Monsanto's Partridge contended that "cherry-picking isolated documents out of context is an attempt by the plaintiffs' attorneys in pending litigation to distract from the science, which is not on their side."
The use of glyphosate has grown exponentially in the past two decades. The chemical has found its way into the food chain -- and into people's bodies. A study published this week in the medical journal JAMA showed that the number of Southern California adults who tested positive for glyphosate in their urine rose dramatically from 1993 to 2016, as did the amount of the chemical in those who excreted it.
In July, California added glyphosate to its list of cancer-causing chemicals under the Safe Drinking Water and Toxic Enforcement Act of 1986. The act, also known as Proposition 65, requires businesses to warn consumers if their products or facilities contain potentially unsafe amounts of any toxic substances known to cause cancer, birth defects or other reproductive harm.
California is the first state in the U.S. to "take regulatory action to protect our residents from this chemical," said Olga Naidenko, senior science adviser for the Environmental Working Group, a nonprofit research and advocacy organization. The move is "a huge step and has global implications."
The state's Office of Environmental Health Hazard Assessment, which is responsible for listing chemicals under Proposition 65, has proposed a threshold of 1.1 milligrams of glyphosate a day for an adult weighing 70 kilograms, or 154 pounds. That's about 122 times more stringent than the federal Environmental Protection Agency's safety guideline.
The state agency is studying more than 1,300 written public comments, along with oral testimony from a June hearing, to decide whether it should implement or revise its proposed limit.
The Prop. 65 listing requires warning labels beginning next July.
Other companies, including Dow AgroSciences and DuPont, also sell products containing glyphosate, since Monsanto's patent expired in 2000.
California's decision to list the chemical was triggered by a 2015 study from the World Health Organization that described the chemical as "probably carcinogenic to humans" and cited "convincing evidence that glyphosate also can cause cancer in laboratory animals."
The organization's International Agency for Research on Cancer found a "positive association" between exposure to glyphosate and malignancy in humans, though it added that other explanations could not be excluded. In particular, the international agency found a possible link to non-Hodgkin lymphoma, the type of cancer that killed Jack McCall.