Last week, The International Agency for Research on Cancer (IARC), the cancer agency of the World Health Organization, classified glyphosate as probably carcinogenic to humans (Group 2A). Since the announcement, several news outlets have covered the topic and social media has been buzzing about what this means for consumers. In this post, we’ll discuss what glyphosate is, share experts’ perspectives and provide a roundup of news articles on this topic to breakdown what this news means for you.

First, glyphosate is the active ingredient in Roundup, an herbicide widely used in conventional agriculture. An FAQ on glyphosate, featuring answers from company and independent experts, is available here. In this document University of Florida professor and horticultural sciences department chairman Dr. Kevin Folta explains, “Glyphosate is amazingly non-toxic to humans or any other animals.”

Dr. Cami Ryan, social sciences lead at Monsanto Company, illustrates the toxicity of glyphosate as compared to many other common household substances in this infographic:

glyhphosate cancer
See the rest at

Prior to IARC’s announcement, GMO Answers’ received numerous questions about glyphosate, and this announcement creates even more questions. To help answer those, we’ve reached out to farmers and toxicologists for their thoughts.

Amanda Zaluckyj, of, explains in this post what a carcinogen is and what the classification means. She notes, “the following things have also been included in the 2A classification: manufacturing glass, burning wood, emissions from high temperature frying, and work exposure as a hairdresser.” Amanda goes on to explain what IARC “found out” about glyphosate and what others are saying about it.

Here, Michael I. Greenberg, M.D., MPH, Chief of Medical Toxicology, Drexel University College of Medicine in Philadelphia, addresses the claim that glyphosate could be a human carcinogen, and provides context to human exposure to glyphosate. He notes, “IARC did not consider the overwhelming scientific and medical evidence demonstrating that glyphosate is not a human carcinogen. This includes the largest epidemiological study of farmers ever undertaken, the U.S. National Cancer Institute’s Agricultural Health Study, which failed to find a relationship between glyphosate and cancer.”

Following are several articles from around the web posted in response to this controversial classification.

In this Forbes article, Henry Miller asks what the IARC’s conclusion means to you and me, he explains “As with common chemicals like sugar, salt and water, and foods like nutmeg and licorice, glyphosate at very high doses is capable of causing harm to humans. That’s what the IARC “2A” designation—“probably carcinogenic to humans”–essentially means.” Read more about IARC’s conclusions, and what government regulators have concluded about glyphosate, on Forbes in “March Madness From the United Nations.

Forbes isn’t the only outlet asking what this assessment means. Nathaniel Johnson from Grist asks precisely that in his article, “So Roundup “probably” causes cancer. This means what, exactly?” He shares a few key takeaways as to what this classification means:

  • There is a real chance that these pesticides could cause cancer, and we should be careful with them.
  • There’s controversy — several scientists disagreed with the designation.
  • Don’t forget that the list of things that probably cause cancer includes … just about everything.

Read more about what this classification means from both sides of the debate on Grist.

What to learn more about what “probably causes cancer” really means? Nathaniel shares this video from University of Michigan’s Andrew Maynard.

Dan Charles from NPR’s The Salt points out that “…the IARC's assessment leaves many questions unanswered, including how much risk glyphosate poses.” Read A Top Weedkiller Could Cause Cancer. Should we be Scared? to learn more about glyphosate’s history, the controversy surrounding it, and to explore answers to some of the questions opened by the IARC’s assessment.

Senior Post-doctoral Research Associate Ariel Pchances glyphosate could cause canceroliandri answers the question of what this classification means in context of other substances and items on the IARC’s list. “This list of “possible/probable” carcinogens include, among others: Whole-Leaf Extract of Aloe vera (2B), coffee (2B) and –wait for it- being a hairdresser or barber (2A).” She continues, “The sad news is that sunlight and –sorry chaps- alcohol consumption are more dangerous than glyphosate, both being classified by IARC in group 1 (carcinogenic to humans).” Read more in her blog post, Glyphosate possibly less dangerous than sunlight, World Health Organization’s listing says.
Andrew Kniss, Associate Professor of Weed Ecology & Management, has a lot invested in this new classification, as he shares, “I work with pesticides (especially glyphosate) on a regular basis, so I take this classification very seriously. If glyphosate is indeed likely to cause cancer, I am in the group of people who is most likely to be affected.”  Since the IARC hasn’t yet released the full monograph that details their reason for the decision, a list of data or references used to come to their conclusion are not available. Andrew took up the job of researching studies and data on his own; read his findings in Glyphosate and Cancer: What does the data say?
Monsanto also issued a statement about the IARC’s classification of glyphosate. “We want to be clear: All labeled uses of glyphosate are safe for human health and supported by one of the most extensive worldwide human health databases ever compiled on an agricultural product. In fact, every glyphosate-based herbicide on the market meets the rigorous standards set by regulatory and health authorities to protect human health.”  Learn more about the reasons why Monsanto, along with fellow members of both the EU and U.S. glyphosate taskforces, disagree with the IARC’s classification on
Science Media Centre has compiled several expert reactions to IARC’s classification of glyphosate as a Group 2A carcinogen. “This sounds scary and IARC evaluations are usually very good, but to me the evidence cited here appears a bit thin” writes Dr. Oliver Jones, Senior Lecturer in Analytical Chemistry at RMIT University in Melbourne. Read all the responses in expert reaction to carcinogenicity classification of five pesticides by the International Agency for Research on Cancer (IARC).
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