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Wearing a mask has become politicized. Science says it shouldn't be.

Calls increase for a national mandate requiring masks in public.
Image: Amid the coronavirus disease (COVID-19) outbreak, Arizona mandates masks
Protesters demonstrate outside the home of Tucson Mayor Regina Romero in opposition to the new mask mandate to prevent the spread of COVID-19 in Tucson, Ariz., on June 20, 2020.Cheney Orr / Reuters

As cases of the coronavirus accelerate in the United States, more state and local governments are requiring masks in public. While most Americans seem to be in favor of wearing a mask, according to a recent Pew Research poll, there’s still considerable resistance to the universal use of face coverings in public.

Part of the confusion around wearing a mask comes from contradictory messages between public health officials and some political leaders, including President Donald Trump who has refused to wear a mask in public.

In a briefing Monday, New York Gov. Andrew Cuomo urged Trump to sign an executive order mandating the use of masks nationwide. Yet, even a national requirement might not persuade some Americans.

“Even if you mandate and people are mandating them, I don't think it's necessarily going to convince people really or even force people to wear them. We need to convince, as opposed to compel or mandate,” Dr. Craig Spencer, director of global health in emergency medicine at Columbia University Medical Center told NBC News.

In the early days of the pandemic, cloth face masks weren’t universally endorsed, even by public health experts.

“One, we didn't know whether they were actually helpful, and two, there was a lot of concern that if people were using medical masks then people like myself, were not going to have access to them,” Spencer said.

The World Health Organization only embraced face coverings for non-healthcare workers in early June, saying that in areas where the virus is spreading, people should wear fabric masks when social distancing is not possible, such as on public transportation and in shops. Mask wearing, which has a long history in Asian nations, might be one reason they are faring much better in controlling the virus, in addition to a more robust contact tracing system.

Still, the change in messaging over masks shouldn't be seen as a flaw, but as the nature of science, Dr. Jeremy Faust, an emergency physician at Brigham and Women's Hospital, said.

“That is what experts, in fact, do. They don't just have an opinion and stick to it,” he said. “They actually let their opinions develop and evolve as better information becomes available.”

What the science shows

As more has been learned about the asymptomatic spread of COVID-19, there has also been a growing body of evidence showing just how effective masks can be.

The new coronavirus is spread by respiratory droplets when an infected person coughs, sneezes or talks. If not blocked by a face covering, the droplets are thought to travel about 6 feet through the air.

In a lab study published May 21 in the New England Journal of Medicine, researchers found that nearly all droplets generated by speaking and talking were blocked when the mouth was covered by a damp washcloth. In another experiment, scientists examined over 100 individuals with a respiratory infection and looked at breathing samples of some who wore a mask and some who didn’t. The research, which was published in Nature, found that masks reduced the detection of respiratory viruses in both droplets and aerosols.

And Tuesday, researchers from Florida Atlantic University found that although all face coverings reduced large droplet transmission to an extent, some were more effective than others. Researchers tested many types of masks on mannequins and simulated how the masks would affect droplets emitted during a cough or a sneeze. The new study showed that well-fitted homemade masks with multiple layers of fabric, as well as off-the-shelf cone style masks, were the most effective in reducing droplet dispersal. Bandannas turned out to be the least effective in reducing transmission.

Other studies have examined how the virus behaves in the real world.

An analysis of 172 studies, with data from SARS, MERS and COVID, showed the chance of transmission of an infection was significantly reduced when a mask was worn. The authors of the analysis, which was funded by the World Health Organization and published in The Lancet in June, cautioned, however, that the certainty of the evidence was "low”.

Recently, researchers from the University of Iowa College of Public Health published a paper in the Journal of Health Affairs examining at the effects of mask mandates. They looked at states which required masks in public and estimated that as many as 230,000–450,000 COVID-19 cases were possibly averted by mandating face coverings.

Last week, the Institute for Health Metrics and Evaluation model by the University of Washington, that was at one point used by the White House, released data showing that if 95 percent of the U.S. population wore masks, 33,000 deaths could be prevented by October.

On Tuesday, investment giant Goldman Sachs released estimates that a national mask mandate could be more effective than lockdowns, and could help businesses reopen safely.

However, the mathematical models around masks only offer a best guess scenario, experts caution.

“Models are just models," Johns Hopkins epidemiologist Nikolas Wada, a co-leader of the 2019 Novel Coronavirus Research Compendium (NCRC), told NBC News. "They can be incredibly useful, but I think it's less useful to focus on specific numbers and projections.”

Oxygen levels and masks

Still, even though computer models don't always reflect the real world, and there isn't yet a randomized control trial for mask use, scientists say it's reassuring that all of the data seems to be pointing in the same direction.

Masks, however, should be only one part of fighting COVID-19, says Johns Hopkins epidemiologist Kate Grabowski, who has experience researching outbreaks of HIV. Contact tracing, hand washing and social distancing are equally important.

“We should start thinking about a little bit more as what we call combination prevention of disease, where we take a lot of different interventions that are somewhat effective. We basically get a suite or package of interventions that are very effective,” she said.

Grabowski also believes in being more compassionate toward people who refuse to wear masks.

“There's a lot we can do to try to understand why people don't wear them, and what the barriers are for some people," she said. “We should be trying to understand, well, what's the problem? Why don't you like wearing them?”

One reason that has gained traction on social media is the fear that wearing a mask could cause blood oxygen levels to drop, or it can lead to carbon dioxide buildup in the body.

When asked about these concerns, Spencer said he is yet to see any evidence supporting this

“There is zero truth to that. Zero,” he said. “Masks may make it more difficult to breathe. If you've ever worn a mask walking uphill, it makes it substantially harder. But it has absolutely no impact on your oxygenation level and has no impact on your ability of your body to receive oxygen or expel carbon dioxide” he said.

There are signs of shifting dynamics around masks in public, as some Republican leaders, including Senate Majority Leader Mitch McConnell, R-Ky. and Sen. Marco Rubio, R-Fla, advocate for wearing them. Ultimately, seeing people in positions of power wearing a mask could help with broader acceptance, Spencer said.

“That would make a bigger difference than us going around and pointing fingers at everyone that decides that they don't want to cover their face,” he said.