Agribusiness giant Monsanto has been ordered by to pay $US289 million ($396 million) to a former school groundskeeper dying of cancer, with a San Francisco jury saying the company's popular Roundup weed killer contributed to his disease.
The lawsuit was the first to go to trial among hundreds filed in state and federal US courts claiming Roundup causes non-Hodgkin's lymphoma, which Monsanto denies.
Jurors in California's Superior Court agreed the product contributed to Dewayne Johnson's cancer and the company should have provided a label warning of the potential health hazard.
Mr Johnson's attorneys sought and won $US39 million in compensatory damages and $US250 million of the $US373 million they wanted in punitive damages.
"This jury found Monsanto acted with malice and oppression because they knew what they were doing was wrong and doing it with reckless disregard for human life," said Robert F Kennedy Jr, a member of Mr Johnson's legal team.
"This should send a strong message to the boardroom of Monsanto."
Monsanto has denied a link between the active ingredient in Roundup — glyphosate — and cancer, saying hundreds of studies have established that glyphosate is safe.
Mr Johnson used Roundup and a similar product, Ranger Pro, as a pest control manager at a San Francisco Bay Area school district, his lawyers said. He sprayed large quantities from a 189 litre tank attached to a truck, and during gusty winds the product would cover his face, one of his attorneys, Brent Wisner, said.
In one instance a hose broke and the weed killer soaked his entire body.
Mr Johnson read the label and even contacted the company after developing a rash but was never warned it could cause cancer.
He was diagnosed with non-Hodgkin's lymphoma in 2014 at age 42.
"The simple fact is he is going to die. It's just a matter of time," Mr Wisner told the jury in his opening statement last month.
But George Lombardi, an attorney for Monsanto, said non-Hodgkin's lymphoma takes years to develop, so Johnson's cancer must have started well before he began working at the school district.
The US Environmental Protection Agency says Roundup's active ingredient is safe for people when used in accordance with label directions.
However, the France-based International Agency for Research on Cancer, which is part of the World Health Organisation, classified it as a "probable human carcinogen" in 2015. And California has added glyphosate to its list of chemicals known to cause cancer.