Two years before Canada's medical-marijuana sector became embroiled in a tainted cannabis scare, the trade organization representing the majority of commercial growers explored using banned pesticides on their products, according to newly obtained documents.

Meeting minutes and confidential e-mails sent in 2015 to more than a dozen companies on the subject, show that some industry members supported using prohibited chemicals such as myclobutanil – a pesticide that produces hydrogen cyanide when combusted and can lead to serious health problems.

Though the application for approval was never carried out, myclobutanil is now at the centre of a controversy over patient safety in the sector after two companies – Mettrum Ltd. and OrganiGram Inc. – were found selling products contaminated with the banned substance.

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The discovery has led to the largest recalls the young industry has seen, resulting in the destruction of more than $1-million of tainted product and it has spawned two proposed class action lawsuits on behalf of patients who unknowingly ingested the chemical.

It has also raised questions about Health Canada's oversight of the new industry.

The industry was created three years ago by the federal government to provide safe, pharmaceutical-quality products that could be trusted by doctors and patients, including those with compromised immune systems.

While myclobutanil is known as a prohibited, potentially dangerous chemical when inhaled, the documents from 2015 show the industry contemplated using it nonetheless.

According to minutes from a Canadian Medical Cannabis Industry Association (CMCIA) conference call held in February that year, two federally licensed medical marijuana growers, Tilray and MedReleaf, were in favour of seeking federal approval for the right to use myclobutanil and were seeking broader industry support for the idea.

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A third company, Thunderbird Medical, wanted permission to use the chemicals AzaMax and Spinosad, which were prohibited under federal rules.

It is not known from the meeting minutes which licensed producers, or LPs, supported the proposal and which opposed the idea. However, a Jan. 28 e-mail obtained by The Globe and Mail shows that one member of the industry group, a company called MedCannAccess, which is now owned by Canopy Growth Corp., wanted to "get input from all LPs" before proceeding.

The documents suggest the desire to use such chemicals in Canada's medical marijuana sector was greater than originally believed. In 2015, the CMCIA represented the majority of the roughly two dozen medical marijuana companies licensed at the time. The group, which has since changed its name to Cannabis Canada Association, hired Ottawa lobbying firm Capital Hill Group to explore the pesticide approvals with the federal government.

Asked about those efforts this week, Tilray executive Philippe Lucas, who sat on the committee that organized the conference call, said he could not remember spearheading the idea. In the minutes from that meeting, Mr. Lucas is listed as the person who would "draft the letter" asking to use myclobutanil.

Reached by phone, Mr. Lucas requested The Globe send its questions via e-mail. A Tilray spokesman then followed up, saying that many licensed producers in 2015 were interested in seeking regulatory approval for using myclobutanil, which is typically used to fight costly outbreaks of powdery mildew that can devastate cannabis crops.

To gain approval, the companies needed assistance from the manufacturer, Dow AgroSciences, which needed to supply Health Canada with safety data for the product. The federal government would have to evaluate "the safety and efficacy of this product for use on cannabis," Tilray spokesman Zack Hutson said.

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The Globe reported in September that Tilray sought to lobby the B.C. government in March, 2015, for help in getting the pesticide approved federally, according to the province's lobbyist registry. However, it was not known that the industry conducted broader discussions and that more than one company supported the use of myclobutanil and other banned products.

Tilray abandoned the lobbying effort in B.C. after Health Canada issued a list of 13 approved pesticides that could be used instead. Mr. Hutson said Tilray has not used myclobutanil. The company has since left the trade group.

A spokesman for MedReleaf, the other company listed in the meeting minutes as supporting the idea, said its CEO Neil Closner does not remember specifics of the trade association's conversations. The spokesman said myclobutanil has never entered the company's facility in Markham, Ont., and that it tests for the compound regularly.

Sandy Pratt, CFO of Thunderbird Medical, now known as Emerald Health Botanicals, said her company was once briefly interested in using AzaMax and Spinosad, but dropped the idea in favour of more natural – and approved – pest-control methods. Her company has never used any prohibited chemicals on its crops and tests regularly for myclobutanil, she added.

The fungicidal pesticide myclobutanil is approved for foods such as grapes, because it can be safely metabolized by the digestive system. However, when used on plants that are smoked, the chemical enters the bloodstream directly through the lungs. When the banned pesticide problem emerged in Canada's medical marijuana sector a few months ago, Dow AgroSciences said it would not support the use of myclobutanil on cannabis.

Not all companies in the trade group supported the idea though. Eric Nash, whose company Island Harvest is seeking to be licensed by Health Canada, was part of the discussions. When contacted by The Globe this week, Mr. Nash said he was shocked by the February, 2015, internal group e-mail asking whether he wanted to be part of a wider push for more chemicals.

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"It gave me an uneasy feeling about the pesticide issue," he said, particularly since he was an organic grower. "[It] certainly made me question: 'Do I really want to be involved in the association if it's going to be condoning the widespread use of pesticides in the industry?'"

Mr. Nash said he had no inclination to get to the bottom of the pesticide issue at the time because the trade group had just notified companies who were not yet licensed, like his, that they would soon be voted out as members.

In September, before the pesticide was discovered at the two companies, Health Canada said it would take a zero-tolerance approach to the use of myclobutanil and other banned products.

However, the regulator told The Globe in January that the government had, in fact, not been testing for banned pesticides, because the industry knew it should not be using those chemicals – which essentially left the companies to police themselves.

Health Canada has since attached conditions to the licences of Mettrum and OrganiGram, requiring them to test products regularly to show they are clean. The regulator also announced the rest of the industry, comprised of 38 companies, would undergo random spot checks. But patients tell The Globe they are wary of trusting the industry, if producers aren't subject to regular testing.

Mr. Nash, an expert witness in the Federal Court case that overhauled the medical-marijuana laws last year, said he has been telling Health Canada for years that it should require third-party testing of all medical marijuana.

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"This plant does not require the use of any pesticide, herbicide, fungicide or insecticide," he said. "My philosophy is that cannabis should be produced as if you were growing it for consumption by a family member, partner or friend that you love. … This should be a guiding principle for the Canadian government, as regulator, and for each producer and supplier as distributors to consumers."