The federal government's handling of marijuana legalization has created problems that Canada's cities are unequipped to handle, Vancouver's mayor says.

Ottawa's plan to legalize the drug – a key piece of the Liberal election platform last fall – has spawned hundreds of storefront dispensaries across the country ahead of the legislation, although the federal government has taken no responsibility for the boom it has created.

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Cities such as Vancouver and Toronto are grappling with problems ranging from policing and zoning to the discovery of potentially dangerous contaminants in some of the dispensary products that pose a threat to public health.

"The lack of federal regulation and oversight has made the marijuana issue a city problem," Vancouver mayor Gregor Robertson told The Globe and Mail in an interview. "And cities don't have the capacity or expertise to deal with it."

Mr. Robertson's comments follow recent revelations that Health Canada was warned about harmful contaminants in marijuana sold at several Vancouver dispensaries, but did not act.

Documents obtained through the Access to Information Act revealed that test results from a Health Canada-accredited lab that were sent to the federal government showed that 13 of 22 samples of cannabis from Vancouver dispensaries contained harmful contaminants, including some not approved for human use.

The contaminants included the pesticide carbamate, which is not permitted for cannabis, and dodemorph, which is not approved for human consumption. The test results were sent to the government nearly a year ago by Tilray, a federally licensed producer of medical marijuana based in Nanaimo, B.C., which called for the government to regulate dispensaries or shut them down.

The names of the dispensaries were redacted from the documents obtained by The Globe due to privacy laws. However, the original documents sent to Health Minister Jane Philpott's chief of staff included information on each location. The government did nothing with the warning, and did not alert the City of Vancouver to the problem.

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Kerry Jang, a Vancouver city councillor, criticized the federal government for sitting on the documents. Dr. Jang, a psychiatrist who is a point person on marijuana issues for the city, called Health Canada's actions irresponsible.

Although dispensaries have flourished, doing a lucrative business out in the open in some places, the Health Minister's office said in a statement that Health Canada considers them illegal, and therefore not part of its responsibility.

"Whether it's illegal or not right now is not the question," Dr. Jang said. "We need to see some action from the federal minister. Not this 'It's illegal and I am hiding.' It's just inappropriate."

While Toronto has attempted to control the dispensary boom through zoning bylaws and sporadic crackdowns, the efforts have not prevented new locations from opening. Vancouver has a nascent licensing program for dispensaries that attempts to exert control over where the retail stores are situated, but the city has no way to influence the safety or efficacy of the product.

Mr. Robertson said the test results published in The Globe suggest more needs to be done at all levels of government. "Knowing what we know now, there's a need to do better," he said.

However, Mr. Robertson said the problems with potentially harmful chemicals finding their way to the public is something the federal government needs to confront.

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"The production side – the products being produced – that ultimately is Health Canada's responsibility," he said. "We can't deal with that; we don't have those tools."