Studies look at glyphosate’s characteristics

Writer cites several studies about glyphosate.


For the Capital Press

Published on April 9, 2014 2:08PM

On Jan, 24, a column by Jack DeWitt responded to my Jan. 17 column. To help advance our industry, I’d like to reply to his points.

Please note, however, the column doesn’t provide any factual sources for his opinions. It just states them as if they were facts. They aren’t facts, they’re opinions. I’ll present substantiation of that.

The column makes an ad hominem attack on those who disagree with him, calling them the “anti-technology” crowd. The studies I list below were conducted at the highest level of scientific, technical expertise. To dismiss a study simply because you disagree with its results is definitely not good science. Science requires three elements:

• Repeatability — Can the test be repeated, or is it simply a one-shot deal, like magic?

• Verifiability — Are procedures transparent, employing good practice?

• Falsifiability — Does the resulting data-set allow negative cross-check?

If any one of these three criteria is missing, it’s not science. Opinion doesn’t include any of these criteria. That’s why opinion is not science.

It’s important to note that testing of glyphosate is divided into two categories: (1) as a stand-alone chemical, the amniophosphonic analogue of the amino acid glycine, N-phosphonomethylglycine (contracted to gly(cine) phos(phon)ate, or glyphosate), and (2) its commercially available forms, combined with surfactants and other additives, identified by trade names.

In his column, Jack launches an unsubstantiated defense of glyphosate as the “most biologically safe … most environmentally safe chemical ever developed.” He claims that “soil contact inactivates” glyphosate. He claims glyphosate decomposes into “carbon dioxide, ammonia, and phosphate.” What Jack doesn’t tell the reader is that this chemical pathway is only theoretic and does not represent actual processes or probabilities. Glyphosate’s metabolic-degradation occurs through hydrolysis to amniomethylphosphonic acid (AMPA), which is slower to degrade, lasts longer, yet has similar disruptive biological effects. (Anadon, et al., Toxicol Let 190(1); Benachour, et al., Chem. Res. Toxicol, 2009)

Glyphosate degradation and mineralization have been studied extensively. Soil interaction is strongly dependent on soil-type, moisture, pH, presence of Fe and Al-hydrous oxide, inorganic phosphate concentration, and ion strength of the liquid applied. Some of the chemical is tightly bound to soil particles. This is called adsorption, or simply sorption, where a substance (liquid, gas or dissolved solid) adheres to a surface of another substance (like soil particles). This portion of the chemical bio-accumulates. It does not degrade, and is not dissolved by water. Glyphosate and AMPA residues have been tracked in the top 5-cm of soil 15 months after application (Capori, et al., Egeis, Feb 2010). The primary-degradation pathway for glyphosate however is microbial mediation. (Franz, et al., Am Chem Soc, 1997). This means glyphosate remains a component in soil micro-flora. The biological processing of glyphosate yields altered micro-organisms whose immediate presence is not readily detectable anecdotally, but is discernible in subsequent disrupted biological processes (see (Samsel et al., Entropy, 2012, 15) noted below).

Glyphosate is highly soluble in water. (Tedesco, et al., Veolia, 2009) Some of the chemical is washed from the application site into adjacent surface waters, streams, rivers and the oceans, where its chemical composition and designed-destructiveness remains active for more than a year (Mercurio, et al., Mar Pollut Bull, 2014). The remainder leaches into ground water (Van Stempvoort, et al., Chemosphere, 2014).

Glyphosate is designed to be absorbed by growing plants, and its goal is to interfere with plant synthesis of certain amino acids involved in protein synthesis. Additional to this absorption effect, however, glyphosate metabolizes into AMPA (see notes above), which is bio-accumulated in the plant through oxioreductase activity (a gaseous-oxygen reaction) that is phytotoxic. This results in gene-mutation and plant resistance to glyphosate. (Duke, J Agric Food Chem, 2011). The above studies clearly dispute the unsubstantiated claim that glyphosate benignly decomposes into “carbon dioxide, ammonia, and phosphate.”

The column further claims that Roundup (glyphosate) “does not disrupt any animal or insect biological process, so is absolutely safe.” He provides no any factual substantiation for his claims. Glyphosate and its surfactants have been found to cause apoptosis (cellular fragmentation), and necrosis (cellular death) in human umbilical, embryonic and placental cells. (Benachour, et at., Chem. Res. Toxicol, 2009). This type of human cellular impact by glyphosate and its chief surfactant polyoxyethyleneamine (POEA) are examples of how the complex chemicals compounded into “Roundup” type herbicides have both acute, and chronic, impact on humans.

In 2013, a study was released (Samsel et al., Entropy, 2012, 15) that examines glyphosate’s residues in the Western diet. It demonstrates that glyphosate inhibits the cytochrome P450 (CYP) enzymes, resulting in toxicity to mammals. The research is extensive, and invites further independent trials to determine how glyphosate affects our bodies, and the processes that support life.

I hope the reader will read the scientific studies noted in this column, and discuss them with everyone interested in the advancement of our industry. We’ll all benefit from the conversations.

Hank Keeton farms 10 acres east of Silverton, Ore., manages three small businesses and is a partner in an ISO-certified testing laboratory for agricultural products.


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