Glyphosate is the key ingredient in Monsanto’s branded Roundup line of herbicides, as well as hundreds of other products, but many scientific studies have raised questions about the health impacts of glyphosate and consumer and medical groups have expressed worries about glyphosate residues in food.

In October, Carey Gillam reported for Reuters that California’s Office of Environmental Health Hazard Assessment (OEHHA), has been accepting public comments about its intention to list glyphosate as a cause of cancer.

Roughly 8,000 comments were filed regarding the state action, according to officials, including those from Monsanto. Several farming, public health and environmental groups sent a letter to OEHHA supporting the listing, and said that rising use of glyphosate presents a danger to people and animals.

The OEHHA gave notice in September that it intended to list glyphosate under proposition 65, a state initiative enacted in 1986 to inform residents about cancer-causing chemicals. State officials said the action is required after the World Health Organization’s (WHO) cancer research committee in March classified glyphosate as a probable human carcinogen.

As we reported in March, the Wall Street Journal and Financial Times reported Monsanto’s call for the World Health Organisation’s cancer agency to retract a report published in the journal Lancet Oncology by researchers for WHO’s International Agency for Research on Cancer.

The WHO’s research unit, however, said it had reviewed many scientific studies, including two out of Sweden, one out of Canada and at least three in the United States before making its classification.

Since the WHO classification, the New York-based mass-tort firm of Weitz & Luxenberg, and other firms representing U.S. farm workers, have filed lawsuits against Monsanto, accusing the company of knowing of the dangers of glyphosate for decades. Monsanto has said the claims are without merit

Monsanto has now urged California not to list herbicide glyphosate as carcinogenic.

It added, in its formal comment, that California’s actions could be considered illegal because they are not considering valid scientific evidence.