Among the many COVID-19 myths that are making the rounds, particularly on social media, is that facial coverings are harmful because they decrease oxygen and increase carbon dioxide levels in the blood. Plenty of scientists have diligently explained the impossibility of getting carbon dioxide poisoning from wearing a cloth face mask, but the myth persists. That’s unfortunate — and dangerous. Such erroneous beliefs are hampering public health efforts to contain the spread of COVID-19.

Last week, Dr. Robert Redfield, the director of the Centers for Disease Control and Prevention (CDC), called on all Americans to wear face masks in public to prevent COVID-19 transmission.

“We are not defenseless against COVID-19,” he said. “Cloth face coverings are one of the most powerful weapons we have to slow and stop the spread of the virus — particularly when used universally within a community setting. All Americans have a responsibility to protect themselves, their families, and their communities.”

‘No clinical evidence of harm’

Four major medical and health organizations that work with and for people with all kinds of breathing problems — the American College of Chest Physicians, the American Lung Association, the American Thoracic Society and the COPD Foundation — agree. In a statement released late last week, the groups said that facial coverings are safe and should be worn in public settings — even by many people with chronic lung disease.

Studies that have looked at the effect of facial coverings on the wearer’s oxygen level have primarily involved heavy-duty N95 masks (the kind used in medical settings), the statement points out.  Those studies have found “a statistically insignificant percentage drop in oxygen levels and an even smaller increase in carbon dioxide levels noted among healthcare workers using masks for prolonged periods of time. There is no clinical evidence of harm.”

“Individuals with normal lungs and even many individuals with underlying chronic lung disease should be able to wear a non-N95 facial covering without affecting their oxygen or carbon dioxide levels,” the statement adds.

The groups acknowledge that some people with lung disease may not be able to tolerate breathing through a facial covering and may want to get a mask exemption from their doctor.

“However, the individual’s concerns should be weighed against societal needs to mitigate spread of the virus,” the groups say. “In some instances, physician reassurance regarding the safety of the facial coverings may be all that is needed. Trying a variety of facial covering types may improve tolerability.”

The groups also make a point of discouraging the general public from using N95 masks — but only because those facial covering should be reserved for front line workers and certain immunocompromised patients, not because they are harmful.

More evidence of effectiveness

Two studies published last week offer new evidence on the effectiveness of facial coverings in preventing the transmission of COVID-19. In one study, published in the Journal of the American Medical Association (JAMA), researchers compared COVID-19 infection rates among 78,000 health care workers at Mass General Brigham hospitals in March and April, before and after those medical institutions established a mask mandate.

The study found that during a three-week period leading up to the mandate, the COVID-19 infection rates among the workers climbed from 0 percent to 21.32 percent, or an average of 1.16 percent per day. During a three-week period after the mandate, however, the rate fell significantly, to 11.5 percent, an average daily drop of 0.49 percent.

The second study comes from the CDC and was published in that agency’s Morbidity and Mortality Weekly Report (MMWR). It found that masks appear to have protected customers in a hair salon in Springfield, Missouri. The customers — 139 in all — received haircuts from two stylists who had developed respiratory symptoms, but who kept working while awaiting the results of a COVID-19 test, which eventually came back positive.

During subsequent contact tracing, health officials found that none of the customers had developed symptomatic cases of COVID-19. Furthermore, all 67 of the customers who consented to be tested for the infection had negative results.

Both stylists and all 139 customers had worn facial coverings during the haircuts.

FMI: You’ll find the statement from the four medical and health groups on the American College of Chest Physicians’ website. For more information about the use of cloth face coverings, go to the CDC’s website.