WASHINGTON, March 20, 2015-- The International Agency for Research on Cancer (IARC), an arm of the World Health Organization, announced today it ranked the herbicide glyphosate as “probably carcinogenic to humans,” inspiring fierce rebuttal from the agricultural science community.

IARC categorized glyphosate—used on millions of acres of commodity crops in the United States—in Group 2A, which suggests the herbicide has “limited evidence” of carcinogenicity in humans and sufficient evidence of carcinogenicity in experimental animals, according to the agency.

Group 2A is one rank higher than IARC’s Group 2B, “possibly carcinogenic to humans,” which includes cell phones and coffee. Group 1 is the next highest category, “carcinogenic to humans.”

Information Technology and Innovation Foundation (ITIF) senior fellow Val Giddings issued a response to IARC’s announcement, saying that “a vast body of relevant information, including dozens of detailed genotoxicity studies, animal bioassays, peer-reviewed publications and regulatory assessments show no evidence of carcinogenicity,” but were ignored by the committee. 

Glyphosate has the highest global production volume of all herbicides, with the largest use in agriculture.

“The agricultural use of glyphosate has increased sharply since the development of crops that have been genetically modified to make them resistant to glyphosate,” IARC noted. In the United States, glyphosate-resistant crops were first commercialized in 1996.

According to US Geological Survey pesticide use maps, the amount of glyphosate used on crops in the U.S. increased from 27 million pounds in 1996 to 250 million pounds in 2009.

IARC said humans are primarily exposed to glyphosate through residence near sprayed areas, home use, and diet, “and the level that has been observed as generally low.”

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In the U.S. Environmental Protection Agency’s review of glyphosate, the agency concluded it does not pose a risk to human health if used according to the label.

The German Risk Agency (BfR) is conducting a glyphosate registration review that began in 2012 for the European Union, and issued an update in January that its investigation “did not provide any indications that glyphosate has carcinogenic [effects].”

Giddings said IARC has previously been criticized for using flawed methodology. “But IARC’s assault on glyphosate breaks new ground, which is all the more ironic given its clearly superior safety profile compared to the likely alternatives,” he said. “Glyphosate lacks the chemical structural characteristics of known carcinogens, and neither IARC nor anyone else has ever offered an even remotely plausible mechanism of carcinogenicity.”

Monsanto, which introduced the widely-used glyphosate herbicide Roundup in 1974, said IARC “received and purposefully disregarded” dozens of scientific studies that say the chemical is not a risk to human health.  

The company issued a request for the World Health Organization to meet with the global glyphosate taskforces and other regulatory agencies to account for the scientific studies used in their analysis as well as those that were not used.

“We don’t know how IARC could reach a conclusion that is such a dramatic departure from the conclusion reached by all regulatory agencies around the globe,” said Philip Miller, vice president for global regulatory affairs at Monsanto.


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