How Effective Are Masks?

Apr 20, 2020 by

Mother Jones

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How effective are masks at containing the spread of coronavirus? A new study suggests they don’t have much effect.

But I have questions. I know this will sound like I’m just defending my pro-mask position, but I promise I’m not. If further research confirms the “meh” position, then that will become my position too. But my first question was: how was the testing done?

Effectiveness of Surgical and Cotton Masks in Blocking SARS–CoV-2: A Controlled Comparison in 4 Patients

Patients were instructed to cough 5 times each onto a petri dish while wearing the following sequence of masks: no mask, surgical mask, cotton mask, and again with no mask.

I’m not too worried about the small sample size. It’s good enough for now. My second question is: how far away was the petri dish?

A petri dish (90 mm × 15 mm) containing 1 mL of viral transport media (sterile phosphate-buffered saline with bovine serum albumin, 0.1%; penicillin, 10 000 U/mL; streptomycin, 10 mg; and amphotericin B, 25 µg) was placed approximately 20 cm from the patients’ mouths….We do not know whether masks shorten the travel distance of droplets during coughing.

Hmmm. That’s eight inches. I don’t really understand that. If you’re going to bother doing this study at all, why not do a second test at two or three feet, which is far more applicable to the real world? After all, it’s possible that masks don’t reduce the volume of virus very much but do slow it down so it doesn’t get very far.

My skepticism also comes from personal experience. As someone with compromised breathing, I can report that when I wear a mask breathing gets a little harder. And if the mask reduces the volume of air reaching me, it surely must reduce virus transmission too. The coronavirus might be teensy, but N2 molecules are even teensier. But maybe I’m thinking about this wrong.

In any case, this seems like a study that should be fairly easy to replicate, and it really should be. In the meantime, I’ll urge everyone to use common sense. Even if you’re wearing a mask, you should cough or sneeze into your sleeve. This is a hard habit to get into for some, but as weird as it sounds you can develop the habit by practicing at home. Seriously. Just spend a couple of minutes a few times a day coughing into your sleeve. Eventually it becomes second nature.

Now all we have to do is get all 330 million of us to do this.


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