Illegal marijuana dispensaries in British Columbia and Ontario say they are developing a system of testing standards amid concerns about contaminants in cannabis – both at unauthorized storefronts and in the federally regulated system.

The proposal from the Canadian Association of Medical Cannabis Dispensaries, whose 25 members represent a fraction of the hundreds of illegal dispensaries operating across the country, to set up a testing system by May comes ahead of federal legislation to legalize the drug. The Liberal government has not said where recreational marijuana will be sold, but dispensaries have lobbied to be included in the new system.

A Globe and Mail investigation last year revealed three of nine samples of dried cannabis from nine unregulated dispensaries in Toronto would not meet Health Canada safety standards for licensed growers. And the testing regime in the federally regulated system has also faced criticism after large recalls involving banned pesticides.

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The Canadian Association of Medical Cannabis Dispensaries said it has created a working group with dispensary owners, cannabis producers, processors and lab owners to design a credible testing program.

The group's president, Jeremy Jacob, noted dispensaries are not allowed to test their products through labs licensed by the federal government.

"We need to empower our member dispensaries of our organization and customers to make educated choices about the cannabis products they're buying," Mr. Jacob said in an interview Wednesday.

"We think it's important to implement a testing program so there's certainty."

Mr. Jacob couldn't say where the testing will be done or what the system will test for, saying those details must be worked out.

Storefront marijuana sales are currently illegal, but dispensaries have been able to operate in cities where authorities have not moved aggressively to shut them down. Vancouver and other cities have created business licences to regulate them.

Little is known about where dispensaries obtain their cannabis, though some say they get it from small-scale individual growers who are permitted by Health Canada to produce marijuana for themselves or other patients.

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The Globe investigation found several different kinds of pathogenic bacteria in the dispensary samples, including one that contained high levels of potentially harmful yeasts and mould, which can lead to serious health concerns if consumed.

At the federal level, two licensed producers – Mettrum Ltd. and OrganiGram Inc. – were found producing products contaminated with prohibited chemicals, leading to a large recall and the destruction of $1-million of tainted product.

Rosy Mondin, executive director of the Cannabis Trade Alliance of Canada and an adviser to Mr. Jacob's organization, said the testing initiative deals with a challenge to dispensaries.

"The biggest argument against [marijuana dispensaries] is that they sell an unsafe and untested product," Ms. Mondin said in an interview.

Neil Boyd, a criminology professor at Simon Fraser University, said it's a credible initiative. "It's a move that one has to applaud because it provides consumers of dispensaries with a lot more relevant information about the product that they're getting, and can assure them that the product that they're getting is safe."

Vancouver City Councillor Kerry Jang, a member of the governing Vision Vancouver party and point person on marijuana issues, said it's "worthwhile" for consumers to have some information on the marijuana they are consuming.

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But he said the testing regimes will have to meet the highest world-class standards.

He said he expects the federal government will have some testing program as part of its move to legalize marijuana, but this proposed testing program can provide some information until then.

"The battle for legalization by cannabis users has already been won. Now it's a matter of setting up appropriate business practices and standards," said Mr. Jang.

"I've always said you have to treat marijuana like you would a dozen eggs in terms of testing," he said.