Does Monsanto’s Roundup cause cancer or not?

Dear EarthTalk: My neighbor uses Roundup in her yard routinely and tells me it’s harmless to people and pets, but I’ve heard that it is carcinogenic. Can you set the record straight?
Maise Alexander, New Hope, PA
 dot trans Does Monsantos Roundup cause cancer or not?                      

Monsanto’s Roundup herbicides contain three key components: the active ingredient glyphosate, water, and a soap-like surfactant blend. The agricultural application of glyphosate has skyrocketed over the past 20 years. According to the U.S. Geological Survey’s “Estimated Agricultural Use for Glyphosate” map, in 2012 over 250 million pounds of glyphosate were used on crops in across the country—a substantial increase from the less than 22 million pounds used in 1992.

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Protestors worry they might be exposed to potentially carcinogenic glyphosate when neighbors apply Roundup to their driveways, yards, gardens and farms. Credit: Grow Food Northhampton, FlickrCC

The U.S. Environmental Protection Agency (EPA) has classified the cancer-causing potential of glyphosate as Category E (“evidence of non-carcinogenicity for humans”), but the International Agency for Research on Cancer (IARC) recently re-classified it as a group 2A “probable” carcinogen. IARC’s recent evaluation of glyphosate found “limited evidence of carcinogenicity in humans for non-Hodgkin lymphoma” and “convincing evidence that glyphosate also can cause cancer in laboratory animals.”

Monsanto struck back, stating that the IARC’s conclusion “conflicts with the overwhelming consensus by regulatory bodies and science organizations around the world…which have found no evidence of carcinogenicity.” Monsanto added: “Further, the 2A classification does not establish a link between glyphosate and an increase in cancer. ‘Probable’ does not mean that glyphosate causes cancer; even at 100 times the exposure that occurs during normal labeled use glyphosate is not a human health risk.”

In September 2015, in response to the IARC findings, the California EPA’s Office of Environmental Health Hazard Assessment (OEHHA) announced its intent to list glyphosate as a carcinogen under the state’s Proposition 65 law. In California, businesses are required to provide “a clear and reasonable warning” before knowingly and intentionally exposing anyone to a Proposition 65 listed chemical. Once a chemical is listed, businesses have a year to comply with the warning requirements. OEHHA is accepting public comments until October 20 on whether glyphosate should be listed under Proposition 65.

“If they decide to list this chemical [under Proposition 65] and it survives the inevitable legal challenges, I think it’s possible that every bottle of Roundup or glyphosate formulation sold in the state of California would have to be labeled as known…to cause cancer,” Nathan Donley, a staff scientist with the Center for Biological Diversity, told Pacific Standard. “It would be a huge deterrent for the purchase of this product, at least in that state.” He added that Monsanto has created a “false narrative” that glyphosate is safe. “That position clearly can’t be maintained anymore…and I think it will probably be a precursor for hopefully federal action, at least federal acknowledgment that glyphosate does cause cancer.”

In addition to the threat of a warning label on their glyphosate products in California, Monsanto is currently facing lawsuits by two people claiming that Roundup caused their cancers. Enrique Rubio filed suit on September 22nd in Los Angeles, claiming that the bone cancer he was diagnosed with back in 1995 was a result of spraying fields of crops with Roundup and other pesticides. The second lawsuit, filed on the same day in New York by Judi Fitzgerald, claims she was exposed to Roundup when she worked at a horticultural products company in the 1990s. Fitzgerald was diagnosed with leukemia in 2012.