CHICAGO, Ill. (Reuters) — Monsanto and U.S. farm groups sued California in mid-November to stop the state from requiring cancer warnings on products containing the widely used weed killer glyphosate.
The government of the most populous U.S. state added glyphosate, the main ingredient in Monsanto’s herbicide Roundup, to its list of cancer-causing chemicals in July and will require that products containing glyphosate carry warnings by July 2018.
California acted after the World Health Organization’s International Agency for Research on Cancer (IARC) concluded in 2015 that glyphosate was “probably carcinogenic”.
Roundup and Monsanto’s glyphosate-resistant seeds may become less attractive to customers if California requires warnings on products containing the chemical.
In the lawsuit, filed in federal court in California, Monsanto and groups representing corn, soybeans and wheat farmers reject that glyphosate causes cancer.
They say the state’s requirement for warnings would force sellers of products containing the chemical to spread false information.
“Such warnings would equate to compelled false speech, directly violate the First Amendment, and generate unwarranted public concern and confusion,” Scott Partridge, Monsanto’s vice-president of global strategy, said in a statement.
California’s Office of Environmental Health Hazard Assessment, which is named in the lawsuit, said it generally does not comment on pending litigation.
The controversy is an additional headache for Monsanto as it faces a crisis around a new version of a herbicide based on dicamba that was linked to widespread U.S. crop damage this summer.
The company, which is being acquired by Bayer AG for $63.5 billion, developed the product as a replacement for glyphosate following an increase of weeds resistant to the chemical.
Monsanto has already suffered damage to its investment of hundreds of millions of dollars in glyphosate products since California added the chemical to its list of products known to cause cancer, according to the lawsuit.
“Everything that we grow is probably going to have to be labelled,” said Blake Hurst, president of the Missouri Farm Bureau, a plaintiff in the lawsuit.