Is Roundup Poisoning Us?

By Jean Clavelle, Farm & Food Care Saskatchewan

Glyphosate is a herbicide — a type of pest control product used to kill plants. It is the active ingredient in the now infamous chemical Roundup, and is one of the most used agricultural chemicals worldwide.

Google glyphosate, originally released as the product Roundup, and you’re faced with results like ‘horrific’ “new evidence about the damage Roundup causes” and “Roundup chemicals are lethal.” One quick search and I can understand why society might have concerns about the pervasive use of glyphosate in agriculture. Reading these statements does lead us to question: is Roundup poisoning us?

Let’s examine the science.

A small amount (think: pop can) is mixed into a tank of water on the back of a special machine called a sprayer. Farmers use these machines to spray the mixture onto the weeds over a large area (that one pop can treats an area nearly the size of a football field) where it is absorbed by the plant. Once inside the plant, glyphosate binds to an enzyme (EPSP synthase), preventing it from building essential amino acids that a plant needs to live and grow. With this enzyme disabled, plants die. Now, the really interesting thing is that EPSP synthase is found only in plants and bacteria; humans and animals do not use this process.

Remember that Google search which told us glyphosate is one of the most toxic chemicals around? Not so. The general standard for acute (short term) toxicity is a value called an LD50. This refers to the median lethal dose, the amount of a chemical needed to cause death in 50% of the animals it is tested on. An LD50 is one way to measure the relative short-term poisoning potential of a compound. The lower the number the more toxic it is. For example, the LD50 of sodium bicarbonate (baking soda, a common ingredient in baking) is 4220 mg/kg; table salt 3000 mg/kg; caffeine (as in our precious morning coffee) is 192 mg/kg; and nicotine (cigarettes) is 50 mg/kg.

So where does glyphosate fit? Glyphosate has an LD50 of 5600 mg/kg. Yes. It is less toxic than baking soda, table salt, and coffee.

Our entire world is comprised of chemicals. Water, salt, and vinegar are chemicals, and even our bodies can be considered walking, talking chemical bags.

You’ve probably heard the old adage of toxicologists “the dose makes the poison”. Even those regular household compounds like salt, vinegar or yes, even water can be toxic if ingested in high enough doses. When glyphosate is used as it is intended, just like salt, vinegar, and water, it has minimal toxicity to humans and animals because the amount used is small.

But how do we know we are not consuming high levels of pesticides? Health Canada scientists review the data from over 250 separate studies before they approve a pesticide for sale or use in Canada. As part of this extensive review before a chemical is approved for sale, they identify the amount of a pesticide that a person could be exposed to without any adverse health effects. These levels are then compared to the maximum amount of residue that might be found on crops after use of the pesticide (a value known as the Maximum Residue Limit or MRL) in order to ensure that consumers are never exposed to an amount that could pose a risk to health. Indeed, MRLs are typically 100-1000 times below levels that are still considered safe.

Thanks to the MRLs established by Health Canada, based on science, we can be confident that if small amounts of glyphosate are ingested through exposure in our food system, we know they won’t be at toxic enough levels to cause damage, even if they are consumed every day over a life time.

I should probably also mention that it is not just Health Canada that has assessed the science around glyphosate. Most other major regulatory organizations around the world, including the European Food Safety Authority, the World Health Organization, and the U.S.’s Environmental Protection Agency, have also reviewed data on glyphosate (available here).

Glyphosate is easily and relatively quickly broken down in the environment. It does not bioaccumulate, meaning it does not build up in the bodies of fish and wildlife (read an example of mercury bioaccumulation here). And finally, it is excreted by our bodies if ingested. Their overwhelming consensus? When glyphosate is used according to label directions, it poses minimal risk to people, wildlife, and the environment.

We need to evaluate claims on the basis of overall weight of scientific evidence behind it. The stronger the weight of evidence, the more confidence we can have in the scientific findings. Glyphosate has been investigated by many scientists from around the world, in hundreds and hundreds of studies (again, available here) all of which have determined that, when it is used as it is intended, it is safe for people, for animals, and our environment.

Being a science geek, I follow facts. And the evidence tells me glyphosate is not the problem a cursory Google search might suggest. If you would like to know how glyphosate is used, the label (which is a legal document authorized by the Pest Control Products Act) can be found here. And if you still have questions, we want to hear them.

For more information/resources:;jsessionid=osa7mo59kVxNtcafSkkP.18


8 thoughts on “Is Roundup Poisoning Us?

  1. Great review of why glyphosate is perfectly safe to use.
    But without explaining to your reader the politics behind why this “misinformation” is out there you are not likely to sway anyone.
    There are real “reasons” this perfectly safe product is being vilified – yet no one seems to want to open that can of worms.
    Time someone does….

  2. A couple of minor corrections / finer points:

    * You say “EPSP synthase is found only in plants and bacteria; humans and animals do not use this process” but in fact microbes in the human gut do have EPSP synthase, and about half of those microbes have the sensitive kind that is highly inhibited by glyphosate (how it kills plants). The other half are not sensitive (like Pseudomonas) but also tend to be the more pathogenic kinds. It may be the case that glyphosate over time favors those microbes over the others.

    * You focus on LD50 but that measures only acute toxicity effects. Chronic toxicity is a different thing and cumulative effects are possible with low levels over time. This is quite important. Smoking 15 cigarettes in one day never killed anyone to my knowledge, but a long-term regular smoking habit kills many.

    * In terms of bioaccumulation, Brewster (1996) shows that around 1% of a single oral dose remains in the bones and carcass of rats after one week. That’s the longest such study i know and it shows glyphosate to be in the body after one week. That may be bioaccumulation.

    • Thank you for your questions. Hopefully this information elaborates.

      RE paragraph 1:
      Was this the report you are referencing?
      [, M-glyphosate effects.pdf ]
      This was an in vitro study (conducted in bacterial culture in the lab). I’m not aware of any studies that have replicated these findings in chickens. GMO Answers covers gut microbes and glyphosate in considerable detail here:

      And has quite a bit about glyphosate as well This article gives an overview of some general and some more in depth points, the expert being Jeff Graybill, MS, CCA, Agronomy Extension Education at Penn State University.

      RE paragraph 2:
      Yes, LD50 is a measure of acute toxicity and does not provide information on chronic effects. However, this is why our regulatory requirements mandate a large battery of studies that cover both acute and chronic effects. Here is the PMRA’s proposed re-evaluation of glyphosate
      It includes a review of the extensive toxicology database for glyphosate.
      Indeed, there are, I believe, six complete regulatory data sets available plus a tremendous body of peer-reviewed and grey literature on the molecule. Based on their review of this extensive data set, the PMRA concluded “There were no dietary risk concerns from the acute and chronic dietary risk assessments (food and drinking water) for the general population and all population subgroups, including infants, children, teenagers, adults and seniors.”

      RE paragraph 3:
      Were you referring to this paper?
      The overwhelming weight of scientific evidence indicates that glyphosate, when ingested, is not metabolized and is rapidly eliminated from the body. This study does verify this conclusion. Total recovery ranged from 95-102% of the administered dose. The authors conclude the following
      “The results from this study indicate that virtually no toxic metabolites of glyphosate were produced since there was little evidence of metabolism and essentially 100% of the body burden was parent compound with no significant persistence of material.”

      This conclusion has been subsequently verified by numerous studies. Table 1 in this article is a useful summary of some of those studies:

  3. Interesting that you include GENERA as part of your proof that glyphosates are ”safe for people, for animals, and our environment”. It being a broad-spectrum herbicide, I think that you would agree that it falls under the title of pesticide, which GENERA does not cover.
    ”Categories of studies not included in GENERA

    Not every study is relevant for inclusion in GENERA. Some are on related topics, so during the process of developing the Atlas, we had to decide on categories of studies that would not be included

    Pesticide toxicity studies
    Studies conducted on the toxicity of pesticides are often listed when discussing genetically engineered crops, since some traits are associated with an herbicide (herbicide tolerance) and others may replace an insecticide or fungicide (insect and disease resistance). However, studies that focus only on the pesticide in question are not relevant for GENERA because they are not about genetically engineered crops per se. However, studies that study pesticide use and toxicity within the context of their use or disuse due to genetically engineered crops may be included in GENERA.”


    You also point to Health Canada’s vetting process as further proof of its safety, but fail to mention that when studying the glyphosates, Health Canada does not research the effects of the adjuvants added to the product for the benefit of field application. While the active substance glyphosates do not seem to be dangerous to the health, can you honestly tell me that all adjuvants used in tandem with the glyphosates (in other words, the glyphosate formulations as applied) are tested by Health Canada as well?

    Looking forward to your response.

  4. I posted a fairly good comment yesterday. I do not see it yet. Are you on top of approving comments? Are you filtering according to an agenda ?

  5. Being a farmer, i have to ask, what should i spray with then? We are just keeping up to global food demand as it is, going to ridiculous land depleting methods like organic are simply not an option – unless of course mass starvation is your goal.

    So if not roundup, what should i use? What do you feel is acceptable for food production on the scale it is required to feed the world?

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