Merchants of Environmentalist Doubt*

Contrary to activist claims, the popular herbicide glyphosate does not cause cancer in people, says a new study.


Rene Van Den Berg/Dreamstime

A new study in the Journal of the National Cancer Institute reinforces a message that scientists have been telling us for years: Glyphosate isn't going to give you cancer. But don't expect activists to stop telling you it will.

Glyphosate, often sold as Round Up, is used to kill weeds by spraying it on crops genetically enhanced to resist it. The study, conducted by researchers at the Agricultural Health Study (AHS), followed tens of thousands of licensed pesticide applicators for about two decades. The paper found "no association" between the popular herbicide and "any solid tumors or lymphoid malignancies overall, including [non-Hodgkin lymphoma] and its subtypes." The study did find "some evidence of increased risk of acute myeloid leukemia" in the highest exposed group, but it added that this association was "not statistically significant."

This finding accords with decades of research. Again and again, scientific panels and regulatory agencies have evaluated glyphosate and concluded that its use is not associated with an increased risk of cancer in people. Nevertheless, in 2015 the International Agency for Research on Cancer (IARC) classified glyphosate as a "probable human carcinogen." This was the result of a carefully crafted anti-biotechnology campaign.

Environmental activists have perfected a highly effective scaremongering playbook, and they have been assiduously running those plays against glyphosate for nearly 20 years. First they scour the epidemiological literature to find any hint that a substance or process might cause human disease, especially cancer. This is not usually a difficult task, because somewhere, sometime, some cagey epidemiologist will have obliged them by torturing highly equivocal data into confessing the possibility of carcinogenicity. These epidemiological phantasms are then bolstered by a dodgy experiments done by activist-funded researchers.

With this chimerical evidence in hand, the activists then invoke the precautionary principle—the demand that any new technology be proved absolutely safe before people are permitted to use it, with no trade-offs allowed. Disingenuously portayed as the hoary adage "better safe than sorry," the principle actually amounts to "never do anything for the first time." As I wrote in my book The End of Doom:

"The problem is that one cannot prove a negative," notes Mercatus Center analyst Adam Thierer. "An innovator cannot prove the absence of harm, but a critic or regulator can always prove that some theoretical harm exists. Consequently, putting the burden of proof on the innovator when that burden can't be met essentially means no innovation is permissible." Just because I can't prove that no minotaurs roam the woods surrounding my cabin in Virginia, that shouldn't mean that regulators can, as a precaution, ban virgins from visiting me. (Minotaurs are notoriously fond of the flesh of virgins.)

After biotech crop varieties became commercially available in 1996, farmers across the globe rapidly began to adopt them, especially the ones resistant to glyphosate. Why? Because they no longer had to rely on plowing to control weeds, which saved substantial amounts time, fuel, and eroded topsoil. This meant reduced greenhouse gas emissions and less runoff into streams, so you might think environmentalists would have embraced biotech crops. They didn't, largely because when biotech crops were being introduced in Europe during the late 1990s, groups like Greenpeace and Friends of the Earth found they could attract funding and members by fanning fears about the new crop varieties.

Since herbicide resistance is the most popular type of genetic enhancement of crops, activists recognized that going after glyphosate would provide them with a bonanza of media attention and donations from a frightened public. And it worked. Prior to 1996, the Environmental Protection Agency had concluded that glyphosate was not a human carcinogen. A rough Nexis search using the search terms "glyphosate" and "cancer" turned up fewer than a score of newspaper, magazine or wire service articles that even mentioned glyphosate before 1996 and none that suggested that it might cause cancer. (In ironic retrospect, Procter & Gamble actually applied for patent on glyphosate to use as a chemotherapy treatment for breast cancer.) In contrast, Nexis found more than 1,000 such articles that have been published in the last three years.

The IARC panel came to its decision after being seeded with researchers beholden to anti-biotech activist organizations. Back in June, Reuters reported that Aaron Blair, the chair of the IARC glyphosate panel, "knew the unpublished [AHS] research found no evidence of a link between glyphosate and cancer" and did not report those results to his IARC colleagues. Furthermore, Blair has acknowledged in depositions that—in Reuters' words—the research "would have made it less likely that glyphosate would meet the agency's criteria for being classed as 'probably carcinogenic.'"

California regulators are now moving to require that glyphosate be listed as a carcinogen, and the European Union is struggling over whether to approve use of the herbicide.

Monsanto, a manufacturer of glyphosate, and various farm groups launched a lawsuit this week against California to stop the state from requiring cancer warnings on products containing the herbicide. Last March the European Chemical Agency concluded that "the available scientific evidence" did not warrant classifying "glyphosate for specific target organ toxicity, or as a carcinogen, as a mutagen or for reproductive toxicity." Nevertheless, the European Union deadlocked over the approval or disapproval of glyphosate last week.

If the anti-biotech scare campaign succeeds in getting glyphosate banned, farmers will be forced to use less benign and more expensive herbicides or to resume plowing, thus increasing topsoil erosion. The result will be higher food prices, more damage to the natural environment, and no improvement in public health.

*In 2010, Naomi Oreskes and Erik Conway published Merchants of Doubt, which argued that groups of industry-connected scientists "ran effective campaigns to mislead the public and deny well-established scientific knowledge over four decades." It is clear that various activist groups and a coterie of fellow-traveling researchers are now similarly engaged in misleading the public and denying well-established science in pursuit of their goals.

Disclosure: About three years ago I bought 100 shares of Monsanto with my own money for $109 per share. They were going yesterday at $117.36 per share.