Lawsuit challenges California warning that links Roundup weed killer to cancer


A coalition of a dozen national and Midwestern agricultural groups sued Wednesday to try to overturn a California decision that could result in labels warning that the popular weed killer Roundup can cause cancer.

The lawsuit filed in federal court in Sacramento seeks an injunction barring California from enforcing what the suit describes as a “false” and “misleading” warning. It alleges that the state’s decision violates constitutional due process and free speech rights and should be superseded by federal regulations.

Roundup’s main ingredient, glyphosate, is not restricted by the U.S. Environmental Protection Agency, and has been used widely since 1974 as a means of killing unwanted weeds while leaving crops and other plants alive.


But the International Agency for Research on Cancer, based in Lyon, France, has classified it as “a probable human carcinogen.” That prompted the California Office of Environmental Health Hazard Assessment to add glyphosate this summer to a list of chemicals known to cause cancer. The listing could eventually lead to a requirement for warning labels on the product.

The plaintiffs include the national wheat and corn growers associations, state agriculture and business organizations in Iowa, Missouri, North Dakota and South Dakota, and a regional group representing herbicide sellers in California, Arizona and Hawaii. The plaintiffs also include St. Louis-based Monsanto Co., which makes Roundup.

The lawsuit contends that California’s “false warning” has harmed Monsanto’s reputation and its investment of “hundreds of millions of dollars” in the herbicide and its related glyphosate-tolerant seeds.

The suit also alleges a ripple effect on food production across the country. It says entities that process crops for food products sold in California would have to stop using glyphosate-treated crops, add warning labels that could diminish demand for their products or engage in costly tests to show that any glyphosate residue is at safe levels.

California’s cancer warning “would result in higher food costs, crushing blows to state and agricultural economies and lost revenue up and down the entire supply chain,” Gordon Stoner, president of the National Assn. of Wheat Growers, said in a statement.

Sam Delson, a spokesman for the California Office of Environmental Health Hazard Assessment, said the agency hadn’t yet reviewed the new filing but is confident its rules are legal.


In March, a California state court judge dismissed a separate lawsuit by Monsanto challenging California’s cancer warning.

Midwestern states and interest groups also have challenged other California agricultural policies.

A federal appeals court panel ruled last year that six states — Alabama, Iowa, Kentucky, Missouri, Nebraska and Oklahoma — lacked the legal right to challenge a California law barring the sale of eggs from chickens not raised in accordance with California’s roomier cage-space requirements. The U.S. Supreme Court declined this year to hear an appeal.