GRANTVILLE, Pa. — Despite a bevy of ominous news stories, no national scientific agency in the world says that glyphosate gives people cancer, a pesticide expert said this week.
Concerns about the world’s most-used herbicide have heated up since 2015, when a United Nations panel determined the chemical a probable carcinogen.
But that determination is not as definitive as it sounds, and it lacks corroboration, said Jason Ferrell, director of the Center for Aquatic and Invasive Plants at the University of Florida.
Ferrell began looking into glyphosate safety because he was surprised by the 2015 hazard determination by the International Agency for Research on Cancer, part of the World Health Organization.
After all, he’d been in graduate school when Roundup Ready crops were coming onto the market, and he’d been taught that the herbicide was one of the safest sprays for people and the environment.
“You could almost say that I got a degree in glyphosate,” he told attendees of the Keystone Crops and Soils Conference on Wednesday via video-conference.
So Ferrell looked at the classification the agency had given the chemical: “probably carcinogenic to humans.”
That means the organization found limited evidence of carcinogenicity in humans, but sufficient evidence in lab animals.
Limited evidence means a causal link is credible, but chance, bias or confounding circumstances cannot be ruled out.
The “probable” category presents glyphosate as less of a concern than known carcinogens such as tobacco, asbestos and plutonium, and at the same level of concern as the consumption of red meat or hot beverages.
To Ferrell, the classification stops short of really saying that glyphosate causes cancer.
Still, the study prompted many national health agencies — including the U.S. Environmental Protection Agency, the European Food Safety Authority, and similar bodies in Australia, Canada, France, Germany, Japan and South Korea — to revisit their positions on glyphosate.
None of them found a link to cancer, Ferrell said.
Differences in methodology likely explain why the UN cancer agency disagrees with all the other findings, he said.
The EPA and other national bodies conducted a risk assessment — Is harm likely given label restrictions and a person’s likely exposure?
The UN body did a hazard assessment — Is harm at all possible?
That broader assessment is not necessarily wrong, but it does tend to classify chemicals to higher levels of concern than does the method used by EPA and other agencies, Ferrell said.
Your Daily Serving of Glyphosate?
Despite the growing pile of findings that glyphosate does not cause cancer, the assault on glyphosate has arguably increased in the past four years.
California required the chemical to be labeled as a cancer-causing agent, though a judge struck down that plan for lack of evidence, and the EPA said it would not approve labels with that warning.
Bayer, which owns glyphosate creator Monsanto, has also lost several high-profile lawsuits involving plaintiffs who supposedly got cancer from glyphosate exposure.
These lawsuits claim that Monsanto knowingly marketed a defective product.
The suits cite internal corporate documents, dubbed the Monsanto Papers, that allege the company sponsored ghostwriting of scientific studies about the chemical, Ferrell said.
The papers’ claims led to a fresh round of re-evaluation by national agencies.
The European Food Safety Authority found that even if the ghostwriting of two papers had happened, it would not have affected the agency’s overall assessment of glyphosate, which drew on 700 scientific references, Ferrell said.
Consumers have also raised concerns about glyphosate in food, beverages and breast milk.
A Washington State University researcher and colleagues checked the breast milk claim and found neither glyphosate nor its primary breakdown chemical.
Citing another academic paper, Ferrell said glyphosate is unlikely to get into breast milk because it is not very fat soluble.
As for a study that found glyphosate in orange juice, Ferrell said the concentrations — 4 to 26 parts per billion — fell below the EPA’s level of concern.
A child would have to drink 100 gallons of orange juice per day to meet the risk threshold, he said.
Tolerances are set by thorough lab animal testing and modeling of likely human exposure.
An extra factor of safety is included to ensure the well-being of children and infants, who are particularly vulnerable to toxins.
These tolerance studies also inform preharvest intervals and usage restrictions, which are designed to minimize exposure to herbicides.
“There are tremendous checks in place to ensure that we are not exceeding those tolerances in our diet,” Ferrell said.
Critics have questioned the EPA’s policy of accepting manufacturer-funded safety studies.
While paid for by the companies, those experiments are generally conducted by third-party research firms, Ferrell said.
Three main companies do such testing in the U.S. for both the chemical and pharmaceutical companies.
“If they are seen to not be providing accurate or reliable data, then they’ll no longer be in that business,” Ferrell said.
When farmers are asked their opinion on glyphosate, Ferrell recommends approaching the question empathetically.
Don’t be dismissive of people who ask those questions. They are not herbicide experts, so they are reacting to the little bit of bad information that they have heard, he said.
While presenting accurate information, farmers should emphasize that they, too, are concerned about public health. “You can’t crush someone’s concerns with data,” he said.
Some people will retort that they don’t trust the EPA to do truthful assessments. Ferrell tells those people that at some point you have to trust somebody, and he chooses to trust the federal agency.
“Sometimes you have to leave it there,” he said.