DW.com - A US jury concluded on Tuesday that the Roundup weed killer was a "substantial factor" in causing cancer in a 70-year-old California man.

The ruling is a blow to Bayer, whose subsidiary Monsanto makes the herbicide. The trial could pave the way for more cases linking glyphosate in Roundup to the development of cancer.

Details of the case:

• California resident Edwin Hardeman was diagnosed with non-Hodgkin's lymphoma after using Roundup for 25 years.
• The San Francisco jury came to a unanimous verdict that the weed killer had contributed greatly.
• Now the trial will enter a second phase to determine whether Monsanto is liable for damages.
• The plaintiff's lawyers may now present evidence showing Monsanto's efforts to sway scientists and influence regulators.

Bayer rejects liability

Hardeman's lawyers said: "Now we can focus on the evidence that Monsanto has not taken a responsible, objective approach to the safety of Roundup."

Bayer, which acquired Monsanto last year, said: "We are confident the evidence in phase two will show that Monsanto's conduct has been appropriate and the company should not be liable for Mr. Hardeman's cancer."

Does glyphosate cause cancer?

While critics are quick to describe glyphosate — the main chemical substance in Roundup — as carcinogenic, research is far from definitive on the question.

According to EU health authorities, "experts, with only one exception, concluded that glyphosate is unlikely to pose a carcinogenic hazard to humans and the evidence does not support classification with regard to its carcinogenic potential."

However, the UN's World Health Organization has said it is "probably carcinogenic to humans."

Pandora's box?

The case is seen as a bellwether trial for more than 11,000 Roundup lawsuits expected to go trial in the US. It is expected to determine settlement options for more than 700 cases consolidated in San Francisco's federal court.

Last year, a judge in San Francisco upheld a jury's verdict that found Monsanto liable for a groundkeeper's cancer. The case is in appeals after the judge slashed damages from $289 million (€255 million) to $78 million.

Editor: Hasbi Maulana