The state of California will add glyphosate — the main ingredient in weed-killer Roundup — to a list of chemicals known by the state to cause cancer next month, signaling just the latest battle for Roundup manufacturer Monsanto after the company was accused of writing at least some of an academic research paper used to demonstrate glyphosate’s safety.
The California Office of Environmental Health Hazard Assessment (OEHHA) announced Monday that glyphosate would be added to the list of cancer-causing chemicals on July 7 as part of Proposition 65.
The safety of glyphosate has been debated for decades, with Monsanto long claiming that the chemical poses no risk to consumers. In 2015, the International Agency for Research on Cancer (a branch of the World Health Organization) classified glyphosate as “probably carcinogenic to humans.”
The inclusion of the chemical to the list comes after Monsanto’s challenge in trial court to prevent the listing was unsuccessful. While Monsanto has appealed the decision, there was no stay granted, meaning the listing can move forward.
California state law requires that certain substances identified by the IARC be listed as known to cause cancer under Proposition 65
By listing the chemical on the cancer-causing list, companies selling products with glyphosate will be required to add warning labels to packaging, notes Reuters. These companies, including Monsanto, will have a year from July 7 to re-label products or remove them from store shelves.
A rep for Monsanto tells Reuters that the decision to include glyphosate on the California list is “unwarranted on the basis of science and the law.”
“This is not the final step in the process, and it has no bearing on the merits of the case. We will continue to aggressively challenge this improper decision,” Scott Partridge, Monsanto’s vice president of global strategy, told Reuters.
Editor's Note: This article originally appeared on Consumerist.