Ask An Expert: Wearing Masks To Prevent COVID-19

Excerpts and edited notes for this blog were referenced from an “Ask An Expert” segment hosted by Stan Bunger aired on Monday, June 22, 2020 at 9:20 am, on KCBS radio station 740 FM, sponsored by Sierra Pacific Financial Advisors. The following blog is presented for viewers to validate, accept and/or decline its content and findings on their own.

As we continue to navigate these unprecedented times, KCBS Radio spoke with Jeremy Howard, data scientist and researcher in residence at the University of San Francisco (USF).

1. Stan: Jeremy, How did you get into this? You are not a medical doctor. You are a data guy. What was it about the whole mask concept that got you into this?

Jeremy: As a data scientist and instructor at a research lab,  I specialize in gathering and analyzing medical data. Earlier this year I randomly picked masks as an interesting topic for the students and I was shocked to discover that the evidence for masks was really strong, that they could be the best tool we have. The last several months I volunteered to put together a team of some of the world’s top scientists to work on this topic and we have been studying and communicating the evidence ever since.

2. Stan: So let’s talk about that evidence because the messaging  has been all over the place on this and  for a lot of people it has become politicized.  Even for people who do not fall into that camp, they are saying, “All right prove it to me”.

Jeremy:  When we started studying this, the Surgeon General said masks don’t work, don’t wear one and CDC stated they were not recommended. Now we know the reason that was said, was that they were trying to protect the supplies for the health care workers which has caused a lot of distrust and confusion.

The evidence shows cloth masks block 99% of the droplets that fly out of people’s mouths when we speak.  They are so small that we cannot see them without using a laser scattering chamber and those are full of millions of virus particles.  Being able to block out about 99% of those droplets has a huge effect when somebody who might be infected wears a mask.  You can’t wait until you have symptoms to see if you are infected or not, because about half of the infections occurs from people who do not know they are sick. That is why we need everybody to wear a mask.  The evidence shows that in the countries which have used masks widely, their transmission rates are about ten times lower than those that don’t.  We see a similar thing now in the U.S.  In states that have masks requirements, they have dramatically lower transmission rates than those that don’t.

3. Stan: And to the question of whether I am wearing it for me to protect you or to protect me from you, where do you come down on that?

Jeremy: If you are mainly protecting others from yourself, it is an altruistic thing to do. The reason is the droplets that come out of your mouth when you are speaking, rapidly evaporate into tiny particles called droplet nuclei. These 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 is why it is important that you wear one to protect others from you. They give you some protection as well, but not as much.

4. Stan:  Do you have any thoughts on how we might depoliticize this whole mask question? It just seems like a whole other round of an endless series of arguments in this country where people cannot agree on anything.

Jeremy: It is exhausting, often depressing why this is happening.   Early on it was a bipartisan campaign and the first person to come out strongly in support was Senator Pat Toomey, Republican, who made a video about the importance of wearing masks. This was before the CDC changed their guidelines.  Laura Ingraham, of the Ingraham Angle, Fox News, was 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. Suddenly things started getting political.  Recent surveys show that the majority of Republican voters want everyone to wear a mask and they feel more comfortable when more people are wearing a mask than not.  We want to save lives and protect the economy. We don’t want to go into a second lock down. And this is something all voters can agree on whether they are on the right or left side of politics.

5. Stan: Which is the better option? Three ply ear loop face masks with fluid prevention or a cloth mask? I am thinking especially of my kid who may have to wear a mask for hours going back to a hybrid form of high school?

Jeremy: That is a good question. I know for my kid, I am mainly interested in what can I do to protect her.  Make sure that it is well fitted and made from the right materials. A mixture of cotton and silk or cotton and chiffon offers about the same level of protection according to a recent academic paper, as an N95 respirator does.  Focus on fit which can be achieved by placing rubber bands over the front.  You can use cloth and paper which has a very good filtration level. The trouble with wearing something like an N95 respirator all day is that it is much less breathable. The surgical masks are not a clear improvement over cloth masks either way. They are designed for different purposes. They have a water proof layer which can cause them to deform. They are specifically designed as the maker suggests to be used in surgical situations to protect against things other than just face droplets. So with kids going back to school, it is a tough call.  Get the best fitting and  highest filtration mask you can get which can be comfortable to be worn all day.

6. Stan: I read a Facebook comment that wearing a mask is dangerous because you are breathing in your own CO2. Please explain why this isn’t so.

Jeremy:  When you breathe out your exhaled air, which is indeed higher in CO2, it has to go somewhere.  If you are not wearing a mask, it goes out to the atmosphere around you. When you breathe in again, you could be breathing some of that back in unless it has good ventilation. If you have got a mask on, when you breathe out, there is really not a lot of room between your lips and the mask to store a lot of that breath you let out. If you did, it would be like a balloon. Again the whole thing gets breathed out into the atmosphere. So the idea that you are re-breathing that CO2, that would only be possible if you were wearing a mask that behaved like a balloon.  Then the mask would blow out and then back in again. Since that is not happening, then you can tell all of that CO2 is cast back out to the surrounding air, just like when you are not wearing a mask.

7. Stan:  Generally, how long do N95 masks last? What expires? I didn’t see a manufacture date, only use by date.

Jeremy: The answer is we don’t know . It does seem a lot of these recommendations around expiring and reuse are overly enthusiastic. They are on the conservative side on the assumption that we are never going to have shortages. If you place an N95 respirator in a warm, not hot oven, like 160 F, not very hot, for half an hour, then it deactivates any virus particles and does not cause any damage to the material, then we can see there is not any reason not to keep using them.

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

Jeremy: Treat your cloth masks the same way you would treat a t-shirt or pair of socks. At the end of the day, pop them in the wash and just like with socks or a t-shirt.  If you drink something and are active and it gets hot and sweaty and disgusting, take it off and give it a wash before the end of the day.

9. Stan: With a long beard, is there any effective mask? Does the beard filter any virus intake? Think about a mask on an airplane, beard and mask is the question.

Jeremy: It  makes it a bit harder, but if you attach it as tightly around your face as you can and you think of cloth as absorbent, it will still catch those speech particles on the way out. It is important to realize that no masks other than medical respirators are going to do much against coughing, because that is something cloth masks cannot do.

10. Stan: What about gaps around the cloth masks? Even with gaps, are the cloth masks better than wearing nothing?

Jeremy: Gaps are a problem after heavy breathing, especially after exercising, or coughing or sneezing. If you have hay fever, then use your elbow. Otherwise, little gaps don’t matter too much. The most droplet spread occurs when the droplets are pushed forward out of the mouth.

11. Stan: In the New England Journal of Medicine, an article discusses the benefits of face shields versus face masks. Can you tell us about that?

Jeremy: That article was designed as an assertion to promote discussion. It was not based on data or research.  Face shields are not a substitute for face masks because they lack absorbency to absorb the viral droplets before they become aerosols. The Hong Kong Consumer Council recommends masks have a layer or paper tissue inside in addition to wearing a face shield on the outside. A simple, inexpensive face shield may be made from a transparent file folder with a headband slid underneath. On a plane flight, this made myself and my family feel we improved our safety a bit.

12. Stan: It has been recommended that teachers wear face shields in lieu of masks in order for students to observe, see and hear then more clearly. Would this be safe to use without a mask in a classroom of 12-20 students? What is your best recommendation?

Jeremy: It is a tough call because the teacher by necessity needs to speak loudly which creates more droplets and the droplets go farther. If the teacher is facing forward and the students are in front of him/her, then the face shield will act as a barrier from the forward movement of the droplets. That can be helpful. Because the face shield is not as absorbent as the mask, droplets can go around the sides. Then ventilation becomes imperative with all doors and windows open to allow airflow.

13. Stan: Is covering the nose important?

Jeremy: To protect yourself, you should definitely cover your nose. To protect others from you, others do not have to wear their cloth masks to cover their noses. Some individuals cannot wear masks over their noses and they should not be shamed for not doing so.

14. Stan: An on-line video shows how paper masks can be folded to be more effective. Is it worth the extra effort.

Jeremy: The paper is folded horizontally in the center and made into a diamond/rectangular shape. It takes a few extra seconds to do so. It is only worth it if you wish to achieve the filtration of a surgical mask.

15. Stan: Does wearing a face shield without a mask meet the state mandate for wearing a face covering?

Jeremy: I am not sure.

16. Stan: Does wearing a cloth mask promote and collect mold?

Jeremy: There is no sign or data to support that. Over 95% of the world now wear masks and there have not been any reports of that occurring.

17. Stan: What is the best type of filter to slip into a cloth mask?

Jeremy: Simple paper towels work well.

18. Stan: Do you think mask wearing should ultimately be left to the individual to decide since we are all ultimately responsible for our own health?

Jeremy: I wish that were possible, but it is similar to drunk driving and speeding. There are things that hurt other people. Me wearing a mask is not enough to protect me. My protection is dramatically more effective if you wear a mask when you are around me because of the droplets you create when you are talking. The problem is that by not wearing a mask, those who do not, hurt others.

19. Stan: What is your position on people out exercising without a mask?

Jeremy: Personally, it is not a problem due to ventilation. Being outside has a twenty times lower possibility of viral transmission than being inside.