Scientific paper questions safety of glyphosate herbicides

Scientists and regulators clash over assessment of glyphosate as a likely carcinogen

Glyphosate is being used more often and in new ways, and that’s prompted a call for re-evaluating the product’s safety in the journal Environmental Health.

The peer-reviewed article, by 13 scientists and an environmental consultant, said the use of glyphosate-based herbicides (GBHs) has grown dramatically at the same time new concerns about its safety have come to the fore. In the paper, published online Feb. 17, the authors noted there have been recent discoveries about the toxicity and human health risks of glyphosate products.

“Our concern deepened when the World Health Organization’s International Agency for Research on Cancer (IARC) reclassified glyphosate as ‘probably carcinogenic to humans,’” they wrote.

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They noted much more glyphosate is applied and in higher concentrations than in the past because it’s sprayed on glyphosate-resistant crops and used pre-harvest to control weeds as well as to dry down crops. As a result, the paper says people are consuming more glyphosate in their food and water.

In 2014, 240 million pounds of glyphosate were applied worldwide — 100 times more than in the mid-1970s, soon after its 1974 introduction, they wrote.

The paper also said most glyphosate studies were done in the 1970s and 1980s and didn’t include other mixes with surfactants or other herbicides that could add toxicity.

“Worldwide, GBHs often contaminate drinking water sources, precipitation and air, especially in agricultural regions,” the paper said. “The half-life of glyphosate in water and soil is longer than previously recognized. Glyphosate and its metabolites are widely present in the global soybean supply. Human exposures to GBHs are rising.”

It all adds up to regulatory estimates of tolerable daily intake for glyphosate in both the United States and European Union that are based on outdated science, the paper stated.

A number of scientists dispute the World Health Organization’s statement that glyphosate probably causes cancer, including members of the European Food Safety Authority.

In 2015 Canada’s Pest Manage­ment Regulatory Agency concluded that the weight of evidence indicates glyphosate is “unlikely” to pose a risk for human cancer. The United States government has also declared glyphosate safe.

In 2013, Monsanto, the maker of Roundup, received approval from the U.S. Environmental Protection Agency to boost the amount of glyphosate applied to Roundup Ready crops.

A Monsanto official wrote in a blog that this latest paper “significantly misrepresents” the safety of glyphosate-based herbicides. Daniel Goldstein, MD, Monsanto’s senior science fellow lead for Medical Sciences and Outreach also challenged the credibility of some of the paper’s authors.

“In evaluations spanning four decades, the overwhelming conclusion of experts worldwide has been that glyphosate, when used according to label directions, does not present an unreasonable risk of adverse effects to humans, wildlife or the environment,” Goldstein wrote.

But the new paper cites recent studies that suggest associations between exposures to GBHs and adverse health outcomes. These include “congenital malformations” in young pigs fed soybeans with GBH residues. The authors also wrote there is evidence mounting that glyphosate damages rat liver and kidneys at exposure levels now considered safe; therefore they conclude the allowable daily intake for glyphosate in humans is too high.

The paper also claimed glyphosate binds strongly to some soils and could pose a threat to soil health and soil microbes, harm fertility and even affect crop productivity.

Monsanto’s Goldstein dismissed the paper, calling it a source of unnecessary confusion and fear that failed to foster a science-based dialogue, adding the paper’s claim about endocrine disruption was erroneous.

“This fact was confirmed by the EPA (Environmental Protection Agency) just last year,” he wrote.

The Monsanto science and health advocate added some of the authors who contributed to the paper. Goldstein also noted several of the paper’s authors had links to pro-environment organizations and researchers.

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About the author


Allan Dawson

Allan Dawson is a reporter with the Manitoba Co-operator based near Miami, Man. Covering agriculture since 1980, Dawson has spent most of his career with the Co-operator except for several years with Farmers’ Independent Weekly and before that a Morden-Winkler area radio station.



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