Nobody loves Monsanto’s omnipresent Roundup herbicide, and its active ingredient glyphosate, more than California farmers. It accounted for 74% of the state’s herbicide use in 2012.

The herbicide scares the hell out of a lot of environmentalists and many scientists, but got a clean bill of health from the U.S. Environmental Protection Agency (EPA) in 1991, six years after its original classification as “possibly carcinogenic to humans.”

Now, the United Nations’ World Health Organization (WHO) has revisited the controversial herbicide, which is used in conjunction with genetically modified crops (GMOs), and determined it “probably” causes cancer. A report from 17 scientists, specializing in biochemistry, molecular biology, epidemiology, toxicology and environmental science, says glyphosate “induced DNA and chromosomal damage in mammals, and in human and animal cells in vitro.”

So what’s new and different about research on glyphosate to prompt the WHO to question the safety of the “highest global production volume of all herbicides?” Nothing really. The scientists reviewed the available literature and determined that there has long been enough data to support a negative review of America’s most-used agricultural herbicide and second-most-used home and garden insect killer.

Glyphosate, which has been around since 1974, is used in more than 750 different products. It is particularly effective in fields where crops have been genetically modified by Monsanto to resist the deadly poison that kills unsuspecting weeds.

The use of glyphosate in California commercial agriculture increased 65% over a 10-year period ending in 2012, according to the state Department of Pesticide Regulation (DPR). Twenty percent was used on almonds, the water-guzzling nut grown in the deserty Central Valley that has received a lot of attention in year four of the drought.

The WHO study looked at previous studies of people, lab animals and cells and concluded that all three lines of evidence indicated the chemical was a problem. The decision among the 17 scientists was unanimous.

One of the studies, which had also been considered by the EPA in 1991 but interpreted differently, involved mice. The EPA was unimpressed that three out of 50 male mice fed a high dose of glyphosate got a rare form of kidney cancer. They called it statistically insignificant.

But WHO group Chairman Aaron Blair, a retired epidemiologist from the National Cancer Institute, said of the tumors, “They literally don’t occur, but they occurred when rodents were dosed with this stuff.”  

Monsanto was not happy with the report. “We are outraged with this assessment,” Monsanto Chief Technology Officer Robb Fraley said in a statement. “This conclusion is inconsistent with the decades of ongoing comprehensive safety reviews by the leading regulatory authorities around the world that have concluded that all labeled uses of glyphosate are safe for human health” and “is a clear example of agenda-driven bias.”

It’s probably a good bet that Monsanto can keep the conversation going about the safety of dosing everyone with Roundup long enough for the herbicide to reach the end of its usefulness. Herbicide-resistant weeds are a natural consequence of any herbicide product, but repeated and widespread use of a single product greatly increases (pdf) the acceleration of that resistance and fosters the creation of superweeds.

–Ken Broder   

To Learn More:

Why Did Gov't Give Big Thumbs Up to Notorious Monsanto Pesticide We Now Believe Causes Cancer? (by Reynard Loki, AlterNet)

Use of Monsanto Pesticide Linked to Cancer Has Boomed in California (by Rachael Bale, The Center for Investigative Reporting)

Monsanto Seeks Retraction for Report Linking Herbicide to Cancer (by Carey Gillam, Reuters)

Weed Killer, Long Cleared, Is Doubted (by Andrew Pollack, New York Times)

Study: Monsanto's Roundup Herbicide Probably Causes Cancer (by Tom Philpott, Mother Jones)

Genetically Engineered Crops Lead to Increase in Use of Herbicides (by Noel Brinkerhoff, David Wallechinsky, AllGov)

Summary of Pesticide Use Report Data—2012 (California Department of Pesticide Regulation)

Sublethal Exposure to Commercial Formulations of Herbicides . . . (American Society for Microbiology)

Carcinogenicity of Tetrachlorvinphos, Parathion, Malathion, Diazinon, and Glyphosate (by the World Health Organization, The Lancet)