A primer on facemasks

Matt Mikus and Britta Greene

MPR News

Gov. Tim Walz told reporters last week that a statewide order requiring all people to wear masks while in public was "on the table" as Minnesota officials weigh next steps to slow the spread of COVID-19.

That led to a fresh round of questions about masks, the research on how they help prevent the spread of COVID-19, and where they're required currently.

Q Where is the proof that masks actually prevent the spread of the virus? I have a health condition that causes me to pass out or have anxiety where I can't breathe.

A A recently published analysis in the medical journal The Lancet examined 172 observational studies across 16 countries and found that wearing a face mask could strongly reduce the risk of spreading COVID-19.

The virus travels in small liquid particles that can move in the air up to about 6 feet. Wearing a mask catches the liquid particles that leave your body when you breathe, talk, cough or sneeze.

Masks prevent the spread of virus by preventing you from spreading it if you have it and don't know it. There's a lot of evidence that the virus can spread when a person is not showing symptoms. Think of it this way: You wear a mask to keep your germs near you, rather than wearing it to protect you from others.

There are two caveats. The CDC recommends that cloth masks shouldn't be worn by children under the age of 2, or anyone who has trouble breathing on their own. If you have a medical condition that affects your breathing, it's better to consult your doctor on whether or not you should wear a mask.

Q Where are masks mandatory?

A Minneapolis and St. Paul both require face coverings inside businesses and other indoor facilities. Minneapolis started the face mask requirement in May, and St. Paul started its new rule for face masks on June 1. Anyone over age 2 who can medically tolerate a face mask is required to wear a mask when in a public indoor space.

Other Minnesota cities, including Edina, Mankato and Rochester, are adding face mask requirements. Many colleges, including all University of Minnesota campuses, are requiring a face covering while inside.

Q Some of my coworkers have said masks can cause hypoxia and asthma. Is this true?

A This is a viral meme feeding misinformation. There's no evidence that masks alone cause hypoxia, carbon dioxide toxicity or asthma.

Again, if you have a medical condition already that affects your breathing, talk to your doctor about whether a face mask could cause additional problems.

Q As a nurse in an ICU, I have been reusing an N95 duckbill mask for multiple shifts. I am wondering if there are any studies on how many uses before they become ineffective?

A A recent study by the National Institute of Health and the National Institute of Allergy and Infectious Diseases on reusing N95 mask examined four decontamination techniques: a vaporized hydrogen peroxide, a heat treatment, ultraviolet light, and an ethanol spray.

While all four methods were able to decontaminate the masks, the ethanol spray damaged the integrity of the mask's fit on the face, making it less protective. The vaporized hydrogen peroxide was determined to be the most effective.

The study recommends that the mask should only be reused two to three times. They also suggest the user check fit and seal after decontaminating the mask.

Q Is a face shield as good or better than a cloth mask?

A Unfortunately, there's not enough research to suggest that they are effective enough to be a replacement for a face mask.

Most of the documentation out there is just anecdotal evidence. So for now, the CDC continues to recommend cloth face masks. That doesn't mean you shouldn't wear a face shield, and it might be a better fit for you if a face mask doesn't work for your medical condition.

A few health experts are suggesting plastic face shields for a number of reasons. You don't have to worry about glasses fogging up; it can help people who use their eyesight for communication; and it can help to prevent you from touching your face.

For more on state developments on the pandemic, visit Minnesota Public Radio News online at mprnews.org.