Does the World’s Top Weed Killer Cause Cancer? Trump’s EPA Will Decide
Every year, farmers spray, on average, almost a pound of the herbicide glyphosate on every acre of cropland in the U.S., and nearly half a pound on every acre of cropland worldwide. Glyphosate is the active ingredient in Roundup, a huge source of income for its manufacturer, Monsanto Co., and the foundation for its epochal foray into genetically modified organisms. If you know nothing else about GMOs and Monsanto, know this: The St. Louis-based company reengineered the DNA of corn, soybeans, and other crops for the primary purpose of making them resistant to Roundup.
Farmers spray the chemical on crops grown from Monsanto’s Roundup Ready seeds. The weeds die, harvests expand, and expensive, laborious tillage is no longer necessary. Large-scale agriculture is built on this model, and not only in the U.S., which is why Bayer AG, the German drug and chemical company, agreed in September to buy Monsanto for $66 billion, pending regulatory approvals. Other than government antitrust objections, about the only thing that could mess up the purchase would be for the U.S. Environmental Protection Agency to reverse its position on the active ingredient of Roundup, glyphosate.
Last December, the EPA convened a panel of outside scientists to peer-review the agency’s long-standing conclusion that glyphosate is unlikely to cause cancer. The peer reviewers, a mix of academics, federal scientists, and chemical industry consultants, gathered at an EPA conference center in Arlington, Va. From the agency’s point of view, this was something of a formality. Federal law requires an EPA health-effects review for every pesticide at least once every 15 years, and glyphosate has enjoyed a clean bill of health since 1991, when the agency cleared the way for Monsanto’s GMO breakout by classifying the herbicide as noncarcinogenic to humans.
Its use in global agriculture has soared almost fifteenfold since Monsanto introduced Roundup Ready seeds in 1996. As a result, traces of glyphosate have been detected in cookies, crackers, chips, breakfast cereals, and honey, and in human urine and breast milk. Monsanto says it’s nothing to worry about. “Glyphosate is about half as toxic as table salt and more than 10 times less toxic than caffeine,” the company says on one of its websites. More than 1,000 farmers and other agricultural workers stricken with non-Hodgkin lymphoma disagree. They’re suing Monsanto in state and federal courts across the country, claiming Roundup caused their cancer. Monsanto is vigorously contesting the claims. “There’s never been a more studied herbicide in the history of farming,” says Scott Partridge, Monsanto’s vice president for strategy. “In more than 700 studies, not one has associated cancer with the use of glyphosate. And in the more than 160 countries that have registered glyphosate for use, not a single government agency has found glyphosate is a carcinogen.”
December’s Scientific Advisory Panel meeting followed the typical script for a federal peer review, with some twists. Officials from the EPA’s Office of Pesticide Programs opened the public hearing by laying out 45 years of study data and describing why, in the agency’s view, they indicate that glyphosate is an unlikely human carcinogen at current exposure levels. The agency’s conclusion, elucidated in a 227-page issue paper released the previous September, reflects the “weight of evidence,” Jack Housenger, then chief of the pesticide office (he retired this year), told the panel. “Now it’s your turn to tell us what you think of our analysis,” he said, “and hopefully put the subject to bed so we can move on.”
Far from settling the matter, eight of the 15 experts expressed significant concerns about the EPA’s benign view of glyphosate, and three more expressed concerns about the data. Their skepticism also raised, again, questions about the independence of the Office of Pesticide Programs, which has the final say on permitting pesticides. The office relies on pesticide manufacturers for the data it uses in making health decisions—and got almost 30 percent of its operating budget from the industry last year.
The EPA paper had a whack-a-mole quality to it. Throughout, the authors included data sets suggesting that glyphosate could cause cancer, only to knock them down. On epidemiology studies, for example, they said farmers’ recollection of their own glyphosate exposure was biased and unreliable. On meta-analyses pooling human data from multiple studies to identify trends, the EPA assessors shaved decimal points from the results, which made it possible for them to shrug off data showing exposed farmers had an elevated risk of cancer.
Many of the reasons cited in the paper contradicted the agency’s own carcinogenicity guidelines, multiple panelists pointed out. “Every time there’s something positive there, you said there’s something wrong with the study,” Eric Johnson, an epidemiologist at the University of Arkansas for Medical Sciences, scolded EPA officials at the meeting. Lianne Sheppard, a biostatistician at the University of Washington at Seattle, says there was “consensus” on the panel that the agency hadn’t followed its own standards. “The available evidence did not fit with the conclusions drawn in the issue paper, particularly when put in the context of the guidelines,” she says.
The EPA’s report on the peer review, posted on March 16, raises obfuscation to a high bureaucratic art. While spelling out the panel’s criticisms, the report gives no indication which, or how many, reviewers felt strongly about which particular problems. Instead, it uses the phrase “some panel members” 76 times—as in “some panel members noted,” “some panel members emphasized,” “some panel members suggested.” The imprecision obscures that the majority of peer reviewers expressed doubts about the EPA’s methods or conclusions. Under the law, the agency must consider the panel’s input in its final evaluation of glyphosate, scheduled for completion later this year. By enshrining the reviewers’ comments in such vague terms, however, the EPA can more easily ignore them.
“I asked for a vote on the main issues to make our guidance clear, but this committee apparently never does that,” says Emanuela Taioli, an epidemiologist at Icahn School of Medicine at Mount Sinai in New York and one of the panelists who disagreed with the EPA’s interpretation of the evidence. “Not giving a tally leaves them more flexibility to interpret our advice.”