The Trouble with Glyphosate

This past February, experts on food safety came from all over the world to Wellington for Food Matters, a conference on ecological agriculture and nutrition. The list of speakers was peppered with leading scientific researchers from four continents. And in their presentations, one chemical name came up repeatedly as a cause for grave concern: glyphosate.

Dr Don Huber is an Emeritus Professor at the University of Michigan (USA), internationally recognised for his research on nutrient-disease interactions. He began by reminding the audience why glyphosate was invented. It was actually developed as a chelator to clean pipes, because it does a superb job of grabbing minerals. When cleaning a pipe, this is helpful. In a soil system, it can inhibit nutrient uptake by plants, causing deficiencies in key micronutrients. Researchers have found that applying glyphosate to herbicide-tolerant soybean plants caused a reduction in both macro- and micronutrients in plant tissue (Zobiole et al 2009). 

The same researchers also found that glyphosate decreases water use efficiency in plants; as more glyphosate is applied, plants become less efficient in their water use, making them more vulnerable to drought (Zobiole et al 2010b).

Glyphosate is also an antibiotic. It has been shown to harm microbial communities in soil, contributing to higher rates of pathogenic root infections (Zobiole et al 2010a).

The effects of glyphosate on human and animal health are also well documented. Another of Food Matters’ visiting speakers, French scientist Gilles-Eric Séralini, has conducted world-leading research on this topic. Séralini and colleagues found that giving rats a diet of maize treated with Roundup residues caused the rats to develop a range of severe health difficulties, including chronic kidney deficiencies, hormonal problems and tumours (Séralini et al 2014). Contrary to its benign reputation, in a laboratory comparison of nine of the most common pesticides and herbicides, Roundup was one of the most toxic to human cells (Mesnage et al 2014).

It’s actually unknown just what in the herbicide formulation causes health problems in animals or humans. The active ingredient glyphosate, when isolated, is toxic to human cell cultures in the lab. However, Séralini and colleagues recently discovered that complete glyphosate herbicide products, including the adjuvants, are significantly more toxic to human cells than glyphosate alone (Mesnage et al 2013). The same has been found for other pesticides as well, with adjuvants increasing toxicity by many orders of magnitude (Mesnage et al 2014). However, most governments make pesticide and herbicide safety determinations based on the active ingredient, rather than on the full formulation. 

Does glyphosate affect vines in the way it has been shown to affect annual crops? The studies have not been done. Are glyphosate’s days numbered? In one way they definitely are, as with sky-rocketing use of the herbicide, the number of glyphosate-resistant weeds has increased worldwide, from a single resistant species 20 years ago to over 30 species today. Glyphosate is now useless against the towering superweeds emerging in some cropping systems.

As for glyphosate’s regulatory status coming under threat, that has yet to be seen. It’s been banned in Sri Lanka due to suspected links with an epidemic of rare kidney disease, but not in larger countries. At the moment, the world’s industrial agriculture systems, particularly genetically modified crops, are heavily tied to this herbicide. However, as the scientific studies accumulate, the writing could be on the wall.