Now that the cold weather has hit, people have moved into the house. Many doctors and scientists urge Canadians not only to not be complacent about wearing masks to prevent COVID-19, but also to take a closer look at whether cloth masks can keep you and others as much as possible. Safety.
“In general, although non-medical masks can help prevent the spread of COVID-19, medical masks and respirators can provide better protection,” the Public Health Agency of Canada (PHAC) said on its COVID-19 mask information webpage , The page was updated on November 12.
The updated guidelines also recommend the use of medical masks or respirators for people who are “at risk of more serious illness or COVID-19 results” and “higher risk of exposure to COVID-19 due to living conditions”.
Respirators (such as N-95 and KN-95 masks) are considered to be the highest level of mask protection, and were previously only recommended for medical staff who are in direct contact with infected patients. In those high-risk areas, respirators need to undergo "fitness testing."
But for wider use, PHAC’s guidelines now say: “Respirators worn in the community do not need to undergo formal fit testing as required in certain occupational settings.”
In response to CBC News’ inquiries about why PHAC’s recommendations have changed, the agency stated in an e-mail that this is “based on the latest scientific evidence on SARS-CoV-2 virus variants, increasing the effectiveness of vaccination and immunity. Population, and new data on the types of masks and their effectiveness."
In addition to the updated online guidelines, Canada’s Chief Public Health Officer, Dr. Theresa Tam, recently released a series of tweets using the analogy of second-hand smoke to illustrate how COVID-19 spreads in the air.
1/5 Hierarchical <a href="https://twitter.com/hashtag/COVID19?src=hash&ref_src=twsrc^tfw">#COVID19</a> protection is the best! <a href="https://twitter.com/hashtag/SARSCoV2?src=hash&ref_src=twsrc^tfw">#SARSCoV2</a> Evidence of viral aerosol transmission shows that the discharged virus particles can spread over long distances and Stay in the small aerosol for a period of time, just like second-hand smoke. <a href="https://t.co/V5p7kz3ioX">https://t.co/V5p7kz3ioX</a>
Many doctors, scientists, and engineers say that this shift in information transmission reflects growing evidence that COVID-19 is spread mainly through aerosols (tiny particles that can be suspended in the air), not just through respiratory droplets. (Larger particles) spread in close contact with infected persons.
They said that, in turn, this means that it is important to reassess the masks we are using.
Dr. Brooks Fallis, an intensive care physician of the William Osler Health System in the Toronto area, said: "This marks the beginning of Canada's recognition of the importance of aerosols and airborne transmission in the spread of this virus."
Fallis said that because aerosol particles are small and accumulate in the air over time, if you are going to stay indoors with other people for a period of time, the best performing mask is essential.
"If you just, you know, suddenly enter the grocery store to pick up a few things, or you...walk along a crowded street and you want to wear a mask, then [wearing a medical mask] is fine. ," Law Liss said.
"But if you are in a closed space with many people, then we should upgrade to higher-level masks, such as KN-95 masks or respirator masks, which provide better fit and better filtration."
Both PHAC and doctors say that even if you are fully vaccinated, masks are important because although this is much less likely, infection with the virus that causes COVID-19—especially the highly transmitted delta variant—is still It may happen.
Experts say that another important factor that has changed since the beginning of the pandemic is the supply of medical/surgical masks and respirators.
"There is a lot of controversy about N-95 masks because medical staff are not enough. So it is understandable that the message at the time was:'Leave these to medical staff and we will use other alternatives,'" University of Toronto Dalarana Said Marianne Levitsky, an industrial hygienist at the School of Public Health.
"But the situation has changed a lot. We now have Canadian manufacturers producing N-95 masks, and their supply range is much wider than in the past," she said.
Experts agree that wearing a mask is better than not wearing a mask because it captures droplets and aerosols from the wearer's nose and mouth and protects others. But more and more evidence shows that high-quality masks can also provide some protection for the wearer.
"Masks or respirators can be controlled in two ways. One is to prevent the infected person from discharging these infectious aerosols into the space, and it can also protect the person wearing the mask from inhaling them," Levitsky said.
Conor Ruzycki, a PhD student in mechanical engineering at the University of Alberta who studies aerosol science and technology, said: "As we move in a better direction, cloth masks will always give us some time."
"Now that we have a better understanding of this disease, we know that these small aerosols are playing a bigger role; we should move towards...using better mask materials."
When evaluating the protective effect of a mask on you and others, there are three F words to keep in mind: fit, filtration, and functionality (also known as breathability).
Ravi Selvaganapathy, a professor of biomedical engineering at McMaster University's Center of Excellence for Protective Equipment and Materials, said: "In terms of how to effectively filter in the actual environment, fit is essential."
"You can have the best quality material, but if it doesn't fit a person's face, most of the air will pass through these large gaps instead of filtering materials."
Selvaganapathy said that the filter materials in medical/surgical masks and N-95 masks are actually the same-but the contour of the mask is more suitable for the human face.
The US Centers for Disease Control and Prevention (CDC) recommends that "knotting" adjustments can improve the fit of disposable masks-including medical masks.
The CDC website says: "Tie the knot where the earrings of the tri-layer mask connect to the edge of the mask." "[Then] fold and tuck the unwanted material under the edge."
Experts say that cloth masks usually have good fit and good functionality (breathability), but their ability to filter virus particles is usually an unknown, experts say, because they are made of different materials and are not regulated.
"There is no standard. When you buy a cloth mask, it usually doesn't tell you what the filter is," Levitsky said. She said they can protect anywhere from 20% to 80%. "So this is a big unknown."
The filtration of medical/surgical masks and respirators is classified by the standard organization ASTM International. Some non-cloth, non-medical masks offered in stores may look like medical masks-but experts say that is not the case, so it is important for consumers to check labels.
ASTM has launched a voluntary certification program for non-medical masks, but at this time, there are not many certified non-medical masks available.
In order to better contain the spread of COVID-19, some countries such as Germany and Austria have mandated the use of medical masks and respirators in public places instead of cloth masks.
Faris said that in many cases, they are distributed for free or subsidized-he hopes Canada will take this initiative.
"I think this is a worthwhile investment because it is another way to reduce cases [and] make high-quality masks a bit cheaper, especially for people... [for them] buying masks is an economic Burden," he said.
Nicole Ireland is a CBC news reporter with a special interest in health and social justice stories. She lives in Toronto and has lived and worked in Thunder Bay, Ontario; Iqaluit, Nunavut; and Beirut, Lebanon.
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