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California to add key ingredient of Monsanto weed killer to list of cancer-causing chemicals

Monsanto's widely used weed killer Roundup on a shelf in Home Depot.
File photo | Eli Chen | St. Louis Public Radio
Monsanto's widely-used weed killer Roundup contains glyphosate, a chemical that's been the subject of multiple lawsuits that allege that it's linked to cancer.

Glyphosate, the active ingredient in Monsanto’s Roundup, will be added to the list of chemicals California warns are known to cause cancer.

The state’s Office of Environmental Health Hazard Assessment has posted a notice on its website that glyphosate will be added to the list on July 7. A California judge denied Monsanto's request to block the state from doing so, but the company has filed an appeal.

California’ Safe Drinking Water and Toxic Enforcement Act of 1986, known as Proposition 65, requires the state to publish a list of chemicals known to cause cancer or reproductive toxicity. It requires businesses to provide warning labels about significant exposure to the chemicals.

Monsanto officials said California’s decision was “unwarranted on the basis of science and law.” The company plans to continue to fighting it.

"This is not the final step in the process, and it has no bearing on the merits of the case,” Scott Partridge, Monsanto's vice president of global strategy, said in an emailed statement. “We will continue to aggressively challenge this improper decision."

Regulators have disagreed about glyphosate’s potential to cause cancer. A group of medical experts with the World Health Organization said in 2015 that the ingredient was a “probable carcinogen.” The Environmental Protection Agency concluded last fall that it’s not likely to cause cancer.

Follow Eli Chen on Twitter: @StoriesByEli

Eli is the science and environment reporter at St. Louis Public Radio.