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Monsanto and growers groups sue California over adding warning labels to glyphosate herbicides

Monsanto's widely used weed killer Roundup on a shelf in Home Depot.
File photo | Eli Chen | St. Louis Public Radio
California added glyphosate, Roundup's key ingredient, to its list of cancer-causing substances in July. That requires Monsanto and other pesticide companies to put warning labels on glyphosate-containing products.

Monsanto and several growers associations filed a federal lawsuit Wednesday against the state of California for adding the herbicide ingredient glyphosate to a list of cancer-causing substances. 

California's Office of Environmental Health Hazard Assessment announced in July it would add glyphosate to Proposition 65. Known as the Safe Drinking Water and Toxic Enforcement Act of 1986, the California law requires the state to publish a list of substances known to cause cancer or reproductive toxicity.


The law also requires companies that sell products containing any of the listed items to place warning labels about significant exposure. Monsanto's suit seeks to compel California to remove glyphosate from the list. 

The state's decision to add glyphosate to the list was based on a 2015 report from the International Agency for Research on Cancer that concluded that the chemical probably causes cancer. A number of farmers have sued Monsanto in the last year, claiming that exposure to Roundup caused them non-Hodgkin's lymphoma. However, Monsanto, the National Association of Wheat Growers and other agriculture industry groups say that putting a warning label on glyphosate products ignores research that's shown no link between the substance and cancer. 

"It's essentially scientific vandalism," said Scott Partridge, Monsanto's vice president of global strategy. "It distorts science and prevents people from having the confidence in science and medicine that they should." 

A study published in the Journal of the National Cancer Institute last week showed no strong link between glyphosate and any form of cancer, after looking at the health of more than 50,000 farm workers over the long term. The Environmental Protection Agency also concluded last year that the chemical isn't likely to cause cancer. 

"California's erroneous warning about glyphosate is unconstitutional and 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 Association of Wheat Growers, said in a statement. 

Follow Eli on Twitter: @StoriesByEli

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