We are seeing jurisdictions everywhere imposing mask bans at a rate that approaches the number of bars being threatened with liquor license revocation for failing to enforce social distancing.  If that sentence seems complicated, then you are beginning to appreciate just how confusing all the arguments are about face coverings.  After all, we have N95s, surgical masks, homemade cloth masks (enjoy the video), and the classic train robber bandana.  Just for good measure, as I wore my cup-style dust mask on my last pass through Costco, I saw staff members wearing required face coverings that came from lathe section at Woodcraft.

Figure 1: Mask styles.

It should be intuitively obvious to the most casual observer that these masks are not all identical in their intended use and possible function against viruses.  The bandana and face shield represent the extreme of one side of the spectrum.  The shield blocks large objects (relative to viruses) traveling from striking the user's eyes at high speeds.  The bandana blocks the good guys from seeing who the bad guy is.  In both cases, breathing around them is very easy, and aerosols aren't blocked.  They may be effective against a sneeze, but ordinary breathing or talking defeats them easily.  The cup-style dust mask falls roughly into that same category.  Let's look at the better masks.

I wore surgical masks daily for 36 years as an anesthesiologist.  Their purpose was to reduce the chance that I would infect an open wound with bacteria from my mouth.  This article of faith has been shown to be false.  If staff who are working outside of the immediate sterile field do not wear masks, there is no increase in wound infections.  And this is in a closed environment where staff will be present for hours.  This casts a very large cloud of doubt on the utility of masks for COVID-19.

Another problem arises when we look at the use of masks by the public.  Even accepting the uncertain premise that masks are useful, "incorrect use and disposal may actually increase the risk of pathogen transmission, rather than reduce it, especially when masks are used by non-professionals such as the lay public."  Given that most "masks" are simply kept handy for use when required, set aside, and then re-used, most mask-wearing by the public is likely to increase virus exposure, not reduce it.

But do properly used surgical masks reduce disease spread in the general public?  To say there are almost no data would not be overstating the case.  When households with sick kids were examined, even rigorous mask-wearing provided no statistically significant improvement in adult infections.

Let's put that in plain English.  Even if you did everything to protect yourself with surgical masks, even keeping it on when your kid wants to see your face, it might reduce your chance of getting sick, but we can't prove it.  And that's in a well designed study intended to get a meaningful result.  "[H]ousehold use of face masks is associated with low adherence and is ineffective for controlling seasonal respiratory disease" (emphasis added).

What about homemade cloth masks?  In a study using influenza, masks made from cotton T-shirts "should only be considered as a last resort to prevent droplet transmission from infected individuals."  They were only one third as effective when worn by the sick person as a surgical mask.  If you're sick, they're better than nothing, but that's not much.  The CDC says, "Cloth face coverings may slow the spread of the virus and help people who may have the virus and do not know it from transmitting it to others."  Translation: It might help, but we don't have any data to back that up.

As we can see from other studies, even surgical masks have minimal benefit in preventing you from getting sick.  This was confirmed in a hospital study.  Cloth masks had a "relative risk" of flu infection thirteen times greater than medical masks.  "Moisture retention, reuse of cloth masks and poor filtration may result in increased risk of infection."

What about the fabled N95 respirator masks?  "Respirators work as PPE only when they are the right size and have been fit-tested to demonstrate they achieve an adequate protection factor."  Translation: If you haven't gone through the fit-testing I've been through (the first model didn't fit!), N95s won't reduce your exposure to the virus.  Sorry.

I think it's pretty easy to see that a mask is not a mask is not a mask.  There are wide variations, and some face coverings are utterly ineffective at preventing the spread of infection.  Others may provide a small degree of protection to other people if you are infected.  Surgical masks are reasonably effective, but carrying a folded cloth to cough into is just as effective.  And you'll probably put it in the laundry more frequently than your mask.

To protect yourself, you need an N95 respirator mask that is properly fitted.  Then you need to re-sterilize it every four hours using UV light or properly dispose of it and start over with a new one.  That is too expensive for most people.

The outside world is the safest place you can be.  The state of Florida has zero cases of COVID-19 that can be traced to outside transmission.  During the day, solar UV kills all viruses very quickly, and there's always enough air movement to disperse aerosols, making them non-infective.  It has become clear that virtually all cases have been spread in closed spaces with prolonged (>10 minute) exposure.  And as the studies I've cited show, other than N95s, masks are no help there.  For that matter, six-foot spacing doesn't help, either, since the aerosols that transmit the virus aren't adequately dispersed.

Caregivers in a high-intensity environment should have all the fitted N95s they need.  Beyond that, it's time to recognize that the only person who should be wearing a mask is the Lone Ranger.