Glyphosate as a Carcinogen, Explained

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Late last Friday afternoon, a designation related to Round-Up was released that created a buzz around the world. My own mother greeted me with the news when I got home: “Did you hear that Europe now says glyphosate causes cancer?” Mom wasn’t entirely correct, though props to her for following the news.

The actual press release came from the IARC and indicated that the agency has now listed glyphosate as a 2A potential carcinogen. You can read the full report here.

But what the heck does that mean? Let me explain…

Who is IARC?

The International Agency for Research on Cancer is a special agency nestled under the World Health Organization. IARC exists to conduct cancer research. In IARC’s own words:


(Source: IARC Mission Statement) One important piece of what IARC does is determine which substances in our environment have the potential for causing cancer. IARC does not conduct any original research; it only reviews studies and research already published to determine carcinogen status. You can read a little more about how they make these type of determinations here.

Nor is IARC the only agency or organization in the world that conducts such reviews and classifies carcinogens. Most advanced countries have similar bodies. What should be mentioned is the contrasting process that IARC employed to make their determination. IARC’s review of glyphosate came after just a week of the agency looking at available data about glyphosate and several other chemicals. On the other hand, reviews of glyphosate by regulating bodies in the United States, Canada, Germany, and other parts of the world take up to 5 years.

What is a carcinogen and what does the classification mean? 

Carcinogens are things that cause cancer. As the American Cancer Society explains, there are four levels for classification according to IARC’s system. They look like this:

  • Group 1: Carcinogenic to humans
  • Group 2A: Probably carcinogenic to humans
  • Group 2B: Possibly carcinogenic to humans
  • Group 3: Unclassifiable as to carcinogenicity in humans
  • Group 4: Probably not carcinogenic to humans

It is important to note here that other reviewing agencies around the world use different classifications. For example, the EPA has its own separate classification system. IARC is the first – and only – reviewing agency to classify glyphosate as a carcinogen. In fact, as I’ll explain a little later, other reviewing bodies have determiend that glyphosate is not a carcinogen.

But before you get worried by IARC’s classification, the American Cancer Society puts this process into perspective:

Even if a substance or exposure is known or suspected to cause cancer, this does not necessarily mean that it can or should be avoided at all costs. For example, estrogen is a known carcinogen that occurs naturally in the body. Also, exposure to ionizing radiation is known to cause cancer, with increased risks even at low levels of exposure. Yet there is no way to completely prevent exposure to natural sources of radiation such as cosmic radiation from the sun or radon in soil. These lists also include many commonly used medicines, particularly some hormones and drugs used to treat cancer. For example, tamoxifen increases the risk of certain kinds of uterine cancer but can be very useful in treating some breast cancers, which may be more important for some women.

In other words: calm down. We have to put risk and the potential for negative consequences into perspective. There are things that we encounter in our environment that may be considered carcinogenic that we either cannot avoid or the benefits outweigh the risk.

So, besides glyphosate, what other things are included in that classification? 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.


What did IARC find out about glyphosate?

In short, nothing new.

No, seriously. IARC does not conduct their own research. Just as most other regulating bodies, they simply look at the data already available and reach their conclusion. Unfortunately, it seems as though IARC seemed to only consider studies that supported its eventual conclusion.

Remember – the dose makes the poison. If you ingest enough of any substance, including water, it has the potential to kill you. When it comes to glyphosate this is even more relevant, because IARC’s conclusions only apply to exposure high enough to meet industrial uses.

As one of the scienists behind IARC’s classification stated:



What do others say about it?

The reaction from scientists around the globe has been pretty much the same – a bunch of noise about pretty much nothing. While it would be impossible for me to quote everyone who has chimed in on this topic, allow me to highlight a few statements that should put this into perspective.

European Crop Protection Agency Director General Jean-Charles Bocquet said in a statement:



Aside from IARC, other regulatory agencies, including the EPA, do routine reviews of all pesticides registered for use. Remember, under federal legislation here in the United States, all pesticides are regulated by the EPA and have to meet agency approval before they can be used commercially. One aspect of that approval is review of the product after so many years. This is a common requirement in regulating agencies.

In fact, the German Risk Agency is currently reviewing the use of glyphosate in Europe. The German’s evaluation has been underway since 2012. That agency has looked at all of the same data and research as IARC and has come to the following conclusions in its draft report:



So, the German review of glyphosate does not classify it as a carcinogen. Aside from IARC, that conclusion has been consistent across many regulatory agencies and scientific studies. (As Henry I. Miller demonstrated in his article on Forbes, there are scientific studies which show no link between glyphosate and cancer, that IARC seemed to ignore. You can find those here and here.)

The EPA has also concluded:


In the Agricultural Health Study, which was a study on human beings working as applicators, scientists concluded there was no link, although there was an “association” with multiple myeloma incidences (mutliple myeloma is a very rare and treatable condition, as explained here by the Mayo Clinic). Otherwise, the study concluded: “Glyphosate exposure was not associated with cancer incidence overall or with most of the cancer subtypes we studied.”

The odd thing about IARC’s determination is that it seemed to completely disregard the overwhelming amount of studies that have been done on glyphosate and, instead, focused on just 3. In fact, one the studies done was shaky, at best, and didn’t seem to control for other factors. Furthermore, the agency has taken a stance contrary to every other regulating body in the world.

Does this mean GMOs cause cancer?

Let’s be very clear about one thing there – this is not about the safety of genetically modified crops, it is only about glyphosate. The reason people get this confused is because, currently, the most common types of GMOs are those that are resistant to Round-Up. That is, when sprayed with glyphosate (the active ingredient in Round-Up), the plants are able to survive. I’ve explained before how that works by changing some enzymes in the plants.

But even though the plants are resistant to glyphosate does not change whether or not they’re safe. We still have lots and lots of studies saying that we don’t need to worry. The bottom line is that this classification means nothing regarding the safety of genetically engineered crops.

Let’s also not forget that the World Health Organization (WHO), has made the following conclusion regarding the safety of GMOs:


Remember, IARC is an agency within WHO. There has been no indication that WHO plans to change their stance on GMOs.

What’s the effect of this? 

For the sake of argument, let’s just assume that this new classification is true. Even then, quite frankly, unless you’re someone that applies glyphosate on a larger scale, there probably isn’t an effect on you. As for farmers, federal legislation carefully regulates how farmers may apply glyphosate (and all other chemicals, for that matter). Personal protection equipment is part of that assessment and must be worn. Most farmers are also protected from exposure because they use cab tractors while applying Round-Up and other safety precautions.

While I have no doubt that anti-GMO activists will try to turn this into a huge deal, and many already have, it is not something that average consumers need to be worried about.

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20 Responses to "Glyphosate as a Carcinogen, Explained"

  1. Thanks, logic may help some folks not ideologically glued to the anti-agenda.

  2. Thanks for the good information!

  3. Thank you for so promptly and appropriately addressing what should really be a non-issue. I would really like to see a comparison of glysophate to the stuff in Food Babe’s make-up kit. Meanwhile, Katy bar the door. The anti folks are going to get all the mileage out of the IARC notice that they posssibly can. Frustrating how they only reference a select few ‘experts’ when it suits their agenda.

    I appreciate what you do, Amanda. The importance can not be overstated.

  4. I don’t know where you get your (mis) information from and where your paycheck comes from. I look at the trends for the past century and there is a definite correlation to glyphosate and Roundup use and the increased GMOs and the rate of cancer, autism, obesity, Type 2 Diabetes, lactose intolerance, gluten intolerance, hypothyroidism and other metabolic disturbances. If it walks like and duck, talks like a duck, do a DNA test to see if it is really a duck or the substantial equivalent.

    • Correlation does not equal causation. If that’s the case, then the increased consumption of organic food is causing autism.

      I have an article about this in the works, so feel free to stick around and read it when it’s available. It may help you understand why things can look like they’re related when they really aren’t. Otherwise, feel free to read this:

    • And we have a double loser. An evidence free “paycheck” remark. And a correlation is causation error. Did you stop to think that perhaps other behaviors might also correlate? Increase in cell phone use and organic food consumption do as well. What about couch potatoism? You need evidence of causation before jumping in the deep end of the pool.

      • Eric, thanks for mentioning the shill accusation. My current employer probably wishes someone else was paying my salary, but they definitely are not!

        • You’re welcome. Seems I have had a lot of practice with that. They jump out at me now. I do need to find some humorous or smart alecky suggestions to improve my phrasing.

    • Science much?

      • Science occasionally Farm and work job mostly. What is your point?

      • Sorry, Knee jerk response. Did not realize you were replying to the great correlator.

        • Sorry, it’s hard to tell where responses will show up especially with an iPhone. I’m a Farmers Daughter fan!

  5. Laura great reasearch on this ridiculous reprot from the IARC-Please send me a copy that I can forward to my congressman. I would encourage everyone to send this to their congresional members and staff.



  6. Jan

    Thanks for the information, Amanda! In the second paragraph, did you mean to print that “the agency has now listed glyphosate as a 2A potential carcinogen” instead of as a 2A probable carcinogen, or was it just a typo? That causes some confusion.

    • Probably! I’m only human. 😉

  7. Thank you Amanda for the obvious effort to research this complicated issue and providing clear explanation without condenscention. This is so helpful.

  8. Tim

    How about this for a correlation – everybody who ate carrots 150 years ago are now dead – Carrots are toxic! They must be banned!

  9. Me thinks the lady (here) doth protest too much: more than where you get your money I think it is incumbent upon you to look beyond the reports that affirm your obvious pre-formulated opinion.

    When you look at the data that has been collected – not only data from government agencies, whose decisions are constanty being influenced by powerful lobby groups – then that is where true science and informed judgements can be made: by opposing results.
    As one example I submit the Ithaka Report from a German University, unfortunately only available in German, here
    but a summary in english is here:

    Clearly these levels of glyphosate in urine are alarming, even if you hold the substance to be benign: it is the concentration that is very forboding. Hell, you can even kill people with salt if you give them enough.

    LASTLY, the reaction of the lobbyists makes me very suspicious: namely, their OVERreaction. Take a look at this investigative clip (very short) in French but with subtitles:

    • Here’s the problem – there’s science and then there’s “science.” All of the studies you cite that purportedly show negative effects of glyphosate aren’t credible studies because they fail to meet scientific standards (you know, things like having a control group, a large enough sample size, etc.). On the other hand, the data by those government agencies are actually credible and meet scientific standards.

      Since you’re so concerned with powerful lobbyist groups, I assume you’re also opposed to companies like Whole Foods and organizations like the Organic Consumers’ Association?

      Finally, I’m not paid for my work here. The “shill” accusations are really old.

  10. Ben

    Just saw this article again after googling “glyphosate carcinogen is it”. I did that in response to the recent news that California is going to start labelling it a carcinogen due the same IARC findings.


    You nailed the prediction on this one, though they got it all the way from “possible” to “does” in California.

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