A dozen Edmonton nurses have defied an order by Alberta Health Services to resume testing for the coronavirus without N95 masks.

Occupational Health and Safety (OHS) confirmed Monday it has launched an investigation after nurses filed a complaint.

It's the latest development in an ongoing dispute after CBC revealed roughly 30 nurses stopped testing for COVID-19.

AHS investigated and determined the work was safe.

But nearly half the nurses ordered to start testing again are refusing, said Sandi Johnson, vice president of Edmonton's local chapter of the United Nurses of Alberta (UNA).

"They're disheartened," said Johnson. "They're feeling that they're not being heard."

Tests for COVID-19 are conducted using a nasopharyngeal swab that collects samples from the back of the nose and throat.

But AHS and the UNA disagree on requirements needed to conduct the test. AHS says the more loosely fitting surgical masks are appropriate but the union argues a higher standard is needed because scientific evidence around transmission is not conclusive.

According to AHS, COVID-19 is known to be transmitted by droplet through contact with nasal and oral secretions. Alberta's guidelines are the known best practice to protect against droplet transmission, the health authority says.

The position of AHS follows the guidelines of the Public Health Agency of Canada (PHAC), the World Health Organization and provinces across the country.

"AHS has not changed its [personal protection equipment] standards and expects all staff to comply with those standards," Williamson said in an email on Monday.

In contrast, the UNA's position is in line with the Canadian Federation of Nurses Unions, the U.S. Centres for Disease Control and the European Centre for Disease Prevention and Control.

"There is conflicting scientific evidence in terms of whether or not COVID-19 is airborne and for how long," said Heather Smith, president of the UNA, adding that the swab tends to trigger a cough or sneeze.

"We say in that case, one should always be erring on the side of highest possible precautions."

Smith said a nurse's clinical judgment should be respected "and if in her or his clinical judgment an N95 is warranted then it should not be denied."

PHAC guidelines also recommend nurses do a risk assessment that includes personal protective equipment to evaluate likelihood of exposure, Johnson noted.

Nurses perform alternate work

Brittany Baltimore, press secretary to Labour and Immigration Minister Jason Copping, said a worker who files a complaint may continue to refuse to perform tasks of concern.

"The OHS legislation allows the employer to assign the nurses temporarily to alternate work," Baltimore said.

The recommendation to use surgical masks rather than N95 masks may be a practical necessity, but it is not based on science indicating that surgical masks provide good protection. - Anice Lowen, influenza virologist

Little research has been done on the transmission of the agent that causes COVID-19 because it is "a very new human pathogen," said Anice Lowen, an influenza virologist at Emory University School of Medicine in Atlanta.

"As a consequence, the recommendation to use surgical masks rather than N95 masks may be a practical necessity, but it is not based on science indicating that surgical masks provide good protection."

Lowen, a former Edmontonian, is the principal scientist at the Lowen Lab, which studies influenza virus evolution and transmission.

In an email, Lowen said to determine which mask is needed, scientists would first need to understand if the virus can transmit over a short distance via an aerosol route

She said aerosols are made up of small droplets that are not effectively blocked by standard surgical masks. And while evidence suggests aerosol does not transmit more than a metre, the "short-range aerosol spread remains unknown."

"We do know that small droplet aerosols are released when humans breathe, speak and cough," Lowen wrote.

"The nurses doing swabbing are in a relatively vulnerable position because any infectious aerosols generated from a patient would not be diluted — through time and space – prior to reaching the nurse."

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