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Stories about a Duke University examination of which face coverings do the best job of stopping our normal, every day, respiratory spray of spittle are everywhere in the news now, but unfortunately most reporting tells only part of a complex story.

Few, if any, reporters have bothered to mention that some of the masks rated best for protecting the public from the COVID-19 pandemic might not be the best for protecting the wearer.

For many, this probably doesn’t matter. If you’re one of those who pulls on a mask to duck into a store, spend a few minutes there, and then exit into clean, fresh, mask-free air, the downside of a particular mask probably isn’t worth worrying about.

If you’re someone whose job now requires you spend the workday in a mask, however, it could be a different matter. The same for if you’re sending your children to school where they will be masked up for much of the day.

In one of the few randomized clinical trials of masks, a team of researchers from Australia, Vietnam and China in 2015 reported that wearing a cloth mask for extended periods of time increased rather than decreased the risk of respiratory infections.

Randomized clinical trials (RCTs) are the gold standard of medical research. The peer-reviewed study was published by BMJ, formerly the British Medical Journal, and was much discussed at the time.

Science Daily topped its report on the study with a headline that read “Cloth masks: Dangerous to your health?”

The headline was misleading in its failure to make clear that the study of 1,607 hospital healthcare workers in 14 hospitals in Hanoi focused on people who wore cloth masks for extended periods of time, but it wasn’t wholly misleading.

In summarizing their own research, the scientists led by Raina MacIntyre from the University of New South Wales School of Public Health and Community Medicine concluded that their “results caution against the use of cloth masks. This is an important finding to inform occupational health and safety. Moisture retention, reuse of cloth masks and poor filtration may result in increased risk of infection.”

“….As a precautionary measure, cloth masks should not be recommended for health care workers, particularly in high-risk situations, and guidelines need to be updated,” the study said.

“Additional research is urgently needed to build on our study’s findings,” MacIntyre herself told Science Daily at the time.

That research never happened. No standards for protection have ever been developed.

The U.S. Occupational Safety and Health Administration (OSHA) has set standards for the use of face coverings in situations where particulates and chemicals pose health threats, but not for infectious pathogens.

The federal agency notes the California state division of OSHA does have rules “aimed at preventing worker illness from infectious diseases that can be transmitted by inhaling air that contains viruses (including SARS-CoV-2), bacteria or other disease-causing organisms….(but the) standard is only mandatory for certain healthcare employers in California.”

Enter Duke

The now widely publicized Duke study, which CNN described as “a simple technique to analyze the effectiveness of various types of masks,” focused not on the SARS-CoV-2 virus driving the pandemic or any other respiratory pathogen, but on the respiratory droplets believed to be the main carrier of the virus.

All mammals emit these droplets in greater or lesser volumes with every exhalation from their lungs. For humans, they are what constitute the invisible water vapor that sometimes causes your glasses, sunglasses or ski goggles to fog.

Duke researchers shot a laser beam through a black box into which people exhaled, and then used a camera to expose the droplets lit up by the beam of light. It was sort of like shining a flashlight into a dusty room to illuminate the dust but on a microscopic scale.

“(Invisible) droplets that propagate through the laser beam scatter light, which is recorded with a cell phone camera. A simple computer algorithm is (then) used to count the droplets in the video,” they reported in a non-peer-reviewed paper published at Science Advances. 

“In this application, we do not attempt a comprehensive survey of all possible mask designs or a systematic study of all use cases,” they wrote. “We merely demonstrated our method on a variety of commonly available masks and mask alternatives with one speaker, and a subset of these masks were tested with four speakers.”

Basically, they documented which masks are best at capturing and holding microscopic droplets of water. The ability of some masks to better capture and retain this moisture has, however, been widely heralded as a ranking of masks “from best to worst” as the New York Post put it.

The Post rankings are, however, based on public protection not personal protection, and their relevance is influenced by the ongoing debate about the ways in which SARS-CoV-2 is transmitted.

The largest of respiratory droplets are thought to be the main carriers of the viruses, but aerosols and fomites have also been implicated.

Aerosols are the tiniest of droplets that can leak through or around the sides of masks and hang in the air for extended periods of time. These particles are smaller than those captured in the photos which comprised the Duke study.

Fomites are the many surfaces from countertops to microscopic particles of dirty on someone’s hands to which the SARS-CoV-2 virus can attach itself.

The jury is still out on aerosols.

“The physics of exhaled air and flow physics have generated hypotheses about possible mechanisms of SARS-CoV-2 transmission through aerosols,” according to the World Health Organization (WHO). “These theories suggest that 1.) a number of respiratory droplets generate microscopic aerosols (less than 5 µm) by evaporating, and 2.) normal breathing and talking results in exhaled aerosols. Thus, a susceptible person could inhale aerosols, and could become infected if the aerosols contain the virus in sufficient quantity to cause infection within the recipient.”

The Duke study recorded droplets of 5 µm and greater.

“….Some outbreak reports related to indoor crowded spaces have suggested the possibility of aerosol transmission, combined with droplet transmission, for example, during choir practice in restaurants or in fitness classes,” WHO said. “In these events, short-range aerosol transmission, particularly in specific indoor locations, such as crowded and inadequately ventilated spaces over a prolonged period of time with infected persons cannot be ruled out. However, the detailed investigations of these clusters suggest that droplet and fomite transmission could also explain human-to-human transmission within these clusters.”

Fomite transmission remains as unproven as aerosol transmission, but there is more of a consensus that it is probable. Fomite transmission is what has driven the global emphasis on hand washing and or the use of hand cleaners.

“People who come into contact with potentially infectious surfaces often also have close contact with the infectious person, making the distinction between respiratory droplet and fomite transmission difficult to discern,” WHO concluded. “However, fomite transmission is considered a likely mode of transmission for SARS-CoV-2, given consistent findings about environmental contamination in the vicinity of infected cases and the fact that other coronaviruses and respiratory viruses can transmit this way.”

Given the massive number of people now wearing masks – many of whom handle their masks rather cavalierly – the odds seem high that someone who doesn’t know they have COVID-19 could easily transfer SARS-CoV-2 from their mask to their hands and then transfer it to who knows where to be picked up by someone else.

Masks do not kill the virus. All masks do is capture the virus – if it is contained in large droplets – and theoretically hold it in the mask.

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Self-protection?

The science here raises something of a moral and ethical quandary between personal and public protection given that the decision on which type of mask is safest to wear for extended periods of time is a practical matter and not part of the bigger debate of whether masks should be worn at all.

Though mask use is now widespread and largely accepted as the new norm in the U.S., that debate has not ended.

Maverick Swedish epidemiologist Ander Tegnell, the man leading that country’s response to the epidemic, this week suggested masks are a make-believe solution to the problem of the pandemic.

“I’m surprised that we don’t have more or better studies showing what effect masks actually have,” he told the Swedish publication Bild. “Countries such as Spain and Belgium have made their populations wear masks but their infection numbers have still risen. The belief that masks can solve our problem is in any case very dangerous.”

A contrarian in his views on the global battle against COVID-19, Tegnell has for months been under fire from much of the global media for Sweden’s restrained response to the pandemic. The heat was especially intense when the Swedish death rate appeared significantly higher than that for the U.S.

They are now similar, according to the Worldometer tracker, with the U.S.  rate at 50.9 deaths per 100,000 and accelerating while the Swedish rate is at 57.1 per 100,000 and slowing.

Sweden is at this time reporting only 33 people in serious condition with COVID-19. The U.S. is reported to have 17,335 in serious or critical condition, but the U.S. is 33 times larger than Sweden.

Still, the per capita rate of serious COVID-19 illness in the U.S. is now about 16 times that of Sweden, and the per capita number of deaths in the U.S. Northeast where the pandemic has hit hardest are three times that of Sweden.

Wearing face coverings in those places is also thought to be the only way to allow society to carry on while trying to limit the spread of the disease. Thus the question of which face mask.

The top-rated mask in the Duke study was the so-called N95 mask, which the general public is still being asked to avoid purchasing to save those for frontline healthcare workers.

Cloth face masks are somewhere in the middle of the Duke ratings, but those are exactly the masks MacIntyre and colleagues warned could be bad for people’s health in 2015.

Face coverings have become a big and growing business around the globe, but there are no safety standards governing production. Grandview Research reported the sale of disposable face masks alone reached $74.9 billion in the first quarter of this year, and sales continue to accelerate.

“The demand for disposable face masks is likely to be driven by the rising popularity of online shopping platforms,” the company reported. “…The popularity of online sales has been creating a healthy demand for disposable designer face masks, most notably among affluent consumers worldwide.”

But Grandview warned of market competition from “the rising prevalence of counterfeit products both in physical stores and on online platforms. The counterfeit masks are usually made in unsterile sweatshops that were previously used to manufacture designer jeans or fake handbags. In this regard, there have been instances of numerous producers labeling their products with fake brand names of reputed medical supply manufacturers, such as 3M.”

The quality of such masks is unknown.

In April, with the pandemic raging, MacIntyre and her colleagues offered an updated view on cloth masks in a BMJ commentary and again warned against simple cloth masks.

“Cloth may become damp and contaminated, posing an infection and self-contamination risk, if not washed daily before re-use,” they wrote. “A medical mask, in contrast, has a fluid-resistant outer layer designed to prevent a stream of liquid entering the mouth.”

“Health workers facing shortages of respirators and medical masks during the pandemic of COVID-19 are searching for evidence about the use of cloth masks, and are asking if they should wear no mask at all rather than a cloth mask,” the scientists noted then.

“We recommend as a matter of work health and safety that HCWs (health care workers) should not be caring for COVID-19 patients without proper respiratory protection. Cloth masks are not a suitable alternative for HCWs.”

There are still places where health care workers are reported to be facing problems obtaining adequate masks, and even where good personal protective equipment is available they have been reported to have three times the general risk of contracting COVID-19. 

But despite these problems, MacIntyre and her colleagues did agree there appears to be potential for public masking to help limit the spread of SARS-CoV-2

“There is enough evidence that in settings where Covid-19 is poorly controlled and there are few other options, that universal face mask use in households and crowded public areas might make a difference to individual protection and population disease control,” they wrote.

There was no discussion of the implications for non-health care workers wearing cloth masks for lengthy periods of time, but the indication from the earlier work is that a warm, moist covering over the mouth creates a welcoming environment for pathogens.

Thus the mention of the need for a “fluid-resistant outer layer” on masks.

People who are required to wear a mask for eight hours per day on the job might want to look beyond the Duke study to masks that prevent moisture build-up.

SARS-CoV-2 outbreaks in meatpacking and fish processing plants where people are masked, along with the increased rates of infection among heath-care workers, have clearly demonstrated that face coverings are not a cure-all. Limiting contacts with other people remains the best way to avoid COVID-19.

And then there is the issue of the neck gaiter.

The worst

“Duke’s COVID mask study got much attention. But neck gaiter industry wants a do-over,” the Charlotte Observer headlined Tuesday.

Up until Friday – when the Duke study emerged – the newspaper noted the pandemic had been good for those in the business of neck gaiters, which offer people an easily worn tube of spandex and cloth they can pull up around their face if they need to enter a business where face coverings are required.

Unfortunately,  Duke suggested the gaiter was to face coverings what a colander is to a bucket. The gaiter, researchers concluded, didn’t really stop any spittle, it just turned it into a finer spray.

“‘The use of such a mask might be counterproductive,’ the researchers wrote in their paper,” noted Observer reporter Richard Stradling. “(But) the headline on The Washington Post article Tuesday morning was more direct: ‘Wearing a neck gaiter may be worse than no mask at all, researchers find.’

“Headlines like that have caused turmoil in the neck gaiter industry, which consists of hundreds of gaiter manufacturers and other companies that print art or words on the garments and sell them, said Chris Bernat.”

Bernat works for a company called Vapor Apparel which was once primarily in the business of making and selling lightweight gaiters for protection from the sun. Think how to avoid becoming a redneck.

Vapor’s gaiter sales exploded along with the pandemic when people recognized their sun protector could do double duty as a face protector. June-July sales were up 450 percent, Bernat claimed, and he suggested Vapor’s gaiters work to block SARS-CoV-2.

Duke, he argued, must have tested some flimsy, “giveaway” gaiter. Duke answered that its test was not meant to be a comprehensive test of all face coverings but a demonstration of how to test face coverings to see which best block droplets.

Add one more log to the fire of the ongoing debate about where and when masks should be worn.

With children – who face low risks of contracted severe cases of COVID-19 – now heading back to school, or not, the U.S. Centers for Disease Control on Tuesday issued guidelines recommending face coverings in schools, but admitted there might be problems.

The plan warned schools of the need to be prepared to deal with “bullying” of those who do or don’t wear masks, and the need for teachers to school students on how “they should not touch their cloth face coverings while wearing them and, if they do, they should wash their hands before and after with soap and water or sanitize hands (using a hand sanitizer that contains at least 60% alcohol).”

Across the country, some schools are requiring masks and some aren’t. In South Dakota, where the governor has opposed masking students, the state’s school board association has warned schools could face legal action if they don’t order students masked.

“District, board, board members, administrators, etc. could be sued during the pandemic should someone be infected, just as they could be sued on other claims before COVID-19 hit,” the Rapid City school board was told before this week voting to require masks.

“…Even (Gov.) Kristi Noem and her in-person mask-discouragement tour may not be able to beat back an argument from the lawyers that masks and other modifications of normal school procedures are part of the ordinary care and skill we can properly expect from every organization to help protect everyone from the harms of a pandemic,” the Dakota Free Press reported. 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

6 replies »

  1. If school kids are required to wear masks and get a respiratory disease other than Covid that can be traced to the pathogen growing in the mask, can the school be sued for that as well?
    Sounds like a lose/lose situation for the schools. We may need some legislation to prevent the lawsuits in both scenarios or they will inevitably be filed.

  2. Any studies on “rebreathing” and the effects of carbon dioxide? Especially those in gyms throughout the country who are forced to wear masks while running on the treadmills and various other forms of strenuous activities inhaling large amounts of carbon dioxide while rebreathing?
    As they say “the cure is worse than the bite”.

  3. That’s a pretty thorough synthesis of the most recent mask research. Thanks, Craig. My son and I hiked Slaughter Gulch in Coop today. There was a mask lying on the ground at the trailhead. It looked like a piece of trash. It was. We also saw a brownie with cubs and a blackie. We had a great walking conversation about what to be concerned about and why in this day and age.

  4. I think masks and gloves built with copper coated thread would be a start .the thread could be woven from some type of plant materials that hampered viral and bacterial acttion maybe soaked in garlic or something similar. Even without covid someone should develop this imo . Each mask needs a valve and face sealing system. Personally im against masks unless a person is imune compromised or fairly sure they are ill . I would argue using standard masks reduces water droplets that would force the virus to the ground. If you reduce tge water then the virus stays airborne longer and can be carried by air currents enhancing the odds it will Be breathed in by someone else and making them ill. The mask doesn’t stop viruses . Its not made for particles that small. Like tge studies suggest its even possible that masks create a high moisture situation that puts the wearers health at risk. Imo tge greatest benefit of a mask against viruses is that when i see someone wearing one I think yikes I should stay far away from him he must be ill! So maybe they do benefit for certain applications.

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