SAN FRANCISCO (CN) - On the 14th day of a California jury trial over whether Monsanto's Roundup weed killer triggered a Bay Area man's terminal lymphoma, a Harvard cancer epidemiologist denied telling the jury that research showing a link between the herbicide and cancer is flawed because Monsanto paid her $100,000.
Running through a number of epidemiological studies finding an association between Roundup's active ingredient glyphosate and non-Hodgkin lymphoma, Lorelei Mucci said the studies suffered from measurement errors and flawed designs that undermined their conclusions that the two are linked.
Mucci, meanwhile, testified that studies that used data from a National Cancer Institute-backed study finding no link and lauded as the "gold-standard" by Monsanto weren't flawed.
She concluded that, although the epidemiological evidence is limited, "there is no causal association between exposure to glyphosate-based herbicides and NHL [non-Hodgkin lymphoma]," the illness from which plaintiff DeWayne Johnson is dying.
Johnson's attorney Brent Wisner, however, pointed out that Mucci wrote in a 2001 study that when such evidence is limited, researchers can assess cancer risk using biological plausibility, a method for establishing a causal relationship between a biological factor and a disease.
"So before you were hired by Monsanto, you turned to biological plausibility to explain it, didn't you?" the Baum Hedlund Aristei Goldman attorney said. "You haven't in this case, have you?"
Mucci countered that her opinions about the two studies differed because she hadn't concluded in her study that a causal link existed between cigarette smoking during pregnancy and developing non-Hodgkin lymphoma during childhood.
"Another difference between this study and what you've presented here today is you were paid 100 grand by Monsanto," Wisner shot back.
Although U.S. and European regulators have concluded glyphosate is safe, the World Health Organization’s International Agency for Research on Cancer classified it in 2015 as a probable human carcinogen, triggering a slew of lawsuits against Monsanto in the United States, including Johnson’s.
Johnson, 46, sued Monsanto in 2016 after being diagnosed with a cutaneous form of non-Hodgkin lymphoma that caused cancerous lesions to form over most of his body. He says he developed symptoms after he was twice drenched in Roundup and regularly had it drift into his face while spraying schoolyards for his job with the school district in Benicia, a suburb of San Francisco.
He also claims Monsanto has known for decades that Roundup is carcinogenic but didn’t disclose it for fear of disrupting its multi-billion dollar global business.
On Tuesday, Mucci praised a controversial 2018 study that used data from the Agricultural Health Study, a cohort study by the National Cancer Institute, the U.S. Environmental Protection Agency and other federal agencies looking at the long-term exposure to pesticides of farmers and other pesticide users. The 2018 study found no association between glyphosate use and non-Hodgkin lymphoma.
Monsanto says the Agricultural Health Study is the best of its kind due to its size and comprehensiveness. But Johnson's experts have slammed the 2018 update for its use of a statistical tool called imputation, which they said caused a 20 percent error in the results that invalidate its conclusions.
Because 40 percent of the study's 54,000 participants dropped out, researchers estimated those participants' cancer outcomes using imputation based on the answers of the remaining 60 percent of participants.
But Mucci said the 20 percent error boiled down to a 1.8 percent error overall because the error only applied to the nine percent of study participants who hadn't been exposed to glyphosate at the beginning of the study.
"We're really talking about a small percentage of the 54,000," she said.
Wisner pointed out that people exposed to glyphosate and already diagnosed with cancer weren't allowed into the study.
"So what we have here is people naturally resistant to cancer," he said.
Mucci said cohort studies follow only individuals who start out healthy.
It is "one of the standard epidemiological practices you take, and it doesn't lead to any bias," she said.
Earlier in her testimony, Mucci flagged factors she said led multiple past studies to overestimate the risk of developing non-Hodgkin lymphoma from using glyphosate. They included various forms of bias, such as failing to adjust results to account for the use of other pesticides, and using proxy data - data about a participant's glyphosate use obtained from family members because the participant has died or become too ill to respond.
But on cross-examination, Wisner presented Mucci with a study she wrote prior to signing on with Monsanto in which she stated that data gathered from proxies "for most categories of questions in epidemiology studies" are reliable.
And in the 2001 cigarette study, Wisner noted that Mucci had said the data "suggest a small excess risk" of a child developing non-Hodgkin lymphoma if exposed to cigarette smoke in the womb.
"The odds ratio is 1.5; that's not statistically significant," Wisner said, referring to glyphosate research Mucci had earlier criticized. "So in this study," he said, turning to the cigarette study, "there's a 1.25 risk ratio that's not statistically significant, but you still reported that as a small excess risk."
Mucci denied interpreting the epidemiology research on glyphosate and non-Hodgkin lymphoma in Monsanto's favor.
"I don't think that's a fair assessment at all," she said.
Glyphosate is the most widely used agrichemical in history. Monsanto introduced it in 1974, and its use exploded in 1996 after the company began selling “Roundup-ready” seeds engineered to resist the herbicide. More than 2.6 billion pounds of the chemical were spread on U.S. farmlands and yards between 1992 and 2012, according to the U.S. Geological Survey.
Monsanto earns $1.9 billion a year from Roundup and $10.2 billion from “seeds and genomics,” most of that category being Roundup-ready seeds.
In June, German pharmaceutical giant Bayer completed its $63 billion acquisition of Monsanto after approval by U.S. and European regulators. Bayer told Reuters that same month it plans to retire the Monsanto name.
Testimony continues before San Francisco Superior Court Judge Suzanne Ramos Bolanos Thursday.
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