The chemical structure of glyphosate, the active ingredient in the Monsanto weed killer Roundup. (via Wikipedia)

OAKLAND, Calif. (CN) – A pathologist who testified in two prior trials over Roundup’s connection to cancer testified Tuesday that years of intense spraying of the world’s most popular weed killer likely caused a Livermore couple’s aggressive lymphoma.

“It’s not a hard call,” Dr. Dennis Weisenburger said on the witness stand Tuesday, adding that using Roundup more than two days per year doubles the risk of developing non-Hodgkin lymphoma.

Alva Pilliod, 76, and Alberta Pilliod, 74, were diagnosed with the most common form of non-Hodgkin lymphoma, diffuse large B-cell lymphoma, within four years of each other. Alberta was diagnosed in 2015, her husband in 2011. Both had sprayed the herbicide around their properties for roughly 30 years.

Weisenburger said the number of years used is actually not as important as the number of days.

“It’s the intensity of exposure that’s more important than the length,” he said.

Weisenburger estimated Alberta used Roundup about 279 times, and Al sprayed 729 times. Neither wore protective equipment as they believed it to be safe.

The Pilliods appeared in court Tuesday for Weisenburger’s testimony, both relying on canes to steady themselves. Alberta Pilliod, who suffered brain damage from her cancer, lost her balance at times and was assisted by one of her attorneys.

Weisenburger, who now works at City of Hope in Southern California, said he was in private practice in Sacramento when in 1983, he decided move to Nebraska to study a sudden increase in cases of non-Hodgkin Lymphoma.

“People were wondering why this is happening. We tried to figure out why was this increase all of a sudden,” he said.

When the National Cancer Institute published a study finding certain pesticides caused non-Hodgkin lymphoma, Weisenburger wondered whether it was related to what was happening in Nebraska.

“That piqued my interest,” Weisenburger said.

He had already begun mapping swaths of eastern Nebraska, looking for a correlation between counties with high rates of non-Hodgkin lymphoma and large concentrations of crops. “I tried to see if there was a correlation between intense agriculture and hematological malignancies, and there was a correlation,” he said.

Weisenburger called up Dr. Aaron Blair with the National Cancer Institute. Along with the Kansas study and a study of farming communities in Iowa and Minnesota, the research they conducted in Nebraska became the basis of a 2003 paper they wrote with Dr. Anneclaire De Roos in which they said certain herbicides may increase the risk of non-Hodgkin lymphoma. One of those herbicides is glyphosate, the active ingredient in Roundup, which came on the market in the mid-1970s.

Asked by the Pilliods’ attorney Michael Miller whether that study formed his conclusion about Roundup and its link to cancer, Weisenburger said, “It’s one piece of the puzzle. At the time there wasn’t much information there, but since then there’s been a lot more research done.”

One of the latest studies came out in February 2019. Along with several colleagues, UC Berkeley toxicologist Luoping Zhang pooled data from several other studies, including the Agricultural Health Study, and performed a meta-analysis which found a statistically significant increase in the risk of developing non-Hodgkin lymphoma when exposed to glyphosate-based herbicides.

Miller noted that the Zhang study seemed to confirm Weisenburger’s 2003 findings.

Under cross-examination by Monsanto attorney Tarek Ismail, Weisenburger acknowledged he never discussed Roundup or glyphosate as a cancer risk factor with oncologists or included it in the pathology reports of the cancer patients he has evaluated.

“I had no reason to,” Weisenburger said, noting that it was beyond the scope “of what pathologists are expected to do.”

There are a number of other risk factors for non-Hodgkin lymphoma – a family history of blood cancers, obesity, viral infections and immunodeficiency among them. Alberta has had bladder cancer and Hashimoto’s disease, a condition in which the immune system attacks the thyroid gland. Al has had skin cancer and meningitis. Weisenburger said he ruled out all of these in the Pilliods’ case.

Ismail, who sought to dismantle Weisenburger’s earlier testimony, pressed him to acknowledge that non-Hodgkin lymphoma is largely idiopathic, meaning there’s usually no known cause for developing this type of cancer. Millions of people who developed non-Hodgkin lymphoma did so prior to Roundup being sold, Ismail said, and “the vast majority of people who are diagnosed with non-Hodgkin lymphoma haven’t used Roundup.”

He also assailed a 2006 article Weisenburger wrote about the rearrangement of chromosomes and agricultural pesticides, specifically the translocation of the t(14;18) chromosome. The paper found that there is an increased risk of developing non-Hodgkin lymphoma when this chromosome tests positive for translocation. For Alberta, the test was negative; the test was never conducted for Al.

Weisenburger protested. “It doesn’t mean that people who don’t have the t(14;18) translocation don’t get NHL,” he said, using the acronym for non-Hodgkin lymphoma. “It’s just a correlation.”

Ismail used that to refute the correlations Weisenburger found between pesticide use and cancer.

The attorney also noted Alva and Alberta were smokers for about 20 years, both starting at a young age. He pointed to a 2007 article Weisenburger wrote that found among women who ever smoked an association with t(14;18) negative non-Hodgkin lymphoma, the kind Alberta developed.

The Pilliods’ case is the third to go to trial to go to trial alleging Roundup causes non-Hodgkin lymphoma. A jury awarded Ed Hardeman $75 million in punitive damages last month, and a state court jury in August 2018 awarded San Francisco Bay Area groundskeeper Dewayne Johnson $289 million in damages – later reduced by a judge to $78 million – after finding Roundup caused his terminal non-Hodgkin lymphoma.