A jury in federal court in San Francisco on Tuesday concluded that Roundup weed killer was a substantial factor in a California man’s cancer. The company denies the connection.Haven Daley/AP

Vanessa Romo reports for National Public Radio 

A San Francisco federal jury unanimously agreed on Tuesday that Roundup caused a man’s cancer — a potentially massive blow to the company that produces the glyphosate-based herbicide currently facing hundreds of similar lawsuits.

After five days of deliberation, the jury concluded the weed killer was a “substantial factor” in causing non-Hodgkins lymphoma in Edwin Hardeman, a 70-year-old Sonoma County man.

The verdict is the second in the U.S. to find a connection between the herbicide’s key ingredient, glyphosate, and the disease. In August, another San Francisco jury determined Roundup had caused cancer in a former groundskeeper. It also decided Monsanto, the company that developed the popular weed killer, deliberately failed to warn consumers or regulators about the product’s risks.

In that case, jurors awarded the plaintiff, Dewayne Johnson, $289 million. However, a judge later slashed the damages payout to $78 million.

The German pharmaceutical and chemical giant Bayer bought Monsanto in June.

In a statement Tuesday, the company said it is disappointed with the jury’s decision “but we continue to believe firmly that the science confirms glyphosate-based herbicides do not cause cancer.”