|Tissue slides from long-dead lab mice could play a pivotal|
role in hearings against Monsanto.
Jan Philip Oeven / Flickr
by Carey Gillam, Environmental Health News, 9 June 2017
Call it the case of the mysterious mouse tumor.
It's been 34 years since Monsanto Co. presented U.S. regulators with a seemingly routine study analyzing the effects the company's best-selling herbicide might have on rodents. Now, that study is once again under the microscope, emerging as a potentially pivotal piece of evidence in litigation brought by hundreds of people who claim Monsanto's weed killer gave them cancer.
This week, tissue slides from long-dead mice in that long-ago research study are being scrutinized by fresh eyes as an expert pathologist employed by lawyers for cancer victims looks for evidence the lawyers hope will help prove a cover-up of the dangers of the weed killer called glyphosate.
Glyphosate, which is the active ingredient in Monsanto's branded Roundup products, is the most widely used herbicide in the world, and is applied broadly in the production of more than 100 food crops, including wheat, corn and soy, as well as on residential lawns, golf courses and school yards.
Residues have been detected in food and human urine, and many scientists around the world have warned that exposure through diet as well as through application can potentially lead to health problems. The World Health Organization's International Agency for Research on Cancer (IARC) declared glyphosate a probable human carcinogen in 2015 based on a review of scientific literature, triggering the wave of lawsuits against Monsanto, and pushing California regulators to announce they would add glyphosate to a list of known carcinogens.
What the expert finds, or doesn't find, is expected to be key evidence in hearings slated for the week of Dec. 11 in dozens of consolidated cases being overseen by a federal judge in San Francisco.
Rewind to 1983
Monsanto, as well as many other scientists and regulatory bodies, have defended glyphosate's safety. They say research showing a cancer connection is flawed and hundreds of studies support its safety.
And yet—rewind to July 1983 and a study titled "A Chronic Feeding Study of Glyphosate (Roundup Technical) in Mice." Following the document trail that surrounds the study offers an illuminating look into how science is not always clear-cut, and the lengths Monsanto has had to go to in order to convince regulators to accept scientific interpretations that support the company's products.
The two-year study ran from 1980-1982 and involved 400 mice divided into groups of 50 males and 50 females that were administered three different doses of the weed killer or received no glyphosate at all for observation as a control group. The study was conducted for Monsanto to submit to regulators. But unfortunately for Monsanto, some mice exposed to glyphosate developed tumors at statistically significant rates, with no tumors at all in non-dosed mice.
A February 1984 memo from EPA toxicologist William Dykstra stated the findings definitively: "Review of the mouse oncogenicity study indicates that glyphosate is oncogenic, producing renal tubule adenomas, a rare tumor, in a dose-related manner." Researchers found these increased incidences of the kidney tumors in mice exposed to glyphosate worrisome because while adenomas are generally benign, they have the potential to become malignant, and even in noncancerous stages they have the potential to be harmful to other organs. Monsanto discounted the findings, arguing that the tumors were "unrelated to treatment" and showing false positives, and the company provided additional data to try to convince the EPA to discount the tumors.
But EPA toxicology experts were unconvinced. EPA statistician and toxicology branch member Herbert Lacayo authored a February 1985 memo outlining disagreement with Monsanto's position. A "prudent person would reject the Monsanto assumption that Glyphosate dosing has no effect on kidney tumor production," Lacayo wrote. "Glyphosate is suspect. Monsanto's argument is unacceptable."
Eight members of the EPA's toxicology branch, including Lacayo and Dykstra, were worried enough by the kidney tumors in mice that they signed a consensus review of glyphosate in March 1985 stating they were classifying glyphosate as a Category C oncogen, a substance "possibly carcinogenic to humans."