Chemical giant Monsanto has been ordered to pay $289m in compensatory and punitive damages to a man who claimed herbicides containing glyphosate had caused his cancer. In a landmark case, a Californian jury found that Monsanto knew its Roundup and RangerPro weedkillers were dangerous and failed to warn consumers. It’s the first lawsuit to go to trial alleging a glyphosate link to cancer.

Monsanto denies that glyphosate causes cancer and says it intends to appeal against the ruling. “The jury got it wrong,” vice-president Scott Partridge said outside the courthouse in San Francisco.

Groundskeeper Dewayne Johnson was diagnosed with non-Hodgkin’s lymphoma in 2014. His lawyers said he regularly used a form of RangerPro while working at a school in Benicia, California. He is among more than 5,000 similar plaintiffs across the US. The California ruling is likely to lead to hundreds of other claims against Monsanto, which was recently bought by the German conglomerate Bayer AG.

Following an eight-week trial, jurors found that the company had acted with “malice” and that its weedkillers contributed “substantially” to Mr Johnson’s terminal illness. Mr Johnson’s lawyer, Brent Wisner, said the jury’s verdict showed that the evidence against the product was “overwhelming.”

The company disagreed. “Today’s decision does not change the fact that more than 800 scientific studies and reviews – and conclusions by the US Environmental Protection Agency, the US National Institutes of Health and regulatory authorities around the world – support the fact that glyphosate does not cause cancer, and did not cause Mr Johnson’s cancer,”

Glyphosate is the world’s most common weedkiller and the science about its safety is still far from settled.

In 2015 the International Agency for Research on Cancer, the World Health Organization’s cancer agency, concluded that it was “probably carcinogenic to humans”. but the US Environmental Protection Agency (EPA) continues to insist that glyphosate is safe when used carefully.

Campaigners question how the EPA assessment was reached, citing evidence of what they say was inappropriate industry involvement in the decision. Some Democrats have even called for a Department of Justice investigation into alleged collusion between government officials and Monsanto.

In California, where a judge recently ruled that coffee must carry a cancer warning, the agriculture industry sued to prevent such a label for glyphosate even though the state lists it as a chemical known to cause cancer.

In Europe the battle over glyphosate has been fierce. French President Emmanuel Macron is trying to ban it despite the resistance of some French lawmakers and the fact that the European Commission recently granted the weedkiller another five-year licence.

The evidence used in the case will likely be used to support industrial injury claims by California workers’ who have had work related exposure to glyphosate and suffer health consequences.