Answering Your Questions About Face Masks

KCBS Radio is answering your questions about all things coronavirus every weekday at 9:20 am

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, sponsored by Sierra Pacific Financial Advisors. 

Today we're focusing on face masks with Jeremy Howard, data scientist, USF Researcher In Residence and co-founder of "Masks 4 All".

Tell us a little about how you got into this. You're not a medical doctor, you're a data guy. What was it about the whole mask question that got you interested?

Sure, I'm a data scientist who specializes in analyzing medical data and I have a research lab at the University of San Francisco that does that, and I also teach. So I had to teach a course about gathering and understanding evidence and I kinda randomly picked masks as an interesting topic for the students three or four months ago and was shocked to discover that actually the evidence for them was really strong, that they could be the best tool we have. So I've spent the last three or four months basically working as a volunteer and put together a team of the world's top scientists on this topic and we've been studying and communicating the evidence ever since.

So let's talk about that evidence because the messaging, I think you would agree, has been all over the place on this. We've seen it become politicized obviously, but also even for people who don't fall into that camp they're saying, "prove it to me."

Yeah it's been a bit of a nightmare around messaging. When we started out studying this research - this is back when the Surgeon General was saying masks don't work and Fauci was saying don't wear one, the CDC was saying they're not recommended. Now we've seen Fauci come out a few days ago and say, "well the reason we said that was because we were trying to protect the supply for healthcare workers." It wasn't that they ever actually believed they didn't work, they were just saying something to protect the hospital supply. And that's naturally caused a lot of distrust and confusion.

The actual evidence around these non-medical cloth masks shows they block about 99% of the droplets that fly out of our mouths when we speak. They're so small we can't even see them without using a laser-scattering chamber, and those are full of millions of virus particles and so being able to block 99% of those speech droplets has a huge effect when somebody who might be infected wears a mask. Now you can't wait until you have symptoms, though, to assume you're infected or not because about half of infection occurs from people that don't know they're sick. So that's why we need everyone to wear a mask. And what the evidence shows is that in the countries which have used masks widely, their transmission rates are about 10x lower than those that don't. And we see a similar thing now in the U.S. In states that have mask requirements, they have dramatically lower transmission rates than those that don't.

And to the question of whether I'm wearing it for me to protect you, or to protect me from you, where do you come down on that?

You're mainly protecting others from yourself, so it's an altruistic, kind thing to do. The reason for this is these droplets I mentioned, after they come out of your mouth when you're speaking, they rapidly evaporate into tiny particles called droplet nuclei. And they are very hard for any kind of mask to filter, especially a non-medical mask. So we want to catch them before they evaporate, and that's why it's important that you wear one: to protect others from you. They give you some protection as well, but not as much.

Let's get to the questions now, which have been sent in by our listeners to Let's start with this one: do you have any thoughts on how we might de-politicize this whole mask question? It just feels like another round in an endless series of arguments in this country where people can't agree on anything.

Yeah it's exhausting, it's depressing. I was worried this would happen right in the early days of this campaign and it was a bipartisan campaign from the very earliest stages. In fact the first person to come out strongly in support in terms of government folks was Senator Pat Toomey, who is a Republican Senator. He made a whole video about the importance of wearing masks. This was back even before the CDC changed their guidelines. And in fact folks like Laura Ingraham on the Ingraham Angle on Fox were also very supportive. She had me on her show talking about the importance of masks. 

And then something happened. I think it might have been partly Donald Trump refusing to be shown wearing one, but suddenly things started getting political. I will say though, the most recent survey shows that still the vast majority of Republican voters want everybody to wear a mask, they feel more comfortable when people are wearing a mask than not. So even though it's becoming partisan, still there's a lot of unity around the idea that we should all be wearing masks. And I think this is the thing, we want to save lives and protect the economy. We don't want to go into a second lockdown, and this is something I think all voters can agree on whether they're on the right or left side of politics. 

Which is the better option - a three-ply ear loop face mask with fluid prevention or a cloth mask? I’m thinking especially of my kid who may have to wear a mask for hours going back to a hybrid form of high school.

That's a good question. In terms of protecting the wearer, so for your kid - I know for my kid I've been mainly interested in what can I do to protect her - you need to make sure that it's well fitted and that it has the right materials. Now in terms of cloth, if you have a mixture of cotton and silk or cotton and chiffon you get about the same level of protection - according to a recent academic paper - that an N95 respirator does. So then you need to focus on fit, which you can actually achieve by putting basically some rubber bands over the front. So in that case you can actually end up with something using cloth or paper that's got a very very good filtration level. 

The problem with wearing something like an N95 respirator all day is they're much much less breathable. The surgical masks are not a clear improvement over cloth masks either way. They're designed for different purposes. They have a waterproof layer, which actually can cause it to deform. They're specifically designed, as the name suggests, for surgical situations protecting things other than just speech droplets. So yeah, going back to school it's a tough call. But get the best fitting, highest filtration mask you can which is comfortable enough to be worn all day.

This next question I've gotten three different variations on: I read a Facebook comment insisting that wearing a mask is dangerous for you because you're breathing in your own CO2. Please explain why this isn't so.

Think of it this way: when you breathe out, your exhaled air, which is indeed higher in CO2, has to go somewhere. So if you're not wearing a mask it goes straight out into the atmosphere around you. When you breathe in again you could be breathing some of that back in, of course, unless you've got good ventilation. Now if you've got a mask on when you breathe out, there's clearly not enough room between your lips and your mask for it to store all the breath that's come out. If it did, it'd be like blowing up a balloon. So again, the whole thing gets breathed out into the atmosphere. So the idea that you're re-breathing your CO2, that would only be possible if you were basically wearing a mask that behaved like a balloon and the whole thing kind of blew out and then back in again. Since that's not happening, then you can tell that all of that CO2 is going back out into the surrounding air just like if you're not wearing a mask.

Generally how long do N95 masks last? What expires? Didn't see a manufacture date, only a use by date. The national stockpile had expired masks and the Governor took and repaired some. What repairs were made?

The answer is, we don't know terribly well. It does seem a lot of these recommendations around expiry and reuse and so forth are a little over enthusiastic. They're on the conservative side, on the assumption that you're never going to have shortages. In fact, if you put a N95 respirator into a warm but not hot oven - something like 160 F, so not very hot - for half an hour, then it deactivates any virus particles that are on it and doesn't cause any damage to the material. So as far as we can see, there's no particular reason not to keep on using them.

I have a couple of cloth masks through the generosity of a local woman that makes them and gives them away to the community. My question is how often is cleaning required and what's the best method for cleaning?

You should treat your cloth masks just the same as you'd treat a t-shirt or a pair of socks. So at the end of the day, pop them in the wash. And just like with socks or a t-shirt, if you do something very active and they get kind of hot and sweaty and disgusting, then maybe take it off and give it a wash before the end of the day.

With a long beard, is there any effective mask? Does a beard filter any virus intake?

Yeah it certainly makes it a little bit harder, but if you still can attach a cloth mask as tightly as you can around your face, the thing about cloth is it's absorbent. So it is still going to catch those speech particles on the way out. It's important to realize that no masks, other than medical respirators, are going to do much against coughing because that's something that cloth masks can't really help with. But as long as you're not showing symptoms - and if you are showing symptoms you should stay home - a cloth mask with a beard is certainly going to be better than nothing.

You do see some people with cloth masks that are a little gapped by the ears. Is that a real problem, from what the data shows, or are we mostly trying to prevent everything happening in the front?

The gaps are a problem in situations of heavy breathing, such as during or after exercise, or coughing or sneezing. So if you're coughing or sneezing, stay home. If it's just a little bit of hay fever that's passing by, use your elbow and keep the mask on as well, of course. Otherwise those little gaps don't seem to matter too much. The important thing is that those speech droplets are being pushed forward as you speak, so it's really the forward bit that matters. Not even the nose, they're not coming out of the nose. So the important thing is to make sure at least your mouth is covered.

This question cites an article from the New England Journal of Medicine discussing numerous benefits of face shields over face masks. The questioner says face shields protect the eyes from being infected - masks do not. Face shields are more comfortable and compliance rates are far higher. Why are face shields always ignored in this conversation? Do the doctors pushing for face masks and refusing to discuss face shields regard the New England Journal of Medicine as somehow fake news and anti-scientific?

(laughs) I question the premise. There's an awful lot of discussion on face shields, and they're a very potentially useful addition to masks. They're not really a replacement for them because they don't have the absorbency I mentioned that's all important. So that article in the New England Journal of Medicine doesn't actually contain any data or experiments, it's just assertions which are designed to be a source of discussion and commentary.

It's certainly of interest, and in fact in Hong Kong the consumer's council's recommended mask has a layer of paper towel and tissue on the inside and a face shield on the outside. And I think that's a really great combination, and in fact I've made a simple face shield myself by getting one of those transparent file folders and just slid a headband into it, and that was a great face shield that my wife, my daughter and I all use. She's only four years old, my daughter. We all used it recently when we all had to go on a plane flight to look after some family members, and yeah it definitely made me feel like we were improving our safety a bit.

I understand there has been recommendations for teachers and substitutes in self-contained classrooms in elementary schools to wear shields in lieu of masks as students would not be able to see or interpret the teacher’s expression. Would this be safe to be used without a mask in classroom sizes from 12-20 students? I also heard that face shields somewhat muffle the voice of the speaker; therefore, students may misinterpret what is actually said. Best recommendations?

Yeah tough call. Schools are in such a difficult situation because the teacher by necessity is speaking loudly. And speaking loudly creates more droplets, and those droplets go further. So I think a face shield's going to help in that situation, because if a teacher is standing at the front and the students are in front of her, the face shield is protecting that forward direction of droplets. So I think that can be helpful. You can create a face shield with less thick plastic, which doesn't really create much muffling at all. The ones I made at home recently really didn't cause any muffling, we found. I would say though, because it's not absorbent it's less protective. You end up with some droplets coming around the sides and the bottom. In that situation, ventilation is going to be even more important to making sure all of the windows and doors are open, maybe some fans on. You really want to get as much airflow as possible.

Cover the nose, yes or no? I suspect yes, but how do we get that message out more?

No, no, the answer's no. It doesn't matter too much either way. For protecting yourself, definitely yes, cover the nose. But for protecting others, which is what cloth masks are better at, it doesn't really matter at all. Covering the nose is not where the speech droplets come out of, and in fact if you're not covering your nose you might even get a better fit around the mouth. So if you see someone else with a mask that's not covering their nose, don't mask shame them. It's not causing any additional risk to you. Probably a lot of extra comfort for them. So I think that's just fine.

There are some videos online by a paramedical professional showing a more complicated way of using a paper mask that involves folding the mask horizontally in the center, tying knots in the ear strings to make loops, tucking in some edges, all of which gives the mask more of a diamond shape. Does seem to make it easier to breathe. Is all of this extra effort worth it?

It's not much extra effort, I've seen that video. It's like 20 seconds and you only have to do it once. This is only for surgical style masks, by the way. I haven't seen any study of data around that approach. It certainly seems sensible, but I don't have any scientific evidence to go on.

Is a face shield without a mask compliant with the current state mandate requiring face coverings?

I actually don't know the answer to that question.

It's funny because I actually have the mandate right here, it says "must wear face coverings," but it doesn't really go on to define "face covering" here.

Yeah in most jurisdictions, mandates tend to be around something that covers your nose and mouth and they don't particularly specify what tightness or material or anything like that, my first guess would be it probably is okay. But I would have to have a look.

As with many things in this whole pandemic, it's kinda confusing. The mandate is three pages long, it just refers to face covering and later it refers to cloth face covering but I'll leave that to the lawyers.

And then of course there's separate regulations in Los Angeles and each county in the San Francisco Bay Area and so forth. It's tough to keep track.

I've been wearing my mask while out and about but now I hear that using a fabric mask can hold mold spores from your mouth, so now I'm breathing in mold and CO2. Is this true? If so, is it harmful?

Not as far as we know. In fact, the countries that have mask requirements or recommendations cover 95% of the world's population. So we have a lot of data about this now, and there's no sign of any increase in illness or death from those kind of illnesses or injuries and there's no mechanistic reason to believe that would be a problem either.

What is the best type of filter to slip into a cloth mask? You can buy filters marked PM 2.5, are those effective? What would be better, if anything?

Those are good, I find they breathe less well. Personally I use a piece of paper towel. Paper towel is super breathable and also super effective. I know other people use coffee filters, I actually don't have any and haven't tried them but they seem like they work pretty well also.

Do you think the mask wearing should be left to the individual to decide as we are all ultimately responsible for our own health?

I wish that was possible, but it's just the same as drunk driving or speeding. These are things where you can hurt other people, and so unfortunately for me to be safe when I go outdoors, I need to make sure that you're wearing a mask. Because me wearing a mask is not enough to protect me. My protection is dramatically better when you wear a mask, if you're around me for the reason we talked about: evaporation of the droplets into droplet nuclei. So if you say it's each person's responsibility to keep themselves safe, that would be like saying, "ok everybody go out and drink as much as they like and drive as fast as they like and if they hurt themselves, so be it." Well the problem is, they hurt others. So this is an issue of personal liberty or freedom, and it's that I should have the liberty and freedom to go out in public and not get infected by your germs. Just like if you throw a punch, you do not have the freedom to follow through until it hurts my nose. That infringes on my rights to have an unbroken nose, more than your right to be able to throw your fist wherever you like.

What's your position on people out exercising, like running or cycling? I've read a lot of information on this and I simply can't find anything that says people keeping their distance outdoors are a danger, whether they're exercising hard or not.

Me neither. There's a certain amount of mask shaming of people not wearing masks when they're running and bicycling. I don't personally see why that's a problem. I know in some jurisdictions, including in San Francisco and Los Angeles, you are required to wear a mask outside. But yeah, I don't see an issue with it either. There's a lot of ventilation, the probability of transmission outside is at least 20x lower than inside. If people are keeping their distance and they're outside, it seems reasonable to me.

And you've been working on a website, Masks 4 All. What is the url?

It's Not .com, it's .co. And there's a lot of links to scientific studies, some information from experts and lots of other stuff as well.

This interview has been edited for clarity.