Post #589: Third mask-oriented post: Maybe the CDC will issue guidance on public mask use.

Late yesterday, the Washington Post reported that the CDC is considering recommending that we all wear masks when in public.

For those of you who wish to avoid newspaper paywalls at this time, in the interest of speed, the trick is to find an add-on that will let you disable javascript in your browser, then disable javascript and reload the page.  For most but not all newspapers, text but not photos will then be visible.

I’m going to talk about that just a bit.  I fervently hope the CDC will recommend public mask use as an adjunct to social distancing.  But for best compliance, I hope they will add some nuances. The reason for nuance is in red below.


In general, I don’t see any need for me to wear a mask while walking around in my suburban neighborhood.  People are thin in the ground. Air currents disperse aerosols.  

I do see a need for me to wear one in any enclosed public place, which these days translates to, while shopping.  And anywhere that I encounter a lot of people, regardless of where it is.

And, of course, this replaces NONE of the existing public-health guidance regarding distancing, hand-washing, and so on.  So, I’d like to see a set of rules along those lines:

Masks as an adjunct to social distancing.

1:  These mask rules do NOT replace social distancing.  Keep 6′ apart, except for immediate family members.

2:  Masks do NOT make it safe to socialize.  All prior guidance about gatherings remains in place.

3:  Always wear a mask in public if you are ill, think you may be ill, or feel that you may have been exposed to flu or coronavirus.

In addition, wear a mask in these situations:

4:  In any indoor public location, such as when shopping.

5:  In any location, anywhere, where you expect to converse with anyone outside your immediate family.

6:  In any crowded outdoor location, meaning, where more than 10 people are nearby, such as a crowded public sidewalk or line awaiting entry into a store.

And finally:

7:  When you remove your mask, don’t touch your face, and wash your hands immediately afterwards.

8:  Put your mask in a paper bag until the next time you use it.

What I’m trying to do, of course, is make an exception for (e.g.) walking around a sparsely-populated suburban sidewalk or park.  If you tell people they have to wear masks in that situation, all you’re going to do is get people not to comply with any mask recommendations.

Item 7 is ill-worded, because it seems like I’m afraid that the mask is contaminated.  Not really.  I mean, that’s possible, but by and large, I think cheap masks probably protect other people, more than they protect you.  Mostly, I’d be worried that my hands were contaminated, and this results in people touching their faces unnecessarily.  I don’t know how to get across the idea that the real problem is dirty hands, not a dirty mask.

With regard to 8, I have taken to wearing a ball cap, and when I unmask, the ball cap goes on the car hood upside down, the mask goes into the ball cap, and the cap and mask go into the trunk until next time.  (I’m not sure of the half-life of coronavirus on whatever-it-is that masks are made of, but I’m pretty sure that after a week in the trunk, the mask is safe.)

The point of this supplement to social distancing is to help reduce droplet transmission, and to reduce (on net) the total contact between hands and face.  This will definitely remind people not to touch their faces, when the mask is on, and you’d need to take some care to remind people not to touch their face, with dirty hands, when the mask is coming off.

Finally, with regard to aerosol (airborne) transmission of coronavirus (as opposed to droplet transmission), there is my totally-untested hypothesis that this may reduce airborne (aerosol) transmission by slowing the velocity of the air mass leaving your mouth.  So, if you are (e.g.) an aerosol superemitter, you don’t hose down the person you’re talking to, with aerosol droplets.


Wet finger whistle test, a bit of armchair science. 

Let me put some armchair science behind that last one Wet your finger, hold it at arms length, and talk loudly.  You will feel the cooling effect of your breath.  Put on an Aseptex-type mask, redo, and … no cooling.  Don’t feel it?  Try it again, whistling at your wet finger, with and without a mask.  Yes, unambiguously, an Aseptex-type mask reduces the velocity of your breath hugely.  To me, the wet finger whistle test is more than enough to tell me that this is well worth considering, even from an aerosol (airborne) transmission standpoint.  And thus I have now confirmed that  cheap masks do, in fact, reduce velocity of exhalations to a material degree.

Without that push, aerosol-sized droplets aren’t going to go anywhere.  I haven’t taken the time to do the calculation (the particle Reynolds number), for a 5 micron water droplet in air, but I bet it’s tiny.  My understanding is that items that size are more-or-less “glued” to the air they sit in.  Stop the forward motion of the air and you stop the forward motion of the aerosol particle.

 


Addendum:  One more reason for CDC guidance on public mask use.

This goes under what a buddy of mine used to call Rule Number 4: Yes, They Can Be That Dumb.

I just got an email from a friend who is currently in Richmond.  Apparently, more-or-less everybody is ignoring the social distancing rules there.  Places like (e.g.) Home Depot are packed.  Families are out shopping, with their kids.  Per report, you wouldn’t know, from people’s behavior in Richmond, that we had a deadly pandemic in progress.

I have to say, that puts a whole new light on VCU dorms being converted to hospital space.  With a native population that stubborn, they’re going to need it.

As I noted in an earlier post, my mom was a public health nurse prior to WWII.  She worked at the Philadelphia Hospital for Infectious Diseases.  She knew physicians who died from the infectious diseases they were trying to contain.  And now, I have a nephew who’s an infectious disease MD in (I think) Charlottesville.  So that’s where this next bit is coming from, in case you care to know.

The US CDC tells you this is a public health emergency, and all you have to do, to do your part to protect America, is stand six feet away from your fellow shoppers.  And you’re too lazy to do that?  Instead, you’d rather have  have health care workers risking their lives to save your sorry asses, a couple of weeks from now?

People of Richmond, if this report is true, you are un-American fools and you deserve what you are going to get.  It’s just a shame that you’re going to take a lot of innocent people out with you.

So my point is, public mask use is desperately needed in those parts of the country where people are too stubborn to heed the CDC.  If only because a public mask ordinance would be unambiguous, and could be enforced.  Show your face on publicly-accessible property without a face covering of some sort, and you are subject to a traffic-ticket-like fine.  I think that would go a long way toward slapping some sense into the heedless.

I just had this argument with an acquaintance just last night.  He was of the opinion that we shouldn’t use the local police to enforce social distancing.  So as to avoid appearing heavy-handed.  By contrast, I was of the opinion that this was a legitimate and needed use of police powers.  I’m fine with stupid people killing themselves.  But failure-to-enforce allows them to kill innocent bystanders.  They locked up Typhoid Mary for, as I recall, the last two decades of her life.  And no knowledgeable person has ever said that was the wrong thing to do.

And until the CDC issues guidance, localities would be on thin-to-nonexistent legal ground for issuing such an ordinance.  But if the CDC issues guidance, then you open the door for having another tool to keep fools from killing themselves.  Which, when you get right down to it, is one of the core functions of public health.

Next post will be on expedient mask design and manufacture.