Surgical masks, N95s both effective at preventing infection in work environments, INSPQ says

The province’s public health institute says that surgical masks and N95 masks are both effective at preventing infection from COVID-19 in the workplace.

The Institut national de santé publique du Québec (INSPQ) released a literature review of the efficacy of both types of masks on the same day that the province announced its plans for teachers and students to return to the classroom on Monday.

Teachers’ unions have been demanding the provincial government provide N95 masks — considered by many experts as the “gold standard” — to teachers as classes resume to make schools safer during the height of the Omicron wave of the pandemic.

In a news release issued Thursday, INSPQ said that those masks, when worn properly, are more effective at reducing exposure to small aerosols based on data from lab tests the institute reviewed.

However, the more widely available medical masks and N95s are both effective and that “scientific knowledge does not demonstrate that one is superior to the other” in work settings.

“No mask is perfect. It is important to choose a mask adapted to each situation, and above all, to wear it correctly. In a real work context, the N95 type mask and the medical mask are effective in reducing the risk of transmission of SARS-CoV-2", wrote Dr. Stéphane Perron, occupational health consultant at the INSPQ.

There is one notable caveat in the institute’s findings, however. The literature review was carried out before the arrival of the Omicron variant, which public health experts say is more highly transmissible than previous variants of the novel coronavirus.

“The best approach to prevent transmission remains the application of multiple protective measures and not only through wearing a mask,” the INSPQ concluded.


Not everyone shares the INSPQ’s opinion in the scientific community.

Geneviève Marchand, a microbiologist and researcher with the Institut de recherche Robert-Sauvé en santé et en sécurité du travail (IRSST), told La Presse that N95 masks are superior to medical masks and the literature reviewed by the INSPQ is “open to criticism” and has “shortcomings.”

Other experts agree that, while they are more expensive, N95s are far superior. The biggest criticism of surgical masks in the context of a COVID-19 pandemic is their fit, since they often leave gaps near the cheeks that can let in airborne particles.

In an interview with CTV News in late December, Linsey Marr, a Virginia Tech engineering professor who studies viruses in the air, said a well-fitted respirator offers more than 95 per cent protection, while the effectiveness of medical masks can range from 20 per cent to 90 per cent depending on how snug it is.

"It's even more critical now to protect yourself and others that we wear high-performance masks, which means they filter out particles well, and they fit well," Marr said.

She believes, however, they shouldn’t be used in all situations.

During a news conference Thursday in Montreal, the province’s new public health director, Dr. Luc Boileau, said he agreed with the previous decision by predecessor, Dr. Horacio Arruda, and others not, to provide teachers with N-95 masks, as some unions have long requested.

"When I arrived, I made sure to be quite aware of all those things and to have an opinion based on science, the most rigorous and solid... science possible," he said. "The analysis that was made is that no, it wouldn't necessarily be safer" for teachers to wear N-95s.

For the most part, "in a school setting, there is no [reason] to believe that there would be any advantage to using that," he said.

However, some specialized schools involve different interactions with children and are more like "care centres" or a health-care setting, he said -- N-95 masks will be provided to teachers in those schools.

With files from CTV Montreal’s Selena Ross and The Canadian Press


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