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 the San Francisco Police Department.
Today we’re looking at face masks and coverings; how to treat them, what works best and more with Dr. Amy Price, senior research scientist at the Stanford AIM Lab and Dr. Larry Chu, associate professor at Stanford University School of Medicine, director of the Stanford AIM Lab and lead of Learnly Anesthesia.
It's fascinating because I'm holding the paper you two put out. It feels like a year ago, but it actually was on March 25th when the big issue was a super duper shortage of face masks for emergency workers and front line medical workers. There was great concern there wouldn't be enough masks. I know there are still spot shortages but at the time, what you were looking into was what could be done to reuse or clean masks. And was this work you had already been doing before the COVID-19 pandemic popped up?
Dr. Chu: Well, we started that report really to help in the form of front line health care workers. And we really pulled the best available evidence at the time from all available sources, including work that our colleagues at Stanford had done. So it was attempting to summarize for everyone the best answers that we could at the time.
Amy, let me ask you, what was out there? Was there a lot of science on this or was this stuff you had to really dig to find?
Dr. Price: We had to really dig. And we were kind of fighting with policy changes by the WHO and the CDC, and there were just small studies available and we were concerned about our clinicians and also the public at large and wanted to get the best evidence for them.
So now we're all mask wearers, as anesthesiologists and scientists and doctors have been for a long time. So let's see if we get to some of these questions and for a lot of them there are still, I think, some obvious disconnects. They may feel that they're wearing a mask to keep from catching the coronavirus that causes COVID-19. What would be your bottom line advice regarding homemade masks and that question?
Dr. Price: Well, probably the easiest way to explain it would be to use the symbol of a baby diaper. So if you have a baby without a diaper and the baby pees on your legs, you're going to get wet. If you have a towel or something on your lap, then it's not going to be quite as bad, but there'll be some residue. But if the baby has a diaper and you have a towel, both of you are protected.
So when I wear a mask and do social distancing, I'm protecting people from me. Because at least 40% of the population, maybe, has no symptoms but still carries the disease. And they are also as a courtesy, they’re also protecting me from them.
And Dr. Chu, maybe from the perspective of an anesthesiologist it’s worth asking before we all started becoming amateur, you know, masked doctors here in our new world what was the thinking behind wearing a mask in a medical environment? Who wore them? What kind did they wear, why, when, how?
Dr. Chu: Well, you know, the purpose of wearing a mask is obviously to trap germs. And I'm an anesthesiologist, we work in the operating room - the purposes for us mask wearers whether we're performing the surgery or we’re assisting, that our germs don't get into the patient that we're operating on.
And so if you can extrapolate that to the real world, we don't want our germs, when we're going shopping in the grocery store, to get on to somebody else. Whether that's the check out person or the person that we're standing next to when we're picking out fruit, we want to keep our germs to ourselves. That's really the point of, if we can get everyone to wear a mask.
You know, if that statement could be said over and over that everybody knows doctors wear masks in the operating room: the reason you wear them is to keep from infecting the patient. Right?
Dr. Chu: Exactly.
Okay, well, let's get into these questions, and we'll let you each take a stab at them if you like. This first one says, I have a question about disposable masks. I want to know if the surgical masks and N-95 disposable masks can be reused. And if I reuse them, how effective are they at protecting me against COVID-19? I've heard the effectiveness of disposable masks last up to four hours. I've been using mine for weeks. Did they still offer any protection?
Dr. Chu: Well, what I can tell you is that the disposable masks - N95 or surgical masks - were made to be disposable. And if they get soiled, if they have virus on the outside, that’s biohazardous material. So from a medical standpoint, we don't like to see people put biohazard waste back onto their face. Reusing masks that are soiled or dirty generally is not a good idea. But I'll let Dr. Price get into how you might reuse a mask if you didn't have a lot of them.
Dr. Price: Well, that would depend on what kind of mask you were using. So if you're using a community mask made with cloth and proper filter in between, then you could literally just wash it with hot water and soap.
For N95, we're looking at ways to decontaminate the masks and two methods that we found may be useful are using hot air for 30 minutes at about 70 ℃ or 158 ℉. The mask is not corrupted, the filtration remains. Whereas many of the other methods that are used require a lot of commercial equipment to do them properly, or they just are not usable in a consumer sense. For instance, many of us have ion sanitizers, but if we put those near the face and then breathe in those fumes, even though we might think they’re de-fumigated or whatever, they're fine for a machine but when you think that you're putting that next to your face, the FDA has actually issued warnings and say, don't use the disinfectant on the disposables.
Dr. Chu: Now for the disposable surgical masks and N95 specifically things like bleach, for instance, and alcohol are really not good.
Okay, good. Dr. Price, on the temperature you mentioned about 150 ℉. And so that's not a number that people at home are likely going to achieve. A home dryer I think is around 125 or 135 ℉. So that's something that would have to be in a more industrial or laboratory environment?
Dr. Price: Well there’s actually some home appliances that work quite nicely. For instance a food dehydrator will get up to 70 ℃, a crock pot; and both those items could be safely kept outside your home so you're not bringing the biohazardous waste into your living environment and you're not trying to do it in your home oven or something.
And what about the microwave? Because I think you did touch on that in your original paper.
Dr. Price: Yeah, the challenge with a microwave is that if you put metal in the microwave, it destroys the metal. It deforms it and it doesn’t do your microwave any favors either. So what happens is some of the particles from the metal can also leak into the mask and it just wasn’t effective. When we tried to do this with microwave ovens, the masks were unusable.
So let's go to this next one. I've heard soap and water and household chemicals don't really work in cleaning a mask for reuse. Is that the case? And if so, what's the best way to clean a mask at home?
And I think here we can stipulate we're talking about the sort of face covering masks that are being ordered under the Bay Area's shelter and place orders.
Dr. Chu: So I think soap and water are fine for cleaning the homemade masks. They're generally made of cotton. And perhaps Dr. Price can elaborate on this, but there’s a difference between that and the kind of surgical and N95 masks that anesthesiologists like I would use in the operating room.
Dr. Price: So the virus is covered with a hard covering that is broken down with soap and water. So the soap actually destroys that covering, and it's great for the cloth masks, to disinfect them. With the other masks, of course, using alcohol, bleach, soap, anything like that, it not only might be bad breathing in because of the fumes, but it's also not good because it degrades the filter material in the mask, which is a special kind of material that is blown out to trap particles. So that's why there is such a difference between the cloth of the community masks and the surgical masks.
So a trip through a typical laundry cycle with laundry detergent ought to do the job on the community masks we’re talking about?
Dr. Price: Yeah and most people are laundering their community masks separate from any other laundry, so they would keep them in a container and then launder them just on their own.
What qualifies as an effective face mask or face covering for going into a store?
Dr. Price: Well, what we've done actually, or other labs have done some testing on this. And what happens is any kind of face covering will provide a little bit of protection. So the mask that’s most important is the one that you'll use - the one that you have with you.
But there's some things that you can do to make your mask more effective. For example, if you look through your mask, you don't want to be able to see any of the pores because if you could see through the pores, that means things can come back in through the mask. You'd want to use something with a couple of layers for extra protection. Masks also work with a little bit of static electricity, and so you want something probably that has a little polyester in, because that will hold the charge.
You don’t want it so dense that you can’t breathe through it. For instance, plastic bags would probably give you great protection, but at the end of breathing through that, where are you gonna be? So it has to be loose enough that you can that you could breathe easily, but as tight as possible.
And a question came in right while you were giving that answer: for making my own mask at home, would putting two layers of polyester chiffon or natural silk in between the cotton help? Because they're said to hold an electrostatic charge.
Dr. Price: Yes, silk actually doesn't hold static electric charge but the polyester does. But silk is actually good right next to the face because it has a natural wicking quality. So it's moisture wicking, so that takes away the moisture from the face and makes it more comfortable to wear. And, of course, silk always feels good against the skin.
So going out from the face, silk-polyester-cotton might be a good approach?
Dr. Price: Yes.
We're all asking these days - and I'll start with you Dr. Chu because I know you've had to wear a mask at work for a long time - how do you keep your glasses from fogging up? What is your best approach?
Dr. Chu: A little piece of tape, right at the section where the mask is next to the nose. That really helps keep your glasses from fogging up. That's my little trick.
Okay, so it's sort of, bridge of the nose kinda like the pro athletes?
Dr. Chu: Yeah.
I have a reusable Vogmask - this is a brand of these face masks that were pretty popular during the wildfires. I went to Costco the other day. They made me cover up the breathing filters with blue tape. Why is that?
Dr. Chu: That's a good question. So it turns out that the Vogmasks - and there are other types of these masks too - that have these little discs on the outside. Those are actually exhalation valves, they're not filters though they appear to look like filters. And they help when you exhale to have less resistance. But the downside of that is that your breath that's being exhaled is not filtered by the mask.
So you remember when I was talking about when we're in the operating room, we wear masks so that our germs don't go into the patient that we're operating on. So with these Vogmasks that have those disks on the outside, essentially it's bypassing the whole purpose of the mask because those disks just let your germs go right out of the mask unfiltered.
Is there any particular fabric or material I shouldn't use for a face mask?
Dr. Price: So some people are using furnace filters as a filter on the inside. The problem with that is some of them contain asbestos, so basically would be breathing glass particles and you would be bringing that into your lungs, which is really not good at all. So anything that you use in the mask, you want to make sure that it's safe to have it next to your face and also safe to breathe at.
Does a costume or Halloween masks count? If so, how should I clean it after using it?
Dr. Price: That's really a good question. And so the reason that's a good question is because the one thing about a Halloween mask is its fitted close to the face, so that would help with the particles. And maybe that would be a good design feature to include in some of the community mouth. The challenge is that it would have to cover your nose, your mouth, a little bit under your chin that regular masks cover to be effective.
And then in terms of cleaning it, you have those same issues. Does it fit close to the face, number one. Number two, what can it be cleaned with? So can you clean it with hot water and soap or are you going to have to sponge it down with some disinfectant? And if it’s disinfectant - Lysol is great to wash floors with, but it's not so great to breathe into your lungs.
If I'm only making trips to the grocery store and walks with my dog, do I need a different mask every time I make a trip or can I reuse the same one?
Dr. Chu: So you should be able to reuse your mask if again, you're just collecting your own germs, though you wanna wash them if the masks get soiled and and obviously if it gets contaminated with germs from the outside. But Dr. Price, do you have anything to add to that?
Dr. Price: Yeah, my concern is that since we have a large number of people with the virus that don't show any symptoms or they’re asymptomatic, if I go to the grocery store and there's a lot of people in the grocery store, all kinds and some of them are wearing their masks properly, some aren't, they’re touching all the food - that's a problem.
So if I go to the grocery store, I wash my mask. If I walk my dog out in the open air, if I go for a run, sometimes I don’t even wear a mask because it's not directly in the public. If I was just walking my dog, didn't come in contact with any people and had considered the social distancing rules, I wouldn't feel the need to wash it.
But I think the one thing that we need to remember is that the virus is invisible. I was shocked, because I am presently in Florida and when I left Florida there was no virus in our state that was declared. After a trip to the UK and California, I came back and it was just days before they closed down the whole state, but at the airport, people were very close to each other. Touching, breathing, any of them could have been infected, but we wouldn't be able to see it. They looked healthy. So I would exercise caution.
This last one has popped up a couple of times. I have a blue UV light cleaner for my cell phone. Does that work for cleaning the face mask?
Dr. Price: The FDA says no.
Dr. Chu: Exactly, it’s yes and no.
Dr. Price: Yes.
Dr. Chu: So those types of light can inactivate the virus, but it depends at what wavelength of light but also how long you leave it on and the coverage - if you're going to get it into all areas of the mask. Therefore, that hesitation that you sense from us, it's generally not a great method because of the user error that can result from, do you have the right light? Are you using the right kind of UV light? Are you putting it in long enough? Are you getting all areas of the mask? It's for those reasons.
Dr. Price: There's also some testing that's going on, and the rays coming from the light are not always consistent. So you don't always know how consistent that light is on the whole cleaning surface of your mask. And if you're using it on the disposable mask, we did a study and what we found was that use of a UV light breaks the mask down in terms of fit and quality very quickly. If it’s a cloth mask, again it’s probably simpler to just put it in soap and water.