Glyphosate: A Carcinogen?

John Deere 4940Every once in a while, a news story is released that has no basis in any real science whatsoever. A few days ago, the International Agency for Research on Cancer (IARC) declared glyphosate, the active ingredient in Roundup and many other brands, to be a class 2A probable human carcinogen.

What does this mean? Does glyphosate, long heralded as one of the safest agricultural pesticides on the market, really cause cancer? Should it be ripped from store and retail shelves, buried, burned and otherwise disposed of? Even banned?

Let’s slow down for a minute here. Glyphosate has been tested inside and out for the past 30 years and has not been shown to be a cancer risk for humans. A mind-numbing number of studies have consistently shown, time and again, that glyphosate is safe. So why the controversy? First, let’s look at the basics.

What is glyphosate and how is it used?

Glyphosate was originally patented by Monsanto in the early 1970’s as the active ingredient in Roundup herbicide. It was introduced to the market in 1974 and has since become one of the DSC_0614best-selling herbicides in the world. Its non-selective mode of action means that it does not discriminate in which weeds it kills. The introduction of this product revolutionized the herbicide market and changed the way farmers kill weeds.

For those interested in the details, glyphosate, a derivative of the amino acid glycine, targets and blocks a pathway called the shikimic acid pathway; which, suffice to say, is required for amino acid synthesis in plants. With amino acid synthesis shut down, plants wilt and die from starvation. Since the shikimite pathway is not found in humans (or any other animal), glyphosate is of very low toxicity. Find even more details here.

Before herbicides were broadly and economically available, farmers were forced to use tillage to control weeds. While other methods helped, such as crop rotation, cover crops and late seeding, tillage was the primary method with which weeds were killed. The problem with tillage is that it is extremely damaging to soil structure and leaves soil exposed to erosion. With the introduction of herbicides, and eventually Roundup, minimum-till agriculture became a realistic possibility, which has decreased erosion substantially on farms that utilize it.

The introduction of Roundup-Ready crops, including corn, soybean, canola, cotton and so on, has allowed for safe, simple, very cost-effective weed control.

Where did this cancer label come from?

Sorting through the rhetoric of glyphosate is a challenge all on its own. Type “glyphosate” into a Google search and you’ll find all kinds of wild claims about cancer, autism, poison, and the like. The fact is that most of what you see is sensationalist news articles with little fact-based information. Let’s cut through some of that rhetoric.

First of all, what does IARC, a semi-autonomous extension of the World Health Organization, mean when it classes glyphosate as a 2A human carcinogen? There are five categories of carcinogens that the IARC lists on their website:

  • Group 1: Carcinogenic to humans
  • Group 2A: Probably carcinogenic to humans
  • Group 2B: Possibly carcinogenic to humans
  • Group 3: Not classifiable as to its carcinogenicity to humans
  • Group 4: Probably not carcinogenic to humans

They listed glyphosate in Group 2A, in which there are 73 agents, which includes the occupational exposure as a hairdresser, shiftwork and high temperature frying. Group 1 includes alcoholic beverages, estrogen and wood dust (source). Yes, that means beer is a greater carcinogenic risk than glyphosate.

What’s everyone else saying?

I think one very important detail that is not being reported on is that the IARC is not the only group that has studied glyphosate. For example, the European Crop Protection Director, General Jean-Charles Bocquet, had this to say:

“The IARC conclusions published in Lancet Oncology contradict the world’s most robust and stringent regulatory systems – namely the European Union and the United States – in which crop protection products have undergone extensive reviews based on multi-year testing and in which active ingredients such as glyphosate and malathion been found not to present a carcinogenic risk to humans.”

 “From the summary conclusions it appears that IARC has made its conclusions as a result of an incomplete data review that has omitted key evidence.” (source)

He’s not the only one. The Environmental Protection Group of the US has done extensive testing of glyphosate, and does not consider glyphosate to be a carcinogen. Other groups, such as Health Canada and the German Risk Agency, are firmly against the notion that glyphosate causes cancer. Put simply, the IARC is the first and only group to label glyphosate as a carcinogen.

Oddly, one of the very few studies they allegedly took into consideration was the fatally flawed Seralini rat study. If you’re unfamiliar with it, it was a shocking study that apparently proved that GMOs caused tumours in rats- but the methodology of the study was so poorly exercised that the journal that published it later retracted it. It is now a laughingstock of the scientific community, and any credible organization that references “information” such as this should thoroughly re-evaluate their credibility.

Is glyphosate actually safe?

I could go into the thousands of studies on the safety of glyphosate, and go into a detailed literature review of why it is such a safe product. But this is a blog; not a scientific journal, and as such I’ll leave the science to the scientists with some links for further reading below. Let me summarize instead; glyphosate lacks the structural characteristics of known carcinogens, and the IARC has failed miserably to link cancer to glyphosate. Interestingly, the IARC actually does not conduct their own research; instead, they look at the data that’s out there and form their own conclusion. Isn’t it telling that they are the first and only group to label glyphosate this way?

The reality is that glyphosate has been applied on billions of acres over the past 40 years, and if it really were that dangerous, wouldn’t there have been some real consequences by now? Wouldn’t livestock and people be getting cancer in droves? This has simply not been the case, and glyphosate has been a wonderful alternative to hundreds of other far more dangerous chemistries out there.

My experience

I have been spraying glyphosate, whether it be Roundup, Touchdown Total, Vantage Plus or whichever of its dozens of formulations, for the past ten years of my life. My father has been spraying it most of his life. My experience with this product is that it is safe, effective, cheap, and is a fantastic tool to combat weeds on our farm. Nobody, in all the years we have applied it, on this farm has ever gotten sick from glyphosate. Not a single friend, neighbor or colleague of mine has ever had a negative health effect from this chemical. Too small of a sample size? How about 60 independent genotoxicity studies with none that imply danger to humans (source)?

The message here is that you can’t believe everything you see and hear. IARC reviewed the data on glyphosate- among other chemicals- for less than a week before making a decision. In contrast, a German study conducted on behalf of the European Union has only just seen its first draft released; a study they have been working on since 2012. Their result? Not a carcinogen!

Don’t trust my claims? Check out my sources. Take the time to understand this issue, and understand the science behind glyphosate and modern agriculture. Glyphosate has been a modern miracle; it’s time we treated it that way.

Further reading:

Along with the links embedded in the post itself, check out these pages for some interesting reading on glyphosate:

Genetic Literacy Project. Is glyphosate–herbicide linked to GMOs–carcinogenic? Not if science matters.

Glyphosate Technical Fact Sheet. National Pesticide Information Center.

Greim, H. et. al. 2015. Evaluation of carcinogenic potential of the herbicide glyphosate, drawing on tumor incidence data from fourteen chronic/carcinogenicity rodent studies.

Kier, LD. 2015. Review of genotoxicity biomonitoring studies of glyphosate-based formulations.

Mink, PJ et. al. 2012. Epidemiologic studies of glyphosate and cancer: A review.

Niemann, L. et. al. 2015. A critical review of glyphosate findings in human urine samples and comparison with the exposure of operators and consumers.

Sorahan, T. 2015. Multiple myeloma and glyphosate use: a re-analysis of US Agricultural Health Study (AHS) data.

The Farmer’s Daughter USA. Glyphosate as a carcinogen, explained. (excellent blog)


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