Ingredient in Monsanto’s Roundup Causes Cancer: California Is First State Expected to Label the Herbicide as a Carcinogen

California will be the first state to label the herbicide’s active ingredient glyphosate as a carcinogen

There have been multiple studies that have hinted at the toxic effects of Roundup’s active ingredients.

For the first time, when you buy a container of Roundup to kill the weeds in your garden, you could be knowingly purchasing a carcinogen. The California Office of Environmental Health Hazard Assessment announced that it will be the first state to label glyphosate, the active ingredient in Monsanto’s controversial herbicide Roundup, as a cancer-causing agent.The new label is part of the California Environmental Protection Agency’s efforts to publish a list of carcinogenic chemicals under Proposition 65, an initiative that was passed in 1986. Glyphosate is expected to be the latest chemical to join the long list.

Earlier this summer, we reported that  The International Agency for Research on Cancer (IARC), the specialized cancer agency of the World Health Organization, had labeled glyphosate as a “probable carcinogen.” Glyphosate is now one of the most common herbicides in the world, widely used by farmers to kill crop-choking weeds. According to the Center for Biological Diversity, glyphosate use has increased more than 20-fold over the past 25 years, paralleling the spread of GMO crops that are modified to withstand near-fatal dosages of the chemical.

Monsanto released the following statement in response to the California Office of Environmental Health Hazard Assessment agency's decision:

"As it has with hundreds of other substances over the years, including aloe vera, the California Office of Environmental Health Hazard Assessment (OEHHA) has announced its intention to list glyphosate under the strict provisions of Proposition 65. The sole basis of OEHHA’s intention to list is the classification of glyphosate earlier this year by the International Agency for Research on Cancer (IARC).  OEHHA interprets Prop 65 to allow it simply to accept the IARC classification without further scrutiny or review.  OEHHA does not evaluate the weight or quality of the evidence considered by IARC. 

The IARC classification overlooked decades of thorough and robust analysis by regulatory agencies, including a multi-year assessment just completed on behalf of the regulatory authority in the European Union.  Another registration review is currently underway by the U.S. EPA.  No regulatory agency in the world considers glyphosate to be a carcinogen.

Regulatory agencies have already reviewed all the key studies examined by IARC – and many more – and arrived at the overwhelming consensus that glyphosate poses no unreasonable risks to humans or the environment when used according to label instructions.  The IARC classification also selectively used and interpreted data and is at odds with the conclusions of three other World Health Organization programs that have evaluated glyphosate.

Monsanto continues to join with the agricultural industry in strongly disagreeing with IARC’s classification.  Glyphosate is an effective and valuable tool for farmers and other users, including many in the State of California.  OEHHA has just announced an intention to list.  But during the upcoming comment period, we will provide detailed scientific information to OEHHA about the safety of glyphosate and work to ensure that any potential listing will not affect glyphosate use or sales in California."     

Although sales of Roundup are not banned in California, businesses would have to provide a “clear and reasonable” health warning on any products containing glyphosate.


“As far as I’m aware, this is the first regulatory agency in the U.S. to determine that glyphosate is a carcinogen,” Dr. Nathan Donley, a scientist at the Center for Biological Diversity told EcoWatch. “So this is a very big deal.”