Safe Or Scary? The Shifting Reputation Of Glyphosate, AKA Roundup : The Salt The world's most widely used weed killer was once seen as one of the safest pesticides. Now it is blamed for causing cancer. Yet the scientific evidence remains disputed.
NPR logo

Safe Or Scary? The Shifting Reputation Of Glyphosate, AKA Roundup

  • Download
  • <iframe src="" width="100%" height="290" frameborder="0" scrolling="no" title="NPR embedded audio player">
  • Transcript
Safe Or Scary? The Shifting Reputation Of Glyphosate, AKA Roundup

Safe Or Scary? The Shifting Reputation Of Glyphosate, AKA Roundup

  • Download
  • <iframe src="" width="100%" height="290" frameborder="0" scrolling="no" title="NPR embedded audio player">
  • Transcript


Roundup is the most widely used weed killer in the world. But now there are questions about whether it causes cancer. The makers of the chemical glyphosate - better known by its trade name, Roundup - are now facing a series of lawsuits. In three civil cases so far, juries have ordered the company Bayer to pay enormous damages to cancer survivors. Thousands more lawsuits have been filed. For Bayer and for this chemical, it's a stunning change in fortunes. Here's NPR's Dan Charles.

DAN CHARLES, BYLINE: John Draper and I are sitting in the cab of a tractor on the research farm that he manages for the University of Maryland. Behind us, there's a sprayer.

JOHN DRAPER: So away we go.

CHARLES: So it's spraying?

DRAPER: It's spraying.

CHARLES: We're spraying glyphosate. Farmers have been doing this for about four decades with a pretty clear conscience, actually - because glyphosate doesn't persist in the environment as much as, say, DDT did. It doesn't build up in groundwater like another widely used herbicide, atrazine. And it's certainly less toxic than some of the alternatives.

DRAPER: If we were spraying Gramoxone - even for you to be standing next to the spray, you'd have to have a respirator on. I'd have to wear a respirator even when I'm in the tractor spraying.

CHARLES: Monsanto started selling Roundup in 1974. And for 20 years, it didn't get much attention. That was Act 1 of the glyphosate drama. Act 2 began in the late 1990s.


UNIDENTIFIED PERSON: This spring, exciting new seed technology was planted for the first time across the Corn Belt...

CHARLES: Monsanto started selling genetically modified crops, GMOs. They were modified so they could tolerate glyphosate, which meant that farmers now could spray this chemical right over their so-called Roundup Ready soybeans and corn and cotton.

And the crops were fine, but the weeds died. It was a farming revolution. Monsanto quickly became the world's biggest seed company. And farmers started spraying a lot more glyphosate - 10 times more. It all happened so fast, it scared a lot of people. There were protests.


UNIDENTIFIED PROTESTERS: (Chanting) No, no GMOs. No, no GMOs. No, no GMOs...

CHARLES: And people started to look a lot more closely at glyphosate. Five years ago, the International Agency for Research on Cancer, or IARC, part of the World Health Organization, decided to carry out a new assessment of its risks. Here's Kate Guyton, a senior scientist at IARC, at a press conference, laying out what they found.


KATE GUYTON: Strong evidence that glyphosate can damage DNA.

CHARLES: There were studies showing that when mice ate glyphosate, they got more tumors.


GUYTON: These two studies gave sufficient evidence of cancer in animals.

CHARLES: And IARC found what it called limited evidence that people exposed to glyphosate had higher rates of a particular kind of cancer, non-Hodgkin's lymphoma.


GUYTON: Taking all this evidence together, this was classified as Group 2A, probably carcinogenic to humans.

CHARLES: I gave Kate Guyton a call last week in France. Have you ever gotten so much reaction from anything you've done before?

GUYTON: No. (Laughter). That's a pretty easy answer.

CHARLES: The Internet kind of exploded, she says. Anti-GMO groups said, we told you it was dangerous. Monsanto's top executives were furious, launched a PR campaign attacking IARC. And in the small town of Orange, Va., a personal injury lawyer named Michael Miller started rounding up clients - people with non-Hodgkin's lymphoma who'd used Roundup.

MICHAEL MILLER: I decided these people needed a voice the courtroom.

CHARLES: The scientific picture got more complicated, though. Other government agencies, including the U.S. Environmental Protection Agency and the European Food Safety Authority, took a fresh look at glyphosate. And they said it probably is not giving people cancer. Dave Eastmond, from the University of California, Riverside, helped conduct one of these glyphosate reviews for another part of the World Health Organization.

DAVE EASTMOND: From my reading of things, you know, if glyphosate causes cancer, it's a pretty weak carcinogen, which means you're going to have to have pretty high doses in order to cause it.

CHARLES: Eastmond says there are several reasons for this apparent disagreement. First, IARC just looks at whether glyphosate can cause cancer. Regulators have to decide whether it actually will, considering how much of it people are exposed to. Another reason is different agencies looked at different evidence. Eastmond's committee considered a whole bunch of studies that are not publicly available because companies like Monsanto paid for them and submitted them to regulatory agencies.

EASTMOND: I have never seen a chemical with as many animal cancer studies as glyphosate.

CHARLES: Eastmond says these company-financed studies are credible. The labs have to follow strict guidelines. But IARC didn't look at most of them because it only considers results released publicly. And finally, sometimes scientists just look at the same study and disagree about what it means.

EASTMOND: We just evaluated the evidence differently. I mean, but, you know, these are honest disagreements.

CHARLES: Act 3 arrived - the trials, three of them, in and around San Francisco. Lawyers for Bayer, which now owns Monsanto, told jurors repeatedly that regulatory agencies don't think glyphosate causes cancer. Lawyers for the cancer victims, though, suggested that the regulators couldn't be trusted because Monsanto had manipulated them.

Matthew Miller (ph) and his legal team showed the jurors internal Monsanto emails. In one, executives described phone calls with an official at the Environmental Protection Agency.

MILLER: Who said, I don't need to see any more studies. I'm going to declare Roundup safe. And I'm going to stop another agency from looking at it.

CHARLES: Another Monsanto executive talked about ghostwriting papers on glyphosate's safety that outside scientists could publish under their own names.

MILLER: And I think the jury was rightfully offended.

CHARLES: All three juries ordered Bayer to pay huge punitive damages - in the most recent case, a total of $2 billion. Alexandra Lahav, at the University of Connecticut's law school, says one lesson from this case is attempts to get favorable decisions from regulators can backfire in court.

ALEXANDRA LAHAV: They then open themselves up for the jury to say, wait a minute. You're trying to convince the regulator not to regulate you, and now you want me to believe that the regulator is completely objective.

CHARLES: Bayer is appealing these verdicts. And the damages probably will be reduced. But more lawsuits are waiting. The total value of Bayer's stock has fallen $40 billion since the first verdict. The next trial is set for August in St. Louis. Dan Charles, NPR News.

Copyright © 2019 NPR. All rights reserved. Visit our website terms of use and permissions pages at for further information.

NPR transcripts are created on a rush deadline by Verb8tm, Inc., an NPR contractor, and produced using a proprietary transcription process developed with NPR. This text may not be in its final form and may be updated or revised in the future. Accuracy and availability may vary. The authoritative record of NPR’s programming is the audio record.