Experts Behind Product Liability Suit Against Monsanto Herbicide Don’t Impress Judge

A lawsuit claiming Monsanto Co.’s popular weed killer Roundup causes cancer was dealt a blow by a judge’s conclusions that the opinions of the experts testifying against it are “shaky,” a potentially devastating development for the case getting to trial.

U.S. District Judge Vince Chhabria is the first judge to weigh in on the toxicity of the world’s most popular herbicide, the subject of a heated debate among scientists and regulators worldwide for more than 30 years. Any key witnesses who are cut from the lineup may profoundly shape the outcome of more than 300 lawsuits collected before the judge — all the cases in federal courts that seek to hold Monsanto liable for its failure to warn about the risks of using Roundup.

The San Francisco judge heard from about a dozen witnesses including toxicologists, statisticians and an oncologist. But he took an especially keen interest in a couple of epidemiologists who study how humans contract disease.

“I do have a difficult time understanding how an epidemiologist in the face of all the evidence that we saw and heard last week” can conclude that glyphosate “is in fact causing” non-Hodgkin lymphoma in human beings, he said Wednesday. “The evidence that glyphosate is currently causing NHL in human beings” at current exposure levels is “pretty sparse,” he said.

Judge to Decide on Evidence to Allow in Monsanto Product Liability Litigation

It remains to be seen which witnesses will be allowed to testify at trial on behalf of more than 700 farmers, landscapers and gardeners claiming that exposure to glyphosate — through skin contact or inhalation — caused their non-Hodgkin lymphoma. The judge didn’t say when he’d arrive at a final decision.

Chhabria gave some credit to Beate Ritz, a public health professor at the University of California at Los Angeles, for having conducted independent analysis. Still, Chhabria described her conclusion that glyphosate is currently causing NHL in humans “dubious.” He gave a strong indication that Ritz may be the only witness he allows to testify for the plaintiffs, and that even she is at risk of being eliminated.

Monsanto isn’t completely off the hook, based on what Chhabria said Wednesday. At this stage of the case the judge is acting as a gatekeeper to exclude evidence not backed by scientific rigor, and evaluating whether the witnesses are qualified as experts to present their conclusions to a jury. He said his role is to decide whether the testimony is “in the range of reasonableness,” not whether glyphosate causes cancer.

Chhabria said he’s concluded after the hearings that epidemiology is a “loosey-goosey” and “highly subjective field.” Because of constraints with regard to eliminating witnesses, that may leave room for Ritz to testify, he said. Maybe Ritz “is operating within the mainstream of the field,” he said. “Maybe that means it’s up for the jury to decide if they buy her presentation.”

All the plaintiffs’ experts except Ritz relied on a 2015 determination that glyphosate is a probable human carcinogen by the International Agency for Research on Cancer, an arm of the World Health Organization, Chhabria said. That’s “not enough” to argue exposure to glyphosate is more likely than not the cause of the plaintiffs’ cancer, he said.

Brent Wisner, a lawyer for the plaintiffs, urged the judge not to reject witnesses based on their reliance on the IARC report alone and to instead “dissect” and consider the “subset of opinions” within their reports and findings.

Michael Baum, a lead lawyer for the group suing Monsanto, said “the weight of the epidemiology, toxicology and mechanistic science strongly supports” the conclusion that Roundup causes non-Hodgkin lymphoma. “Our experts used valid methodologies to arrive at their conclusions,” he said in an emailed statement. “Ultimately, we think courts will agree.”

The case is In re: Roundup Products Liability Litigation, MDL 2741, U.S. District Court, Northern District of California (San Francisco).