Mon. Dec 6th, 2021

Now that the cold weather has hit and people are moving inside, many doctors and scientists are urging Canadians to not only resist being complacent about wearing masks to protect against COVID-19 – but also to take a closer look at whether it fabric mask keeps you and others as safe as possible.

“In general, while non-medical masks may help prevent the spread of COVID-19, medical masks and respirators provide better protection,” the Public Health Agency of Canada (PHAC) said on its COVID-19 mask information page, which was updated on 12. nov.

The updated guidance also recommends medical masks or respirators for persons “at risk of more serious illness or outbreak of COVID-19” and those “at higher risk of exposure to COVID-19 due to their life situation.”

Respiratory protection – such as N-95 and KN-95 masks – is considered the highest level of mask protection and was previously only recommended for healthcare professionals who come into direct contact with infectious patients. In these high-risk areas, respiratory protection requires an “adaptation test”.

But in a nod to more general use, PHAC’s guide now says, “A community-worn respirator does not have to be formally fit-tested, as is required in some work environments.”

In response to a CBC News inquiry as to why PHAC’s recommendations have changed, the agency said in an email that it was “based on the latest scientific evidence on SARS-CoV-2 virus variants of concern, increased understanding of the effects of vaccination and immunity in the population and new available data on mask types and their effectiveness. “

In addition to the updated online guide, Dr. Theresa Tam, Canada’s head of public health, recently posted a series of tweets illustrating how COVID-19 could be spread through the air, using the analogy of passive smoking.

Many doctors, scientists, and engineers say that this shift in messages reflects a growing body of evidence suggesting that COVID-19 is widespread through aerosols (small particles that can hang in the air), and not just through airway droplets. (larger particles) transmitted by close contact with an infected person.

In turn, this means that it is important to re-evaluate the masks we use, they say.

“This marks a transition in Canada towards a recognition of the importance of aerosol, airborne transmission in the transmission of this virus,” said Dr. Brooks Fallis, a critical care physician at the William Osler Health System in the Toronto area.

Because aerosol particles are smaller and can accumulate in the air over time, Fallis said the best-performing masks are critical if you need to be indoors with other people for a while.

Some doctors recommend wearing a respirator like this N-95 mask if you are in an enclosed indoor space with other people for an extended period of time. (Adrian Wyld / The Canadian Press)

“If you just, you know, pop into the grocery store to grab a few things, or you … walk along a crowded street and want a mask on, then that’s fine. [to wear a medical┬ámask]said Fallis.

“But if you’re in a closed room with a lot of people, then we should upgrade to higher level masks, such as the KN-95 masks or a breathing mask that provides better fit and better filtration.”

Masks are important even when you are fully vaccinated, say both PHAC and doctors, because even though it is much less likely, infection with the virus that causes COVID-19 – especially the highly transmissible delta variant – can still occur.

Better availability of higher quality masks

Another important factor that has changed since the beginning of the pandemic, experts say, is the availability of medical / surgical masks and respirators.

“There was a lot of controversy about N-95 masks because there were not enough for the healthcare staff. So the message at the time, quite understandably, was: ‘Save them for the healthcare staff and we will use other alternatives,'” said Marianne Levitsky, an industrial hygienist. at the Dalla Lana School of Public Health at the University of Toronto.

“But things have changed a lot. We now have Canadian manufacturers making N-95 type masks and they are much more available than they used to be,” she said.

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Experts agree that any mask is better than no mask because it catches drops and aerosols coming from the user’s nose and mouth and protects others. But there is growing evidence that a higher quality mask can also provide some protection for the wearer.

“The masks or respirators control them in two ways. One can prevent an infected person from emitting the infectious aerosols in a room, and they can also protect the person wearing them from inhaling them,” Levitsky said.

Conor Ruzycki, who studies aerosol science and technology at the University of Alberta, says that respirators such as the Canadian one he wears provide better protection against aerosol transfer of COVID-19. (CBC)

“Dust masks were always something that would give us some time as we move toward something better,” said Conor Ruzycki, a graduate student in mechanical engineering at the University of Alberta who studies aerosol science and technology.

“Now that we understand this disease better, we know that these small aerosols play a bigger role; we should move towards … using better mesh materials.”

The 3 Fs by selecting a mask

There are three F-words to keep in mind when assessing how well a mask will protect you and others: fit, filter, and function (also called breathability).

“Fit is essential to how effective filtering happens in a real setting,” said Ravi Selvaganapathy, professor of biomedical engineering at the Center of Excellence in Protective Equipment and Materials at McMaster University.

“One can have the best quality material out there, but if it does not fit one’s face, then most of the air goes through these large holes that exist and not through the filter material.”

The filter material in both medical / surgical masks and N-95 respirators is actually the same – but respirators are better suited to a person’s face, Selvaganapathy said.

A “knot and tuck” adjustment can improve the fit of disposable masks – including medical masks, advises the Centers for Disease Control and Prevention (CDC).

“Tie the ear hoops on a three-layer face mask, where they join the edge of the mask,” the CDC website says. “[Then] fold and store the unnecessary material under the edges. ”

Fabric masks often offer good fit and good function (breathability), but how well they filter virus particles from is usually a wild card, experts say, because they are made of different materials and are not regulated.

“There are no standards. When you buy a fabric mask, it usually does not tell you what the filtration is,” Levitsky said. They can protect anything from 20 percent to 80 percent, she said. “So it’s a big unknown.”

Filtration for medical / surgical masks and respirators is classified by the standard organization ASTM International. And some non-drug, non-medical masks available in stores may look like medical masks – but are not, experts say, so it’s important for consumers to check the label.

Medical / surgical masks are classified by ASTM International. Experts warn that some non-medicated disposable masks are similar but not certified. (CBC / Radio-Canada)

ASTM has started a voluntary certification program for non-medical masks, but at present there are not many certified non-medical masks available.

In an effort to better curb COVID-19 transmission, some countries, such as Germany and Austria, have mandated medical masks and respirators instead of fabric masks in public areas.

In many cases, they have been distributed for free or subsidized, Fallis said – a step he would like to see Canada take.

“I think it’s a valuable investment because it’s a different way of bringing things down [and] to make higher quality masks a little bit cheaper, especially for people … [for whom] it’s a financial burden to buy masks, “he said.

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