Widely used herbicide glyphosate is “probably carcinogenic”

The herbicide glyphosate, widely used in U.S. crop production, especially for genetically engineered corn and soybeans, is “probably carcinogenic to humans,” says the specialized cancer agency of the UN World Health Organization. The herbicide is known under the brand name RoundUp in the United States. The International Agency for Research on Cancer reviewed glyphosate and four other organophosates on the recommendation of an advisory committee that dozens of pesticides should be examined because of substantial new data on them.

Monsanto, the giant seed company, disagreed with the IARC classification and said, “There is no new research or data here.” It says there is “a wealth of evidence science” to show the herbicide is safe. The Associated Press said the EPA, “which make its own determinations, said it would consider the French agency’s evaluation.”

The EPA originally classified glyphosate as possibly carcinogenic in 1985 but revised the classification in 1991, declaring it non-carcinogenic in humans based on tests that used laboratory animals. The WHO agency said there were “several more recent positive results” that justify a conclusion that the herbicide causes cancer in lab animals, but there is limited evidence of it causing cancer in people. In a statement, the WHO agency said its monographs provide evaluations based on a comprehensive review of scientific literature, but noted that it is up to individual governments to decide on regulations.

Glyphosate is the most widely produced herbicide in the world, according to WHO, and is used mainly in agriculture. Use increased sharply with the development of crops that are engineered to tolerate the weedkiller. The Environmental Working Group said the IARC classification of glyphosate was a reason to require labeling of GE food. “Consumers have the right to know how their food is grown and whether their food dollars are driving up the use of a probable carcinogen,” said EWG president Ken Cook.

The IARC monograph, “Carcinogenicity of tetrachlorvinphos, parathion, malathion, diazinon, and glyphosate,” was published in the journal Lancet Oncology, and is available here.