Critics ask why three-layer mask guidance took so long
Experts, Conservatives say health agency isn’t being transparent enough
Canada’s public health agency owes the public answers as to why it took until this week to say that COVID-19 can be transmitted through the air, and that Canadians should wear a three-layer mask, experts and critics say.
The Public Health Agency of Canada (PHAC) updated its guidance on those two issues this week — months after national agencies elsewhere and the World Health Organization had already done so — but has provided little information for why it took until now to make that decision, and based on what specific data.
The conflicting messages around mask wearing in particular — a three-layer mask is better, but don’t throw away your two-layer mask either, the agency said this week — points to an overall failure of communication by the organization, some infection control experts say.
“I just think it’s communication incompetence,” said Toronto infection control epidemiologist Colin Furness. “This three-layer mask they say may have a better benefit. How? Can they quantify it? Let’s see the data. What did they do?”
Conservative health critic Michelle Rempel Garner echoed the sentiment and said the agency is not being transparent with the public when it comes to some of its public health guidance.
“With this becoming a habitual pattern, I worry about Canadians losing trust in the agency, and therefore also I worry about compliance longer term,” she said.
“It’s long overdue that PHAC start explaining to the Canadian public in a transparent way how they are making public policy decisions when it comes to advice regarding COVID.”
PHAC quietly updated its online guidance Tuesday regarding how COVID-19 can be transmitted, as first reported by the CBC. The new guidance includes the possibility that it can be transmitted through very small particles that linger in the air known as aerosols.
Prior to that, PHAC maintained that the only mode of transmission was large respiratory droplets, such as from coughing or sneezing, that can land on another person in proximity or quickly fall onto surfaces. The agency has said a person touching a contaminated surface and then their eyes, nose or mouth can become infected.
Chief Public Health Officer Dr. Theresa Tam briefly mentioned aerosol transmission in a Tuesday media briefing, when she also announced a recommendation that Canadians should begin wearing threelayer masks, which would include a filter between two pieces of tightly woven fabric, ideally cotton.
“The virus that causes COVID-19 spreads from an infected person to others through respiratory droplets and aerosols created when an infected person coughs, sneezes, sings, shouts or talks,” she said.
“The droplets vary in size from large droplets that fall to the ground rapidly within seconds or minutes near the infected person to small droplets, sometimes called aerosols, which linger in the air under some circumstances.”
Vicki McKenna, president of the Ontario Nurses’ Association, said she was angry that the acknowledgment only came this week, when her organization was demanding better personal protective equipment earlier this year, fearing the virus could be airborne.
She said public health should have assumed the possibility of aerosol transmission, which would have required a higher level of PPE, until the science was more clear.
“So much of this could have been prevented, it really makes me angry,” she said. “The major lessons of SARS is that until the science is clear, you err on the side of caution.”
The WHO first recommended in June that masks be three layers, and acknowledged the possibility of aerosol transmission in July, followed by the U.S. Centers for Disease Control and Prevention in October.
PHAC said in an initial statement to the Star that Canadian health experts “have been researching and reviewing other studies in Canada and around the world” since the WHO’s June mask recommendation.
“We always work to do our own analysis to determine what is appropriate for Canadians, rather than just accept recommendations from the WHO or other organizations,” the agency said.
In a followup, the agency refused to say which studies.
“The reference list is extensive. Not all references consulted would have contributed to decision making, nor would one reference in particular have driven decision making,” the agency said.
The agency reiterated that it doesn’t want Canadians to throw out their current masks, but rather modify them by adding a filter, or making sure to buy one with three layers the next time they’re out shopping for masks.
As to why it only acknowledged aerosol transmission this week, PHAC said it is “continually reviewing new evidence and research as it emerges during the pandemic, and this new evidence guides our response to Canadians.”
A three-layer mask that includes a filter can both help trap aerosols better than a two-layer mask — therefore preventing the spread of the small particles — but can also help protect a person from inhaling them, said Linsey Marr, professor of civil and environmental engineering at Virginia Tech.
Tam didn’t specify Tuesday that the three-layer mask recommendation is a direct result of PHAC’s acknowledgment of aerosol transmission. In response to a reporter’s question, she said “because we’re learning more about droplets and aerosols, it’s just another layer of protection.”
The two updated guidelines are almost certainly connected, said Duncan Phillips, global practice leader for computational fluid dynamics, building performance and ventilation at RWDI, a Guelph-based engineering firm.
“If you are all of a sudden recommending a three-layer mask, it means you are trying to catch the smaller droplets,” Phillips said. “The third layer is about acknowledging that maybe those smaller particles are more important than we thought.”
Marr said now is an important time to begin wearing threelayer masks, as the colder weather draws more people indoors, and buildings are tightened up to prevent heat from escaping, but which also prevents fresh air from getting in and flushing out aerosols.
She said it’s also crucial that buildings have proper ventilation to constantly bring in fresh air from outside.