© Justin Tang/The Canadian Press via AP Canadian Prime Minister Justin Trudeau.

OTTAWA — Canada's public health authority says around one million KN95 respirators acquired from China have failed to meet federal Covid-19 standards for use by frontline health professionals.

As a result, the federal government did not dispense the noncomplying masks to equipment-hungry provinces and territories, said Eric Morrissette a spokesperson for the Public Health Agency of Canada.

The failure of these respirators to meet Canadian requirements is yet another challenge for the country as it fights to secure PPE and medical supplies amid what has become a ferocious global competition.

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The KN95 is a Chinese model similar to the N95, which is a crucial type of personal protective equipment used to defend nurses, doctors and other health workers in the fight against Covid-19. In general, Canada has authorized the KN95 for use as part of the Covid-19 response, but individual shipments are being inspected.

China has become the source of around 70 percent of Canada's imports of PPE, with much of the rest coming from the U.S., the United Kingdom and Switzerland, a senior Canadian source told POLITICO this week.

The international race for medical gear, fueled by shortages around the world, has led countries to connect with new suppliers and manufacturers, Morrissette said. The Public Health Agency of Canada, he added, has been verifying the quality of purchased and donated supplies to ensure they meet federal technical specifications for Covid-19.

"To date, PHAC has identified approximately 1 million KN95 masks as non-compliant with specifications for health-care settings," Morrissette said in a statement. The number of rejected masks was first reported by the The Globe and Mail.

Canada's effort to extract PPE and medical supplies from China has run into complications.

Prime Minister Justin Trudeau said two airplanes sent to China to pick up shipments of badly needed medical products were forced to return to Canada on Monday empty. Trudeau cited transportation delays on the ground and strict rules that limited how long planes were permitted to wait at Shanghai's airport, a statement the Chinese government has disputed.

A spokesperson for Procurement Minister Anita Anand said four flights carrying N95 respirators, surgical masks, coveralls and testing reagent from China managed to arrive in Canada last weekend with their cargo. The government has been expecting more plane loads to land in Canada from China this week.

Earlier this week, Conservative MP Chris Lewis asked Health Minister Patty Hajdu in the House of Commons if Canada had experienced problems with PPE from China as had been reported by other countries.

"Yes... some of the equipment we received was not suitable for medical care workers, and we are looking at that equipment to see if it can be re-purposed for other kinds of workers who do not need the same level of protection," Hajdu said in her response.

Indeed, the rejected masks may still be useful, but away from hospitals.

"Although such products are non-compliant with the specifications for the front-line healthcare response, they are subsequently assessed to determine potential use in non-healthcare settings," Morrissette said.