She rolled her eyes hard.

The policy at Sandy Farm, run by Korean immigrants, reflects a new reality in Vancouver, where mask wearing is becoming increasingly mainstream, residents trade tips on making them, and authorities crack down on the resale of commercial versions.

Mask wearing as an anti-coronavirus precaution has been relatively common in the region’s Asian communities for a couple of months, and recently appears to have caught on beyond.

But BC authorities have tried to deter the increasing public use of commercially produced masks, which risks interrupting fragile supply chains, potentially putting health workers at risk. A care-industry group is urging the public to donate masks instead of keeping them for personal use.

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British Columbia’s provincial health officer Bonnie Henry said that providing enough protective gear for health workers had become a “wicked problem”, and supplies were at a “tenuous” level in the province, where there have been 725 confirmed Covid-19 infections, and 14 deaths.

“The burn rate [of protective gear], as we call it, is much higher than we expected,” she said Wednesday.

A few days earlier at Sandy Farm Market, masked customers were mostly East Asian but included a handful of Caucasians and others.

The bulk of Kerrisdale’s ethnic makeup closely matches that of Vancouver City as a whole, with 51 per cent of the suburb citing English as their mother tongue and 21.5 per cent citing a Chinese language, according to the 2016 census.

Upon entering Sandy Farm, customers were directed to a hand-sanitising station and told to keep their distance from each other, a challenge in the narrow-aisled shop.

Staff were all masked and gloved, with cashiers refusing to touch reusable bags, and sanitising or changing their gloves between cash transactions. Clear acrylic screens dangled from the roof, separating cashiers from customers and their exhalations.

Unmasked customer were not simply turned away; a store assistant asked some what they wanted and did their shopping for them instead.

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Meanwhile, at the much-larger PriceSmart supermarket in the Vancouver satellite of Richmond, about half of all customers on a recent afternoon were wearing masks. The city is predominantly Chinese, but PriceSmart’s masked clientele included plenty of Westerners too.

BC’s Centre for Disease Control has not explicitly ordered the public not to wear face masks, but has sought to deter their general use in the healthy community, saying that doing so “may be less effective” than usage by people who are unwell and might otherwise spread infection.

That reflects subtle language used by the World Health Organisation, which says it is “not required” for the healthy public to wear them, that no evidence of their efficacy in the community exists, and that they must be used in combination with hand hygiene.

Although home-made masks performed less well, “any type of general mask use is likely to decrease viral exposure and infection risk on a population level, in spite of imperfect fit and imperfect adherence, personal respirators providing most protection,” the researchers from the Dutch National Institute for Public Health and the Environment concluded.

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But it has told the public “you do not need to wear a face mask unless you are caring for someone who is sick”, warning of shortages for care givers.

Jennifer Lyle, CEO of SafeCare BC, an industry group for the continuing-care sector, said members had been calling daily to raise alarm about equipment shortages, and some had been unable to find masks to buy, even in hardware stores.

She urged the public to donate their personal stash of masks and other gear to SafeCare’s Operation Protect, for care workers in nursing homes and elsewhere.

“Although masks provide people [in the community] with a sense of security, in this environment what that ends up doing is having the unintended consequence of taking supplies away from health-care workers … who need these supplies to truly stay safe.”

Operation Protect has received more than 29,000 items, including 24,000 pairs of gloves and 2,400 N95 masks.

BC’s government on Wednesday announced it was banning the resale of medical supplies, gloves and masks, to end what public safety minister Mike Farnworth called a “shameful black market”.

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Dr Caroline Wang, a Vancouver family doctor, said she would no longer shop at Sandy Farm Market, which was once her neighbourhood grocery store.

Its mask policy was “not only contrary to the evidence but also discriminates against people from accessing food and produce that ought to be considered as essential goods and services”, she said.

“There needs to be a clear message to the public that wearing a surgical mask alone does not provide protection against viruses,” Wang said, adding that “this example [of Sandy Farm Market] actually shines a light on the need for better public policy guidance and regulations in BC for grocery stores and supermarkets”.

If the market wanted people to wear masks, it should provide them, she said.