Monsanto Loses Challenge to Prop. 65 Cancer Listing

By William Vogeler, Esq. on April 25, 2018 | Last updated on March 21, 2019

This just in: Roundup, the weed killer, is also not good for humans.

Or as a California appeals court explained in Monsanto Company v. Office of Environmental Health Hazard Assessment, Roundup contains a chemical that is "probably carcinogenic to humans." It is not exactly news because state health officials concluded glyphosate is a potential carcinogen last year.

However, the court decision is big news to an industry that fought against the official taint on the widely used herbicide. It is probably not death to agriculture companies, but it's enough to make them sick.


California's OEHHA determined glyphosate was a probable carcinogen under Prop. 65, which requires state officials to identify and publish a list of known carcinogens. The law also mandates businesses to provide public warnings if they "knowingly and intentionally expose any individual to a chemical known to the state to cause cancer or reproductive toxicity."

Monsanto, joined by six major agricultural groups, challenged the Prop. 65 listing in state and federal courts. A federal judge ruled the state agency could not impose the warning requirement, saying the U.S. Environmental Protection Agency found no link to cancer.

In state court, however, a judge threw out Monsanto's complaint to delist the chemical. The judge said international studies supported the Prop. 65 listing.

On appeal, Monsanto argued that California improperly delegated its authority to a foreign agency.


The Fifth District Court of Appeal rejected the argument. The appeals panel said the state has authority to delegate legislative authority under long-settled principles "consistent with republican forms of government."

"Absent any specific ruling by a higher court that such disputes should be resolved by the courts, we conclude the general notion that such questions are nonjusticiable controls here," the judges said.

The appeals court also said Prop. 65 has built-in safeguards to protect against "potentially arbitrary or abusive determinations" that certain chemicals may cause cancer. The statute creates exemptions when exposure poses "no significant risk assuming lifetime exposure at the level in question."

In Monsanto's case, the OEHHA determined glyphosate was a probable carcinogen based on conclusions by 17 scientists working through the World Health Organization in Lyon, France.

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