Is glyphosate really dangerous?

John Giesy uses an orbitrap ultra high resolution liquid chromatograph/mass spectrometer 
to identify and quantify organic chemicals in his lab at the school of biological sciences at the University of Saskatchewan March 24. The machine has a resolution between 1/100,000 and one million atomic mass units. |  William DeKay photo

John Giesy is not a household name, but if you want to learn about glyphosate, he’s the go-to expert

John Giesy doesn’t speak frequently with the media and most people have probably never heard of him, despite an ongoing controversy in a field for which he is best known.

The World Health Organization recently reclassified glyphosate into a more hazardous substance category, which sparked consumer alarm and prompted governments worldwide to rethink their positions.

Last week, the worldwide expert in toxicology agreed to speak on the record.

“You might be able to show that (glyphosate causes cancer) in an in-vitro test…. But in an animal model, at a reasonable dose, would that occur? My reading of the literature is that it won’t.”

Giesy is a professor and Canada research chair in environmental toxicology at the University of Saskatchewan. He is also a professor or honourary professor at six other universities, an Einstein Professor with the Chinese Academy of Science and a fellow of the Royal Society of Canada. Globally, he is the most cited author in the combined fields of ecology and environmental sciences.

Google Scholar, which rates academics according to citations, ranks Giesy in the top 0.001 percent of all scientists in the world.

So if a government agency needs an expert on how chemical compounds affect humans or wildlife, Giesy is a good place to start.

Just more than a year ago, the WHO changed the conversation about glyphosate, the active ingredient in Roundup, and the most popular herbicide in the world.

Members of the International Agency for Research on Cancer (IARC), a WHO agency, announced that glyphosate “probably causes cancer.”

The IARC decision had a massive impact:

  • In response to pressure from citizens and consumer groups, the U.S. Food and Drug Administration said it would begin testing food and grains for glyphosate residues.
  • The European Union was expected to extend its approval of glyphosate in March. The decision has been postponed because France and other countries oppose renewing its registration.

Giesy has reviewed the IARC classification. He said the agency likes to err on the side of extreme caution.

“You have to understand how IARC panels work,” said Giesy, who was born in Ohio and spent most of his academic career at Michigan State University.

“It’s difficult to ever get (them) to say it absolutely won’t cause cancer…. If there is any literature out there that suggests it might they protect themselves by saying it’s a possible human carcinogen… or probable carcinogen.”

In part, IARC said glyphosate is a ‘probable’ carcinogen because some research shows it causes cellular mutations or changes to DNA.

“The… data provide strong evidence for genotoxicity,” IARC said in its report.

But in-vitro research, where cells are exposed to a chemical, is dubious because scientists use an unreliable method to detect cellular mutations.

“The literature that would indicate it (glyphosate) might possibly be genotoxic is an Ames test, which has something like 30 percent false positives…. If you test industrial chemicals and pesticides half of them can be shown to be carcinogens in this Ames test,” Giesy said. “Even natural products that are in food, you can show in the Ames test that they’re a potential human carcinogen.”

There is also the matter of dose. Many chemicals can have genotoxic effects or cause DNA to break in a lab, but usually the doses are extremely high, Giesy said.

There’s little evidence that glyphosate exposure levels in the real world cause cancer, said Giesy, who has published approximately 1,000 peer-reviewed articles and is regarded as an expert in ecological risk assessments on agricultural and industrial chemicals.

Giesy is worried about the state of science because advocates are now using research to confuse the public.

He said environmental groups and lawyers, hoping to file class-action suits, routinely hire a “like minded” scientist to produce research showing that chemical X causes horrible disease Y.

The resulting papers, usually published in second rate journals, cloud out the valid science, he said.

“That kind of stuff is going on all the time…. When they go to court they can point to (the study) and say well, it’s published. It’s got to be true,” Giesy said.

“There’s a paper that came out that basically cherry picked the literature and made claims… of associations with glyphosate with everything you can imagine. From criminal behaviour, spousal abuse… Parkinson’s, you name it.”

Bernhard Url, executive director of European Food Safety Authority (EFSA), which reported in November that glyphosate doesn’t cause cancer, has neatly summarized how empirical science has been reduced to an internet popularity contest.

“This is the… Facebook age of science. You have a scientific assessment, you put it in Facebook and you count how many people like it,” Url said at a EU hearing. “For us this is no way forward. We (the EFSA) produce a scientific opinion, we stand for it but we cannot take into account whether it will be liked or not.”

Giesy said he also takes a de-tached approach. He evaluates data and offers advice to governments based on the evidence.

However, toxicology is more than raw data because chemicals can potentially be deadly. Giesy has had cancer, a disease that changes how someone views the world.

“Certainly you wouldn’t wish it on anyone. But whether it’s caused by glyphosate, in my opinion, is highly unlikely.”

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