A Canadian medical marijuana company has taken matters into its own hands amid a tainted cannabis scare that has left Health Canada struggling to reassure patients the products sold by federally licensed producers can be trusted.

CanniMed Therapeutics Inc., based in Saskatoon, has taken the unusual step of commissioning independent lab tests on some of its products and making the data public to show consumers that its medicine contains no banned pesticides.

The move is an effort by the company to distance itself from industry recalls over the past few months since three federally licensed producers were caught selling medical marijuana that contained the banned pesticide myclobutanil. The chemical emits hydrogen cyanide when burned and is not approved for any plant that is smoked.

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Mettrum Ltd., Organigram Inc., and Aurora Cannabis announced recalls after the pesticide was discovered in medicine sold to clients. The problem was discovered almost by accident when Aurora tested a bulk shipment it bought from Organigram for resale to clients.

The recalls have raised serious questions about Health Canada's oversight of the new industry, which was set up to produce safe products for patients who use the drug to treat everything from cancer-related pain to epilepsy.

Health Canada officials told The Globe and Mail recently the department has not required the industry to test for illegal pesticides because the companies know chemicals such as myclobutanil are banned, and therefore should not be using them. However, dangerous yet highly effective chemicals could save a company's revenue stream when pests threaten crops, providing a financial incentive to use them.

Brent Zettl, chief executive officer of the medical marijuana producer CanniMed, said he sees no reason companies should not be required to prove their products do not have pesticides. CanniMed decided "proactively" to test four product lots in the company's storage vaults for 56 pesticides, and is publishing the results. The tests were conducted by B.C.-based Anandia Labs, a federally certified facility, and turned up no detectable levels of pesticides.

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Although Mr. Zettl acknowledges the four product lots represent only about a quarter of the medicine the company has in storage, he is not opposed to testing everything and making the results public. He hopes other companies follow suit.

"Every [licenced producer] should take it very seriously that this is a medicine. … It's for the patients' safety," Mr. Zettl said.

"There is nothing to say that Health Canada cannot put the onus on the [licensed producers] that you have to demonstrate that the product is safe in this regard, and just say, in a directive, you guys must test."

The myclobutanil problem was first discovered at Mettrum, but neither Health Canada nor the company disclosed in public announcements that the controversial pesticide, used to treat mildew, was behind that recall until The Globe uncovered the fact in December.

Thomas McConville, a former Mettrum employee, told The Globe he saw employees spraying the chemical directly on plants as far back as 2014, knowing it was banned. To evade detection when Health Canada inspectors visited the facility, an employee hid the pesticide in the ceiling tiles of the company's offices, Mr. McConville said.

Mr. Zettl said the cost of pesticide testing is not prohibitive. CanniMed paid $350 to have each of the four one-kilogram lots tested. "If you do the math on that, you're talking pennies a gram to test for pesticides," he said.

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The tainted marijuana scare has damaged the sector's credibility on quality control. Although only three companies have issued recalls, several patients told The Globe they now do not know which of the 38 federally licensed medical producers can be trusted, because there is no regular testing.

In recent weeks, Health Canada has mandated that Organigram and Mettrum, which has since been purchased by Canopy Growth Corp., begin testing all their products. Health Canada has also said it would introduce random pesticide testing for the industry.

Canopy Growth Corp. issued a statement on Thursday saying it has taken steps to correct the problem, and that Mettrum's products "have been tested at third-party labs over and above Health Canada's requirements, including rigorous testing for pesticides." The company also destroyed nearly $800,000 worth of plants.

"The application of pest control products not registered for use on cannabis at Mettrum was inexcusable," Canopy CEO Bruce Linton said. "Restoring confidence in Mettrum requires more than just changes going forward. It requires openness and transparency starting today."

Mr. Linton did not say if the company would make its lab results public so consumers could see where the testing was done, and what the results were.

Mr. Zettl said the industry needs to address customers' legitimate fears.

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"The pesticide issue is a big issue," Mr. Zettl said. "You could make the obvious argument, if nobody's controlling this and nobody's checking on it, then what the heck difference is that [product] to the stuff that's grown anywhere else [illegally]. How is a licence, and being a licensed producer, protecting the patients?"

CanniMed's parent company, Prairie Plant Systems, was the first government-licensed medical marijuana producer. In 2004, the company faced criticism when a patients' group tested some of its products and found mould, touching off a heated debate over the results and Health Canada's oversight. Mr. Zettl still contests those results because the group never made them public.

Mr. Zettl said he would like companies to publish test results, so patients can not only see the data and which lab was used, but assess whether the methods were credible.

He hopes the effort by CanniMed sends a message that the company is not using pesticides. "We don't even have ceiling tiles in our facility to hide stuff," he said.