Defense expert denies link between Roundup and cancer

SAN FRANCISCO -- Monsanto's expert epidemiologist in the first of the federal test cases arguing the company's weedkiller causes cancer urged the jury on Friday to weigh human studies more heavily than the animal or mechanistic analyses as the initial phase of the trial draws to a close.

The studies testing real world exposure in real life populations are the "highest level of evidence" to understand whether Roundup is linked to cancer, according to Lorelei Mucci, a Harvard School of Public Health professor.

"Based on my evaluation of all epidemiological studies, there's no evidence of a causal association between glyphosate exposure and the risk of Non-Hodgkin lymphoma," Mucci added.

Attorneys on both sides have keyed in on the dispute as among the central issues in the trial, which wrapped up its second week of testimony. Plaintiffs' lawyers have repeatedly said the entirety of the scientific literature -- the epidemiological, animal and mechanistic studies -- proves an association between glyphosate and cancer, and Bayer AG-owned Monsanto is ignoring inconvenient evidence.

The defense, in turn, has argued the National Cancer Institute's Agricultural Health Study is the most comprehensive analysis on the matter. The study followed the health outcomes of nearly 45,000 farmers who sprayed glyphosate-based weedkillers and spawned several follow-up studies.

U.S. District Judge Vince Chhabria has repeatedly emphasized the trial verdict will hinge on the independent analyses of both sides' experts.

He has limited testimony on the findings and methodology of regulatory bodies, including the Environmental Protection Agency and International Agency for Research on Cancer, because he wants the jury to consider the question on their own based on the experts' opinions.

Mucci told the jury the studies the plaintiff's attorneys have offered suffer from an insignificant number of participants who were not followed long enough and fail to adjust for exposure to other pesticides, while the cancer institute's study has been "repeatedly validated" and has statistical significance and a substantial number of participants.

Plaintiff Edwin Hardeman's allegations are the first of three test cases in the consolidated litigation. In re Roundup Products Liability Litigation, 16-MD02741 (N.D. Cal., filed Oct. 4, 2016).

Since the trial is split into two phases, the jury will only hear accusations of misconduct and whether additional damages are warranted if it finds Monsanto liable for causing Hardeman's cancer.

After he excused a juror for hardship previously, Chhabria excused another last week because of the flu and concern over getting others sick. There are now six members of the jury, the minimum for federal court.

The judge said he wants closing arguments to be heard Tuesday.

Both sides will submit their presentations in advance after the judge sanctioned a plaintiff's attorney, Aimee H. Wagstaff of Andrus Wagstaff PC, for discussing inadmissible evidence during her opening remarks.

Addressing arguments by the plaintiff's attorneys that the Agricultural Health Study suffered from "massive exposure misclassification," Mucci said the study participants want to give accurate information because they "care about their health and what's happening to them," which drew a speculation objection from Wagstaff that was overruled.

The epidemiologist continued that if exposure to Roundup really does cause Non-Hodgkin lymphoma, participants in the institute's study would have a higher rate of cancer than those in the general population, which is not the case.

The depositions of Monsanto toxicologists William Reeves and Donna Farmer were also played for the jury on Friday concerning internal company communications.

The trial continues Monday with testimony from defense expert Alexandra Levine, a specialist on Non-Hodgkin lymphoma.