Letter from Washington — From the September 2015 issue

Weed Whackers

Monsanto, glyphosate, and the war on invasive species

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Then came a massive speed bump. This past March, seventeen scientists met in Lyon, France, under the auspices of the International Agency for Research on Cancer, an arm of the World Health Organization, to assess the carcinogenic potential of several chemicals. The group was led by Aaron Blair, an internationally renowned epidemiologist and the author of more than 450 scientific papers, who spent thirty years at the National Cancer Institute. Among the chemicals they evaluated was glyphosate.

As Blair explained to me, the group reviewed three kinds of data: lab tests on animals, epidemiological studies on humans who had been repeatedly exposed to glyphosate, and “mechanistic” analyses of the ways in which the compound could cause cancer.

The animal studies, Blair said, “found excesses of rare tumors.” Absent glyphosate exposure, the tumors “are really rare. They almost never just occur.” The studies on human beings, conducted in the United States, Canada, and Sweden, pointed to an equally grim conclusion. “They showed a link between people who used or were around glyphosate and an increased risk of non-Hodgkin’s lymphoma. Different studies, in different places, suggested that they might go together.”

3 When asked about Blair’s report, the Monsanto spokesman reiterated that “glyphosate is not a carcinogen” and cited a 2013 EPA study that concluded, “Glyphosate does not pose a cancer risk to humans.” He also noted that the I.A.R.C., in its own words, identifies cancer hazards “even when risks are very low with known patterns of use or exposure.”

According to Blair, there were good grounds to declare that glyphosate definitely causes cancer. This did not happen, he said, because “the epidemiologic data was a little noisy.” In other words, while several studies suggested a link, another study, of farmers in Iowa and North Carolina, did not. Blair pointed out that there had been a similar inconsistency in human studies of benzene, now universally acknowledged as a carcinogen. In any case, this solitary glitch in the data caused the group to list glyphosate as a probable (instead of a definite) cause of cancer.3

The reaction from Monsanto was predictably irate. GMO Answers, a P.R. website put together by the biotech-food industry, featured a host of derisive posts about the study. Sympathetic journalists went to bat on behalf of the lucrative toxin. Hugh Grant, Monsanto’s chairman and CEO, was curtly dismissive: “It’s unfortunate that junk science and this kind of mischief can create so much confusion for consumers.”

As it had on previous occasions, the company demanded a retraction of the report. When we talked, it didn’t sound as if Blair was likely to do any such thing. “Historically, the same thing happened with tobacco, the same thing happened with asbestos, the same thing happened with arsenic,” he said. “It’s not junk science.”

The French government agreed, promptly banning the sale of Roundup by garden stores in response to Blair’s report. The Colombian authorities meanwhile halted the coca-spraying program, over U.S. government protests. The program had not been a huge success, of course, given the target plant’s remarkable ability to survive the spray.

But unintentional glyphosate resistance is not confined to coca. Although Monsanto scientists had deemed such a development nearly impossible for weeds targeted by the Roundup Ready system, species subjected to prolonged exposure began to adapt and survive even as farmers were harvesting their first bioengineered crops. “It’s a disaster,” said Benbrook. “As resistant weeds spread and become more of an economic issue for more farmers, the only way they know how to react — the only way that they feel they can react — is by spraying more.” It has now become common for farmers to spray three times a season instead of once, and Benbrook estimates that the extra doses of herbicide will add up to 75,000 tons in 2015.

All of which brings us to horseweed, or mare’s tail, a plant native to North America and once highly prized for its medicinal qualities. It has hairy stems, and grows about four feet tall. A nuisance in corn and soybean fields, it has naturally been a glyphosate target. But in recent years, farmers have been encountering a new kind of mare’s tail: a superweed produced by years of glyphosate treatment. Not only does it refuse to die when drenched with four times the recommended dose but it appears to gain strength from the experience, growing up to eight feet tall, with stems thick enough, according to one farmer, to “stop a combine in its tracks.”

In other words, a very alien invasive, made right here in America.

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is the Washington editor of Harper’s Magazine and the author, most recently, of Kill Chain: The Rise of the High-Tech Assassins.

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