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ATA Turf Times – Jason Ferrell & Stephen Enloe – Professor & Associate Professor, UF/IFAS Center for Aquatic & Invasive Plants

There is significant clamor these days about glyphosate and whether it can or should be used as a part of an integrated pest management program. The concerns over this molecule are many and focus on both the science of health risk and public perception. Therefore, let’s briefly consider where we are with the science and see if we can find a path forward.

The concerns with glyphosate started in 2015 when the International Agency for Research on Cancer (IARC) reclassified this molecule as “Probably Carcinogenic”. This change in classification sent shockwaves across the world since we have been told for decades that glyphosate was essentially benign to humans and the environment. This reclassification was a significant move and has since prompted many countries to re-review the data on glyphosate and determine if additional changes in categorization are required.

The independent re-reviews conducted by the US EPA, European Food Safety Administration, Health Canada, Australia, Germany, Brazil, and South Korea have all failed to agree with the IARC assessment. In short, none of these other agencies have concluded, from the available data, that glyphosate poses a significant health risk. So this begs the question, why does everyone seem to disagree with IARC?

This is a complicated and very technical question. If you are interested in diving into this issue, we would highly recommend reading Tarazona et al. 2017 for a full explanation. However, we will attempt to give you a very short and largely insufficient answer on why these agencies disagree with the IARC. 1. The IARC did not make this decision because they are activists that want to penalize pesticides. The IARC is a group of very talented researchers with a long track record. So, this was not a political move. 2. According to Tarazona et al. (2017), the assessment of all the data show that the IARC and EFSA (European Food Safety Authority) were in very close agreement. However, there were a couple of papers that the IARC included in their analysis that the EFSA didn’t feel should be included. These differences, and others, were enough for the IARC to elevate the classification of glyphosate. However, it is important to understand that though these agencies appear to be at odds, they still agree on most points. 3. What does Probably Carcinogenic mean? It means that there is limited evidence that it causes cancer in humans, but sufficient evidence in model species (mice and rats). If (and it is still an “if”) glyphosate is a probable carcinogen, it moves it into a classification that also contains consumption of red meat, consumption of beverages heated to >65C, and workplace exposure to haircare products. Known carcinogens like sunlight and tobacco are in a completely different classification than glyphosate. Please understand, the IARC is not saying that glyphosate causes cancer. They are suggesting that it may be possible for glyphosate to cause cancer, just like consuming very hot beverages. But again, it is important to remember that just because IARC has made this designation doesn’t make it so. Many other similar agencies currently disagree with this assessment and the IARC continues to stand alone.

Now let’s complicate things a bit more. The state of California moved to require warning labels on glyphosate indicating it was a carcinogen. This move was twice struck down in a California court saying there was insufficient evidence for labeling. Moreover, the US EPA then took a strong stance saying that no state could add warning labels to pesticides that had successfully completed their registration process. But then, three separate plaintiffs successfully sued and were awarded large settlements since the court felt that sufficient evidence was brought forward linking glyphosate to their respective disease. So which is it? Different courts in California say glyphosate does and does not cause cancer. Lastly, Bayer (the primary registrant for glyphosate) recently moved to settle thousands of similar lawsuits for an estimated $10B. Does this indicate guilt? Is it simply a business decision to put this matter behind them? The decision on this is yours to make.

So where does this leave us? There are volumes of data on this subject that have been exhaustively reviewed by experts in numerous countries and the overwhelming consensus is that glyphosate does not likely pose a risk of cancer. Therefore, we would suggest that until additional and more convincing data are developed and published, glyphosate remains an effective member of an integrated pest management plan. However, we must remain willing to change this opinion if the data proves otherwise. We would also suggest that we dedicate ourselves and our staff to education on this issue. Social media and blog posts are not a sufficient venue for unbiased information, so maintaining a connection to the dispassionate facts will help us navigate this important topic.

Tarazona JV, Court-Marques D, Tiramani M, Reich H, Pfeil R, Istace F, Crivellente F. Glyphosate toxicity and carcinogenicity: a review of the scientific basis of the European Union assessment and its differences with IARC. Arch Toxicol. 2017 Aug;91(8):2723-2743. doi: 10.1007/s00204-017-1962-5. Epub 2017 Apr 3. PMID: 28374158; PMCID: PMC5515989.