In what could be the beginning of a tidal wave of litigation, a U.S. farm worker and a horticultural assistant have filed lawsuits against agribusiness giant Monsanto for health problems related to the use of the company’s blockbuster weed killer Roundup. The lawsuits accuse the company of knowingly putting an unsafe product on the market and misleading the public about the health risks of using the product.

The lawsuits come on the heels of a recent World Health Organization (WHO) decision that the active ingredient in Monsanto’s Roundup, glyphosate, would now be “classified as probably carcinogenic to humans.” That classification provides support for those suing Monsanto, who claim that the corporation put out an “unreasonably dangerous” product and either knew or should have known that glyphosate would endanger people’s health.

While Monsanto has been pushing back hard against WHO’s decision, the evidence linking glyphosate to cancer cannot be so easily dismissed.

While by no means a slam dunk case, the research arm of the WHO on cancer known as the International Agency for Research on Cancer (IARC) provided sound reasoning for its conclusion [PDF] on the link between glyphosate and cancer. The IARC cited animal studies where exposure to glyphosate caused tumors in mice and studies from the US, Canada, and Sweden which suggested a link between exposure to glyphosate and non-Hodgkin lymphoma.

The IARC also noted the US Environmental Protection Agency (EPA) classified glyphosate as “possibly carcinogenic to humans” in 1985. The EPA reversed its classification, but the IARC still found the research that led to EPA’s previous view relevant.

Though the EPA has not gone as far as the WHO in terms of how it classifies glyphosate, the agency will now, thanks to a legal settlement with the Center for Biological Diversity, more thoroughly study the effects of exposure to glyphosate on human health and the environment.

Furthermore, this week the EPA finalized new rules for workers using pesticides that include training on how to deal with hazardous chemicals and earlier in this month the State of California’s EPA began moving to label glyphosate as a carcinogen. Though the regulatory wheels are slow-moving, they are turning.

As The District Sentinel noted, agribusiness firms such as Monsanto fought aggressively to stop to the EPA’s new pesticide rules and will likely continue the battle against the federal rules and California’s incoming regulations.

And Monsanto has reason to fight. Glyphosate is one of the most used herbicides in the United States and the world. And though Monsanto’s patent on the chemical expired in 2000, it still makes billions on Roundup and selling genetically modified crops that can survive being sprayed with glyphosate. If glyphosate becomes broadly seen as carcinogenic, Monsanto could lose a fortune.

The fate of these lawsuits may determine the future of glyphosate and Monsanto.