe. So it's a comfort thing, but it actually makes it a bit less effective.
I transport medical personnel as a bus driver. When the pandemic began, I pulled out a high quality ski mask I had and have used it ever since. Three layers, inner is steamed fleece, center is silk, outer is cotton. I cannot see light through it. Is this an effective solution?
Yeah, it sounds great. As we talked about earlier, that combination of materials are great materials and you've got different materials there, that's good. So the only question is the fit. As long as there's no big gaps around your nose or the side of your face, that sounds like a great idea.
If a mask prevents outgoing virus, we keep hearing we should wear one to protect others. Why doesn't it prevent incoming virus?
Well, as we just talked about it, it does. The challenge is that it's harder to predict incoming virus. The reason it's harder is that when we speak, the droplets that come out - which is the main way that this virus is transmitted, we believe, among people without symptoms - those droplets rapidly evaporate. After they evaporate they're very small and they're very hard to filter. So it's much easier to stop the virus at the source. So, in other words, to protect others from an infected person by having everybody wear a mask.
The ability of a mask to filter out the smaller, evaporated nuclei, because it's much harder it means you need to have a more precise type of material and a much better fit. So that's really the difference between the two sides. It helps in either place, but it's much easier in the outgoing direction.
I have a construction mask. It's a Trend Air Stealth, half respirator mask. It is a NIOSH N100 labeled. I can't find any info on the box or website about virus or bacteria filtration. Is this better than an N95 mask?
Yeah, it is. And the N versus P simply refers to whether it handles oil matter or not, so that obviously doesn't affect COVID-19. And the 95 vs 100 is whether it filters 95% or 100% of particles. So yeah, N100 will filter more particles than an N95.
I'm confused about the social bubble. When we get together, we thought that meant we could do "bring your own drink" but it's difficult to wear a mask, all having a drink or a snack. Are we allowed to unmask sitting six feet away during bubble time? Or is there a mask that works when we want to eat or drink together?
Yeah, so this is a complicated one, and I've talked to lots of friends and family about this. They're obviously very keen to spend time with friends and family. But drinking and eating is, you know, it's just an unsafe thing to do because you can't do it while wearing a mask. So the most important thing I'd say is, if you're going to do it, do it outside. Because outside you do not get a build up off the droplets and therefore, you don't get that same viral load. As long as there's at least some breeze, it'll gradually be blown away.
The second is distancing. Indoors, six feet is not enough to remain safe, particularly when you're not wearing a mask. So if you're gonna be indoors try to be further than six feet if you can. The best you can do - well, try not to eat and drink would be the best. Just have a chat without food and drink, even though that's what we're used to. And if you really do need to eat and drink, take the mask off, have a couple of mouthfuls and put it back on again to minimize the number of times that you're breathing or speaking without the mask. And particularly when you do take the mask off to eat or drink, don't talk. Don't talk until you put it back on again because talking created 10 times more droplets than breathing.
At my workplace not everyone is six feet away, not all are wearing face masks. I wear a KN95 mask. Am I as protected as I would be if wearing an N95? What's the difference between the N95 and KN95?
There's not much difference. They're just different standards in different countries. N95 is the American standard, and in fact in the U.S. at the moment, the FDA does allow KN95 instead of N95 in certain situations due to the mask shortage. KN95 often wrap around the ears rather than around the back of the head. Some people find that more comfortable, some people find it less.
If you are less than six feet away from people indoors for extended periods of time, that is a dangerous situation and as well as wearing a mask I would strongly advise wearing goggles as well, because this virus can also come in through the eyes.
And I actually got a couple questions on that. Which option protects the eyes better? Face masks or face shields?
Well face masks obviously don't protect the eyes at all. Face shields provide some protection to the eyes, but not as much as more tightly fitting goggles. The best thing to do, actually, is to combine face shields and masks together.
There's a lot of information on asthmatics and a lot of assumptions made about people's ability to shelter in place. I have emphysema not severe enough to need oxygen. I must go out at times for essential business. I must use public transportation. I may be medically exempt from wearing a mask, but I wouldn't leave home without one. I hear virtually nothing about what's best for people with COPD, emphysema and similar lung diseases. What do you recommend?
Well, this is tough. In that situation, those comorbidities, you are at higher risk of a higher level of symptoms or even death if you do get COVID-19. So you certainly want to protect yourself outside. On the other hand, the best way to protect yourself is with a N95 respirator or better, which are not widely available and are much harder to breathe through than a cloth mask. So I'd say the best thing you can do is to wear the highest quality mask you comfortably and safely can, and combine that with a face shield. Keep your distance when you do have to go out as best as you can. But it's a really rough place to be in.
How good at protecting are disposable KN95 masks when they get wet due to transpiration and sweat? How long can they be reused and still be effective?
We don't have great answers to the first question. So in the absence of evidence, he might want to be cautious about trying not to let them get through wet. On the latter question, it seems that they could be reused quite a number of times as long as after use you put them in a 160 F oven for at least half an hour, or in some way warm them up - maybe you've got a dryer or something you could use. So they just need to be kept at that warm level. Not any harder than that though because it can damage the mask. They are harder to clean than just a cloth mask, which is one of the reasons you might want to avoid them if you can.
On a standard surgical mask, where does one place the wire type side? Over the nose or under? Does it matter which side we place in or out? The white side or the blue or yellow colored side?
That moldable piece goes over the top of the nose and then you mold it to your nose. And then you want the soft absorbent side to be close to your face so that it's actually absorbing the droplets.
Does a layer of cotton batting or non-fusible, non-iron on interfacing increase protection?
Yeah there are certain things that can increase protection. Any kind of electro-statically charged material can help because it can help protect from smaller particles such as the evaporated nuclei we mentioned. So yes, those are potentially useful for helping to protect you.
The thin disposable paper masks so common around look somewhat flimsy. Do they do a good job of protecting the wearer as well as others?
They do an okay job. The big problem is with the fit. We talked about how they have a moldable nose piece: if you use that effectively then that can help. But they do tend to leave a gap around the outside of the face. You can close that gap by stringing three rubber bands together - and you can find information on how to do this on the Internet and using that to kind of create a tight seal all the way around your mouth. But yeah overall, the surgical masks are not that great at protecting the wearer.
I have five cotton print masks. They don't fit tightly around the nose. What can I buy to add structure and will I need to know how to sew?
You don't really need to know how to sew. I would use one of three things. The easiest thing is to get some aluminum foil, cut out a rectangular piece that's wide enough to go over your nose and the top of your cheekbones and then fold or roll it up until it's moldable and firm. And so then you can attach that through the top of the mask. You can either try to just cut a little hole and thread it in, or you can tape it or staple it. You don't really need to sew.
My mother-in-law was actually kind enough to create a little strip along the top with her sewing machine for me (laughs) so maybe you can find somebody to help you like I did.
(Laughs) One good thing about people who sew: they're usually ready to help.
This question says: I heard you speak last time on "Ask An Expert" say that officials lied to us about the effectiveness of masks to protect the supply. I've looked this up, I can't readily find it. Where can I find this information so I can point to proof when in conversation?
Let's do this. If you can send us a link or something, we'll add it into the transcript on today's episode, does that work?