Two federally regulated medical-marijuana companies caught up in a tainted-cannabis scare are facing proposed class-action lawsuits from patients who unknowingly ingested banned pesticides.

Mettrum Ltd. and OrganiGram Inc. were both found selling medical marijuana that contained unauthorized chemicals, including the controversial pesticide myclobutanil, which produces hydrogen cyanide when combusted and can lead to serious health problems.

The suit against OrganiGram was filed in Nova Scotia Supreme Court on Monday by Halifax-based Wagners Law Firm, while a separate action against Mettrum was filed in Ontario Supreme Court by the firm Roy O'Connor LLP.

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Both actions are seeking certification from the courts and are asking that the companies be forced to refund patients' money, in addition to paying out further damages.

The OrganiGram suit is led by Halifax patient Dawn Rae Downton, who was not previously a marijuana user but was prescribed medical cannabis to alleviate serious back pain, the documents allege.

After taking the product daily, "Ms. Downton began to suffer from severe nausea and vomiting within approximately two weeks after first consuming the Affected Product," the documents allege. "The severity of the symptoms restricted her ability to stand, walk or leave the house. She was confined to her home and bed for the majority of the time. Even light household chores became unmanageable."

The Mettrum suit is led by Erin Christiansen, a Thunder Bay woman who unknowingly ingested tainted product purchased from the Toronto-based company, which has since been purchased by Canopy Growth Corp., Canada's largest medical-marijuana producer.

"I was disturbed to learn that unapproved pest-control products were used on Mettrum's medical-marijuana plants," Ms. Christiansen said in a statement. "If I had known there was a risk that Mettrum's plants had been treated with an unapproved pesticide, I would never have purchased the products."

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Neither OrganiGram CEO Denis Arsenault, nor Mettrum's owner, Canopy, were immediately available for comment Monday. The allegations have not been proven in court.

The tainted-cannabis problems have led to management shakeups at both companies. Last week, OrganiGram announced a new CEO, Greg Engel, would be taking the reins on March 13, while Mr. Arsenault is moving to the board of directors as executive chairman. And former Mettrum CEO Michael Haines was not retained by Canopy when it closed the deal to purchase the company Jan. 31.

The problems emerged several months ago when Mettrum issued a series of recalls in late 2016 due to the discovery of an unauthorized pesticide, pyrethrin. That led to subsequent tests that turned up banned myclobutanil.

While Mettrum informed some patients of the situation, neither the company nor Health Canada disclosed the discovery of myclobutanil to the broader public, including prospective patients, in their press releases announcing the recalls.

When The Globe and Mail called Mettrum's customer help line in December, a reporter had to specifically ask about the presence of myclobutanil before the company offered up the information.

Soon after the Mettrum problem came to light, OrganiGram announced its own recall due to myclobutanil, along with a second banned pesticide, bifenazate. Alberta-based Aurora Cannabis Inc. discovered the issue with OrganiGram's supply when it purchased a bulk shipment from the company and had it tested for contaminants.

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The discovery of banned pesticides in a regulated product sold as medicine has called into question Health Canada's oversight of the nascent medical-marijuana industry, particularly because the government does not require companies to prove through regular testing that their products are safe and free of unauthorized pesticides such as myclobutanil, which is considered carcinogenic.

Health Canada told The Globe that it didn't require companies to test for such chemicals because the industry knew they were banned and therefore shouldn't be using them – which effectively left companies to police themselves.

Myclobutanil, a fungicidal pesticide, is used to rid crops of mildew, and is often employed as a dangerous shortcut by unscrupulous cannabis growers in order to save crops hit by an outbreak. While the chemical is approved for some food crops, such as grapes, because it can be safely broken down by the digestive system, it is not approved for plants that are smoked. Dow AgroSciences, which manufactures the chemical, warns against using the product on cannabis.

A former Mettrum employee told The Globe he witnessed myclobutanil being sprayed directly on the company's plants as far back as 2014, despite knowing it was prohibited, and provided e-mail evidence showing that management was aware of the problem. Mettrum's former CEO, Mr. Haines, has not responded to numerous requests for comment by The Globe.

"Various individuals have clearly expressed their concern and disappointment over this situation and the [Mettrum] recalls," David O'Connor of the firm Roy O'Connor, said Monday. "This proposed class-action can provide these individuals with an efficient avenue to have their claims addressed in court."

Meanwhile, OrganiGram said last week that it conducted an internal investigation into its recall and could not determine how the chemical got into the company's plants.

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Wagners Law Firm said more than 2,000 customers are estimated to have purchased contaminated products from OrganiGram, which is based in Moncton, N.B.

The proposed class-action suit against OrganiGram alleges that the company "manufactured its organic medical-cannabis product without having in place adequate quality-control protocols."

The suit also alleges OrganiGram "took no immediate steps to modify its manufacturing practices once it became aware of the presence of prohibited pesticides in the Affected Product."

In particular, the suit claims customers of the company were misled on the safety of the medicine by the company's organic designation, which was provided by certification agency Ecocert Canada. That designation has since been suspended.

OrganiGram has offered customers a credit for the products they purchased. However, the suit seeks to have OrganiGram refund the financial proceeds made from the recalled products, in addition to other damages.

"OrganiGram has acted in such a high-handed, wanton and reckless or deliberate manner, without due regard to public health and safety as to warrant an award of punitive damages," the suit alleges.