Glyphosate toxicity: Looking past the hyperbole, and sorting through the facts. By Credible Hulk

You may at some point have heard people speak of glyphosate as being “less toxic than caffeine or table salt.” What they’re referring to when they say that is what we call its LD50, which a standard way of quantifying acute toxicity. A substance’s LD50 is the dose at which 50% of the subjects who ingest that amount will die of complications from an acute overdose, and it is measured in units of mass of the substance per unit mass of the subject (usually mg/kg). See, one of the most fundamental principles in all of toxicology is that “the dose makes the poison,” which was famously coined by Paracelsus, the father of toxicology.  Most substances have some amount beyond which they become toxic. Many substances that are benign, beneficial, or even essential to human health in one range of concentration will become harmful if taken in sufficiently large amounts. Even water can be toxic if you drink enough of it. So, you can’t just look at it as though there were some toxic things in the world and some non-toxic things, or that something that is toxic at one dose is bad in any dose, simply because that’s not how toxicology works.

Here you can find a very brief introduction to concepts in toxicology, but for now, suffice it to say that students are generally taught about three main types of toxicity: acute, chronic and subchronic.

By the acute standard of LD50, glyphosate (albeit not necessarily round up brand mind you, which also contains surfactants) is indeed less toxic than either caffeine or table salt.

It has an LD50 of 5600 mg/kg based on oral ingestions in rats, according to EPA assessments, placing it in Toxicity Category III. The EPA ranks chemicals in four categories, I being the most toxic and IV being the least.

To compare, caffeine has a much lower LD50 of 192 mg/kg based on oral ingestion in rats. Similarly, sodium chloride (table salt) has an LD50 of about 3000 mg/kg. Rotenone, which is used on some organic farms (though less so in the US in recent years), has an LD50 162-1500 mg/kg, and Copper sulfate, which also sometimes used on certain organic farms, has an LD50 of  30mg/kg. This is permissible by organic certification due in part to the fact that it is completely naturally occurring, which of course has little to do with its safety or environmental effects. The purpose of these comparison is not to make caffeine and table salt, which most people take for granted as being fairly safe, seem dangerous, nor is it to demonize these other pesticides to make them seem unacceptable; rather, the purpose is to show that idea that glyphosate is this abnormally dangerous toxic substance, a notion popular among many laypeople, simply isn’t accurate.

However, that was only a matter of acute toxicity. Many opponents are willing to concede that the acute risks are fairly minimal, but they worry about the risks of long term low-level exposure. The EPA took that into account as well.  The EPA dealt with this issue by setting maximum safe levels of residues called “tolerances.” The USDA tests crops each year to make sure that herbicide residues do not exceed the permitted tolerance levels. If any crops contain residue amounts higher than tolerance levels, the USDA reports the information to the FDA, who has the regulatory power to recall foods, levy fines and take other actions to prevent the foods from reaching consumers.

In case you’re wondering how these tolerances were arrived at, the EPA tested glyphosate on numerous animal species. They then used the result from the MOST sensitive species tested as the basis for setting the Reference Dose. The RfD represents the level at (or below) which daily aggregate dietary exposure over a lifetime will not pose appreciable risks to human health.

The RfD is determined by using what’s called the “toxicological end point” or the “NOEL” (No Observable Effect Limit) for the most sensitive mammalian toxicological study. The EPA uses an uncertainly factor of 100 in deriving it (which is pretty high in order to be conservative) so as to ensure the sufficiency of the RfD, and based on the assumption that certain segments of the human population could be as much as 100 times more sensitive than the species represented by the toxicology tests. In rat studies on glyphosate, doses of up to 31 mg/kg/day were administered with no observable adverse effects at all, and dog studies have gone as high as 500 mg/kg/day with no negative effects.

The EPA’s assumption about how much people would eat was very conservative. In order to insure you don’t get over 2 mg per kg per day they use a “worst case” dietary risk model of an individual eating a lifetime of food derived entirely from glyphosate-sprayed fields with residues at their maximum levels.

Here are examples of the residues of Glyphosate permitted on our food:

Vegetable, bulb, group 3-07 – 0.20 ppm

Vegetable, cucurbit, group 9 – 0.5 ppm

Vegetable, foliage of legume, subgroup 7A, except soybean 0.2ppm

Vegetable, fruiting, group 8-10 (except okra) 0.10ppm

Vegetable, leafy, brassica, group 5 – 0.2ppm

Vegetable, leafy, except brassica, group 4 – 0.2ppm

Vegetable, leaves of root and tuber, group 2, except sugar beet tops 0.2ppm

Vegetable, legume, group 6 except soybean and dry pea 5.0ppm

Vegetables, root and tuber, group 1, except carrot, sweet potato, and sugar beet 0.20ppm

Note that most are all less than one part per million.

Now to put that in perspective, let’s assume you are a vegetarian and eat a mix that is on the extreme high end and you consume food which is at an average of 5 ppm per day.

So 200 grams of food would yield 1 mg of glyphosate.

You weigh 70 kg or 154 lbs.

To get 2 mg per kg you would need to get 140 mg of glyphosate residue.

So you would need to eat 200 * 140, or 28,000 grams of this 5 ppm produce to get to the 2 mg per kg per day level.

There are 28 grams in an ounce, so that’s 1,000 ounces.

There are 16 oz in a pound, so you would need to eat 62 lbs of produce.

We’re talking about EACH DAY here, and even if you managed that, that would only get you to a level that is 100 times less then the NOEL level in the most sensitive species tested.

Supposing you wanted to do similar calculations on your own upon looking up the EPA tolerances for a particular food item. How would you do that? How about I just derive the formula for you, and you can plug and chug for any given food based on its tolerance (even though, in actuality the residues will seldom be right up at the cutoff level). That way, this formula will apply no matter what the specific tolerances are for the item in question.

Let the Tolerance level of a particular food = x ppm,

which conveniently also equals 1mg/kg,

(which btw is one of the reasons I love the SI system of units).

Let m1= your mass in kg.

We want to see how much of a given food we would have to consume such that our intake of glyphosate residues exceeds 2 mg/kg,

so let m2 = the mass (in kg) of that food you’d have to consume each day to reach 2mg/kg.

So, we have

m2*x = m1*2 mg/kg.

Solving for m2 yields

m2 = 2*m1/x

So, supposing for example that the tolerance of a given crop is 10 ppm, and say you are only 50 kg (about 110 lbs).

Then the mass of that food you’d have to eat every day to exceed 2 mg/kg would be 2*50/10 = 10 kg = 22 lbs per day. Easy, right?

For someone my size, it’d have to be over 52 lbs a day just of that one product, and for an extended period of several years, and even then, only if the farmers were really pushing the limits of what they could get away with, which obviously wouldn’t make much sense from a business standpoint, since that stuff costs them money, and the whole reason they use it is to be more efficient: that is, to get the greatest output for the least input.

Another issue worth addressing is the recent IARC and WHO reclassification of glyphosate as a Class 2A carcinogen. The IARC classification process isn’t designed to serve as a statement on risk analysis, and for that reason, it did not take into account actual common usage practices. They placed glyphosate in the 2A category, which includes “probable” (albeit unconfirmed) carcinogens such as emissions from frying food, hairdresser products and burning wood. It mainly pertains to application protocols rather than minuscule trace amounts in food.

Consequently, banning glyphosate as a knee jerk reaction to its recent classification would be similar to never going out of the house in the daytime because sunlight is carcinogenic. Actually, it would be even less sensible because sunlight is in an even higher class of carcinogen than glyphosate. Think about it. It’s in the same classification as manufacturing glass, burning wood, emissions from high temperature frying, and work exposure as a hairdresser. Alcohol and sunlight are both higher on their carcinogen scale than glyphosate, and neither of those cause cancer with conservative exposure either.

Should proper precautions be taken during application procedures? Of course. Are the trace amounts in food, which are usually on the order of parts per million (ppm) or less even prior to being washed, a threat to consumers? No. The bottom line is that hazard is not the same thing as risk, and the latter is dependent largely upon exposure levels as well as type of exposure.

Moreover, as Kate Guyton, one of the scienists behind IARC’s classification stated:

“I don’t think home use is the issue. It’s agricultural use that will have the biggest impact. For the moment, it’s just something for people to be conscious of.”

Basically, what that means is that it’s the people actually applying the herbicide who are thought to be at increased risk. But applicators have their own set of protocols and certification requirements, and they are generally pretty well-versed in how to properly apply glyphosate.

The Farmer’s daughter USA wrote an informative and easy to understand piece on this. It may also be worthy seeing what various other scientists had to say about the reclassification of glyphosate and what they think it means in this article here.

It’s also worth noting that the IARC also classifies some organic pesticides as carcinogenic, and so do studies at the UC Berkeley.

Does that mean that they cause cancer at in the amounts consistent with actual practical usage?

Not necessarily. But the extreme emphasis some people are putting on glyphosate’s reclassification to the exclusion of the other “natural” compounds is quite a double standard, and double standards are pretty good indication of a strong bias on the part of the people making the most noise about it.

There are legitimate concerns over the evolution of glyphosate-resistant weeds. In fact, it’s one of the few of the common criticisms of glyphosate and GR crops that has any legitimate merit to it, but that’s an issue that affects all methods of weed control (even hand tilling), and although weed resistance has slightly increased, the RATE at which herbicide resistant weeds have been developing since the rise in glyphosate resistant GMO crops has not increased. It has always been an issue, and there are ways of dealing with it, but that’s a discussion for another day.

In closing, the take home message is that glyphosate is not the monumentally dangerous herbicide that its opponents have hyped it up to be. When the proper application procedures are practiced by applicators and usage on food crops are kept within the regulatory parameters, it is fairly innocuous, particularly when compared to many of its more toxic alternatives, many of which were phased out in conjunction with the rise in glyphosate’s popularity. Opponents of glyphosate often seem to hold this unfounded notion that, if they can manage to get glyphosate banned or simply willingly abandoned, then it would mean an improvement in both food and environmental safety, but the truth is it would likely be the exact opposite of that. Weeds are a legitimate problem in farming that has to be dealt with one way or another. In its absence, it would have to be replaced with something else, and it would likely be something more caustic: not less.

 

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67 Comments

  1. Pingback: About those more caustic herbicides that glyphosate helped replace: By Credible Hulk - The Credible Hulk

  2. Just to be clear. Does your chart list toxicity as measured by an LD-50 in mice? What about bees and other non-pest invertebrates? I prefer we try to genetically modify the crop to make them resistant to specific pests than apply indiscriminate pesticides. 🙂

    • In this case, the LD50 was obtained from rat experiments. Usually at least a few animal models are used. However, it’s worth noting that acute toxicity is rarely a big issue. I had to include it, simply because it’s an important part of assessing toxicity, but ultimately the levels of exposure are typically so low that chronic and subchronic toxicity, as well as carcinogenicity are considered more pertinent questions when it comes to real life pesticide use. As for “indiscriminate pesticides,” my question is why would anyone want to do that? Pesticides are expensive, especially when buying enough for a really big farm. The goal is efficiency of pest management. In the case of herbicides like glyphosate, there is also the advantage of no till farming, which is desirable because excessive tilling can compromise the integrity of the soil.

    • If even half of what I’ve read about genetically modified foods are accurate, I’d rather eat non GMO food sprayed with roundup than GMOs. GMOs are sooo much worse than spray on pesticides!

      • In that case, it’s likely that far less than half of what you’ve read about genetically modified foods is accurate. That’s understandable because there has been tremendous amount of push back by anti-GMO ideologues cluttering up the conversation with smear pieces, and not everyone is equipped to sort through the rhetoric to determine what the preponderance of scientific evidence really says.

        There is an international scientific consensus on their safety which is based on thousands of studies from a wide variety of scientists and funding sources, and they all corroborate the conclusion that the currently available commercial GM crops are at least as safe as their conventional and organic counterparts. No other class of foods or breeding techniques undergoes much safety testing at all, let alone on the order of what GM does.

        Massive review reveals consensus on GM safety Real clear science
        http://bit.ly/18hMKbW
        http://www.realclearscience.com/blog/2013/10/massive-review-reveals-consensus-on-gmo-safety.html
        (Nicolia report summary)

        Here’s a GM Myths Debunked – link collection
        http://bit.ly/1mbe5D4
        http://www.dangeroustalk.net/a-team/GMO

        “With 2000+ global studies, GM foods are among the most analyzed subjects in all of science” (JoAnn Wendel) http://bit.ly/KnzAnI http://www.geneticliteracyproject.org/2013/10/08/with-2000-global-studies-confirming-safety-gm-foods-among-most-analyzed-subject-in-science/#.UtlnBtIo6t8 

        A decade of EU funded GMO research
         http://bit.ly/LzldJf http://ec.europa.eu/research/biosociety/pdf/a_decade_of_eu-funded_gmo_research.pdf

      • Roundup is not used on non GM crops. It would kill them as it is non selective.

        • Actually, Roundup (glyphosate) is indeed used on non GM crops, as well as GM crops. It is used as a dry down agent for crops that are harvested dry. This is evidenced by the glyphosate residue in Canadian lentils that were rejected a few years back in Europe because the glyphosate residue was higher than acceptable levels. The Canadian government then told the farmers to switch to a different herbicide so they wouldn’t lose the EU market.

        • It is common proactive to ripen off many crops with Roundup, while they can be gmo for other traits, it is just not gmo resistance. The practice is pervasive in sugar, grain, and soybean harvesting. It is even leaves more residue because it is performed just before harvest, and even concentrated in sugar cane/beet processing.

      • GMO foods are virtually identical to non-GMO foods, but in fact, can be engineered to be healthier and better for you if that is the goal. The reason big long term studies aren’t done about GMO food is that they contain the same chemicals in virtually the same proportions so your body has no way of knowing the difference or reacting any differently. It is in its infancy now, but food could be engineered that destroys cancer or retards aging or to come packed full of additional nutrients. Plants could be engineered to keep bees healthy.

        I grow Neem trees to give away to people for shade trees and they have medicinal properties and are also quite toxic if taken in large quantities. Being “natural” or “organic” doesn’t make it safer. GMO is a revolution in health and longevity in process, not to mention planetary health and interspecies survival.

      • Discredible Hulk

        Research it, discredible hulk is believing his own propaganda. Example after example have shown that the life span of a person that can prove a so called conspiracy/fact is extremely short. Dr. Missing, ceo that kill themselves by getting thrown iff a roof top. Financial reporters killed. Love of money and power breeds evil and corruption. CIA is the most evil entity out there i.e. fast and furious, 9/11 etc. Research it just DON’T push the i believe button; drink the kool aid or walk willingly into the gas chamber.

      • GMOs actually cause glyphosate to be sprayed on, as most GMOs in crop production are Roundup Ready which is used with a lot of glyphosate, which causes cancer in animals according to the IARC and probably in humans. So avoid it all.

        • Not all GMOs are glyphosate resistant, some non-GMOs are resistant to more toxic herbicides, and glyphosate is not exclusive to GMO crops. Please stop spreading false information. As for the controversial Lancet IARC report (the IARC is a branch of the WHO) on which the re-classification of glyphosate was based, even the IARC themselves have explained that their concern does not pertain to food safety, but rather to pesticide applicators who are exposed to much larger quantities than consumers, but who already have procedural protocols for safe application. They authors state:

          “There was limited evidence in humans for the carcinogenicity of glyphosate. Case-control studies of occupational exposure in the USA, Canada, and Sweden reported increased risks for non-Hodgkin lymphoma that persisted after adjustment for other pesticides. The AHS cohort did not show a significantly increased risk
          of non-Hodgkin lymphoma.”

          The relevant studies are as follows:

          http://www.ncbi.nlm.nih.gov/pubmed/18623080

          http://www.ncbi.nlm.nih.gov/pubmed/11700263

          http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1740618/

          The IARC’s Kate Guyton even said “It’s agricultural use that will have the biggest impact. For the moment, it’s just something for people to be conscious of” on public record. There is really no excuse for people misrepresenting their position.
          http://thinkprogress.org/climate/2015/03/22/3637297/monsanto-herbicide-probably-causes-cancer/

          The IARC classification process isn’t designed to serve as a statement on risk analysis, and for that reason, did not take into account actual common usage practices. They placed glyphosate in the 2A category, which includes “probable” (albeit unconfirmed) carcinogens such as emissions from frying food, hairdresser products and burning wood. It mainly pertains to application protocols rather than minuscule trace amounts in food. Alcohol, sunlight and bacon are all in the carcinogenic category above glyphosate (I.e. confirmed carcinogens rather than merely suspected), and none of those cause cancer with conservative exposure either.

          In other words, ditching glyphosate because of its recent classification would be similar to never going out of the house in the daytime because sunlight is carcinogenic. Actually, it would be even less sensible because sunlight is in an even higher class of carcinogen than glyphosate. It’s in the same classification as manufacturing glass, burning wood, emissions from high temperature frying, and work exposure as a hairdresser.

          http://www.cancer.org/cancer/cancercauses/othercarcinogens/generalinformationaboutcarcinogens/known-and-probable-human-carcinogens

        • There actually are stringent procedures on introducing new agrochemicals, and on the manner, timing and quanties in which they can be implemented. Now days, every pesticide (whether man made or otherwise) has to undergo extensive testing on toxicity: (acute, chronic and subchronic), the former of which involves (among other things) the discovery of its LD50, the dose per unit mass at which half of the subjects will die of acute overdose, and the latter of which involves extensive multi-animal testing to find reference doses (RfD) using an experimentally derived quantity known as the toxological end point, or the No Observable Adverse Effect Limit (NOAEL), from which the EPA computes what they call “tolerances,” which are typically at least an order of magnitude or two lower than the lowest dose ever observed to have any observable effect in the most sensitive animals (that extra cushion is to account for variability in sensitivity across the population). If trace residues are found to exceed these tolerances, the food cannot be sold.

          It is also common to assess for carcinogenic potential, mutagenic and potential effects on fetal development.

          My experience is that most people are not taught about these standards and how they are accomplished, and thus it’s easy for them to imagine worse case scenarios because they don’t realize how tightly regulated things are now days. 

        • Also, GMOs have actually helped reduce pesticide use: not increase it (contrary to anti-GMO and organic industry mythology). 

          According to the latest Brookes and Barfoot paper, biotech crops have decreased pesticide use. More specifically, it shows an 8.6% decrease in pesticide use (by mass). They’ve also helped cut greenhouse gas emissions due to farming by the equivalent of removing 12.4 million cars from the road, and reduced the Environmental Impact Quotient (EIQ) by 19.1%. 

          Abstract

          “This paper updates previous assessments of how crop biotechnology has changed the environmental impact of global agriculture. It focuses on the environmental impacts associated with changes in pesticide use and greenhouse gas emissions arising from the use of GM crops since their first widespread commercial use in the mid 1990s. The adoption of GM insect resistant and herbicide tolerant technology has reduced pesticide spraying by 553 million kg (-8.6%) and, as a result, decreased the environmental impact associated with herbicide and insecticide use on these crops (as measured by the indicator the Environmental Impact Quotient (EIQ)) by 19.1%. The technology has also facilitated important cuts in fuel use and tillage changes, resulting in a significant reduction in the release of greenhouse gas emissions from the GM cropping area. In 2013, this was equivalent to removing 12.4 million cars from the roads.”

          http://www.tandfonline.com/doi/abs/10.1080/21645698.2015.1025193
          GE insect resistant (Bt) crops in particular have led to a reduction in insecticide usage (see pg. 63).

          http://www.ers.usda.gov/media/1424185/eib124.pdf
          Moreover, although the rise in popularity of glyphosate-resistant (GR) crops in particular has coincided with an increase in the use of glyphosate, what critics invariably fail to mention is that its rise in popularity also coincided with the phasing out of other herbicides, most of which were significantly more toxic than glyphosate.
           
          http://www.crediblehulk.org/index.php/2015/06/02/about-those-more-caustic-herbicides-that-glyphosate-helped-replace-by-credible-hulk/

          • There is no amount of cars removed which can compensate for poisoning the guts and brains of children and adults. The simple facts are, that increased pesticide/BT and Roundup exposure increases with gi disease, autism, asthma, etc… Fact is, now Roundup ripening is pervasive, but not publicized. I sat next to a Roundup pushing rep trying to get a farmer to ripen off to increase moisture and weight. My other neighbor almost lost a bull. And horse to triclopyr. It is ludicrous to ignore the damage of the practice, despite the benefits from no-till.

          • “The simple facts are, that increased pesticide/BT and Roundup exposure increases with gi disease, autism, asthma, etc… ”

            – You don’t get to come here claiming something as “fact” without citing credible evidence if you expect to be taken seriously. None of what you’re saying is consistent with the preponderance of evidence.

  3. Great article! One common response when I provide the above logic is the concern that glyphosate is an endocrine disruptor and has a low-dose response curve (to which I have found little credible evidence). Have you encountered this, and if so, what have you found as an appropriate response?

  4. steven.broyles@cortland.edu

    I posted your article on my facebook wall, Here is a response from one of my science colleagues. Would you care to comment back? I’m having a hard time holding back on this one! You are going to base food safety on the LD50 values determined in rats! Uugh! The data are telling us VERY LITTLE about what these things are doing in the human body over years of exposure. They are measuring death in a rodent model. What about looking at more subtle things like autoimmune disorders, allergies, autism, cancer, and all the other countless problems that are on the rise. This is crappy science reporting. I use LD50 values all the time in my research, but to conclude that these values directly relate to how safe these agents are for every system in the human body is naive.

    • Considering the fact that I DID cover carcinogenicity as well as chronic toxicity, NOAEL values and how they are used to compute the EPA tolerances, it sounds like he just shut down his brain activity at the mere mention of acute toxicity and didn’t read the article. I didn’t conclude safety in the basis of LD50, so his knee jerk criticism is invalid. The fact that he even seriously entertains the notion that glyphosate might “cause autism” does not bode well for his credibility.

  5. Excellent! Keep up the good work.

  6. You should enable sharing buttons on your page.

  7. Terre Dunivant

    You don’t answer the bee question. Can you answer the bee (and butterfly) question?

  8. Eliot W. Collins

    The Roundup Weed and Grass Killer in the graphic is 2% Glyphosate and 2% Pelargonic & other related fatty acids. How does it compare with other Roundup products and with other herbicides. I really don’t care how it compares with headache remedies.

  9. Arthur Doucette

    I’ve updated that post you borrowed from (no problem)

    Here’s the updated version:

    Here are examples of the residues of Glyphosate allowed on our food:

    Vegetable, bulb, group 3-07 – 0.20 ppm
    Vegetable, cucurbit, group 9 0.5 ppm
    Vegetable, foliage of legume, subgroup 7A, except soybean 0.2ppm
    Vegetable, fruiting, group 8-10 (except okra) 0.10ppm
    Vegetable, leafy, brassica, group 5 0.2ppm
    Vegetable, leafy, except brassica, group 4 0.2ppm
    Vegetable, leaves of root and tuber, group 2, except sugar beet tops 0.2ppm
    Vegetable, legume, group 6 except soybean and dry pea 5.0ppm
    Vegetables, root and tuber, group 1, except carrot, sweet potato, and sugar beet 0.20ppm

    oilseeds, group 20, except canola at 40 ppm;
    vegetable, root and tuber, group 1, except carrot, sweet potato, and sugar
    beet at 0.20 ppm;
    carrot at 5.0 ppm;
    sweet potato at 3.0 ppm;
    vegetable, bulb,group 3–07 at 0.20 ppm;
    vegetable, fruiting, group 8–10 (except okra) at 0.10 ppm;
    fruit, citrus, group 10–10 at 0.50 ppm;
    fruit, pome, group 11–10 at 0.20 ppm;
    and berry and small fruit, group 13–07 at 0.20 ppm.

    Note that most are all less than one part per million.

    Here are the residues allowed on Animal Feed.

    Animal feed, nongrass, group 18 – 400ppm
    Grain, cereal, forage, fodder and straw, group 16, except field corn, forage and field corn, stover 100 ppm
    Grass, forage, fodder and hay, group 17 – 300 ppm
    Kenaf, forage 200 ppm
    Leucaena, forage 200 ppm
    Teff, forage 100 ppm
    Teff, hay 100 ppm

    Or in general ONE THOUSAND or more the level allowed for humans.

    So if glyphosate was an issue, we would certainly see it in our Livestock.
    We don’t.

    New allowable levels on crops such as flax, canola and soybeans have been increased from 20 parts per million to 40 ppm, because our main use is for OIL and because tests show glyphosate does NOT make it through the refining step.

    They also increased the amount allowed on Carrots to 5 ppm because it is being used to desiccate the green tops, which aren’t eaten, but are tested.

    But what they determined is the MINOR change to the allowed levels would not cause a person to exceed the Reference Dose. See below for description but first consider their documented tests:

    A 1-year feeding study with dogs fed dosage levels of 0, 20, 100, and 500 mg/kg/day with a no-observable-effect level (NOEL) of 500 mg/kg/day.

    A 2-year carcinogenicity study in mice fed dosage levels of 0, 150, 750, and 4,500 mg/kg/day with no carcinogenic effect at the highest dose tested (HDT) of 4,500 mg/kg/day.

    A multigeneration reproduction study with rats fed dosage levels of 0, 3, 10, and 30 mg/kg/day with the parental and pup no-observed-effect level of 30 mg/kg/day

    So the EPA used these and other tests to set the Reference Dose (RfD).

    The RfD represents the level at or below which daily aggregate dietary exposure over a lifetime will not pose appreciable risks to human health.

    The RfD is determined by using the toxicological end point or the NOEL for the most sensitive mammalian toxicological study.

    To assure the adequacy of the RfD, the Agency derives an Acceptable Daily Intake (ADI) and uses an uncertainly factor of 100 less than the RfD in deriving it, based on the assumption that our species could be 10 times more sensitive to the compound than the most sensitive species
    tested and that some segment of the human population could be 10 times more sensitive than the average person.

    The Agency has determined an ADI of 1.75 mg/kg/day based on the maternal toxicity NOEL of 175 mg/kg/day from the developmental study with maternal rabbits.

    So that’s the maximum of what the EPA allows in our food, 100 times less than the NO OBSERVABLE EFFECTS LIMIT in the MOST sensitive species tested.

    BUT

    To ensure that, they set the Maximum Residue Limit (MRL) on all of our food.
    The MRLs are set are ALSO very conservative, to insure you don’t get over 1.75 mg per kg per day they use a “worst case” dietary risk model of an individual eating a lifetime of food derived entirely from glyphosate-sprayed fields and all with residues at their maximum levels.

    To see how all these conservative assumptions work together let’s assume you are a vegetarian and eat a mix that is on the extreme high end of residue levels and so you consume food which is at a very high average of 5 ppm per day.

    So 200 grams of food would yield 1 mg of glyphosate.

    You weigh 80 kg or 176 lbs.

    To get 1.75 mg per kg you would need to get 140 mg of glyphosate residue.

    So you would need to eat 200 * 140, or 28,000 grams of this 5 ppm produce to get to the 1.75 mg per kg per day level.

    There are 28 grams in an ounce, so that’s 1,000 ounces.
    There are 16 oz in a pound, so you would need to eat 62 lbs of produce.

    Each day.

    And if you managed that, that would only get you to a level that is 100 times less then the NOEL level in the most sensitive species tested.

    Arthur

  10. Arthur Doucette

    Note, I’m pretty sure the actual ADI is 1.75 mg/kg/day. I got the 2 mg/kg/day because apparently
    many sites had rounded the 1.75 up to 2 mg. This updated post reflects the actual value as determined by test on rabbits with a NOEL of 175 mg/kg/day.

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  27. What does this mean for bees, small creek fed ponds?

  28. I have been engaging in an online discussion with a family friend regarding GMOs- it is worth it because this person is genuinely interested in my opinion (rare in the online-science-duel, especially for an immunologist like myself). I want to response well and with informed citable material, however I am newer to engaging in anti-GMO discussions as most of what I know best are vaccines etc. I am stuck on a question that was posed and hoping you can help me to respond:

    Is glyphosate active in the gut against microbiota? Can it actually be killing gut microbes and causing issues for people in that way? I haven’t been able to relate dosing in mammalian cells to the pharmacology of the compound in the GI and the associated microbes there.

    Any help and citations would be much appreciated (especially via email if possible).

    • That’s a possibility that was of concern to some people early on, and it has been looked into. There was a really poorly done paper by Samsel and Seneff which made some pretty extraordinary claims about it being a problem, but neither of them had any training in the requisite field, and more importantly, the study was of poor quality. However, others have looked into it as well.
      This is one of the early papers looking at glyphosate inhibition in bacteria. Not only is the level of glyphosate needed to inhibit the target enzyme in the shikimate pathway much higher in bacteria than in plants, but the inhibition of growth can be corrected for by addition of the aromatic amino acids made by the shikimate pathway. In other words, if the bacteria have a source of those amino acids in their surroundings, they don’t need the shikimate pathway to make their own. I’m thinking that there may be aromatic amino acids floating around those bacteria in the digestive tract after protein is broken down. Sorry for the delay. I’ve been way behind. I hope this was of some help.

  29. Pingback: Roundup: What It Is (and What It Isn’t) - It's MomSense

  30. Pingback: A Catalog of Information on GMOs, Monsanto, and Related Topics | Inside the Mind of Michael Kovich

  31. The IARC agrees with Monsanto’s own 1980s rat studies that are shown in the 1991 EPA memo, that glyphosate causes cancer in animals. And probably in humans.

  32. LD50 is a red herring – it’s not the kind of toxicity that people need to worry about and so going on at length about the relative safety of glyphosate re acute poisoning is a red herring, a distraction, and you know it. The long-term effects on outcomes is the serious issue.

  33. Your quote of Kate Guyton doesn’t mean what you say that it means. You write

    <>

    That quote does not follow to that conclusion. If that is what the IARC meant, then that is what the IARC would have written. Their language in the monograph is very clear. They are speaking about the chemical, and most of their underlying evidence refers to ingestion of the chemical. The evidence that glyphosate causes cancer in animals (their actual conclusion) is based on ingestion by rats primarily.

    • That is not correct. You don’t get to change the meanings of other people’s words just because it doesn’t conform to your incorrect beliefs. As for the controversial Lancet IARC report (the IARC is a branch of the WHO) on which the re-classification of glyphosate was based, even the IARC themselves have explained that their concern does not pertain to food safety, but rather to pesticide applicators who are exposed to much larger quantities than consumers, but who already have procedural protocols for safe application. They authors state:

      “There was limited evidence in humans for the carcinogenicity of glyphosate. Case-control studies of occupational exposure in the USA, Canada, and Sweden reported increased risks for non-Hodgkin lymphoma that persisted after adjustment for other pesticides. The AHS cohort did not show a significantly increased risk
      of non-Hodgkin lymphoma.”

      The relevant studies are as follows:

      http://www.ncbi.nlm.nih.gov/pubmed/18623080

      http://www.ncbi.nlm.nih.gov/pubmed/11700263

      http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1740618/

      The IARC’s Kate Guyton even said “It’s agricultural use that will have the biggest impact. For the moment, it’s just something for people to be conscious of” on public record. There is really no excuse for people misrepresenting their position.
      http://thinkprogress.org/climate/2015/03/22/3637297/monsanto-herbicide-probably-causes-cancer/

      The IARC classification process isn’t designed to serve as a statement on risk analysis, and for that reason, did not take into account actual common usage practices. They placed glyphosate in the 2A category, which includes “probable” (albeit unconfirmed) carcinogens such as emissions from frying food, hairdresser products and burning wood. It mainly pertains to application protocols rather than minuscule trace amounts in food. Alcohol, sunlight and bacon are all in the carcinogenic category above glyphosate (I.e. confirmed carcinogens rather than merely suspected), and none of those cause cancer with conservative exposure either.

      In other words, ditching glyphosate because of its recent classification would be similar to never going out of the house in the daytime because sunlight is carcinogenic. Actually, it would be even less sensible because sunlight is in an even higher class of carcinogen than glyphosate. It’s in the same classification as manufacturing glass, burning wood, emissions from high temperature frying, and work exposure as a hairdresser.

      http://www.cancer.org/cancer/cancercauses/othercarcinogens/generalinformationaboutcarcinogens/known-and-probable-human-carcinogens

  34. Sorry, in the above comment, i attempted to quote a passage by enclosing it in angled brackets but that was interpreted by the system as html and there is no option to edit the comment, so here is the passage intended to be quoted:

    “I don’t think home use is the issue. It’s agricultural use that will have the biggest impact. For the moment, it’s just something for people to be conscious of.”
    Basically, what that means is that it’s the people actually applying the herbicide who are thought to be at increased risk.

  35. What an excellent article. Thank you so much for the time you took to write it.

  36. Pingback: NeuroLogica Blog » The Cost of Banning GMOs

  37. Pingback: Glyphosat – schlimmstes Gift aller Zeiten oder geeignet für die Homöopathie? | Post Skriptum

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