Is glyphosate toxic or carcinogenic? This Latest Review, full of sound and fury, seems to signify nothing

GEITP has had previous discussions about the herbicide, glyphosate. The attached review is the latest summary of where this controversial chemical stands. Glyphosate is the most applied agricultural chemical worldwide and has become nearly ubiquitous throughout the environment. Glyphosate is an effective herbicide because it disrupts the shikimate pathway, which is responsible for the synthesis of essential amino acids in fungi, plants, and microorganisms.

Given that there is no known target for glyphosate in higher organisms including vertebrates, its toxicity to humans and other animals is heavily debated — especially after the (likely erroneous) 2015 IARC ruling that “glyphosate is carcinogenic.” Today, a growing body of literature shows no conclusive cell culture, intact animal, and epidemiological evidence for any toxicity of glyphosate across animal species. With the application of glyphosate increasing globally, authors felt it was important to discuss these reports, to enable a broader conversation on glyphosate toxicity and its impact on human and environmental health. Authors (from University of Calgary, Canada) summarize the recent glyphosate literature and discuss its implications [see attached].

Structural formula of glyphosate | Download Scientific Diagram

The chemical structure of N-(phosphonomethyl)glycine (glyphosate; Figure) is incredibly simple. Glyphosate, the active ingredient in glyphosate-based herbicides (GBHs), is the most used herbicide globally. Today, ~280 million pounds are applied annually in the United States alone. First discovered by a Monsanto scientist, glyphosate was initially under patent as “RoundUp” (Monsanto), a broad-spectrum GBH containing glyphosate as the active ingredient — in a mixture with water and inert adjuvants. GBHs were quickly adopted into agricultural practices due to their perceived low toxicity to animals. Specifically, glyphosate inhibits 5-enolpyruvylshikimate-3-phosphate synthase (EPSPS), an enzyme unique to fungi, plants, and microorganisms.

Because higher organisms lack this enzyme, it was assumed that this chemical would be safe in animals (including humans). EPSPS is critical for the synthesis of the essential aromatic amino acids — tryptophan, phenylalanine, and tyrosine, and further secondary metabolites; as such, this makes glyphosate an especially effective herbicide.

Chemist Dr. Henri Martin invented glyphosate in 1950, but its herbicidal importance was not fully realized until the 1970s, when Monsanto patented the glyphosate mixture RoundUp. Monsanto monopolized the glyphosate market until 2000, when their original patent expired. Since 2000, other companies have capitalized on glyphosate’s effectiveness; today, more than 750 GBHs are sold in the U.S. alone. These mixtures contain glyphosate as the active ingredient — most often in isopropyl ammonium salt form, to constitute 40%–60% of most GBH products. “Inert” ingredients such as water, heavy metals (i.e., arsenic, cobalt), and a proprietary mixture of surfactants, commonly of the polyoxyethylenamine family, comprise the remaining volume.

Authors summarize the cell culture, laboratory animal, and clinical data — and we find nothing conclusive. The International Agency for Research on Cancer (IARC) suggests glyphosate is “a probable carcinogen,” whereas both the European Food Safety Authority (EFSA) and U.S. Environmental Protection Agency (EPA) disagree, suggesting glyphosate is not a concern to human and animal health. 😊😊
Toxicol Sci Mar 2023; 192: 131–140

Thanks for the review; this topic is very familiar to me, because as a Panel member of the EFSA pesticide panel (PPR Panel), I was involved in first-tier glyphosate evaluation last year. The final EFSA assessment should be out in July this year. The case is now in the hands of higher-level scientific bodies at EFSA, and the “verdict” is eagerly expected.
Personally, or as a PPR Panel member, I think that the huge body of research has not been able to identify any really significant toxicity in humans or animals, let alone something more serious such as cancer. It was somewhat depressing to go through hundreds of articles on glyphosate and see the questionable quality of most articles.
Best wishes, OP

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