Masking Rules

Robin Schoenthaler, MD

Feb 17·5 min read

Why the CDC Changed Them

On Feb 8, 2021 I wrote, “There’s no science yet showing you should double mask.” On February 10, 2021, boom, the CDC published new science showing just that.

Because, boom, that’s how it works. Science marches on and with Covid more than ever we need to keep our science game up.

The CDC prioritized mask studies throughout January. They did new mask experiments and it turned out they showed much less particle transmission using double masking or tight masks so they have now changed their recommendations to reflect hat.

This is a good reminder once again about three things:

a) with Covid we need to stay humble and open and non-smug about everything because it is a wily virus and

b) science marches on and

c) this is how science works. One study leads to a hopefully better one which leads to another even more refined one.

So just a little background.

When a new bug/disease comes along, the first thing we need to figure out is how you catch it. Because as soon as we figure out how you catch it, then we can investigate how you can KEEP from catching it.

With malaria, you get it from a mosquito. With norovirus and most “cruise ship” infections you get it from fecal-oral contact — you touch a contaminated surface or food and then touch your mouth (I know: gross but true, and why your mama always told you to wash your hands).

With Covid, the virus comes to us from inside another person. It is transmitted from an infected person’s respiratory tract (their nose/throat/lungs) to a never-before-exposed person’s respiratory tract (their nose/throat/lungs).

So if the infected person blocks the exit of virus from his mouth/nose/lungs with something, he can reduce virus from getting out and presenting a danger to you.

And if you block your own mouth/nose/lungs with something, you can prevent virus from getting IN and presenting a danger to yourself.

I know for many of you this sounds incredibly elementary but it took a lot of science to get to this place.

It’s often like this — scientists can’t just say, “Oh, that’s so obvious, of course masks will help.” It has to be scientifically “proven” again and again, in multiple ways — which in this situation has been quite complex and has involved things like “aerosolology” which I promise you we did not study in medical school.

One of the reasons the science is complex is because you can’t just take somebody with Covid and have them cough on some poor chap — that would be illegal, not to mention immoral.

You have to build models, or “simulations” and maybe the simulated set-up is a good approximation of real life, or maybe it doesn’t reflect reality in the slightest and you have to start all over.

The recent studies, which resulted in the CDC recommendation for tight-fitting masks and double masking, came from using dummies and mouthpieces and a certain kind of particle (“0.1–7 μm potassium chloride particles”) and different settings representing “a female performing light work” or “a male or female engaged in moderate work” and then they tested different mask configurations to see whether masks blocked a little or a lot.

1. Is this the same as real life? No.
2. Is it more accumulated information? Yes.
3. Is it “proof”? No, science almost never proves something beyond a shadow of a doubt.
4. Might recommendations change in the future? Possibly, as someone comes up with a better/different model or a different way of testing the spread.

What did they learn?

Remember, this involved dummies and simulations, not real life.

Let’s say Uncle Maskless is the sick dummy and he isn’t (as usual) wearing a mask. Let’s say he’s positioned in front of the Aunt Petunia dummy, and the scientists have him “cough.” This is what happens to Aunt Petunia:

• If Uncle Maskless is not wearing a mask, and Aunt Petunia is wearing a lousy loose mask, the particles that reach her only go down by 7%.
• If she’s wearing a tight mask, the number of particles that get past her mask go down 65%.
• If she’s wearing a double mask, her exposure goes down 83%.

Let’s say Uncle Maskless gets Covid and Aunt Petunia says she’ll come over and help him out but he has to wear a mask, so he finally FINALLY puts one on.

If they are both well masked (tight or double masked), the particles that get to Aunt Petunia — even from an infected Uncle Maskless — go down more than 95%! This is a fantastic number (and why not every health care worker contaminated everybody in their family all these months).

So the CDC looked at these numbers and others and were like, “Well, this is clear. Clear enough to issue new guidelines” which basically add up to three things:

• Mask up
• Mask well
• Mask twice.

My Nerdy Girl friends at Dear Pandemic (one of my favorite sources of science-based English language info) say their ratings of masks are as follows:

1. N95
2. KF94 (Korea) and FFP2 (Europe)
3. KN95s with NIOSH Certificate to avoid counterfeits
4. “Double” mask (cloth mask on top of surgical mask or cloth mask with filter insert)

5. Well-fitting surgical mask

6. Good-fitting cloth mask

So those are the recommendations for now. They may change in the future as the science evolves in its halting and human search for knowledge.

I will add:

We are a culture that often needs things to be cut and dry/black and white/yes or no. Just like it’s “hard to watch sausage get made,” I think it’s been hard watching the Covid “scientific sausage” evolve as well.

But that’s how it works. It’s not “They keep changing their minds!” — it’s that science marches on. And now we march down to Etsy or CVS or whatever and buy better stronger tighter and doubled masks.

{Robin Schoenthaler, MD is a Boston-based cancer doctor who has been writing straightforward fact-based no-blame-no-rumors-all-science-all-the-time essays about Covid-19 since March 2020.}