17 Questions About Glyphosate

Many worry about pesticides for health or environmental reasons, and the most common target of general concern is undoubtedly glyphosate, the active ingredient in the famous weedkiller RoundUp. I find that the best thing to do when something worries me, is to
1find out more about it.  I’ve delved into the details behind the 17 most common concerns I’ve encountered. Questions 1-11 are mainly about health, whereas 12-16 focus on environmental aspects, and lastly, 17 delves into the question of the integrity of research. I will do my best to present useful evidence-based resources on all the following topics. If you would like to listen to a summary of this series you can head on over to my guest appearance on the podcast Talking biotech with Kevin Folta – I was very honoured for the opportunity to join his great series.

After receiving valuable feedback from my readers, I decided to break these questions into blog posts of their own, either alone or in groups of a few connected questions per post. This way the list below can also serve as a hyperlinked table of contents:

  1. Does glyphosate cause cancer?
  2. Could glyphosate have other health effects? What about the surfactants in RoundUp, or glyphosate breakdown products?
  3. What about studies claiming glyphosate causes celiac disease, autism, obesity etc? A look at Seneff et co.
  4. Does glyphosate harm our gut bacteria?
  5. Could glyphosate be another case like DDT or Thalidomide – should we apply the precautionary principle? The important difference between persistent and non-persistent pesticides
  6. Is glyphosate an especially dangerous pesticide?
  7. Is there glyphosate in the air and rainwater?
  8. Is there glyphosate in urine?
  9. What about breastmilk?
  10. Should we worry about glyphosate in wine?
  11. Is wheat toxic because of glyphosate?
  12. Are crops drenched in glyphosate?
  13. Does glyphosate use enable bad farming practices?
  14. What about resistance and superweeds?
  15. Does glyphosate interfere with soil organisms or nutrient availability?
  16. Does glyphosate harm Monarch butterflies or bees?
  17. Can glyphosate research be trusted? What about conflicts of interest?

The basics

Glyphosate is a modified glycine-molecule (the smallest of our essential amino acids) which has a phosphoric acid (or to be exact, phosphonomethyl) group attached at the end (GLYcine PHOSphonATE). You can find out more about the specifics here. This small molecule binds to an enzyme in plants and many bacteria, which they need in order to synthesise a class of amino acids (aromatic ones). If the plants cannot synthesise these amino acids, after a number of days they will die. Animals do not have this enzyme. Instead, we rely entirely on our diet to provide us with these aromatic amino acids (Trypthophan and Phenylalanine – and Tyrosine, also an aromatic, can be synthesized from Phenylalanine), which means that the inhibitory effect of glyphosate has no direct target in our cells.

But as you can see from above, there is a lot more to the discussions about glyphosate – in fact, conversations on the topic often sprawl into so many directions at once that it can be confusing and exhausting for anyone to try to make sense of them. Which directions may warrant real concern and which not? The general impression left may be a vague feeling of unease. If there are so many questions, surely there must be something problematic with glyphosate? Should we use it at all? EU is currently in the process of determining this very question, and according to the vice chair of EU’s environmental committee, their hesitancy is influenced by the vocal campaigns of activist organisations like Avaaz who are calling the reliability of research into question. So instead of another 15 year renewal, glyphosate has been given an 18 month continued allowance period while European Chemicals Agency (ECHA) comes to a conclusion, expected in December 2017.

But there are several comprehensive literature reviews in scientific publications, and other scientific bodies in Europe and elsewhere in the world who have already concluded comprehensive reviews on glyphosate research that can give us a good idea about the topic.

1. Does glyphosate cause cancer?

Much media and public attention on glyphosate followed after World Health Organisation subgroup, International Agency for Research on Cancer (IARC) declared that according to their classification, glyphosate falls under substances 2A – “probably carcinogenic”. What the media attention often failed to report is that IARC does not actually look at risk – how big is the risk for said carcinogenic effects? What levels are safe and what aren’t? Instead it aims to classify a kind of absolute possibility as a hazard: would the exposure to agent x be carcinogenic in any possible scenario, dosage, length of exposure? Its classification of glyphosate to a “probable carcinogen” has been under some criticism, considering that IARC excluded much of the existing reputable evidence on the topic, that the IARC made connections to human effects where certain study authors themselves did not agree, and also for non-declared political conflict of interest within the IARC, and the way these actors have used the classification for political lobbying (for more, see The Shady Politics Of The IARC Glyphosate Hazard Assessment – the site is down for the moment, meanwhile there’s also a GLP aggregate page for it).

But even if we set these questions about the validity of the assessment aside, and simply assume it to be accurate, what does classification as a 2a substance mean? The scale IARC uses includes the following groups:

  • 1) definitely carcinogenic
  • 2a) and 2b), probably and possibly carcinogenic
  • 3) not classifiable, and
  • 4) probably not carcinogenic.

Bloomberg has a very user-friendly graphic in their article on red meat as a carcinogen, where they give an overview of a multitude of substances (and other exposures, such as occupations) classified within the IARC system. You can find a screenshot of their great interactive graphic below, with processed meat featured from group 1, and red meat from group 2A (in the same class as glyphosate). They write:

It’s important to note that the agents at the top aren’t necessarily the most dangerous. They’re the ones with the clearest evidence of hazard. WHO seeks to identify carcinogens “even when risks are very low at the current exposure levels, because new uses or unforeseen exposures could engender risks that are significantly higher,” the agency says. In other words, even though WHO has determined that red meat is a carcinogen, the report doesn’t quantify how much meat it would take to cross into the danger zone.

Screen Shot 2016-09-01 at 21.34.30

Bloomberg’s article and interactive graphic is definitely worth taking a look at. Just a screenshot sample pictured here.

So far out of all the near thousand substances evaluated, IARC has named only one ‘probably not’ a carcinogen. Of course, most of the substances studied are chosen because an idea that they may under certain circumstances cause cancer. IARC does provide potentially useful information, just not the kind which a typical consumer might think of when they read the headlines. IARC provides no insight about which kind of exposure would be significant for our day-to-day lives. IARC is not a consumer information service – after the media attention given to IARC’s classifications, Ed Yong over at the Atlantic went as far as to call for “a separate classification scheme for scientific organizations that are “confusogenic to humans.” To steer ourselves further away from the confusion, let’s remember that exposure and dose remain the crucial questions when it comes to making good health choices.

There are several scientific review papers (collected here on this excellent resource wiki of the Food and Farm Discussion Lab) that have looked at real world data of glyphosate exposures and their connection to health effects. Four of these review articles look specifically at cancer and genotoxicity, and they all conclude that there is no connection between glyphosate and cancer incidence.

So why did IARC classify it as a probable carcinogen? To make things less confusogenic, there is a very illuminating blog post from weed ecology professor Andrew Kniss, over at WeedControlFreaks blog, on the studies IARC used in their monograph: Glyphosate and cancer what does the data say? Andrew Kniss provides a very useful graphic to help us make sense of the evidence landscape:


See the excellent blog post, Glyphosate and cancer – what does the data say? Over at WeedControlFreaks.

If you are interested in the spike of Non-Hodgkins Lymphoma, it good to start with mentioning that those were case-control studies, where the number of people actually exposed to glyphosate were very small – tens, not hundreds, and even within the population of cancer sufferers, only a few percent had glyphosate exposure, as Andrew Kniss lays out in his piece. This means that the evidence is far from conclusive. Now, let’s compare Andrew Kniss’ graphic to this one from another great piece in Vox, This is why you shouldn’t believe that exciting new medical study:


From This is why you shouldn’t believe that exciting new medical study, based on Schoenfeld and Ioannidis paper in American Journal of Clinical Nutrition.

One way to sum it up: cancer – it’s not that simple. Evidence that seems to support or reject a hypothesis may still be wrought with complexities that eludes simple interpretation. It is no wonder if it’s difficult for lay people to try to put all the data from scientific studies into proper context and perspective. The Farmer’s Daughter helps with the effort by comparing the classification to that of other known definite or probable carcinogens: sausages, wood dust, and shift work for instance, which also fall under class 2A, are all things we can more intuitively assess (it’s better not to eat all too many sausages, or breath in wood dust, or get yourself too exhausted with shift work, especially if it doesn’t suit you). She writes:

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.

But what’s even more revealing are the things that have been classified in Group 1, things that do cause cancer: drinking alcohol, formaldehyde, radon, solar radiation, wood dust, and estrogen. So these are things that will cause cancer, while glyphosate (according to IARC) might cause cancer.

So, if glyphosate could cause cancer, does it? According to several reliable sources, no.

An actual risk assessment on glyphosate by the WHO and the United Nations Food and Agricultural Organisation (FAO) finds no reason to think glyphosate in the amounts found in our food or through normal occupational exposure would be carcinogenic to humans.

Evaluations by Environmental Protection Agency (EPA) in US and European Food Safety Authority (EFSA, report here), as well as the German Federal Institute for Risk Assessment (BfR statement here, and their evaluation in English here) have also reached the same conclusion. The WHO statement as reported by Reuters:

“In view of the absence of carcinogenic potential in rodents at human-relevant doses and the absence of genotoxicity by the oral route in mammals, and considering the epidemiological evidence from occupational exposures, the meeting concluded that glyphosate is unlikely to pose a carcinogenic risk to humans from exposure through the diet,” the committee said.

Update: Recent European Chemicals Agency review on glyphosate has also concluded that Glyphosate is not classified as a carcinogen:

ECHA’s Committee for Risk Assessment (RAC) agrees to maintain the current harmonised classification of glyphosate as a substance causing serious eye damage and being toxic to aquatic life with long-lasting effects. RAC concluded that the available scientific evidence did not meet the criteria to classify glyphosate as a carcinogen, as a mutagen or as toxic for reproduction.

If you would like to watch a video on the topic, this civil and informative discussion where two scientists are interviewed in a Canadian News show does a good job of neatly clarifying many of the important aspects in just 15 minutes. They illustrate the difference between a ‘hazard’ and a ‘health risk’ by likening the risk of glyphosate to the consumer to a visit at the zoo. Is the bear in the zoo a risk to your health? In the right (well, wrong) context, yes. But should you be afraid to visit the zoo? No.

Added: A 2013 review on glyphosate and glyphosate formulations concludes neither to be genotoxic under normal human or environmental concentrations. The most recent review on glyphosate and cancer from 2015 concludes:

The lack of a plausible mechanism, along with published epidemiology studies, which fail to demonstrate clear, statistically significant, unbiased and non-confounded associations between glyphosate and cancer of any single etiology, and a compelling weight of evidence, support the conclusion that glyphosate does not present concern with respect to carcinogenic potential in humans.

2. Could glyphosate have other health effects? What about the surfactants in RoundUp, or glyphosate breakdown products?

Number of different health concerns have been raised for glyphosate, not just worries about cancer. There is a trend in many of these concerns. Often the chain of conclusions is rather loose, and the argument relies on “glyphosate can be detected in x” – leaving it up to the reader to draw the conclusion that this detection must be significant and should make us worry about health effects, even though the evidence on those is left out or only loosely implied.

The other tactic is to claim that high levels of glyphosate could have an effect x, so we must be wary of the substance in any form, leaving aside the discussion about what the realistic levels of exposure are and how they relate to that risk. This idea of absolute avoidance creeps into our thoughts quite easily when it comes to new ‘invisible’ chemical risks which we are not personally in control of, whereas with familiar risks, such as salt (which is more toxic than glyphosate) and alcohol (which is definitely carcinogenic in the amounts commonly ingested), we tend to naturally understand that moderation is key.

The important question is whether there is a realistic basis to worry about health risks. The best way to find guidance to that question is to rely on the collected wisdom of the best and most comprehensive recent reviews on the research (examples here and here, or you can check out the collection of all glyphosate review papers in Food And Farm Discussion Labs wiki page). There have been at least eight reviews looking at human health and glyphosate science in the last 20 years, and all of them find no harm to human health caused by normal glyphosate use. Another good place to begin is at Biofortified, where plant geneticist Anastasia Bodnar has written an overview of the research landscape:

…three recent reviews that summarize the literature on glyphosate and humans: Epidemiologic studies of glyphosate and non-cancer health outcomes, Epidemiologic studies of glyphosate and cancer, and Developmental and reproductive outcomes in humans and animals after glyphosate exposure. These reviews looked at epidemiological studies, ones that look at disease incidence in large numbers of humans with varying levels of exposure to G or that look at exposure to G in a population that has a disease.

Now, epidemiology isn’t perfect, but with carefully designed studies it can be a powerful way to look for connections in real human populations. Even better when we can look at reviews that put multiple studies all in one place. These reviews cover a lot of studies that find there is no correlation between glyphosate exposure and cancer or non-cancer diseases.

She also cautions for perspective when it comes to single studies conducted in the lab with cell cultures:

There are occasionally alarm-inducing papers like Glyphosate induces human breast cancer cells growth via estrogen receptors. This paper, and others like it, tend to use human cells in a petri dish rather than whole animals. I had the misfortune to do some research on cultured human cells myself and let me tell you, those are some tricky buggers to work with. Even when everything is working perfectly, it’s still very hard to tell if the results you are getting will hold true when repeated in a whole animal model. Something that causes a reaction in naked cells may not react the same when applied to your skin or taken in through your digestive system (both of which have evolved to keep you safe from many things).

Only a combination of animal models and cell studies can give us the full picture (even better if we can pair these up with some epidemiology).

What about the surfactants (soap-like substances) in pesticides?


Schematic molecular structure of different surfactants.

To allow for better spread, glyphosate mixtures usually contain surfactants, and it is worth adding, that in a wide array of studies, the substance under study is a mix of glyphosate and surfactants – most commonly one called polyethoxylated tallow amine (POEA). Surfactants are substances such as soaps and other amphiphilic molecules, which have the ability to change surface tension properties between liquids (or liquids and solids). They also help solubilise fats and proteins , that is, they act as detergents. Sometimes there may also be other pesticides added (combination pesticide mixtures). Each agent will have an effect of its own, which of course becomes pronounced if the target animal or cell culture is exposed to high enough concentrations for a long enough period of time.

Not surprisingly, cells do not like direct exposure to large concentrations of agents that solubilise their structural components, such as surfactants. Neither do aquatic animals. We can tolerate washing our hands with soaps because of the barrier-function of our skin, and the small amounts that might be ingested (from our own soaps, or from pesticide residue) are so vanishingly small as to be of no concern. But we would also most certainly experience some adverse effects if we actually drank soap, and we do not tend to require that our soaps should be safe if ingested in large amounts, because this is not their intended use. This is the relevance we need to look for in studies: that they look at realistic exposures (whether it’s about soap or glyphosate). It is the dose that makes the poison. 

Glyphosate breakdown product AMPA



The major breakdown product of glyphosate is aminomethylphosphonic acid (AMPA), which has been found to have similarly low profile of toxicity as glyphosate according to the report from Food and Agricultural Organisation of the WHO. One review from 2000 has looked at both glyphosate, the surfactant POEA, and AMPA specifically. They conclude:

The oral absorption of glyphosate and AMPA is low, and both materials are eliminated essentially unmetabolized. Dermal penetration studies with Roundup showed very low absorption. Experimental evidence has shown that neither glyphosate nor AMPA bioaccumulates in any animal tissue. No significant toxicity occurred in acute, subchronic, and chronic studies. […]

Therefore, it is concluded that the use of Roundup herbicide does not result in adverse effects on development, reproduction, or endocrine systems in humans and other mammals. […]

It was concluded that, under present and expected conditions of use, Roundup herbicide does not pose a health risk to humans.

A quick a nod to the topic of cancer, which I delved into more in the first post of this series: the field is indeed complicated. Even among our common foodstuffs, you can find evidence for a great number of them as having both, a cancer-causing and a cancer-protective effect. To illustrate this point, when I dived into the studies on PubMed, one of the most recent studies on AMPA from 2016 actually looks at the substance as a prospective cancer treatment:

these results demonstrate that AMPA can inhibit prostate cancer growth and metastasis, suggesting that AMPA may be developed into a therapeutic agent for the treatment of prostate cancer.

This goes to show that single studies may raise alarm or give hope about any number of substances as either harmful or beneficial. Time and accumulating number of quality studies that either support or reject those views, are the critical factor in making sense of the science. So far this process has found neither glyphosate, nor its common companion surfactants, or breakdown products, to pose a risk for us or the environment through normal exposure.

Could glyphosate be an endocrine disruptor? Enter Seralini et al.

The French researcher Seralini has published a paper that claims glyphosate to be an endocrine disrupor. This is a good example of what Anastasia Bodnar cautioned about above: the study was done entirely on cell lines, which gives us little idea about the relevance when it comes to food residues. Exposing cells cultures directly to high levels of glyphosate and its formulations with surfactants will most likely have adverse effects on the cell lines, which they observed.

There are some red flags here too. Three years after this study, Seralini published another one, which he is probably most famous for. It was a genetically engineered corn feeding study on a specific kind of laboratory rat breed which is naturally prone to tumours. He kept the rats alive and suffering well past any ethically defensible time-frame (two years), and had his study redacted due to its confusing study design, flawed statistics, and a conclusion not supported by the data. If you are interested, you can read more about the affair in Nature or Wikipedia.

It may come as no surprise, then that even his earlier endocrine disruption study has not lead to more research that would have confirmed the suggested endocrine effects. A 2015 report from Environmental Protection Agency (EPA) concludes that there is no convincing evidence that would warrant more extensive testing:

Based on weight of evidence considerations, mammalian or wildlife EDSP Tier 2 testing is not recommended for glyphosate since there was no convincing evidence of potential interaction with the estrogen, androgen or thyroid pathways.

It is one thing to suggest that an adverse effect observed in a a single cell line study would have greater relevance. If the results are not confirmed in other ways, however, and if the data simply does not get support in any of the epidemiological studies from decades of human populations exposure to the pesticide residues, then the suggestion is probably not that relevant after all.

Science-based Medicine has also summarised the topic of glyphosate’s health effects in their piece Glyphosate – The New Bogeyman, coming to a conclusion very similar to the one Anastasia Bodnar made above:

…numerous published systematic reviews show clear evidence that glyphosate has very low toxicity. More careful study when it comes to any agent being used as heavily as glyphosate is always welcome. Science is complicated, and it is always a good idea to consider factors that may have been previously missed. However, failure to show any adverse effect from glyphosate in epidemiological studies is very reassuring. Given its widespread use, any adverse effect must be tiny or non-existent to be missed by the evidence we have so far.

The evidence, however, will not stop ideologues from cherry picking, misusing evidence, presenting pure speculation as if it were evidence, assuming causation from correlation, and generally fearmongering about a safe chemical in order to grind their ideological axe.

3. What about studies claiming glyphosate causes celiac disease, autism, and obesity, etc? A look at Seneff et co.

For scientists, it may be easy to navigate the landscape of scientific publications, but most people have no experience and knowledge of how to easily discern whether the claims being made are incredibly far-fetched or fundamentally lacking in evidence; if it is so that the authors are not actually qualified in the field in question; or that the publishing journal itself is of a questionable nature.

To get a better understanding of the latter factor, you can read more about predatory journals in discussed in this piece in Nature. There are also questionable publishing groups which are  buying up small but previously reputable journals in order to increase their revenues from having less successful scientists pay for the semblance of credibility they get from publishing their pieces in what technically qualifies a scientific publication. These publications are not very hard for professional scientists to spot, but they might fool any number of outsiders to the field. This is why it is best for outsiders to the field rather to rely on the views supported in large review papers which work to summarise a topic.

In the thousands of small ditches between the open waterways of mainstream scientific publishing, you can find all kind of puddles of muddled semi-scientific attempts. As an example, there is a paper that looks at results from a fish study. The analysis is written by an electrical engineer S. Seneff and a retired consultant A. Samsel, and they use computer science methods such as Natural Language Parsing to analyse papers in order to ‘help her figure out the story’ behind them. Using these methods, they claim that they can see that glyphosate causes celiac disease. The claim is based on an Indian fish study, where fish were kept in water which was supplied with many times field-realistic levels of a glyphosate mixture for weeks. Importantly, the mixture included surfactants, which are not allowed in aquatic use in the first place, because surfactants are very harmful to fish. There was no control for the surfactant. And the connection to celiac disease? It was their ‘logical conclusion’, seeing as the fish had seriously damaged intestines after six weeks in this surfactant bath. I think I do not need to point out that general intestinal damage in fish after 1.5 month long potent pesticide-soap-bath hardly equals proof about celiac disease. You can read more from Steve Savage in a fishy attempt to link glyphosate and celiac disease.

Seneff, together with Samsel, does not stop there, but they also claim that glyphosate is behind a whole host of ‘modern diseases’ (they seem to subscribe to the strange notion that most diseases did no exist before modern times). According to Seneff’s analysis, glyphosate is also behind the development of, hold on to your hats: gastrointestinal disorders, cancer, obesity, diabetes, heart disease, autism, Alzheimer’s disease, depression, anxiety syndrome, Parkinson’s disease, prion diseases, infertility, and birth defects. In an interview, Seneff goes as far as to blame glyphosate (RoundUp) for school shootings and the Boston Bombings. I don’t even know what to say to that. Maybe we should also blame glyphosate for climate change?

The red flags could not be much more numerous. Let’s list some: 1. Seneff is not a chemist, a biologist or a medical doctor, so she is publishing outside of her field. 2. The claim that any one specific thing is the cause of a wide variety of startlingly different kinds of diseases. (Same warning goes for any one thing that supposedly cures every number of different diseases.)  3. She doesn’t produce any actual new data, just reinterpretes old data. 4. She publishes in low-quality, pay-to-play predatory journals, some of which are not even connected to the field of biology. Seneff’s article on glyphosate and gut microbiota is actually used as a good example of how to spot a bogus scientific journal. In the piece they write:

This article is attributing pretty much all the chronic diseases of the modern world to a single agent, glyphosate. Wouldn’t it be fantastic if just by getting rid of one chemical we could be as healthy and happy as we have never been?

Need I mention, once more, that several comprehensive reviews by actual experts in human disease and biology have not found any epidemiological connection between any of these diseases and glyphosate?

To address concerns about several of these hypothetically connected diseases listed above, the US National Academies of Science included in their 2016 report a comparison of the rates of disease incidence between USA (where glyphosate use is much more abundant) and other countries such as UK. For the prevalence of celiac disease, autism and food allergies, they found no difference between USA and UK:

Celiac-disease detection began increasing in the United States before the introduction of GE crops and the associated increased use of glyphosate; the disease appears to have increased similarly in the United Kingdom, where GE foods are not typically consumed and glyphosate use did not increase. The similarity in patterns of increase in autism spectrum disorder in children in the United States and the United Kingdom does not support the hypothesis of a link between eating GE foods and the prevalence of the disorder. The committee also did not find a relationship between consumption of GE foods and the increase in prevalence of food allergies.

A word about autism

To lift out one of the topics on that list, I would like to make a comment about what the scientific evidence has to say about the causes of autism. The Autism Science Foundation gives good overviews of autism research, and if you look at their reports on studies about autism risk factors and environmental factors, the list of possible connections to autism is really long (note, it does not contain glyphosate):

Maternal age, paternal age, mother’s influenza/untreated fever during pregnancy, diabetes, air pollution, cigarette smoke, lead, methylmercury, polychlorinated biphenyls, arsenic, and toluene, manganese, fluoride, chlorpyrifos, dichlorodiphenyltrichloroethane, tetrachloroethylene, and polybrominated diphenyl ethers, organophosphate pesticides, maternal childhood abuse, placental folds…

Autism is fundamentally a genetic disease, and autism spectrum is viewed as a neural ‘type’, not a disease. It is something that is largely hereditary, it develops during gestation, and it can be exacerbated by additional (related) new point mutations connected to neural development before or during fetal development. There is a lot of research into what could cause potential epigenetic and other factors that would make some of the more difficult aspects of autism more pronounced.

Considering the number and diversity of these factors, it’s best to wait for comprehensive meta-analyses or reviews on these topics before making too strong conclusions. One of the recent meta-analyses was about maternal age:

The results of this meta-analysis support an association between advancing maternal age and risk of autism. The association persisted after the effects of paternal age and other potential confounders had been considered, supporting an independent relation between higher maternal age and autism.

The topic is complex enough without somebody manufacturing hypotehtical connections and creating more noise for the worried parents and dedicated researchers to wade through.

If you would like to read more about all the wild claims and innumerable logical lapses in Seneff’s papers, there are many good places to turn to. Here are a couple: at Biofortified Medical Doctors Weigh in on Glyphosate Claim, Orac on Oh no GMOs are going to make everyone autistic, or even Snopes in their piece on Glyphosatan – Unsupported claims assert that one in two children will be autistic by 2025 due to the use of glyphosate (Roundup) on food crops.

4. Does glyphosate harm our gut bacteria?

This is one of the favourite returning points for many people who repeat a selection of different scary scenarios of what glyphosate might do. Some studies on the area are clearly of a very poor quality, and their flaws are easy for scientists and even laymen to detect if given a careful look (like one here on Skeptoid). That does not stop many from theorising that glyphosate could cause a host of things through unknown mechanisms on the gut microbiome. Kevin Senapathy’s comment (below) sums up the stumbling point of these claims, however: there is no evidence for glyphosate having a harmful effect in our gut bacteria.

Targeting the shikimate metabolic pathway in weeds, glyphosate interferes with protein synthesis in plants, bacteria, fungi and other organisms, but not in animals. There is no evidence that glyphosate residues on food affect the shikimate pathways of bacteria in the human gut.


The pesticide residues on produce in general are really very low – Nurse Loves Farmer provides perspective on the dirty dozen.

But the lack of evidence of harm does not necessarily give a layman the reassurance it may relay to a researcher. Let’s make it more tangible. To help us with the effort, firstly, the very thorough and detail-oriented skeptical activist Credible Hulk has kindly dug out the exact figures on allowed levels of pesticide residue on a number of different plants in his post, where he lays out the math: a 70 kg person in the US would have to eat 28 kg or 62 lbs of produce at the highest level of allowed residue every day in order to reach the limit set by Environmental Protection Agency (EPA) as the still safe level for the consumer – 2 mg glyphosate per kg body weight per day. This allowed level already has a hundred-fold built-in safety margin: it is set hundred times lower than the level for no observed adverse effects (NOAEL) in the most sensitive lab animal species tested. It is physically not possible to eat enough of normal produce to reach that level. And what about gut bacteria?

Neuroscientist Alison Bernstein aka Mommy, PhD, has tried to illustrate the implausibility of us ever ingesting enough of glyphosate to have the chance to influence our gut bacteria in any meaningful way, here:

Many people are concerned that pesticides, in particular, glyphosate, alter the gut microbiome and somehow cause autism. […] We can calculate how much glyphosate you would ingest on average from one piece of produce and see if that is enough to kill bacteria. So if you eat a 5 ounce (~150 g) piece of vegetable treated with glyphosate (5 ounces is about the size of an average apple for reference). Using his [Credible Hulk’s] high estimate of 5 ppm [glyphosate residue], we calculate that you get 0.75 mg of glyphosate. 98% is not absorbed so let’s assume it stays in your stomach for as long as it takes to pass through your digestive system. The 2% lost is not enough to worry about for this estimate. So 0.75 mg in 1 L (the volume of a full stomach) is 4.4 uM (micromolar). The papers I found looking at toxicity of glyphosate in bacteria were using MOLAR range concentrations of glyphosate. Micromolar means 10e-6 molar, or 0.000001 Molar. So 4.4 micromolar is 4.4 x 10e-6 Molar or 0.0000044 Molar. This is so far below the doses (and they did full dose response curves) that had an effect as to be utterly meaningless.

[…] You’d get GI issues from eating too much vegetable mass long before you ingested enough glyphosate to alter your gut microbiome.

Even studies (here and here) which look at an inhibiting effects on the growth of bacterial cultures require millimolar concentrations of glyphosate: thousand times larger concentration than the micromolar concentrations potentially present in our stomachs, demonstrated in the calculation above. To reach that same inhibiting effect they saw in the studies in our gut, one would have to ingest roughly 150 kg or 330 lbs of legumes (as legumes have the highest set limit for pesticide residues, and here we’ll assume they come near that limit) at once.

Keep in mind that in the study above they note an energy drain, but the bacteria were not killed. They simply stopped replicating for the time that glyphosate inhibited the enzyme needed for synthesizing necessary aromatic amino-acids. Supplementing the culture with said aromatic amino acids resulted in recovery of bacterial growth. Think for a moment about the human gut: it is a protein-rich environment, where all the nutrition from our food is broken down into its constituents. It is basically a soup of amino-acids. Even if we ate more than our own weight in legumes, we would probably not manage to inhibit our gut bacteria with glyphosate, since they would not have to depend on their inhibited enzyme and could just absorb their amino acids from our food.


Jonathan Eisen’s summary slide from NAS

This is in line with the epidemiological evidence discussed earlier, which has found no connection between glyphosate and cancer, non-cancer, or reproductive health outcomes. Microbiome researcher Jonathan Eisen from University of California, Davis, was asked to present an introduction to glyphosate and microbiome research for the US National Academy of Science in 2015. He notes that most papers on the topic of glyphosate and gut bacteria base their ideas on a paper from Seneff and Samsel (see section 3. above) where the hypothetical connection is described. Jonathan Eisen concludes the topic as follows (quote and slide on the left can both be found in the presentation soon after the 22 minute point):

I could not find anywhere in the literature much if any direct evidence that glyphosate would lead to first altering the microbiome then leading to health problems.

5. Could glyphosate be another case like DDT or Thalidomide – should we apply the precautionary principle?

Hearing science-speak conclusions like “failure to show adverse effects”, or “no correlation found”, or “not likely to pose risk” often leaves a layman out cold in the mists of the inherent scientific uncertainty. For our everyday logic, there is a threshold of such little perceived risk, where we simply declare something safe. But science holds fast to the humble intellectual honesty of saying “despite all our best efforts, there is still a very slim chance of an effect that could become evident in some unknown context in the future”. That may make our everyday brains feel uneasy.

An oft surfacing thought amongst the sea of possibilities is along the lines of: isn’t it better to be safe than sorry? It’s happened before – we have realised too late that an approved of chemical has turned out to have unexpected harmful effects. Two specific arguments frequently offered in support of the value in precautionary thinking include the examples of DDT and thalidomide.

The problem is that ‘something has at some point caused harm’ is not a useful way to guide our actions, unless there are reasonable grounds that the mechanism of said harm is similar. If there are no significant similarities, then how do we choose where to apply our absolute better-safe-than-sorry caution? Should we apply it to any medicine? Any household chemical? What about natural pesticides produced by plants themselves, half of which also have carcinogenic potential? We need to find some reasonable basis for our caution.

5a) Are there parallels between glyphosate and the case of thalidomide?

As an exercise in evaluating relevance, let’s first look at Thalidomide and glyphosate. Firstly, Thalidomide is in a special class of compounds (chiral molecules), which have special properties depending on the stereoisomer – like our left and right hands, these stereoisomers are very alike, almost identical, but they have such 3-d structure that they can’t be superimposed onto each other. The S and R Thalidomide molecules are distinct mirror images of each other, and one of these forms causes drastic harmful effects for a developing foetus.


The hydrogen and nitrogen atom bonds, described with a wedge vs dashed, point in different directions, a bit like the thumbs of right and left hand bend in different directions if viewed superimposed.

Glyphosate however is not chiral. It does not belong to this group of molecules at all.

Thalidomide was a drug used by humans, particularly pregnant women. Glyphosate is not a drug, it isn’t taken in a dose aimed at having a tangible effect on humans, instead it is found only in our food in trace amounts – only modern wonders of measurement technique can detect these levels. Thalidomide was taken in large doses by pregnant women before it had been tested for teratogenicity (birth defects). Glyphosate is not taken at all, but it’s effects have been tested by a whole body of research.

Thalidomide was used by a group of people during two years, and problems arose immediately. When they did, a clear molecular mechanism of its harmful action was found. At this time Thalidomide had still not in fact been approved for use. It was undergoing regulatory evaluation, but select doctors were prescribing it for their patients prematurely before FDA approval.

Glyphosate, on the other hand, has been approved for use and indeed used for 40 years, and rodent tests as well as epidemiological human studies have found no cause for concern. No clear mechanism of action has been proposed.

The lack of similarities makes it equally relevant to compare glyphosate to any substance within the mountains of medical compounds that have been brought to market and have saved countless of lives.

5b) But what about DDT?


DDT or Dichloro-Diphenyl-Trichloroethan

It’s a pesticide, just like glyphosate. It was approved for use and turned out to linger in the ecosystem. It is about ten to forty times more toxic than glyphosate measured in LD50 (113-450 mg/kg for DDT vs 4900 mg/kg for glyphosate). What is more important, is that DDT is a so called Persistent Organic Pollutant (POP) which is biomagnified in living organisms – it is not cleared, but accumulates in the body. Had its use not been discontinued, it could have caused great harm for animals higher up in the feeding chain.

This was the absolute key to the problem with DDT: it persists in the environment. It is not cleared from our bodies, and neither is it broken down by sunlight, plant or animal metabolism, or soil microbial activity. This is also where the similarities with glyphosate end. Glyphosate is readily broken down in plants and in the soil, and the minute residues we encounter are cleared from our bodies through normal metabolism. Agricultural geneticist Kevin Folta has written an informative piece on glyphosate where he lays out the math:

glyphosate is degraded, both in the plant and in the soil, so that 83 mg per square meter (…”Speaking metrically, that’s 340 g of active ingredient per acre.”…) is going away as soon as it is applied. It is not taken up by roots, so what is not applied to the plant itself goes into the soil and is degraded with a half life of 3-130 days depending on soil type and other factors.

Jeffrey Smith’s Institute for Responsible Technology says that it persists for 22 years, which is certainly possible when a half life is 130 days. After 22 years there likely are a few molecules still hanging around at least if the math is right.

A word on persistent vs non-persistent pesticides

Neuroscientist Alison Bernstein, who has studied the role of pesticides in Parkinson’s disease, wrote the following analysis of persistent vs non-persistent pesticides on her Facebook page, Mommy, PhD:

Persistence and toxicity are interrelated and bioaccumulation is critical when considering toxicity. […] The answer is, for a non-persistent pesticide, [at the allowed level of residue] you could not possibly eat enough produce to get to a dose that is toxic. Add to the fact that since the pesticide is not persistent, it is also cleared from the body. So the exposure is low and then it is cleared. In short, you cannot eat enough to approach doses that have acute toxicity and the chemical doesn’t stick around long enough to have any chronic effects.

[…] The switch from persistent to non-persistent pesticides is major progress for reducing our toxic exposures. We have come a long way since thinking that DDT was good for us.

Glyphosate has not been found to persist, or bioaccumulate, in living organisms, and neither has it’s breakdown product, AMPA (you can find a review here). In fact, a recent study on dairy cow metabolism found that 61 % of glyphosate was excreted, 8 % removed in urine, none found in milk, and found that a significant portion of both glyphosate and AMPA may become biodegraded in the rumen.

Regulatory (r)evolution – why DDT could not happen today

DDT was used as an insecticide starting around 1945, its effect on mosquitos helped eradicate malaria in North America, as well as control typhus and malaria during WW2. During this time in the US, there was no established regulation of pesticides – they did not have to be registered or tested, and their use was not controlled. The first attempt to even introduce marketing control (to ensure the companies sell what they promise) came 1947, and the first concerns for safety were introduced to regulation between 1954-1959, such as establishing safe levels, not allowing carcinogens, and requiring pesticides to be registered (find out more in the Wikipedia outline on pesticide regulation history).

The sixties and seventies saw more political and regulatory hurdles aimed at increasing control, largely thanks to the spread of awareness of the harm from pesticides, most notably from DDT, which was banned in the US in 1972, one year after the Environmental Protective Agency (EPA) was founded. Through seventies and eighties the agency struggled to get on its legs and working properly, including things such as having adequate funding, revealing fraud in an important independent testing company, political twisting on different amendments, and actually getting down to the task of evaluating all chemicals already in use (and farmers have been using methods of chemical pest control at least since the time of ancient Rome, more about that in this piece on pesticide history by entomologist K. Delaplane).

In the nineties important amendments were finally in place, such as the Food Quality Protection Act 1996. Neuroscientist Alison Bernstein, who studies the effect of pesticides on Parkinson’s disease, notes several other amendments which have continued improving the process in her article on pesticides:

Other laws (the Food Quality Protection Act of 1996, the Pesticide Registration Improvement Act of 2003, the Pesticide Registration Improvement Renewal Act of 2007 and the Pesticide Registration Improvement Extension Act of 2012) have amended this process.

Under these laws, new pesticides need to be registered before the can be sold and distributed. Existing pesticides must be reevaluated every 15 years to incorporate new data and ensure that they continue to meet current safety standards. All pesticides registered prior to the introduction of the Food Quality Protection Act in 1996 were also reassessed.

In other words, nowadays all pesticides must go through extensive testing before they can become registered and taken into use. From the Food Quality Protection Act 1996:

These tests include: acute toxicity test (short-term toxicity test) and chronic toxicity test (long-term toxicity test). These tests evaluate: whether the pesticide has the potential to cause adverse effects (including cancer and reproductive system disorders) on humans, wildlife, fish, and plants, including endangered species and non-target organisms; and possible contamination of surface water or ground water from leaching, runoff, and spray drift.[9] The registration process can take upwards of 6 to 9 years, and the cost of registration for a single pesticide is in the range of millions of dollars (Toth, 1996).

There is no way something like DDT could pass these tests today. DDT was an endocrine disruptor, it is lipophilic, (it likes to stick to fatty environments such as those found inside organisms), and its half life in humans 6-10 years.

Glyphosate however is not an endocrine disruptor, it is not lipophilic, it is cleared mostly through the gut, and rest through urine. Rats clear all glyphosate from their system within a week, and in known human cases of acute glyphosate poisoning (drinking large amounts of glyphosate), the levels dropped to almost undetectable after 12 hours. The half-life has been estimated to 3 hours, and an analysis of 601 cases of self-poisoning attempts, the fatality rate was 3.2 %, fatalities associated with larger ingested amount and greater age.

Nowadays endocrine disruptor activity, as well as cumulative effects, are some of the standard things that must be tested before something can be approved as a pesticide:

The EPA must find that a pesticide poses a “reasonable certainty of no harm” before that pesticide can be registered for use on food or feed.[9] Several factors are addressed before a tolerance level is established[9]

  • the aggregate, non-occupational exposure from the pesticide (this includes exposure through diet, drinking water, and the use of the pesticide in and around the home);
  • the cumulative effects from exposure to different pesticides that produce similar effects in the human body;
  • whether there is increased susceptibility to infants and children, or other sensitive subpopulations, from exposure to the pesticide; and
  • whether the pesticide produces an effect humans similar to an effect produced by a naturally occurring estrogen or produces other endocrine-disruption effects.

Interestingly, from 60s through 80s, European scientists were criticising US for implementing overly cautious regulations more on the basis of public concern rather than scientific evidence, and European regulations were much less restrictive, which might come as a surprise as people are much more used to thinking the opposite. It was only after the eighties when it was Europe’s turn to rely more heavily on precautious principles, even against the better judgement of the scientific community – you can read more about that over at The Regulation of GMOs in Europe and the United States: A Case-Study of Contemporary European Regulatory Politics.

To conclude: people had good cause to raise alarm about the harm from pesticides back in the mid 20th century, as this was the first time the issues were noted with appropriate gravity. The environmental movements of the time were championing for a good cause. As recently as 1980s, there were still hiccups in ensuring a properly meticulous process when it came to regulating pesticides. But when advances are made, it is also important to update one’s information. Many pesticides back in the day were risky, some with potentially grave consequences – but just because all pesticides fall under the same category of usage, it doesn’t mean that a pesticide substance today would be anything like arsenic or DDT.

To get a better understanding of that, let’s look at how glyphosate, and pesticide usage in general today differs from pesticides used before.

6. Is glyphosate an especially dangerous pesticide?

There are many pesticides that have been in use for hundreds of years which carry clear potential for harmful effects for the consumers, such as lead arsenate and other arsenate compounds. The use of these, luckily, has largely been banned or discontinued between 1950s and 1980s. Other pesticides, such as DDT and 2,4,5-T (responsible for much of the ill effects in Agent Orange), were introduced around last mid-century and also became banned a few decades later after clear evidence of harm to humans or the ecosystem had surfaced. The substances introduced during this time (when regulation was non-existent, as outlined above) are probably responsible for much of the reputations pesticides still carry today.

But most of the pesticides in use today are significantly less toxic than those used even a few decades ago, and despite what many might think, glyphosate is actually among the safest of the bunch. If you look at the doses that have proven lethal to half of the laboratory animals tested, the so called Lethal Dose 50 (LD50), you find that some of the most common organic herbicides, such as clove oil, acetic acid, and cinnamon oil, are also more toxic than glyphosate. In fact, when it comes to the lethal dose, even table salt is more toxic than glyphosate (see table below: 3000 vs 4900 mg/kg – toxicity studies on glyphosate LD50 can be found at EPA here, and studies determining the No Observable Adverse Effects Level (NOAEL) here). Other common substances and their LD50 values described here.

This doesn’t mean we don’t have to be careful about glyphosate’s effects – we wouldn’t want to sprinkle salt or concentrated plant oils on our fields either without a good understanding of the consequences.

Screen Shot 2016-09-02 at 09.31.02

University of Florida Pesticide Information Office compared the toxicity of herbicides and household chemicals. The lower the LD50 (dose at which half of lab animals die) value, the more potent the toxicity of the compound. Glyphosate (LD50 4900) is less toxic than table salt (LD50 3000).

In fact there is a lot more focus on what consequences there are to using pesticides than there used to be. DDT, 2,4,5-T, and lead arsenate have been banned. Farmers in the US no longer treat apple orchards with arsenic-containing pesticides (which still contaminate the grapes of some wineries growing in their place, and whose use continued for longer in other countries, such as China).

This switch to less toxic pesticides, which Alison Bernstein talked about above, is part of a process which many consumers may not be aware of. During the past several decades, science and regulatory agencies have moved modern agriculture away from persistent and acutely toxic substances. Milder, more targeted, and much less generally toxic pesticides have replaced older, harsher agents. Thanks to wide adoption of Integrated Pest Management and biotech crops, overall pesticide use is also down.

Agricultural scientist and journalist Steve Savage has written in detail about the kinds of pesticides in use today. Using pesticides in California as his example, he illustrates the major shift toward essentially non-toxic substances, and he compares changes in amounts and toxicities of pesticides used between 1990 and today. He writes:

Most pesticides today have oral ALD(Acute Oral Toxicity)50s of more than 5,000 mg/kg (Category IV) and are less toxic than table salt, vinegar, citric acid, vanillin and many other familiar food ingredients.

University of Florida Pesticide Information Office has also put out a report on this trend towards much more harmless herbicides, called Herbicides: How Toxic Are They? In it, they write:

Although there have been pesticides that were toxic and dangerous to handle, most of these products are no longer used and have been replaced by newer chemistry. Pesticides now must go through rigorous testing by the U.S. Environmental Protection Agency (EPA) before they can be sold. This has led to many herbicides that possess little or no mammalian toxicity and are less harmful than many everyday household products (Table 1). Surprisingly, household chemicals that many of us store under the kitchen sink pose more risk to the handler than herbicides.

For other comparisons, see the excellent piece here by Cami Ryan: The Dose Makes the Poison. Her table also illustrates that rotenone (rarely used in organic farming) and copper sulphate (very common in organic farming) are much more toxic than glyphosate. This begs the question, why are so many people worried about glyphosate, and not other, more toxic pesticides?

The Credible Hulk has written a piece documenting the effects of many of the pesticides which glyphosate has directly helped make redundant, many of which we would need to resort to again, should glyphosate become banned in the EU. In life we rarely choose from a scenario where there is only the risk of one thing to consider. Choosing not to do something has different consequences, and those also carry a risk. What we need to consider, is which of the risks is larger. In his piece, The Credible Hulk writes:

Many people never even hear about the herbicides that were phased out in favor of glyphosate simply because they aren’t pertinent to the anti-agricultural biotech narrative, and because their popularity had waned by the time it had become trendy to demonize GMOs and everything remotely associated with them.
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 harmful: not less.

7. Is there glyphosate in the air and rainwater?

Despite the case for there being less need to worry about glyphosate than most other pesticides, there are still many arguments around which rely rather on making scary claims about the abundance of glyphosate in our environment. They make the silent implication that this level of detection must be significant and should make us worried about health effects. But often the claims of glyphosate in something or other are either misleading or downright false.

One case of hasty reporting about glyphosate being detected in air and rain water has been outlined well in Biofortified, RoundUp in 75 % of air? What the report actually says. It serves to show how people will be quick to grab on to a factoid and make it sound scarier than it is.

The report actually showed that glyphosate use had reduced the overall traces of pesticides found, and replaced many of the older more toxic pesticide traces found earlier (see more about environmental effects in section 13) – and this directly on fields where the pesticides were used. In any case, the study deals with mind-bogglingly fine-tuned detection with mass-spectrometry (as an example, satellites and spacecraft use mass spectrometers for the identification of the small numbers of particles intercepted in space). The pesticides were present in concentrations millions to billions of times below any biological relevance – the ability to even detect them is an ode to the wonders of modern measurement techniques.

Now let’s look at a couple of other more relevant locations (food, bodily fluids) where claims of detection of glyphosate has been used to create alarm.

8. Is there glyphosate in urine?

Hearing that there is glyphosate in your urine may make even small potential health risks seem more personal and tangible to you. Should you worry? If something can be detected in urine it is, firstly, a sign of something being cleared from your body – glyphosate does not accumulate. All of it gets removed from your system. Secondly, with the incredibly sensitive measuring techniques we have at our disposal, we can detect traces of innumerable amount of substances nowadays in most any source. We also ingest minuscule amounts of a mind-blowing number of molecules on a daily basis, a great many of which would cause great harm if they were present in high enough concentrations. But any minuscule number of certain type of molecules will have very little possibility of having a tangible effect on our body simply because of the daunting task of how many of the molecules of our biochemistry the few molecules would have to interact with to actually make a difference. They will drown in the flood of water, stomach acids, bacteria, proteins, fats, carbohydrates and minerals constantly a-flush in our digestive system.

So, what does the science say about the amounts of glyphosate residue detectable in urine? This review-article, A critical review of glyphosate findings in human urine samples and comparison with the exposure of operators and consumers, concludes as follows:

A critical review and comparison of data obtained in a total of seven studies from Europe and the US was performed. The conclusion can be drawn that no health concern was revealed because the resulting exposure estimates were by magnitudes lower than the ADI [acceptable daily intake] or the AOEL [acceptable operator exposure level].

And we know from the examples earlier that even the acceptable daily intake is set at an incredibly low level – hundred times lower than the level which has showed no observable adverse effects in the most sensitive lab animals tested. The levels of glyphosate in urine, in other words, are ridiculously small.

Anyone trying to scare others about the levels of glyphosate in their urine is making irresponsible claims and using a ethically questionable emotional tactics. If someone is making claims of harmful levels of glyphosate in urine, they are doing so without reliable scientific evidence.

9. What about breastmilk?

The claim of risky levels of glyphosate in breastmilk (along with many other out-there ideas about glyphosate – see for instance her latest claim and its flaws laid out here: ‘there is glyphosate in vaccines‘) originates from the activist organisation Moms Across the America (MAA). Journalist Kavin Senapathy has tried to engage the MAA leader Zen Honeycutt in civil discussion several times without much success. She has also written about Zen’s campaigns on Forbes. In one of her articles Kavin Senapathy writes:

MAA promotes the evidence-scarce “glyphosate as bogeyman” tale as gospel. Though the herbicide is less acutely toxic than caffeine, table salt, and some pesticides used in organic farming, Honeycutt insists that residues affect our gut microbiomes, which Moms Across America has linked to myriad ailments including autism, allergies, infertility, eczema, fibromyalgia, Crohn’s Disease, childhood tantrums and pneumonia.

If there was evidence for a role of glyphosate in any of the above mentioned ills, it would be easy to see why glyphosate in breast milk would scare you. But the evidence for that, or any realistic connection between glyphosate and tantrums, autism, or any other ailment from that list, is sorely lacking. The ‘finding’ itself – of glyphosate residue in breastmilk – comes from an incorrectly processed assay of ten samples with a method that is known to generate false positives, gathered and reported by none but Zen Honeycutt herself, and made public by her posting about it on her MAA website. Meanwhile, real scientific study by a lactation physiologist confirms the opposite. WSU reserachers find breastmilk is glyphosate free:

“The Moms Across America study flat out got it wrong,” said McGuire, who is an executive committee member for the International Society for Research in Human Milk and Lactation and a national spokesperson for the American Society for Nutrition. “Our study provides strong evidence that glyphosate is not in human milk. The MAA findings are unverified, not consistent with published safety data and are based off an assay designed to test for glyphosate in water, not breast milk.”

For a great discussion about breast milk research, as well as the ELISA assay and its limitations, you can listen to the podcast where geneticist Kevin Folta interviews the lactation researcher McGuire and the analytical chemist Thomas Colquhoun: Glyphosate in breast milk and wine?

There has also been a german study of 114 mothers, which did not find any glyphosate in breast milk, and a study outlining the flaws and implausibility of the MAA ‘finding’ based on earlier animal studies. Yet another study confirmed the lack of glyphosate in any of the following:

Residues were not detected in soy milk, soybean oil, corn oil, maltodextrin, sucrose, cow’s milk, whole milk powder, or human breast milk.

The claim from MAA is an example of a particularly unethical practice: fabricating an issue for breastfeeding parents to worry about, in a time when the world is so safe, that worry and anxiety themselves are real and larger concerns (see the Harvard overview on Anxiety and Physical Illness) than many of the things we actually worry about.

10. Should we worry about glyphosate in wine?

You may have heard a warning about glyphosate residue in wine. This warning has been coupled with an out-of-context alarm about glyphosate as a carcinogen. Sometimes the lack of perspective is so tangible it boggles the mind. Please read Kevin Folta’s apt summary on the issue below:

wine glyphosate

Kevin Folta on fears of glyphosate residue in wine. Photo at GLP

Again, for a great discussion about the unqualified wine ‘finding’, as well as ELISA assay and its limitations, you can listen to the podcast where geneticist Kevin Folta interviews the analytical chemist Thomas Colquhoun: Glyphosate in breast milk and wine?

More on glyphosate omnipresence

Considering that new scares about glyphosate in x drops in, I might as well add some here as they come.


Latest headlines: glyphosate in honey found mentioned in a FOIA request on FDA. As there isn’t much more information on the data, let’s just assume these three samples tested were accurate. They apparently found 22, 41, and 170 ppb levels of glyphosate residue, which is 0.022-0.170 mg/kg honey. If you notice, even the rumour about glyphosate in wine above claimed 1 ppm (1000 ppb). So, is there need to worry? To get to the most restrictive daily allowed limit (the European one at 0.5 mg/kg body weight per day, note this is the still safe limit with a hundred-fold safety margin) a person would have to ingest about 3 kg honey per kg body weight in one day.

To even attempt a temporary inhibitive effect from glyphosate on our gut bacteria (see more in Does Glyphosate Harm Gut Bacteria?), you’d have to aim higher – around 3000 kg, 3 tons, of honey in one go. Though we may have become pickled in honey long before, and the sugar concentration would have effectively killed most bacteria, not to mention suffocated the poor human drowned in that pool of honey, large enough to submerge even a big person.


The claim ‘there is glyphosate in vaccines’ originates from another not-qualified-use of ELISA assays by the activist organisation Moms Across the America (MAA) and Zen Honeycutt (who is not only against modern farming methods but also vaccines). This assay has not been validated for anything apart from water, and even in water is used as a first screening step because of its chance of giving false positives. That’s why these results of 0.1-3 ppb traces can’t be used as any indication that there would actually be glyphosate in vaccines. Parts per billion, meanwhile are so far below biological relevance that they could not have an effect on our health even if they were there. More about this from Vaxopedia.
For a longer discussion about these claims you can also listen to the podcast Weed killer in vaccines? by the geneticist Kevin Folta, who writes:

They use a kit you can buy on the internet, but fail to use it in the way it is designed. Instead of using it on water, they use it on complex mixtures that yield false positives that are interpreted as legitimate signals.


An Argentine scientist claims they detected glyphosate in female hygiene products at the level of 4 ppm. There is no study, there is a rumoured conference presentation and a video in Spanish from 2015. Nothing has been published. Even if the claims were true, which we can’t tell, 4 ppm is below the highest allowed residue level of 5 ppm, deemed of no risk to the consumers by all scientific literature reviews and a whole slew of scientific organisations like the WHO, FAO, EPA, EFSA… More on this claim from Dr. Jen Gunter at: No, your tampon still isn’t a GMO-impregnated toxin-filled cancer stick.

11. Is wheat toxic because of glyphosate?

Seneff is also the person behind much of the hype about wheat being toxic, for more on that, please see question 3. over at Glyphosate and Health Effects A-Z. Specifically, what comes to celiac disease, the National Academies of Science report in 2015 found no difference between incidences of celiac disease in USA and UK, whereas the countries’ glyphosate usage trends are markedly different:

Celiac-disease detection began increasing in the United States before the introduction of GE crops and the associated increased use of glyphosate; the disease appears to have increased similarly in the United Kingdom, where GE foods are not typically consumed and glyphosate use did not increase.

There are a couple of other people claiming that wheat is toxic, too, but most of those choose to put their bets on wheat itself, not glyphosate. See for instance an analysis of Dr William Davis, author of the Wheat Belly, who blames wheat for causing some 60 widely varied illnesses. The most common denominator for many of them seem simply to be obesity. Toxic wheat -claims have been widely circulated by several mommy-bloggers in many forms.

There isn’t much to add to this sorry tale, other than that it lacks evidence, that pesticide residues in food are carefully monitored and stay extremely low, and again, epidemiological studies have not found any connection between glyphosate and the numerous purported illnesses. For more on the details of glyphosate use in wheat, you can read what agricultural scientists and farmers have to say about it over at WeedControlFreaks, or from the perspective of Nurse Loves Farmer.

When it comes to diets, vilifying any one food ingredient, or even food group, such as carbohydrates, has little basis in scientific evidence. Moderation is the key. Eat a varied diet, lot of vegetables and fruit, don’t eat too much calorie-dense foods – wheat, or any other food, eaten in excess will bring any number of negative health effects, at the very latest as a consequence of obesity.

But what about the environment?

Even if glyphosate poses no risk for the consumers, perhaps its problems lie in the effects on the environment? Let’s look at some of the details. You may have run into one or more of these common concerns below.

  • Are crops drenched in glyphosate?
  • Does glyphosate use enable bad farming practices?
  • What about resistance and superweeds?
  • Does glyphosate interfere with soil organisms or nutrient availability?
  • Does glyphosate harm Monarch butterflies?

Is there any truth to these claims? Let’s look at that next.

12. Are crops drenched in glyphosate?

Some very good sources to turn to on questions about pesticides, farming, and weed control, are agricultural scientist Steve Savage and the weed ecology Professor Andrew Kniss. Steve Savage writes for Forbes, and also publishes most of his journalistic pieces on his blog Applied Mythology. On top of his work on weed science, Andrew Kniss also blogs over at WeedControlFreaks to make agricultural science more accessible to the public. Steve Savage has made some apt comparisons of what we understand as drenching, dousing, or slathering, and how that relates to the amounts of pesticide applied on crops – the amounts are generally hundreds to thousands of times smaller than the words would imply. Most of any pesticide spray consists of water.

To put things in another kind of perspective, Andrew Kniss has written about a comparison of glyphosate and common home-made herbicide mixture of acetic acid, salt, and soap. In his piece Salt, Vinegar, and Glyphosate, he writes:

At the higher labeled rate of 2.5 fluid ounces of product per gallon, there would be 0.07 lbs of glyphosate acid per gallon of mixed product. Similarly converting this to the same units as the LD50 values, 0.07 lbs equals 31,751.5 mg. So it appears that glyphosate, the less toxic chemical, is being applied at a rate 6-times lower compared to acetic acid.

roundup beer

The Iowa Farm Babe made this easy illustration of the rate of glyphosate use

Andrew Kniss also comments on some of the more out-there health-claims made about glyphosate, by pointing out how easy it is to find scary sounding information about common household substances by lifting concepts out of context and misleadingly blowing up their relevance for the consumer:

Truth is, it is easy to make a chemical (any chemical) sound pretty nasty, even if you use verifiable, factual information. For example, sodium chloride, one of the ingredients in the homemade herbicide solution, is mutagenic for mammalian somatic cells and bacteria. Another ingredient, acetic acid, is highly corrosive, can aggravate respiratory disorders, and even cause permanent vision loss. Does this sound like something you want to be spraying in the same yard where your children and pets play? Should you be dousing your yard with a potent chemical cocktail that causes mutations in humans and causes blindness? And now we learn that this chemical cocktail is nearly 10 times more lethal to mammals than glyphosate, one of the most potent weed killers on the planet! If you’re less scrupulous about your sources, you can even find links between acetic acid and a multitude of disorders, including eczema, psoriasis, shingles, and herpes. You read that right; THIS HOMEMADE HERBICIDE MIXTURE MIGHT GIVE YOU HERPES!

So glyphosate is used in small amounts, and it has helped replace many more toxic herbicides. But there is more to the story: how other environmentally crucial farming methods have changed with glyphosate use.

13. Does glyphosate use enable bad farming practices?


Glyphosate helps preserve soil with no-till

Glyphosate is often used in combination with genetically engineered crops, particularly ones which are able to synthesise their aromatic amino-acids even in the presence of glyphosate. They are called RoundUp Ready (RR) crops, and are a big part of the existing Herbicide Tolerant Crops (HTCs). Many people believe this combination of RoundUp and GMO crops to be detrimental to the environment, but there tends to be little evidence to back up their assumption.

The USDA has actually documented the benefits to the environment from the combined use of herbicides and HTCs such as RR crops. The key benefit comes from how glyphosate enables farmers to omit the tilling step – move to no-till. Tilling leads to erosion and nutrient run-off, among other things, and avoiding it has many benefits. At USDA they write:

These trends suggest that HT crop adoption facilitates the use of conservation tillage practices. In addition, a review of several econometric studies points to a two-way causal relationship between the adoption of HT crops and conservation tillage. Thus, in addition to its direct effects on herbicide usage, adoption of herbicide-tolerant crops indirectly benefits the environment by encouraging the use of conservation tillage.

Should farmers be forced to stop using glyphosate, and revert to more tilling as their method of weed control, the prospects of increases in fuel use, reduced sequestration of soil organic matter, increased nutrient leeching, and increase in emissions would be significant.

GMOs and CO2 updated

Infographic from GMOs and the Environment

In other words, glyphosate use is part of the emission reductions attributable to biotechnology crops, which I have discussed earlier in my piece GMOs and the Environment.

This effect would be pronounced even in Europe, where the benefits of glyphosate use are not as large, as it is mostly not used in combination with biotech crops (which brings further benefits). To give an idea about that effect, I translated excerpts of a Finnish news piece on the topic below:

The [potential glyphosate] ban directly affects the cultivation technique. Instead of no-till the fields will have to be tilled. After that, the fields often need to be turned once more and stones must be collected,” the Copa-Cogeca Secretary-General Pekka Pesonen said.

“Without glyphosate, fuel consumption per-hectare will increase 20 to 30 liters. There will also be more work for the farmer, 15 to 18 hours more per hectare,” the German sugar beet farmer Bernhard Conzen said.

Tilling is one of the most detrimental methods for the environment. The less we rely on tilling, the better for the goal of sustainable farming practices. For more on that, you can read an excellent piece on what sustainable practices mean on Biofortified. The weed ecology professor Andrew Kniss has also written on the subject. In his excellent piece about trade-offs in agriculture, he writes:

If we truly want to encourage crop diversity, then glyphosate use can be a powerful tool in allowing those diverse crop rotations while still managing weeds.

And what about the environmental costs of reducing glyphosate use? One study estimates that using glyphosate herbicide in conjunction with glyphosate-resistant corn and soybean have prevented 41 billion lbs of CO2 from being released into the atmosphere between 1996 to 2013. Adoption of glyphosate-resistant soybean was recently estimated to have increased soil conservation tillage practices by 10, and notill adoption by 20%.These practices help reduce soil erosion, and the many environmental problems associated with soil erosion. Is a reduction in glyphosate worth an increase in erosion and worsening climate change? I acknowledge this trade-off is far too simplistic, as there are ways to mitigate these impacts. But those options have costs also.

It is not enough to pose the question: does glyphosate present a risk? We also have to take in consideration the question: what are the risks if we do not allow farmers to use glyphosate?

If you listen to the sugar beet farmers who are hurt by companies yielding before popular fears of glyphosate and biotechnology, the risks are great indeed. In the NPR piece  As Big Candy Ditches GMOs, Sugar Beet Farmers Hit A Sour Patch:

Part of Grant’s intense interest in [GMO] beets definitely stemmed from his own farm’s experiences with the “traditional regimen” of herbicide products and application timing and methods. “It was a nightmare,” he recalls of those pre-Roundup days. “We had failures all the time — fields that would become unharvestable because of our failure to control weeds. We had an army of people applying herbicides around the clock or just at night. We did micro-rates, we did maxi-rates, you name it.”

“We had one sprayer for every 500 acres, so eight sprayers running around,” Grant relates. “They would work whenever they could. It might be all night long; it might be 24 hours straight because they had a window.

“It was a horrible life. Just last spring (of 2011), as the Roundup litigation was progressing through the courts and it was unclear whether we’d be able to plant Roundup Ready seed, my sugarbeet manager flat-out told me, ‘If we have to be conventional again, I’m quitting. I can’t do it.’


Glyphosate spraying scheme for RoundUp Ready sugar beets, from WeedControlFreaks.

Andrew Kniss takes a detailed look at the fate of the sugar beet farmers in his piece As consumers shift to non-GMO sugar, farmers may be forced to abandon environmental and social gains, including these alternatives for pesticide application schemes.


What farmers used to spray before RoundUp Ready sugar beets, from WeedControlFreaks.

To summarise: glyphosate is an important tool that helps make farming a more environmentally friendly practice with reduced carbon emissions.

Glyphosate and The Field Ecosystems


Monarch caterpillar feeding on milkweed photo from Wikimedia CC BY 2.0

In my series 17 Questions about Glyphosate, question 14. deals with glyphosate resistant-weeds: whether they pose a problem, and why campaigners against glyphosate should be the last ones to worry about this particular issue. Question 15. looks at the soil ecosystems: what do we know about the effects of glyphosate on soil micro-organisms? Does it affect nutrient balance and mineral uptake? Plus comments on what one troubled study found out about earthworms. Question 16. delves into whether there is a relationship between glyphosate and the situation of Monarch butterflies or bees.

14. What about resistance and superweeds?

Firstly, by talking about superweeds we are getting farther away from understanding a problem. Let’s instead talk about something well defined, without the embellishments and vague impressions added by the term superweed.

A better question would be: is there a problem with glyphosate-resistant weeds? Certainly, weeds developing a widespread resistance against glyphosate would nullify all of its earlier outlined environmental benefits, and farmers would have to revert to tilling as a means of weed control, as well as older, more toxic herbicides. That would be a big blow to the farmers and the environment. Conversely, it would also make the campaigns for a glyphosate-ban redundant, as glyphosate would no longer be used, or its use would be greatly reduced. So… from the perspective of said campaigs against glyphosate, problem solved?

palmer-amaranthThis is the extent of the resistance problem: if resistance becomes all too problematic, farmers stop using glyphosate. Conversely, most people who worry about glyphosate would not deem cessation of its use an issue at all. Isn’t it rather more problematic (from their perspective) that glyphosate use is not creating enough glyphosate-resistant weeds in order to undermine its usefulness to for farmers?

But putting that seemingly solved dilemma aside, are glyphosate-resistant weeds a problem? Will farmers be able to continue its use? If you would like to read more about the world of herbicide resistance, its history, management tools, and future prospects, you can read several informative pieces on that from, you guessed it, the weed ecology professor Andrew Kniss. For instance: The Cost of Precenting Herbicide Resistance, or Herbicide Resistance Predates Herbicides by 80 Years. In The Large-scale Impacts of Herbicide Resistance, he writes:

Since the discovery of glyphosate-resistant Palmer amaranth, arguably the most damaging of all the so-called superweeds, cotton yield in the affected states continues to increase.

To be clear, though, I don’t want anyone to get the impression that glyphosate-resistant Palmer amaranth hasn’t had a major impact. On the contrary, there is ample evidence that farmers in the South have had to adapt to this particular problem by using other herbicides, re-introducing tillage, or using cover crops. These additional weed control practices cost money, and growers with glyphosate-resistant weeds may very well have seen a reduction in their net economic return. There are surely many examples of individual cotton fields where yield was significantly reduced by this weed. But I think it is important to note that these herbicide-resistant weeds have not had the devastating impact on crop yields, at least not on a macro-scale, that is often implied by the sensational coverage of this topic.

15. Does glyphosate interfere with soil organisms or nutrient availability?

There are a couple of claims on glyphosate’s effects in the soil, basically along the lines of: glyphosate interferes with plant mineral uptake in soil, or causes other problems with soil dynamics. The short answer to that is, that there is no evidence of unwanted effects in soil characteristics with appropriate use of glyphosate.

One of the older reviews on the topic, from 1992, has characterised glyphosate in relation to the environment and other organisms as follows:

There is no residual soil activity, it does not leach into non-target areas, and it is non-volatile. It is practically nontoxic to mammals, birds and fish, showing no bioaccumulation in the food chain; it is biodegraded into natural products. When used correctly, glyphosate poses no threat to the environment and its inhabitants.

A 2012 review article published in the Agricultural and Food Chemistry Journal found no difference in plant diseases or mineral nutrient availability with or without glyphosate or RoundUp Ready (RR) crops. That’s not to say that when it’s sprayed, glyphosate could probably have an inhibiting effect on soil bacteria before it gets broken down. At least a temporary inhibition is what happens with sufficient millimolar concentrations in the lab (see here and here), although the dynamics might be different in soil: one study found that glyphosate antibacterial effect seems to be neutralised by the presence of humic acid, which is the major organic component of the soil. This could be part of the reason why an earlier study, from 2001, also found that glyphosate did not affect microbial communities in the soil, and noted that artificial media assays were of limited relevance to what actually happened in the farmed soils. You can also read more about the studies on glyphosate and soil at Biofortified: Does glyphosate restrcit crop mineral uptake?

Jonathan Eisen, the earlier cited microbiome researcher who presented on this topic before the US National Academy of Science, also made the following comment in the discussion following one his blog posts:

I am actually interested in how glyphosate might affect microbiomes. I think it is incredibly unlikely that ingestion of glyphosate in food has any significant effect on microbiomes in animals. But I do think it is possible that glyphosate affects soil and plant microbiomes and that in turn could affect what microbes come into animals (via eating the plants). So I think this is interesting and worth pursuing. This notion is not about glyphosate good or bad. Just about testing the possibility that it indirectly affects animals microbiomes (and if so, this could be a beneficial effect).


Tilling, USDA public domain.

This is an interesting area of research, and it’s always good to keep an open mind and a critical eye out on new evidence accumulating on the topic. A recent seven year field-study, published in 2016, found no effect from glyphosate with RR crops or non-RR crops with regards to macronutrients or exoenzymes (which are signs of microbial activity) in the soil. In fact, no-till and conservation tillage, which glyphosate enables, has a documented positive effect on the soil physiochemical and microbiological properties  – seeing how traditional tilling method is actually a very soil-disruptive type of weed management.

Most  laboratory studies worry about glyphosate’s potential inhibory effect on bacteria, observed when glyphosate concentrations are high enough, but there is also a field study published in 2013, which found that glyphosate present in 50 millimolar concentrations increased bacterial activity and heterotrophic bacterial population:

The results show that in a soil with a long historical use of glyphosate (soil 1), the heterotrophic bacterial population was significantly (p<0.05) increased. Also, by increase in the bacterial population, the herbicide existence as the possible nutrient source is enhanced.

They conclude that said increased microbial activity may be beneficial or detrimental toward plant growth, soil microbial ecology, and soil quality. Perhaps glyphosate use could enrich microbial communities both thanks to no-till and directly through its presence in low concentrations. Perhaps in some situations the concentrations would get too high – like in areas where long cold winter conditions slow down natural breakdown processes – and there could be a noticeable negative effect on the microbial populations. But to determine that, we need good, tangible data of field conditions. The potential relationships at work here are far from simple, and proper conclusions can never be drawn from hypotheses alone.

The gist of this question is quite practical, really: if glyphosate did cause big issues for beneficial soil microbes or nutrient problems for plants, that would soon lead to problems for the farmers. Note that glyphosate has been used for 40 years, and to the best of my knowledge, no such shift has happened. Impacts such as reduced yields, poorer soils, more bacterial diseases, or abnormal development would be something that farmers would be very quick to get to the bottom of.

One of the latest studies on a different vein, but raising alarm about glyphosate in the soil, was one where the researchers claim to show its effect on earthworms. They also make a somewhat contrary finding about glyphosate use increasing soil nutrient levels. Andrew Kniss, again, makes an illuminating analysis of the study in his piece Dead Plants Are Probably Bad For Earthworms.

The short of it is: the amount of glyphosate was an order of magnitude higher than real life scenarios; glyphosate was used in combination with an organic herbicide and the effects of the two can’t be separated; basic understanding of nutrient balance was missing; and vital controls were overlooked. Earthworms did not do as well in soils where all plants had died. The study authors had not thought that this factor would need its appropriate control – a plot where all plants were hand weeded, for instance, or the soil would have been tilled to kill the plants, or another method of plant removal was used. When such crucial controls are lacking, the information content of a study unfortunately drops significantly. Andrew Kniss concludes:

All of the effects on earthworms and nutrients observed in this study could simply be due to killing the plants in the pots. It is perfectly plausible the exact same effects would be observed if the plants were clipped or pulled out of the pots.

In either way, even if this study would not have such blatantly obvious flaws, we could not draw too many conclusions based on its results alone. Science is really not about one study one way or another. To account for bias, misconduct, poor design, random chance, etc, a study needs to go through the scrutiny of the scientific community as well as stand the test of time – it must be confirmed by independent groups of scientists, through several robustly designed studies presenting multiple lines of evidence. Shoddy studies do get published – but they get buried under the larger context of pieces which demonstrate more solid methodology and which do get confirmed by yet other independent research groups. Science works by accumulation. To date, it has not accumulated a convincing body of evidence supporting the existence of big problems for the soil ecosystems from the glyphosate used in farming.

16. Does glyphosate harm Monarch butterflies or bees?


Photo by Ari Helminen, licence CC BY 2.0

Glyphosate is a herbicide, in other words, it is toxic to plants. Its target enzyme is not found in animals, so it is generally not very harmful for insects – and as confirmed by a recent study, even direct sprays are not lethal to bees.

Glyphosate could have an indirect effect on Monarchs, however, because it has enabled great advances in weed management, and as a result, while other farming impacts such as use of resources and nutrient leeching are reduced, the number of weeds such as milkweed, which the Monarchs thrives on, have decreased. In the keynote address which Ted Nordhaus from the Breakthrough Institute gave at the first annual Institute for Food and Agricultural Literacy Symposium, he makes an eloquent point on this issue, should it be so that efficient weed control were behind Monarch decline:

There is a correlation between glyphosate use and butterfly decline. But it’s not that glyphosate is killing the butterfly. It is an herbicide that targets plants, not insects. Rather, glyphosate is killing milkweed, a weed in which monarchs lay their eggs. While the decline of monarch butterflies is an unintended consequence of glyphosate use, the elimination of milkweed is not. It is one of the weeds that the herbicide is supposed to get rid of.

The trade-off here is straightforward and zero sum. You can either have more milkweed in cornfields or higher yields, but you can’t have both. If you choose more milkweed, then you are choosing lower yields, and, all else being equal, that means putting more land under cultivation to achieve the same level of agricultural output. With that comes attendant losses of habitat and biodiversity elsewhere.

Ultimately, the only way to have more monarch butterflies without reducing agricultural output or saving monarchs at the expense of other species is to create more monarch habitat outside of cornfields. This is an effort that a lot of people more concerned about monarch preservation as opposed to scoring ideological points about the food system have begun to focus on.

Another hypotheses put forward in Impacts of genetically engineered crops on non-target herbivores, Bt-corn and monarch butterflies as a case study, is that Monarch populations first boomed a few hundred years ago thanks to farming land area increase, as Monarchs may actually thrive better on cultivated land. Either way, the concern about the Monarchs does not stop at providing them large enough areas for breeding habitats in the US. The piece Monarch Butterfly Studies Tell a Perplexing Tale over Science magazine brings up other crucial aspects:

“But if the problem is that the monarchs are dying during the migration,” Davis says, “I’m not sure just trying to produce more at the start of the [fall] migration is the answer.” Other steps, such as protecting migratory pathways, may also be needed.

The overwintering habitat loss indeed seems to be the bigger factor in Monarch butterflies decline, as the conclusion of a recent study confirms:

…there are statistically significant negative temporal trends at the overwintering grounds in Mexico, suggesting that monarch success during the fall migration and re-establishment strongly contributes to the butterfly decline. Lack of milkweed, the only host plant for monarch butterfly caterpillars, is unlikely to be driving the monarch’s population decline. Conservation efforts therefore require additional focus on the later phases in the monarch’s annual migratory cycle. We hypothesize that lack of nectar sources, habitat fragmentation, continued degradation at the overwintering sites, or other threats to successful fall migration are critical limiting factors for declining monarchs.

Bee health simple

Glyphosate is not on the list of bee problems. If You Care About Bees, Look Past Neonicotionoids as well. It’s more complicated than that.

If we truly are concerned about the fates of endangered species, we should be meticulous in evaluating the evidence for what really are the biggest factors influencing their place in the ecosystem. When it comes to farming, it is important that we use pesticides in a way to make sure we target the harmful insects and reduce the harm on others. The situation of many insects is complex – like in the case of bees, who, while essentially not affected by glyphosate, can be harmed by pesticides, but also do have several larger problems than the widely publicised neonicotinoid pesticides. More often than not, it is farming itself that brings about this difficult balancing act of providing for us while reducing the impacts on the environment. It’s the fact that we are so many, that what we do and the space we take up does greatly affect the environment. It is not an easy problem to solve, but efficient farming methods that leave as much nature outside of cultivated areas as possible are an important part of that puzzle.

Next up, the last question in my series, which could also have been a good starting point:

17. Can mainstream research on glyphosate be trusted? What about conflicts of interest?

science-306840_960_720In my series 17 Questions about Glyphosate, last but not least comes a post about the integrity of research, how funding may influence research results, and what corporate involvement with scientists may entail. And if scientists mostly are not influenced by industry, why are there so many conflicting study results?

What about conflicts of interest and industry funding?

This question often comes up whether the one posing the question knows about a definite connection to industry or not. Sometimes the concern goes as far as to include the ‘medical establishment’ as a pressuring actor that hinders scientists from publishing differing results. What many don’t realise, is that new and different results are the best a scientist could hope for. As long as you have quality evidence supporting your findings, publishing new results that go against an earlier understanding is one of the most exciting things that could happen to a scientist.

What comes to connections to industry, there is a worrisome state of affairs around the concept ‘Conflicts of interest’, or COI. In discussions online people often look first at who has funded a study. That in itself is fine, and it’s good information to have in the background. But that is not what usually happens. Instead, if they find that the study authors have an (openly declared) COI of some kind, they announce that to be the end of discussion – the study’s findings can be dismissed directly.


This break-down of 197 randomly selected safety studies on GE foods demonstrates the lack of funding bias: all the studies follow the same trend no matter funding source. The GENERA database has a collection of over a thousand studies and their funding information.

This is intellectual dishonesty at its finest: using the existence of a COI as a magic weapon that frees one from the need to consider evidence, especially if one does not like the direction of its conclusions. In some contexts, merely implying that a scientist has a connection with industry – any connection, at any point of their career, however flimsy – is taken as near-certain evidence of fraud. Take the case of Kevin Folta: an independent genetics researcher whose non-profit outreach program, where he volunteered his time, received modest amounts of travel money from Monsanto for speaking engagements. When this came to light, he was widely trashed in social media, personally harassed, and his office was broken into – the whole campaign was an attempt to smear him as if he was ‘bought and paid for’.

I was once laughed at by a commenter who implied how ridiculous it was even to consider my words on vaccines – because I had once worked for a pharmaceutical company (but not in vaccine research). Take a moment to think about this. Think of some of your previous employers – or even current ones – what is your relationship to them? Would you wish to distort the truth in order to twist important facts so that they appear in some former employers favour? What lengths would a company have to go to, even a current one, to get you to compromise your integrity by committing fraud, and in so doing endangering your credibility and career?

Being bought and paid for is far less likely, than the option that people on any side of a debate – activists, skeptics, scientists – simply believe they are doing the right thing and think they are seeing things from the correct perspective. But if they all equally sincerely believe they are doing the right thing, how can we know who is actually in the right? The best tool for determining which view indeed lies closest to the truth remains the objective assessment of data. We are easily blinded by our biases, especially when our beliefs are an essential part of our identity. Whoever disagrees with you is not the enemy – the important fight is against our own cognitive failings. This is the science fight: to weed out bias, and get us closer to understanding what truly goes on in the world.

It is bizarre for people to declare a person ‘dirty’ on the basis of them building bridges between the academia and the industry, or for testing an important part of a company’s research at an independent location, or even for something as simple as having once earned a living in one’s field. But it does make for a convenient excuse for not having to listen to anyone with the relevant know-how, and for not getting into the complicated workings of the scientific process.

In science, credibility is everything

It’s important to keep in mind that having a COI does not mean that a study is biased. Alison Bernstein, aka Mommy, PhD, has  written a great piece about this, titled Credibility is Our Currency, over at Biofortified:

While conflicts of interest may lead to research misconduct, they are not evidence of misconduct nor are conflicts of interest necessarily misconduct on their own. The presence of a COI may demand closer scrutiny of the research to determine if misconduct or bias affected the interpretation of the results. However, a COI itself is not research misconduct, nor does the existence of a COI automatically mean that research misconduct occurred. This is not to minimize the importance of the disclosure of COIs. It is this very transparency that allows us to identify problems, limit COIs and scrutinize research that may be biased. In science, credibility is our currency.


No sweetening the deal here

It is very grave and risky business for a researcher to commit misconduct, one that could cost them their entire career. Not only that, to become a researcher is a painstaking and not very well paying process that is hardly attractive if your primary motivation is monetary gain, and unless you actually are interested in finding out how the world actually works. Turning one’s back on all of that may not happen so easily. For perspective, there are a couple of striking examples of results that even go against the clear COI of their authors: Honey-industry funds a comparison study of honey, and the researchers find honey is not better than high fructose corn syrup:

Honey has an aura of purity and naturalness. Fresh air, birdsong, forests and meadows. High-fructose corn sweetener? Not so much. So you might think that honey is better for you. But a study published this month compared the health effects of honey and the processed sweetener and found no significant differences.

The honey industry funded scientists studying honey. And the scientists… swiftly surrender their morals and go against the essence of being a scientists in order to produce a paper that shows how great honey is? If you’ve listened to much of the anti-glyphosate and anti-GMO rhetoric, that surely is the logical conclusion. Funnily enough, in this case the scientists found nothing to make the honey industry happy and went forward to report it anyway. Fancy that! Could it be that these scientists were in it for the science?

There was another ironic case, when an anti-vaccination organisation funded an autism study, and the study showed no connection between the condition and vaccines. The organisation had hoped to confirm a preliminary inclination of some measurable difference in monkey babies’ development after vaccines, but the data came up empty. Needless to say, the group behind the funding was unhappy with its results: Administration of thimerosal-containing vaccines to infant rhesus macaques does not result in autism-like behavior or neuropathology. Newsweek reported on it as well: Anti-vaxxers accidentally fund a study showing no link between autism and vaccines.

But biased studies do get published

So COI alone is definitely not proof of manipulated data or even a study conclusion drawn in the funding parties’ favour. But that doesn’t mean that research misconduct motivated by a conflict of interest could not happen or would not have happened at all. Sadly, sometimes even when a scientist is directly and fully funded by industry advocacy groups, and a Freedom Of Information email request uncovers a clearly communicated expectation that the scientist should find and publish evidence to support a preconceived conclusion, the COIs are swept under the rug by the media.

This, in fact, is what happened with the only case of misconduct/undeclared COI which has come to light on a study of glyphosate. This particular interest which conflicted with objectivity of the research was the interest to find evidence that would reflect negatively on glyphosate and genetically modified crops. The case concerns economist Charles Benbrook and his undisclosed ties to the organic industry, which ended with him losing his position at Washington State University. It was reported on FarmOnline Emails expose anti-GM science for hire, and over at Genetic Literacy Project here and here:

University of Melbourne senior lecturer in food biotechnology and microbiology, agriculture and food systems David Tribe said the FOI email exchange showed that there was a PR plan to produce a predetermined outcome on the efficacy of GMs — not a scientific one.

“This exchange shows that Kailis is prepared to pay for research that has a preordained outcome and is confirmation of bias,” he said.

The hard currency of evidence

But even before the undeclared and inappropriate conflicts of interest came to light, the most important analysis of Benbrook’s claims had already been made. Secondary to any potential agenda or bias he might have had, scientists went straight to the data presented in his studies, they critically evaluated his methods, and pointed out how the conclusions he drew ignored some important factors entirely. They focused at first hand not on what his monetary incentives may have been, but on the value of his work from the perspective of the only hard currency in science: that of evidence.


An example of the hierarchy of evidence in human health topics Wikimedia CC BY-SA 4.0

Evidence is what we should use to evaluate a claim, whether we like the claim or not. Resorting to smear-tactics only obscures the really important discussion underneath. If we want to understand how the world works, critical thinking and careful evaluation of data is what counts.

Some people look at cases of misconduct (cases do get revealed, and papers retracted), at COIs, at single studies which never get confirmed, or point in starkly different directions, and say that science is broken. But this is just the messy process of science in action. Could the process be improved? Certainly, it should be, and improvements do happen.

Meanwhile, scientific process is still, has been for a long time, and will continue to be the best bet we have at getting at true knowledge. This is why we should turn to science with our questions. No matter how much science improves, however, it will always be true that a single study does not a fact make. Science is about degrees of uncertainty – only through entire bodies of research, which together point in a certain logical direction, can we come to any kind of less uncertain conclusion about how the world actually seems to work. A great look at the faulty sides of science and analysis of its self-correcting nature can be found on the journalist blog fivethirtyeight. They write:

…headline-grabbing cases of misconduct and fraud are mere distractions. The state of our science is strong, but it’s plagued by a universal problem: Science is hard — really fucking hard.
If we’re going to rely on science as a means for reaching the truth — and it’s still the best tool we have — it’s important that we understand and respect just how difficult it is to get a rigorous result.

In fact, industry influence has rarely if never managed to sway the state of research – one biased study quickly gets left behind as confirmations fail. This is why the bigger industry bias in fact can be found in marketing and political lobbying, as succinctly presented here by the farmer and science communicator Farm Babe. An academics review paper on Organic Marketing Report shows that wealth of funding is being poured into organisations which oppose pesticides, spend their fund by purchasing adds and billboard campaigns, and targeting parents and health-conscious consumers by scare-campaigns.


The intricate network of activist ‘grass-root’ organisations who are against pesticides and biotechnology and their funding ties to the organic industry from the Organic Market Report.

But haven’t industries influenced the state of research before?

Even in the much publicised recent case of the 70s sugar industry scandal, it’s important to remember the following, very well outlined in this piece: the nutritional sciences field was full of incomplete and uncertain results, and there were many independent scientists looking at both, the health effects of fats as well as sugars, and some simply thought the evidence on one or other was more alarming. One of the scientists who already subscribed to the idea that sugar was the lesser evil, later received undisclosed funding from the sugar industry – a clear breach of research ethics. These ideas were already being battled by several independent scientists, however, and the funding simply aligned with a team who already thought there was more support for the dangers of fats (there are, but that doesn’t mean sugar isn’t also harmful) and the field of human nutrition is an especially hard one, seeing as it is hard to conduct controlled long-time experiments.

Nutritional scientist Andrew Brown examines the topic well in his article, So what if the sugar industry funds research? Science is science, in Slate. He writes:

…a single narrative review was unlikely to sway academic thought for 50 years. The evidence that the nutrition evidence-base was compromised by the review is weak.
Down-weighting or ignoring data from people or sources we dislike without empirical reasons to mistrust the data is to willingly position ourselves in a world with less information in the thin hope that the remaining information will somehow be better—but with no such guarantees.

Science has come a long way from those times both in our knowledge about nutrition and the metabolism, as well as the regular scrutiny of funding sources – this kind of undisclosed sponsorship would never have gone unnoticed today. In any case, scientists and research are much more difficult to influence than public image in the minds of consumers (as the tobacco industry, for instance, learned a long time ago, well outlined in this piece by the Credible Hulk), and the returns of investment are much greater in an avenue where teams of independent scientists aren’t continually poised to go on picking apart any flaws or inconsistencies in the narratives offered.

Thank you for reading my series on glyphosate, especially if you have made it this far! A few concluding words…

New innovative research is always welcome, especially for a substance as widely used as glyphosate. We should always strive to honestly evaluate the evidence before forming our views on a topic. As the numerous examples of this series of 17 Questions About Glyphosate demonstrate, the greatest glyphosate-resistance around may indeed be one of a more psychological kind: it has become a fix idea in many minds that glyphosate must be behind a whole host of ills in our world. Trying desperately to fit the evidence into the idea, rather than allowing our ideas to be shaped by the evidence, is what has resulted in this process of claim-whack-a-mole. I have no doubt that next month some new variation of glyphosate-sensationalist news will give wings to yet another far-fetched or misleading claim. The game might never come to a real conclusion, for it may be that for many, the only acceptable kind of world is one where glyphosate can only be a bad guy.

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If you are interested in other environmental or health topics, you can find my other pieces and further resources under Farming and GMOs, The Environment, and Vaccines and Health. If you would like to have a discussion in the comments below, please take note of my Commenting policy. In a nutshell:

  1. Be respectful.
  2. Back up your claims with evidence.

About Thoughtscapism

Cell Biologist, volunteer science communicator, and fiction writer.
This entry was posted in agriculture, biology, chemistry, environment, health and tagged . Bookmark the permalink.

8 Responses to 17 Questions About Glyphosate

  1. Pingback: 17 Questions About Glyphosate | Thoughtscapism | Rationally Thinking Out Loud

  2. Andy Murray says:

    Thanks. That’s the best roundup of the facts i’ve read so far. Wasn’t meaning to pun but there we go. Thanks for spending the time researching and writing the article. It was totally worth it.

    Liked by 1 person

  3. Pingback: 17 Questions About Glyphosate | Thoughtscapism – Vegan GMO

  4. Pingback: 17 Questions About Glyphosate – GMO Building Blocks

  5. Ross Leadbeater says:

    Great information…
    Thanks for taken the time to put it together in away that is easy to understand.


  6. Jonathon says:

    An older piece, I know, but I have only just discovered this blog. I have always believed glyphosate to be one of the safest of agchems. Yes, I know, ‘belief’ but this is based on things I have read. Don’t get me wrong though because I’m no fan of the overuse or unnecessary use of any chemical. This summary neatly puts the hype into perspective and even mentions my biggest concern with this substance which is the potential to increase resistance and therefore sideline a safe and useful product. I use it myself in a limited way but would stop if I thought it was toxic or persistent in the environment. Well done Iida!


  7. I agree with all the comments; this is an excellent presentation of the issues around glyphosate. Very informative. I like the general aspects of what science can do and not do, also the aspect of vested interest by commercial companies. I would like to see a study of how Monsanto dealt with the initial IARC report and reports prior to it that may have put their product in poor perspective. I know it shouldn’t change the conclusion of the EPA report but experience of how vested interests protect their product is interesting. I think of the sugar industry, tobacco, Shell after Rachel Crason’s ‘Silent Spring’, the dairy industries and ‘fat’ and cholesterol etc.


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