Did Monsanto Ignore Evidence Linking Its Weed Killer to Cancer?

Did Monsanto Ignore Evidence Linking Its Weed Killer to Cancer?

Did Monsanto Ignore Evidence Linking Its Weed Killer to Cancer?

This could be the company’s “Big Tobacco” moment.


In 1970, John E. Franz, a 40-year-old chemist from Springfield, Illinois, hit upon a discovery that would profoundly change agriculture: a chemical that works its way into the leaves of weeds and down to their roots, eventually killing them. Franz sold the patent for the breakthrough to his employer, Monsanto, for $5. Four years later, Monsanto released Roundup.

“Weeds? No problem. Nothing kills weeds better,” announced the actors in the commercials for Roundup as they attacked dandelions with spray bottles. The product was an instant success, and in 1987 Franz won the National Medal of Technology for his discovery. Today, Roundup is the most popular herbicide in the world, generating more than $4 billion in annual revenue for Monsanto.

Roundup’s active ingredient, glyphosate, is widely perceived to be innocuous in the environment because it targets an enzyme not found in animals or humans. When it comes to plants, however, the chemical kills indiscriminately—except for those plants genetically designed to withstand it. In the 1990s, Monsanto began to sell its patented “Roundup Ready” seeds, allowing farmers to spray for weeds without damaging their crops. The combination of herbicide and resistant seeds helped Monsanto become one of the world’s most powerful agriculture corporations. Today, over 90 percent of domestic soy, corn, and cotton crops are genetically engineered to be glyphosate–resistant, accounting for more than 168 million acres.

But the future of the ubiquitous herbicide is in question. Monsanto is currently fighting allegations that glyphosate might not be as safe as advertised, particularly when combined with other chemicals in Roundup. In 2015, an international science committee ruled that glyphosate is a probable human carcinogen, countering previous determinations by regulatory agencies in the United States and other countries. Soon after, more than 200 people sued Monsanto in a federal case now centralized in California, claiming that Roundup caused them to develop non-Hodgkin’s lymphoma, a common blood cancer. Over 1,000 people have filed similar suits against the company in state courts in Arizona, Delaware, Missouri, Nebraska, and elsewhere.

Attorneys and activists have accused Monsanto of manipulating the science around glyphosate’s health impacts—in essence, of following the playbook written by Big Tobacco. Documents revealed in the federal case also suggest a cozy relationship between the company and regulators at the Environmental Protection Agency, which is currently reviewing glyphosate’s safety. For its part, Monsanto maintains that Roundup is harmless. “Our lawyers have produced over 10 million pages of documents, and the plaintiffs’ lawyers managed to cherry–pick a handful that reflect the use of some inappropriate language by some Monsanto folks,” said Scott Partridge, Monsanto’s vice president for global strategy. “There’s not a single document that reflects that glyphosate, the active ingredient in Roundup, causes cancer.”

The public brawl couldn’t come at a more pivotal moment. Monsanto is currently pursuing a mega-merger with the German chemical giant Bayer AG, a $66 billion deal that still has to be approved by American and German antitrust regulators. The EPA’s latest safety assessment of glyphosate is expected soon, and the European Union is also deliberating whether to relicense its use. (French officials have said they will vote against relicensing.) Meanwhile, the chemical at the center of the safety debate has lost some of its power to increasing weed resistance. Glyphosate–resistant “super-weeds” like pigweed, which can grow three inches a day, reaching heights of up to seven feet, have already invaded some 90 million acres of American cropland, forcing farmers to use more powerful chemicals in larger doses.

Since Franz’s discovery in 1970, Americans have sprayed 1.8 million tons of glyphosate on their crops, lawns, and gardens; globally, the figure stands at 9.4 million tons. Glyphosate residue has been reported in many popular foods, from cherries to Cheerios, and early research has found it in 86 percent of a sampling of people in regions across the United States. Another preliminary study reported glyphosate residue in 90 percent of a sample of pregnant women in the Midwest, with higher levels correlated to premature births and low birth weights. (Both studies were limited by small sample sizes, underscoring the need for further research.) Paul Winchester, the medical director of the neonatal intensive–care unit at the Franciscan St. Francis Health system in Indianapolis and lead author of the Midwestern study, said such findings should alarm anyone who cares about health and safety.

“We should be concerned,” Winchester said. “This is mass exposure.”

One warm day in July, Teri McCall drove a four–wheeler down a winding track through groves of citrus, avocado, and persimmon trees. McCall’s husband, Jack, always joked that she would never work on their 20–acre farm on the Central California coast, four hours south of San Francisco, because she “might break a nail.” But since Jack’s death in 2015, Teri has been doing most of the work. “The first year, the lemons just fell to the ground,” she said. “I wasn’t able to do anything, I was so distraught. Now I’m in constant battle with the gophers.”

McCall remembers her reaction when a doctor said the rash on Jack’s neck was cancer: “I just laughed and thought, ‘How could that be true?’” Jack was 65 at the time, working on the farm full-time and surfing on the weekends. The doctor diagnosed the condition as primary cutaneous B-cell lymphoma, usually benign and confined to the skin. But the rash persisted. Four years later, Jack felt swelling in his lymph nodes. That time, the diagnosis was grim: non-Hodgkin’s lymphoma.

Undergoing chemotherapy and radiation, Jack grew thin and weak. On Christmas Eve, Teri found Jack with his eyes rolled back and his mouth twisted up; he’d had a stroke. Teri and the children spent the night by Jack’s bedside in the hospital, and the next morning—six months after the diagnosis—she decided to have him taken off life support. “It was the worst moment of my life,” Teri said.

Jack preferred not to use chemicals, but he believed Roundup was safe and used it regularly for more than 30 years. According to Teri, it was the only herbicide he ever used. As the family sat around Jack’s bed on his last days, his son read on the Internet about potential links between Roundup and non–Hodgkin’s lymphoma. After Jack’s death, Teri could barely get out of bed, but eventually she began reading the reports herself. She now believes Roundup was responsible for his death—and maybe their dog’s, too. Duke, a black Lab, spent every minute with Jack until the day he died of lymphoma in 2009.

In early 2016, McCall joined other farmers, gardeners, migrant workers, and landscapers, represented by multiple law firms, to sue Monsanto in federal court. One plaintiff, John Barton, 68, has lived and worked on California farms for most of his life. “We’ve used Roundup since it came out for weed control on our reservoirs and the ditches of cotton fields,” he said. Barton’s cancer has spread to both sides of his body; he’s retired from farming and no longer uses Roundup. But he’s continually exposed to the chemical because he lives in the heart of the San Joaquin Valley, one of the most productive agricultural regions in the world. “Right across the road from me is GMO alfalfa; the dairies do GMO corn,” he said, speaking of the fields planted with crops that have been modified to resist repeated dousing with Roundup.

McCall and Barton’s case hinges on a determination made by the World Health Organization’s International Agency for Research on Cancer (IARC) in March 2015. The IARC, which has been developing reports on expected and known carcinogens since the 1970s, classifies materials into categories, from carcinogenic to humans (Group 1) to “probably not carcinogenic” (Group 4). The agency’s evaluation of glyphosate was conducted by a group of 17 experts from 11 countries and led by Aaron Blair, an epidemiologist with the National Cancer Institute. In the months prior to and then during a weeklong meeting in Lyon, France, the committee pored over the publicly available scientific literature—hundreds of pages of published journal articles and reports.

The IARC concluded that glyphosate should be categorized in Group 2A, meaning “probably carcinogenic to humans,” alongside DDT, the insecticide malathion, and strains of human papillomavirus. The IARC experts considered studies of disease patterns in human populations and experiments on human tissues and cells as well as on lab animals. They reported convincing evidence that glyphosate causes cancer in animal models. They also concluded that studies clearly show DNA and chromosomal damage in human cells—damage that can lead to the emergence of cancer.

They did not, however, go so far as to report that the chemical definitely causes cancer in humans. “There wasn’t enough evidence to say that we know this stuff causes cancer as we say with smoking, alcohol, and benzene—for those, there’s no quibbling,” Blair explained. “‘Probable’ means there’s quite a lot of evidence that it does cause cancer, but there’s still some doubt.”

Monsanto immediately released a statement denouncing the IARC verdict: “Regulatory agencies have reviewed all the key studies examined by IARC—and many more—and arrived at the overwhelming consensus that glyphosate poses no unreasonable risks to humans or the environment when used according to label instructions.”

But the company couldn’t contain the firestorm ignited by the IARC ruling, which had immediate regulatory and legal implications. Within months, nearly 600 scientists in 72 countries signed a manifesto calling for a ban on the spraying of glyphosate–based herbicides. (Even before the release of the IARC report, some countries—El Salvador, Colombia, Brazil, Bermuda, Germany, France, the Netherlands, and Sri Lanka—had already instituted a ban or were considering some form of one.) California uses IARC classifications as the basis for registering chemicals under Proposition 65, which mandates the labeling of all chemicals known to cause cancer, birth defects, or other reproductive harm; Roundup sold in the state must soon be labeled. Then there are the lawsuits: By the fall of 2015, Monsanto faced the first of what would become a cascade of suits connecting Roundup to cancer.

Monsanto had long been preparing to challenge the IARC report, according to a six-page confidential strategy document unearthed in the federal suit. In its defense of glyphosate, the company claims that the IARC overlooked important research and selectively interpreted data to arrive at its “probable carcinogen” classification. Monsanto also frequently points out that the EPA—as well as regulatory agencies in Canada and Europe—lists glyphosate as noncarcinogenic.

The discrepancy between the IARC and other regulatory agencies is in part due to the fact that they have different goals. “IARC looks at the literature and makes a determination of whether, in some circumstances, under some conditions, under some types of exposure, this stuff might or might not present a cancer hazard,” Blair explained. “What IARC does not do is to say which circumstances those are, and how much exposure you have to have to really be worried—that’s risk assessment, and that’s what EPA does.”

But there are also serious questions about the EPA’s own processes for evaluating chemicals—questions amplified by a trove of e-mails, text messages, letters, and memos between Monsanto and high–ranking EPA officials that were unsealed in the court proceedings and obtained via Freedom of Information Act requests by the consumer group US Right to Know.

Marion Copley was an EPA toxicologist who worked for 30 years researching the effects of chemicals on mice. In March of 2013, as she was dying of breast cancer, Copley wrote a striking letter to Jess Rowland, deputy director of the EPA’s pesticide division. Rowland led the Cancer Assessment Review Committee, which was evaluating glyphosate; Copley also served on the committee. In her letter, Copley described how the property that makes glyphosate such a potent pesticide—its ability to target an enzyme that plants need to grow—also plays a role in the formation of tumors in humans. She named 14 specific methods by which it could do the job. “Any one of these mechanisms alone…can cause tumors, but glyphosate causes all of them simultaneously,” she wrote. “It is essentially certain that glyphosate causes cancer.”

Then she got personal. “Jess: For once in your life, listen to me and don’t play your political conniving games with the science to favor the registrants.” She closed the letter: “I have cancer and I don’t want these serious issues to go unaddressed before I go to my grave. I have done my duty.” Copley died the next year.

Rowland’s job required him to work closely with registrants, but the documents suggest a strikingly friendly relationship with Monsanto employees. One April 2015 e-mail indicates that Rowland told the company he would try to kill a planned review of glyphosate by the Department of Health and Human Services’ Agency for Toxic Substances and Disease Registry (ATSDR). That agency, along with the Centers for Disease Control and Prevention (CDC), is charged with evaluating potential adverse health effects from exposure to manmade chemicals. “If I can kill this I should get a medal,” Rowland said of the review, according to an e-mail written by Dan Jenkins, Monsanto’s lead liaison to government agencies. “I doubt EPA and Jess can kill this; but it’s good to know they are actually going to make the effort,” Jenkins wrote to his colleagues in the same e-mail.

Other EPA officials weighed in against the ATSDR’s proposed review, claiming it was unnecessary since the EPA was conducting its own evaluation. “I am looking at it from the standpoint of it being a duplicative government effort given that we are currently in the midst of our review now,” Jack Housenger, director of the EPA’s Office of Pesticide Programs, wrote to a colleague at the CDC on May 22.

Monsanto got what it wanted: By October 2015, the ATSDR review was officially on hold, and Monsanto was anticipating good news from the EPA. Jenkins updated his colleagues: “Spoke to EPA: is going to conclude that IARC is wrong.” Six months later, on a Friday in April 2016, the EPA’s long–anticipated report on glyphosate, signed by Rowland and stamped “final,” was released on the Internet. But it lasted only the weekend; EPA retracted the report first thing Monday morning, calling its release premature. Still, Monsanto had just enough time to dispatch a press release with the headline “Once Again, EPA Concludes That Glyphosate Does Not Cause Cancer.”

Rowland retired within weeks of the release. That came as no surprise to Monsanto: The previous September, Jenkins had told his co-workers, “Jess will be retiring from EPA in 5–6 months and could be useful as we move forward with ongoing glyphosate defense.”

In March, Congressman Ted Lieu (D-CA) called for the Justice Department to launch a special investigation into reports suggesting collusion between Monsanto and EPA employees reviewing glyphosate. The EPA’s Office of the Inspector General has said that it’s looking into it. Rowland’s attorney and the EPA did not respond to repeated requests for comment about Rowland’s relationship with Monsanto. The company denies that it tried to improperly influence the agency. “The [regulatory] process requires a tremendous amount of contact and interaction with the government,” said Monsanto’s Partridge in an interview. Partridge maintained that Rowland’s comment about getting a medal referred only to his desire to avoid duplicative studies at the taxpayers’ expense.

The EPA has often been criticized for its chemical–screening processes, in large part because it relies on research funded or conducted by the chemical companies themselves. In 2015, the agency determined that there was “no convincing evidence” that glyphosate disrupts the human endocrine system—a determination based almost entirely on studies funded by Monsanto, other chemical companies, and industry groups. None of the industry studies, which were obtained by The Intercept’s Sharon Lerner, concluded that there were any health risks, despite the fact that some of their data suggested otherwise—and in contrast to a few of the small number of independent studies considered by the EPA, which did find evidence that glyphosate harms the endocrine system. Unlike the EPA, the IARC considers only published, peer-reviewed science, and does not consider—or, in most cases, even have access to—a corporation’s studies.

An additional limitation in the EPA approval process is that it examines only the main active ingredient in a product—glyphosate, in the case of Roundup—and not the complete formula, which includes inert ingredients. (The IARC’s assessment considered studies of both the full Roundup formula and glyphosate alone.) These additional chemicals are often withheld as trade secrets, making it more difficult for independent researchers to study their risks. But scientists have recently begun to identify many of the other components in Roundup, and have found some to be more toxic to human cells than glyphosate itself.

Plaintiffs claim that Monsanto “knew or should have known that Roundup is more toxic than glyphosate alone” but continued to advertise the product as safe. In a 2002 e-mail, Monsanto product–safety strategist William Heydens wrote to Donna Farmer, one of the company’s leading toxicologists: “What I’ve been hearing from you is that this continues to be the case with these studies—glyphosate is OK but the formulated product (and thus the surfactant) does the damage.” (Surfactants reduce the surface tension of water, helping the herbicide cling to leaves instead of flowing into the soil.)

In a November 2003 e-mail to Monsanto CEO Sekhar Natarajan, Farmer wrote that the company “cannot say that Roundup is not a carcinogen” because “we have not done the necessary testing on the formulation to make that statement.” She added, “We can make that statement about glyphosate and infer that there is no reason to believe that Roundup would cause cancer.”

Other documents released in the legal case raise questions about Monsanto’s influence on glyphosate research. One tactic outlined in Monsanto’s plan for responding to the IARC was to “support the development of three new papers on glyphosate focused on epidemiology and toxicology.” Heydens proposed in a February 2015 e-mail to colleagues that Monsanto “ghost-write” part of a paper by outside scientists: “We would be keeping the cost down by us doing the writing and they would just edit and sign their names so to speak,” he said, explaining that this was how Monsanto “handled” an earlier paper on glyphosate’s safety. That earlier paper, published in 2000, acknowledged Monsanto’s help in data collection, but it did not list any company employees as co-authors, contrary to the transparency standards upheld by most journals. In response to questions about the apparent ghostwriting, Partridge objected to the term—even though Heydens used it himself—adding that the activities described “were entirely professional and aboveboard.”

Monsanto also hired an outside consulting firm, -the Intertek Group, to orchestrate a so-called “independent” review of glyphosate’s health effects to refute the IARC’s cancer assessment. A disclosure accompanying the review, which was published in Critical Reviews in Toxicology, reported that Intertek was paid by Monsanto but claimed that “neither any Monsanto company employees nor any attorneys reviewed any of the Expert Panel’s manuscripts prior to submission to the journal.” In fact, internal e-mails indicate that Heydens and other Monsanto employees reviewed and edited drafts before the report was published. “I have gone through the entire document and indicated what I think should stay, what can go, and in a couple spots I did a little editing,” wrote Heydens in a February 2016 e-mail to Ashley Roberts, senior vice president in Intertek’s food and nutrition division. Partridge defended the review’s independence: “It did not amount to substantial contributions, editing [or] commenting—nothing substantive to alter the scientists’ conclusions.”

Doubt is our product,” a cigarette-company executive once wrote, “since it is the best means of competing with the ‘body of fact’ that exists in the mind of the general public. It is also a means of establishing a controversy.” For 50 years, Big Tobacco manufactured uncertainties about the health impacts of cigarettes, with ads featuring smoking physicians and a media campaign claiming that there was “no proof” of any health concerns caused by smoking. In defending glyphosate, plaintiffs say, Monsanto is following a familiar playbook: hire scientists to produce friendly results, fund front groups—Monsanto has contributed to the American Council on Science and Health, which defends glyphosate and other chemicals from “junk science”—and use the media to sway public opinion.

“It appears as though we are seeing the unraveling of a very carefully crafted corporate narrative about the safety of a well-known product used around the world, just as we saw when the dark and dirty secrets of the tobacco industry came to light,” said Carey Gillam, research director for US Right to Know and the author of a new book, Whitewash: The Story of a Weed Killer, Cancer, and the Corruption of Science. “Monsanto’s own internal communications indicate that it has worked long and hard to suppress scientific research showing dangers with its herbicide while at the same time setting up secret networks of straw men to push product propaganda.”

Monsanto has also tried to undermine the credibility of scientists on the IARC committee. “The basic strategy is: Attack people who’ve done the research you don’t like—mercilessly,” said epidemiologist Devra Davis, a former appointee to the US Chemical Safety and Hazard Investigation Board and president of the nonprofit Environmental Health Trust. “They go after the researcher, they go after their funding…. Even the scientists who reported the formation of the ozone hole were vilified before they got their Nobel Prize” in chemistry.

Specifically, Monsanto argues that Blair, the IARC committee chair, was aware of but discounted data that showed no cancer link. The data came from the Agricultural Health Study, an epidemiological survey of cancer and other health problems in a cohort of nearly 90,000 farmers, licensed pesticide applicators, and their families in Iowa and North Carolina. (Blair was a senior researcher for the survey.) Monsanto asserts it is “the most comprehensive study on farmer exposure to pesticides and cancer” undertaken and says that if data from the study had been considered, the IARC would have categorized glyphosate as noncarcinogenic.

Some researchers familiar with that study say there’s a good reason that it wasn’t included—namely, that it hadn’t been published yet. “If you evaluated everything unpublished, you’re going to get a bunch of garbage,” said Peter Infante, an epidemiologist who has evaluated carcinogens for the Occupational Safety and Health Administration and has participated in other IARC reviews. Infante believes that there are other major problems with the survey: The control group—which had not been exposed to glyphosate—was exposed to another pesticide suspected of causing non-Hodgkin’s lymphoma. That’s a problematic comparison, Infante said, akin to asking “whether high testosterone levels elevate the risk of heart attacks in men and then comparing those men with a group that already has heart disease. Obviously, you’re going to underestimate the risk.”

The current task for the attorneys representing Teri McCall and other plaintiffs is to convince presiding Judge Vince Chhabria that there’s enough evidence to indicate that glyphosate “generally” causes cancer. If that effort succeeds, Chhabria will begin to hear individual plaintiffs’ testimony next year and decide whether Monsanto must pay compensatory damages, which could run into the tens or hundreds of millions.

Cancer victims have won a few recent cases against chemical companies. In August, Johnson & Johnson was ordered to pay $417 million in damages to a woman who developed ovarian cancer after decades of using the company’s talcum powder. In February, DuPont and another chemical company agreed to pay more than $900 million to settle some 3,500 lawsuits, after a federal court ruled that Teflon production at a plant on the Ohio River in Parkersburg, West Virginia, caused cancer in workers and residents.

“The law requires these companies to be truthful about what’s in their product, but they frequently don’t submit the information; they suppress it,” said Robin Greenwald, an attorney with the New York City–based firm of Weitz & Luxenberg, who won multimillion–dollar settlements for victims of the 2010 BP oil spill and represents dozens of plaintiffs in the Roundup case. “Fifteen, 20 years later, all these people have certain cancers and certain illnesses, and we ask why. Then scientists connect the dots, and then litigation happens. And in litigation, you get documents from the defendant, and then lo and behold: They knew.”

The stakes in these cases are high—for Monsanto, for cancer victims, for consumers, and for farmers. For better or worse, today’s agricultural system relies on pesticides, “all of which come with inherent dangers,” said William Curran, a plant-science expert at Pennsylvania State University who works with farmers combating glyphosate–resistant weeds. “If Roundup is removed, we might be left with herbicides that are far worse—if you can’t use glyphosate, what are you going to use?”

Many agronomists are optimistic about new practices and technologies to control weeds with fewer chemicals. One promising invention involves a piece of machinery that attaches to a combine at harvest time and pulverizes weed seeds so they won’t sprout up in spring. Certain farming methods can reduce the need for pesticides, including “integrated weed management,” which uses a combination of herbicides with plowing and crop rotation. Some farmers reduce the use of chemicals by planting winter cover crops, such as legumes and grasses, which add nutrients to the soil, reduce erosion, and prevent weeds from gaining a foothold. “It’s not like we need to go back to our old agrarian ways,” Curran said, though he acknowledged that it can be tough to persuade farmers to change their practices.

The federal lawsuit itself may not resolve the dispute about glyphosate’s safety: The research is still evolving. “Every time a product gets looked at for the first time, this scientific debate goes on,” said Blair. “This is not unusual. In fact, that’s what science is. Studies are carried out, findings occur, people evaluate them, not everybody agrees.” Eventually, enough information is gathered to reach some consensus—but that can take decades. Meanwhile, with every year that passes, another 300 million pounds of glyphosate is sprayed upon the land.

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Katrina vanden Heuvel
Editorial Director and Publisher, The Nation

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