A Saskatchewan farmer is leading a class action lawsuit alleging that the widely-used herbicide Roundup caused him to develop cancer, teeing up a legal fight with one of the largest pharmaceutical companies in the world.

The farmer, identified in a statement of claim as 62-year-old Gary Gadd from Moose Jaw, regularly sprayed the weed killer on his farm and others, according to his lawyer, Tony Merchant.

“He was a heavy user for a couple of decades,” Merchant told CTVNews.ca. He said his client received training “a couple times” on how to safely handle herbicides. “And he has said to me, nobody was told to pay any attention to the fumes.”

Roundup's active ingredient is glyphosate, a Health Canada-approved herbicide that is in more than 130 products sold across Canada.

But three recent lawsuits in the United States ruled in favour of plaintiffs who alleged that Roundup was linked to their cancer. Earlier this week, a jury in California awarded US$2 billion to a couple who used the chemical and were diagnosed with cancer.

And those cases could be the tip of the iceberg. An estimated 13,000 plaintiffs across the U.S. have pending lawsuits against the company over Roundup.

In the statement of claim, filed in a Saskatchewan court, Gadd alleges that using Roundup caused him to develop non-Hodgkin’s lymphoma five years ago. He does not have a family history of cancer.

The statement of claim describes Roundup as “more dangerous than an ordinary customer would expect” and says the defendants “knew of or ought to have known that Roundup posed a risk of cancer and other serious illness.”

The statement of claim names defendants as Monsanto, which makes Roundup, and Bayer, which bought Monsanto in 2018.

The class-action case has yet to be certified by a judge.

In a statement to CTV News, Bayer insisted that glyphosate is safe.

“While we have great sympathy for the plaintiffs, glyphosate-based herbicides are not the cause of their illnesses and we will rigorously defend our products,” the company said in a statement.

“Glyphosate has been extensively studied globally by scientists and regulators, and results from this research confirm it is not carcinogenic. We firmly stand behind the safety of glyphosate-based products and as a company devoted to life sciences, assure Canadians that their health and the environment are our top priority.”

Bayer added that case is “at a very early stage” and there has been no decision on the merits.

Merchant said he has already been contacted by about a dozen other people, mostly from Quebec, who believe Roundup caused them to develop cancer. But he expects that more are out there.

Merchant’s firm, Merchant Law Group LLP, specializes in class action cases, and is possibly best known for its successful Sixties Scoop litigation against the federal government.

Merchant said he’s taken on Bayer before in cases involving prescription drugs – “but this is bigger than a drug.”

“Because their sales are so huge and their sales are worldwide, and this is an unmanaged product,” he said.

Merchant described Gadd as an “ideal” plaintiff to lead the case because he took courses on how to properly handle herbicides like Roundup.

“I say ‘ideal’ because one of my expected defenses by the companies will be that you didn’t follow the labels or you didn’t do what you were supposed to be doing. And he has been,” Merchant said.

The lawsuit highlights a lack of oversight in Canada over products like Roundup, Merchant says. He says the product isn’t tracked as closely by federal authorities as medical devices or medications, which means that there isn’t a large pool of historic data on cancer rates and Roundup.

“Nobody is monitoring this issue with Monsanto,” Merchant said.

Without a federally-regulated pool of data, it’s difficult to determine just how many people developed cancer after using Roundup versus the general population. But Merchant said his team has experts who say using Roundup “significantly increases” a person’s risk of developing cancer.

The case will also refer to public reports and “sundry different sources” to determine a link.

Merchant said taking on Bayer and Monsanto will be “a difficult undertaking.”

“They have more money than God,” he said. “They will have the best lawyers in the universe descend on me. I’m used to that. Sometimes I walk into courtrooms and there are 25 lawyers and I feel like Rambo.”

Health Canada approved glyphosate for use in Canada in 2017 during a scheduled reassessment. The in-depth review, carried out by federal scientists, considered more than 1,300 studies.

Earlier this year, Health Canada ordered a team of 20 scientists to review the 2017 decision. The team reaffirmed that the weed killer is safe.

"The objections raised did not create doubt or concern regarding the scientific basis for the 2017 re-evaluation decision for glyphosate," said Connie Moase, a director in the health-effects division of the Pest Management Regulatory Agency.

Shares in Germany’s Bayer plummeted in March after a California jury unanimously ruled in favour of a 70-year-old man, saying that Roundup was a substantial factor in his cancer. The plaintiff was awarded US$80 million. The company said it would appeal the case.

Last fall, an advocacy group found traces of glyphosate in a number of common food items, including cookies, donuts and bagels.

With files from The Canadian Press