It has only been a few weeks since the world’s long-term agribusiness juggernaut Monsanto was folded into the new agribusiness juggernaut Bayer, and already the new market leader finds itself facing a flood of lawsuits.

In San Francisco, California, a US district court judge on Jul. 10 gave the green light for hundreds of previously pending claims against Monsanto filed by cancer sufferers or their families to proceed to trial. The plaintiffs contend that the company’s Roundup-branded herbicide – containing the controversial chemical glyphosate as an active ingredient – caused their tumors.

According to one estimate, some 4,000 glyphosate-related lawsuits are pending against the US company. Robert F. Kennedy Jr, an environmental lawyer and son of the late US senator attorney general, said his law firm has 700 clients "in the pipeline" with Roundup cancer cases.

Parallel to the San Francisco ruling, the first trial on the cancer allegations began in the same city. An attorney for DeWayne Johnson, a 46-year-old groundskeeper at a California school who was diagnosed in 2014 with non-Hodgkin’s lymphoma, alleged that Monsanto knew about the risks associated with the herbicide but failed to warn buyers or users.

While acknowledging that evidence that the chemical causes cancer is “rather weak," the judge said the opinions of three experts linking glyphosate to non-Hodgkin’s lymphoma “are not junk science". Monsanto has consistently rejected any connection between Roundup and cancer. In the past, it sued California’s Office of Environmental Health Hazard Assessment for adding glyphosate to a list of potential carcinogens, but lost the case.

In his opening statement at the current trial, Johnson’s attorney, Brent Wisner, said his client used a Monsanto generic version of Roundup called "Ranger Pro" repeatedly in his job. Not only did the company not warn consumers of the risks, Wisner told the jury, instead, it "fought science" by playing down the suspected link to cancer and also went out of its way to “bully scientists and fight researchers".

 The international discussion over whether glyphosate is a carcinogen has been raging for some time, in particular since 2015, when the International Agency for Research on Cancer – an agency of the World Health Organization (WHO) – classified the chemical as "probably carcinogenic to humans", which led to the California listing.

The US Environmental Protection Agency (EPA) has been on both sides of the issue, most recently concluding that glyphosate is not a likely carcinogen. A US Department of Health study has suggested its toxicity is limited.

In Europe, the heated discussion and pending studies last year delayed for months an EU decision on renewing the registration of glyphosate. Both the European Food Safety Agency (EFSA) and the European Chemicals Agency (ECHA) downplayed any threat to health when the herbicide is applied as directed.

Although the EU license was renewed for five more years in November – over the opposition of France, after Germany changed its vote at the last minute – opposition to the chemical remains fierce in Europe.  France has pledged to phase out its use by 2020.

In June of this year, a beekeeping cooperative in northern France filed a legal complaint against Bayer after traces of the controversial herbicide ingredient glyphosate were found in batches of honey.