Glyphosate is the active ingredient in the most widely used herbicide, Roundup, which is made by Monsanto. The use of glyphosate is one of the most contentious issues in the agricultural business today. Mass protests recently erupted in Europe at the end of last year after the EU, after a great amount of discussion, granted an extension of five years for a license to use glyphosate in various agricultural uses in the EU.
Glyphosate is used in Roundup and is popular with farmers because it is powerful. Farmers rely upon herbicides with glyphosate to kill weeds and other unwanted vegetation and have done so for more than 40 years. But its use has sparked much debate, especially since 2015. That was when the World Health Organization concluded the chemical was probably carcinogenic, adding it to a category that includes red meat. This was after earlier conclusions from the EFSA and EPA that glyphosate is probably not a serious risk to humans.
There is little question that the debate about this chemical is very politicized in recent times. Environmental forces argue that exposure to glyphosate has been linked to cancer, autism, celiac disease, fatty liver disease and much more. On the other hand, reviews backed by the chemical and herbicide industries have argued that the pesticide has no risks.
Where does the science on this matter come down?
Lab Effects and Results
Glyphosate is a very small compound that has been sold as a major ingredient in herbicides for more than 40 years. It has been marketed as having little effect on animals because it is made to inhibit a key enzymatic pathway that is needed for the synthesis of protein, and thus, growth, that is unique to plants.
Over time, regulatory agencies have been evaluating its possible effects on other organisms. But newer assessments are more focused on carcinogenicity and genotoxicity, according to Deborah Kurrasch, who is a neuroscientist at the University of Calgary. In the last 10 years, she notes, evidence has been accumulating in the scientific literature that there could be other serious toxic effects. There are many systems other than cancer that can be affected by the chemical, she states.
Research that is funded by the Natural Sciences and Engineering Research Council of Canada and is being headed by Kurrasch, has started to look into glyphosate for several years. She was surprised by the lack of studies that were seen in the literature. There was little for this chemical that all of us are exposed to, she noted at the time.
For example, with the compound bisphenol A (BPA), she said that we can view the molecule and note that it binds to estrogen receptors. It also can be understood that the mechanism has an effect on estrogen signaling. But she said this is not well understood for glyphosate. It is not exactly clear what it is binding to.
Some evidence indicates that glyphosate has some sort of an effect on mitochondrial function. In an experiment several years ago, Kurrasch and other researchers exposed the embryos of zebrafish to low concentrations of glyphosate during certain development windows. The seemed to chance mitochondrial function and lead to a decrease in respiration. This, in turn, seemed to impair larvae locomotion.
Other studies have shown that glyphosate may reduce mitochondrial function and sperm motility in zebrafish at very high concentrations. It also may be able to alter neurotransmitter activity in rats’ brains. Other researchers think that the toxicity of glyphosate is probably low in common environmental concentrations, rather than in the whole pesticide formulation it is commonly used in.
Glyphosate and Roundup Differences
The chemical glyphosate is rarely used alone in the field. Herbicide products have many other products, including surfactants that assist glyphosate in its entry into plant cells, and several other additives that extend the shelf life of the product. This is what spurred Kurrasch to compare effects of glyphosate by itself to the effects of Roundup. Interestingly, she found that Roundup had the opposite effect as just glyphosate. When used on zebrafish, they moved more and their basal respiration was actually higher. They also had very different gene expression profiles of mitochondria linked genes in the brain. This suggests they could have different action mechanisms. Glyphosate may be doing something and the adjuvants are doing something else.
One of the problems for researchers who are studying pesticide effects is that major producers of herbicides, such as Monsanto or Syngenta, do not have to state all of the ingredients that are in their products.
In the EU and US, they must print on the package how much of active ingredients the product has. This is not usually the case for many other ingredients. These are considered inert as they do not contribute to the herbicidal activity of the product. So it makes it harder for toxicologists to test various ingredients to determine what is actually the most toxic, or what is adding to the problem. From the research perspective, it is difficult to tell which chemical may need to be changed to reduce toxicity.
Generally, the science shows that glyphosate does not create a brain that poorly functions or have serious effect on brain development. But the effects are very subtle and can take years of exposure to cause problems. That is why it is complicated to convince major regulatory bodies that there is a possible problem.
- How Toxic Is the World’s Most Popular Herbicide Roundup? (2018). https://www.the-scientist.com/news-opinion/how-toxic-is-the-worlds-most-popular-herbicide-roundup-30308