They acquit the asymptomatic who might spread "WuFlu" and comfort those who fear it.  They may be nothing more than a pocket full of posies, as discussed by Drs. Brosseau and Sietsema, but aren't their psychological effects beneficial?  What if masks do worse than nothing?

At the beginning of the WuFlu, the CDC recommended against masks.  The CDC now claims that based on recent research, certain types of respirators are effective against SARS-CoV-2.  The CDC cites decades-old research concerning asymptomatic and pre-symptomatic transmission, but it fails to cite any direct research on the effectiveness of masks at reducing viral transmission.  Instead, the CDC and WHO assume that masks block the droplets emitted by coughing and sneezing, and they probably do.

Medical practitioners wear masks to reduce the chance of infecting open wounds with spittle from their mouths as they talk above their patients and to protect themselves as patients sneeze and cough within a couple feet of their health care providers.  Despite the protective equipment, nurses and doctors still catch infections from and give infections to their patients, but properly worn equipment reduces close quarters spread by as much as 75%.

Great for the E.R. and ICU, but masks have been mandated to prevent spread from the asymptomatic in the general population, who rarely cough, sneeze, or spit into the faces of others except as a form of assault.  If the droplets emitted from coughing and sneezing fall to the ground within six feet, does it make sense that a virus spreads even without masks?  A garden hose on mist is good for plants two feet away, but not so good for plants four feet away.  Moreover, are the asymptomatic coughing and sneezing at all?

Aerosols, not droplets, are the primary mechanism of spread among the public.  In 2005, research found that sub-micron virus particles produced deep in the lungs were exhaled into the air by normal breathing.  Place your hand in front of your mouth as you exhale.  That moisture is an ultra-fine aerosol of particles too small to see under a microscope and, assuming that your mask was designed to filter outgoing air (they rarely are), too small to be effectively filtered.  Less than a micron in size, these particles hang in the air indefinitely, like smoke or odors, which are composed of similarly sized particles.  Consider an infected person as a smoker or stick of burning incense.  Where and when you can smell smoke is where and when you can catch their virus.  Can you smell smoke through your mask?

As expected, SARS-CoV-2 was experimentally found to penetrate surgical masks via normal breathing and even when rigged as powered air filters between hamster cages (a joke of Chinese slapdash science).  Mask-wearing Asian countries have no less influenza that non-wearing Western countries.  Studies on arms-length spread within the general population are few, but they generally show masks as ineffective.  Even the best N95 respirators are unlikely to show much effect; the virus is a third of the particle size they filter.

Ironically, anti-smoking laws may have helped viruses spread.  Restaurants, hotels, and bars once used strong upward ventilation and electronic air cleaners or HEPA filters to remove smoke.  HEPA sets N100 (99.97%) at 0.3 microns and may have some efficacy at removing viruses.  Modern eateries and clubs have no need for filtering indoor smoke, so they have efficient HVAC systems that circulate the air around and use filters suitable only for dust bunnies.

Masks and HEPA filters are depth filters, which are random meshes that impede the paths of particles.  Impede does not mean stop.  Push the particles long enough, and they will get through.  Put enough particles into the filter, and they push through those ahead.  One study showed that freshly opened surgical masks reduced the exhalation of bacteria by 75%, but after 120 minutes of use, a surgical mask no longer blocked bacteria, and after 150 minutes, a surgical mask exposed the patient to 50% more bacteria than no mask.  Change your filters, be they for masks, engines, oil, or water.

If soiled masks spray patients with bacteria, what about the lungs of the wearer?  Ventilator-associated pneumonia is a leading cause of death.  William Shatner tells you to clean your CPAP for a reason.  The lungs normally expel bacteria, but when the ventilator or mask blocks them and sends them back in, people develop pneumonia.  The research on self-inflicted pneumonia due to prolonged facial covering is scarce.  The CDC recommends changing masks after every patient.

There is considerable research on ventilator associated pneumonia (VAP).  The use of ventilators for COVID-19 is mind-boggling.  Intubation carries about a 1% risk of pneumonia per day, and pneumonia carries a 20% fatality rate in the ICU.  Put a COVID-19 patient on a ventilator for ten days, and that means a total risk of death of 2% from VAP, which is about half the risk of an ICU patient dying from COVID-19.  CPAP-style ventilation has a tenth of the risk of intubation, but hospitals used intubation.  Medicare pays a lot better for intubation than CPAP, and Congress sweetened the pot just for COVID-19.

Assuming that masks carry a similar risk to CPAP, wearing the same mask for an eight-hour workday carries a 0.03% chance per day of pneumonia.  Multiply by five for a week, and then 0.2 for the chance of dying from pneumonia, and that produces a 0.03% chance per week of death due to wearing a mask at work.  There are currently about 4 million retail sales workers, which would mean 1,200 excess pneumonia deaths per week caused by retail mask mandates.  According to the CDC's data, thousands more people than normal are dying every week of pneumonia with no connection to COVID-19.  Point zero four percent is the estimated infection fatality rate for SARS-CoV-2 in people under 70.  In this estimate, wearing a mask for a work week is about as dangerous as getting the "WuFlu."

At my workplace, 13% of the employees have complained to me about how unhealthy they feel wearing their masks.  I have overheard retail workers complaining to coworkers about how they feel sick, burning in their lungs, and coughing because of their masks.  Masks are the "sorry," not the "better safe."  Those at greatest risk from the "WuFlu" venture out, unaware of the odorless death penetrating their masks.  Those who are knowingly ill venture out, thinking their masks are protecting others.  Wearing masks for hours at a time exposes the wearer's lungs to unhealthy levels of bacteria.