• Sebastian Leck

FACT CHECK: Is wearing a mask bad for your health?

FALSE. Claims that wearing masks reduce oxygen intake, cause wearers to inhale toxins, or shut down their immune system are not supported by evidence.

In July, a group calling itself Hugs Over Masks began distributing paper pamphlets in downtown Toronto that make a number of claims about mask wearing: that masks decrease “oxygen intake” and make breathing difficult, cause “toxin inhalation,” shut down your immune system, increase the risk of catching viruses, and that they have not been proven to work. The same information has been shared on social media.

Most of these claims have no factual basis. Others—like the assertion that there is little science supporting the use of masks—are somewhat true, but misleading.

Masks do not decrease oxygen intake, cause carbon dioxide intoxication, or increase toxin inhalation

Let’s start with oxygen. There is no evidence that cloth or surgical masks cause difficulties with breathing because they don’t fit tightly enough to impede air flow, as a number of doctors and infectious disease specialists told Medical XPress. N95 masks are a little different because they fit tightly against the face and, in some cases, could lead to changes in carbon dioxide or oxygen levels in the body. However, they are only recommended for use by medical professionals and shouldn’t be worn by the general public.

Toxins also don’t get trapped in masks and aren’t re-inhaled. According to Iris Gorfinkel, a physician and medical researcher in Toronto, there’s enough airflow that masks wearers can breathe air in and out without re-inhaling carbon dioxide. She told CTV News that she isn’t aware of any cases where a user had breathed in toxins from a mask itself.

Masks won’t shut down your immune system or make you more susceptible to viruses

The Hugs Over Masks group claims that the lack of oxygen intake, increased carbon dioxide, and “toxin intake” weakens the wearer’s immune system. None of these claims are accurate; non-medical masks don’t cause oxygen deficiency or carbon dioxide intoxication, and they are unlikely to lead to increased toxin inhalation.

Reuters journalists found no evidence that masks weaken the immune system in other ways, and the American Centers for Disease Control and Prevention has stated that people who are immuno-compromised are more at risk of serious complications from COVID-19. This makes it even more important that people around them wear masks.

The Hugs Over Masks pamphlet says that masks encourage “triggering & infection from dormant retro viruses already in the body, taking advantage of a weakened immune system due to mask wearing.” It’s not clear what that means. There are only a few kinds of retroviruses that infect humans, such as HIV, and medical experts say that masks do not cause dormant viruses to activate—mainly because they don’t affect the immune system.

The Canadian government recommends against wearing masks for health reasons in only a few specific cases: for children under two years old, people who already have difficulty breathing, and people “who suffer from an illness or disabilities that make it difficult to put on or take off a mask.”

Masks can help protect against droplet transmission, but the science is still not clear on their overall effectiveness

The pamphlet goes on to say that the COVID-19 virus is eighty to 140 nanometres in length, which it claims is small enough to fit through the fibres of a typical mask, like a “chain-link fence to a mosquito.” This is misleading. The virus itself (around 100 nanometres) is smaller than the weave of a mask, but the virus is primarily spread through respiratory droplets that are many times larger.

Masks reduce our overall exposure to respiratory droplets—and since it normally takes more than one droplet to get infected, they can be a good way of protecting ourselves. “You have to be exposed to enough respiratory droplets containing enough virus to establish an infection to actually become infected,” Angela Rasmussen, a virologist at Columbia University, told Politifact. “Reducing droplet dispersal by wearing a mask greatly reduces this exposure risk, though it does not eliminate it completely.”

It’s true that the effectiveness of cloth masks hasn’t been studied enough. According to the World Health Organization (WHO), there is limited evidence about whether they work and the WHO doesn’t generally recommend their use. The organization does, however, say that in settings where physical distancing isn’t possible—like on public transit or in crowded areas—masks “could be helpful to provide a barrier to limit the spread of potentially infectious droplets from someone who is infected.”

However, there are some promising studies emerging that suggest masks can be beneficial. A study published in Health Affairs found that state mandates to wear masks were associated with declines in the daily growth of COVID-19 cases, and another study in the Proceedings of the National Academy of Sciences of the United States of America suggested that face masks may have reduced the number of infections in Italy and in New York City.

Recent research published in Nature Medicine, meanwhile, found that breath samples from people with coronaviruses contained fewer infected droplets when they were wearing masks. These are preliminary studies, though, and more work needs to be done.

Overall, all of the claims in the pamphlet and social media posts being shared by Hugs Over Masks are entirely false, with the exception that the effectiveness of masks has not yet been adequately studied. We’ll need more research to know how much protection masks provide. In the meantime, they appear to have few downsides and potentially life-saving benefits.