Judge skeptical of plaintiffs’ expert in Roundup case

SAN FRANCISCO — A federal judge said Wednesday he is skeptical about the plaintiffs’ ability to show an ingredient in Roundup weed killer products causes cancer.

The case involves claims the weed killer led to cases of non-Hodgkin’s lymphoma in the agricultural industry.

The lawsuit is not the same as a longstanding Proposition 65 battle over whether the weed killer had to be labeled as containing a known carcinogen.

U.S. District Judge Vince Chhabria told the plaintiffs they were relying too heavily on the International Agency for Research on Cancer’s decision to add a Roundup ingredient, glyphosate, to its list of substances that are “probably carcinogenic.”

The agency relied on data showing the chemical can lead to that specific form of cancer in animal tests, Chhabria said.

“The first easy issue is: Does the IARC’s conclusion that glyphosate is a probable carcinogen get the plaintiffs where they need to go? Answer, no,” he said.

The plaintiffs needed their expert, epidemiologist Dr. Beate Ritz, to provide enough evidence to go with the agency’s study to show that glyphosate has actually led to documented cases of non-Hodgkin’s lymphoma in humans, not just animal studies, Chhabria said.

“The IARC makes very clear what it is doing is reaching a conclusion about whether the chemical is capable of causing cancer,” he said.

The judge said the findings demonstrated that humans could theoretically get cancer from glyphosate if exposed to very high levels of the chemical, but the plaintiffs haven’t shown that any humans are getting that amount of exposure.

“The evidence that glyphosate is currently causing lymphoma in human beings at the levels of exposure they are currently experiencing is pretty sparse,” the judge added. “There’s at least a strong argument that the only reasonable conclusion one could draw right now is that we don’t yet now.”

He added that Ritz’s report seemed to cherry pick data and reached conclusions that weren’t fully supported by the research she cited. Chabbria said this didn’t necessarily mean Ritz would be excluded from testifying at trial, but that he was leaning in that direction.

Eric G. Lasker, a partner with Hollingsworth LLP and lead attorney for Monsanto Co. and several co-defendants, agreed that data was being cherry-picked by the plaintiffs. “Why is she presenting an abstract hypothesis instead of looking at the data?” he asked.

Chhabria said the plaintiffs’ expert seemed to mostly cite studies that didn’t account for the possibility that other pesticides might have contributed to high cancer rates among farmers.

“We know farmers had elevated non-Hodgkin lymphoma numbers before glyphosate ever came on the market,” he said.

Aimee H. Wagstaff, a partner with Andrus Wagstaff and lead attorney for the plaintiffs, argued that epidemiology is a complex field requiring a scientist to combine a wide swath of data points and determine which parts to emphasize in drawing conclusions.

“Our experts are looking at the totality of the evidence,” she said.

U.S. District Judge William Shubb, who is overseeing the Proposition 65 labeling cases regarding Roundup, said he was similarly skeptical of science linking glyphosate to cancer when he issued a preliminary injunction in late February temporarily halting requirements that the product be labeled as carcinogenic.