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Rochester and Mankato have joined the Twin Cities in 

 in businesses and other indoor facilities in an effort to help slow the spread of COVID-19. 

 is also considering a mask mandate, and so is Gov. Tim Walz, who is 

 to implement one by health officials. Still, there is some opposition and masks have 

To get some medical thinking behind masks, MPR News host Tom Crann spoke with Dr. Jon Hallberg, medical director of the 

University of Minnesota Physicians Mill City Clinic

Their conversation is transcribed below, or you can hear it using the audio player above. It has been lightly edited for clarity and length.

We are hearing there might be some evidence that masks protect the wearers, but is protecting others still the main reason to wear a mask? 

Yeah, that's still the overwhelming thought, and I think all the evidence really supports that being the primary reason to wear the masks. 

And I think it's important to think of masks as a hierarchy; at the lowest level, you've got something like a bandanna draped around you that's not well fitted and the fabric is sort of porous, you go up a step to some of the homemade masks, one more step up you've got a surgical mask on, and on top of that you've got the N-95 masks. At that level, those masks are both keeping droplets in and they're making it very difficult to breathe in very, very tiny particles.

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So cloth masks won't be 100 percent effective?

In fact, all masks are porous to some degree — we have to be able to breathe in and out. 

Those masks at the bottom of that hierarchy are much more porous. Think of them as being like a chain link fence. But for cost and availability reasons, masks at the lower end are much more practical. And if what we're really trying to do is to stop the spread of droplets as we're talking, sneezing, coughing and laughing, those makes a lot of sense.

Which is best?

Are there studies saying masks are effective in mitigating the spread of COVID-19?

Oh, there sure are. Something like 170 different studies have been done looking at masks.  

Health Affairs recently published a really interesting 

 that estimating that perhaps 200,000 to 400,000 people might have been spared COVID-19 infections in places where masks were mandated. 

So we're getting scientific information and data supporting the use of such a simple device.

Here's why

What about people who are concerned about the ability to breathe with a mask on? Is there any physiological evidence to support that?

No. I mean, if you're wearing a cloth mask, for example, and soon after applying it, you feel like you can't breathe or you're getting lightheaded or sweaty or dizzy, that's not because of the mask itself. It's not that tight. It's not that obstructive. 

What's probably happening is that people often suffer from claustrophobia and start to hyperventilate. So it's really sort of an anxious reaction that's happening. There's just no physiologic evidence that the mask itself is causing any of those problems, or is going to decrease your blood oxygen level or increase your carbon dioxide level. That just isn't happening.

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What do you, as a doctor and practitioner, want people to know about masks?

This generally inexpensive, readily available thing is a life-saving device. This is not a political thing. This is actually something that's helping one another. 

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Correction (July 15, 2020): This story previously stated that the article in Health Affairs had been rushed to publication and has not been peer-reviewed. It has been peer-reviewed and was published online before appearing in the print journal.

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What is the evidence for wearing face masks to prevent the spread of COVID-19, and what about people who say they can’t breathe while wearing one?

Dr. Hallberg answers frequently asked questions about masks

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