Track the facts

COVID-19: 4 myths about masks

News - image_intro
Wearing a mask to fight the pandemic has been touted by some and dismissed by others. It finally seems to have earned its credentials in most countries that have ended their lockdown. But the exact nature of its effectiveness is still hard to establish. The Rumour Detector takes a look at 4 tenacious myths about masks.  


1) Does wearing a mask lower the blood oxygen level? False. 

The mask lets oxygen molecules pass through easily. The proof? When people wear a mask, their heart doesn’t have to beat faster to meet their oxygen needs. That’s according to a study published in the Journal of Biological Engineering in 2016. 

Dr. Alain Vadeboncoeur of the Montreal Heart Institute took the test in July. He successively wore a visor, a surgical mask and an N95 mask for a few minutes. The result? His oxygen rate stayed at 98% or 99%. (A 95% rate is considered normal.) Even when he doubled, tripled and quadrupled his face protection, the oxygen saturation of his hemoglobin was maintained.  



2) Does a mask mainly protect the wearer? False 

The mask mainly protects the people around the wearer. It blocks most of the particles this person emits when coughing and sneezing, but also when speaking or breathing. This is the main way the virus is transmitted. The Royal Society in Great Britain and the Centers for Disease Control (CDC) in the United States agree on this point. 



3) Does the mask harm the immune system of people who wear it? False. 

Adherents of this theory claim that people who wear masks breathe in their own carbon dioxide emissions. They then are at risk of hypercapnia (too much carbon dioxide in the blood). This weakens their immune system.  

In fact, masks are designed to block droplets. They aren’t tight enough to prevent gaseous molecules like carbon dioxide from passing through. Healthcare professionals wear masks for  

hours, without changing the carbon dioxide rate in their blood. Victoria Forster, a researcher at Toronto’s Hospital for Sick Children, pointed out this fact. She also noted that hypercapnia can cause confusion, loss of consciousness, difficulty breathing and even death. 

Some Internet consumers fear that they will have less contact with microbes or bacteria if they wear a mask. They claim their immune system will become lazy and less able to respond to the next attack by foreign microorganisms. In reality, even if people wear a mask a large part of the day, there are plenty of other ways to catch microbes or bacteria. Like eating an apple or kissing the love of your life



4) Does wearing a mask give people a false sense of security and compromise the efforts to stop the virus from spreading? Relatively false 

The public authorities fear that mask wearers, out of a false sense of security, will neglect other sanitary measures, such as physical distancing and hand washing.  

The authors of the scientific literature review Face Masks concluded it was unlikely such a casual attitude would eliminate the benefits of generalized mask wearing. They referred to the scientific literature produced after it became mandatory to fasten a seat belt or wear a motorcycle helmet. They pointed out these measures didn’t trigger a resurgence of risky behaviours. Instead they generated a greater sense of security.  


Other questions about mask wearing... 


Have the authorities changed their minds about the usefulness of masks? Yes and no.  

At the beginning of the pandemic, in both the United States and Canada, the public authorities recommended against mask wearing. Then they strongly suggested it where physical distancing measures can’t be maintained. Or else they made it mandatory in public places.    

One of the reasons explaining this change of direction was the fear of running out of stock, particularly for N95 and surgical masks. That’s according to Face Masks Against COVID-19: An evidence review. “Strategies to manage this critical shortage of PPE [have] been to appeal to the public to reduce their use of medical masks,” the authors wrote.  

It’s also possible another argument played a role. In the past, the experts weren’t unanimous on masks. Some studies had concluded that mask wearing didn’t protect against influenza or the common cold, in particular.  


Can you quantify the risk reduction when you wear a mask? No. 

The research isn’t there yet. Scientists still can’t quantify the reduction of the risks of contagion due to mask wearing, according to the fact-checking column Les Décodeurs. But scientists are getting better at measuring the percentage of droplets a mask can block

Community transmission depends on several factors. There’s the place where two people are found. Is it an open or confined space? Does it have air conditioning? How long were these people in contact? And what was the infected person’s viral load.  


Have masks made a difference in how the virus has spread in different countries? We don’t know. 

According to a report in The Atlantic, “no single factor can explain differences across nations or regions”.    

Japan, Singapore, Hong Kong and South Korea flattened their “curve”, particularly by imposing mask wearing. These countries were better prepared to establish strict policies (mass screening, lockdown, isolation, etc.). That’s because they were on the front line against the SARS epidemic in 2003.  

New Zealand and Iceland also flattened their curve fairly quickly, without making mask wearing a recommended practice.  

“When used in conjunction with widespread testing, contact tracing, quarantining of anyone that may have been infected, hand washing, and physical distancing, face masks are a valuable tool to reduce community transmission,” according to the authors of the Face Masks evidence review. 


This article was originally published on the website of L'Agence Science-Presse (French only).


Back to news list