The Rundown on Roundup: A Cancer-Causing Weedkiller?

Reading time: 4 minutes

Ariana Cardillo

If you’ve been to the Midwest, it’s hard to miss the endless fields dedicated to the agriculture industry. If you live there, you are accustomed to the growing cycles and crop rotations of the fields.  You probably are even desensitized to the massive machinery used to maintain these crops. However, something of growing concern to farmers and their neighbors are the weedkillers necessary to keep crop yields high. Chances are they are using a chemical called Roundup™.  Ever heard of it? In May, a jury awarded $2 billion to two Californian landscapers who claimed Roundup™ is the cause of their cancer of immune cells (non-Hodgkin’s lymphoma).   This case highlights not only the risk of this weedkiller to industrial farmers but also to landscapers and citizens alike who have prolonged exposure to this chemical.

            Roundup™ was first introduced for commercial operation in 1974 for nonselective weed control.  It’s main ingredient, glyphosate, inhibits the shikimate pathway in most plants.  This pathway makes specific amino acids that are essential for plants’ growth, however, it is not present in animal cells.  This trait can be desirable when genetically modified (GM) crops are engineered to include a glyphosate-resistant gene. When these GM crops are sprayed with glyphosate, they will survive, while all other invasive and unwanted plants will die.  Since its creation, glyphosate is the most widely used weedkiller in the United States, and in the world. Roundup™ has been in the news with possible class action lawsuits in multiple states within the U.S. and around the world. But it’s manufacturer, Bayer AG, previously Monsanto, continues to deny all allegations against the product causing cancer.  In their defense they use their more than 800 previous studies submitted to the U.S. Environmental Protection Agency (EPA) during the original registration process of their product.  So, what is the verdict? 

Estimated Agricultural Use for Glyphosate in USA

            In 2015 the International Agency for Research on Cancer (IARC), part of the World Health Organization (WHO), classified glyphosate as “probably carcinogenic to humans.” Following this, in 2016 a scientific review article was published in the journal Environmental Health, outlining the increasing risks of glyphosate.  Because invasive weeds are now becoming more resistant to glyphosate, larger amounts of the weedkiller must be used to kill off the weeds and maintain agricultural profits, thus increasing human exposure.  One of the main conclusions from this review is that previous studies have undermined the possibility that glyphosate, and other chemicals that are formed when converted by enzymes in plants and animals, may interact via other biological processes, including those associated with larger animals.  Considering glyphosate has been found in water sources, runoff water, in fish, and in plants, this chemical poses risks of exposure to individuals who never directly come in contact with the weedkiller. The EPA and European Food Safety Agency maintain that there is no risk to public health with respect to glyphosate.  However, these agencies, unlike the IARC, looked at numerous privately funded research; some of which were funded by Monsanto.  (IARC is only looking at studies that are publicly available). Current research, which is available to the public, has found that glyphosate affects the endocrine system and possibly affecting the function of important enzymes within the body that require metals.  

            A review published in the journal Carcinogenesis in 2019, concluded that studies on the effects of glyphosate on biological processes of vertebrates have been happening at concentrations much lower than the regulatory limits, and  studies at such low concentrations may have been overlooked in the past. They also concluded that the exact mechanism causing non-Hodgkin’s lymphoma may be more complex than the more well-known pathways being studied.  More significant was the conflicting evidence of the involvement of glyphosate in diseases. But Roundup™ is not only made of glyphosate. It also contains surfactants which are present in soaps and detergents, which allow the weedkiller to be sprayed and stay on the targeted weed.  Glyphosate also degrades into a chemical called aminomethylphosphonic acid, (AMPA) which has been shown to damage genetic material within human and mouse models.  

            Does glyphosate cause cancer? The jury may still be out on this one, but there is a clear need for more research to be done. The research must not look at glyphosate alone, but in combination with the other ingredients of Roundup™ like the surfactants, and its degradation product AMPA.  But caution should be taken by those with prolonged and frequent exposure to these chemicals, whether using Roundup™ or other weedkillers.

Works Discussed:

Davoren, M. J., & Schiestl, R. H. (2018). Glyphosate-based herbicides and cancer risk: a post-IARC decision review of potential mechanisms, policy and avenues of research. Carcinogenesis, 39(10), 1207-1215.

Meshkini, S., Rahimi-Arnaei, M., & Tafi, A. A. (2018). The acute and chronic effect of Roundup herbicide on histopathology and enzymatic antioxidant system of Oncorhynchus mykiss. International Journal of Environmental Science and Technology, 1-10.

Myers, J. P., Antoniou, M. N., Blumberg, B., Carroll, L., Colborn, T., Everett, L. G., … & Vandenberg, L. N. (2016). Concerns over use of glyphosate-based herbicides and risks associated with exposures: a consensus statement. Environmental Health, 15(1), 19.

Swanson, N. L., Leu, A., Abrahamson, J., & Wallet, B. (2014). Genetically engineered crops, glyphosate and the deterioration of health in the United States of America. Journal of Organic Systems, 9(2), 6-37.

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