Several years ago I was going to write a post about Roundup and glyphosate, its active ingredient, but decided against it because several very good science-based reports were produced by others. Unfortunately, those reviews were not directed towards gardeners and based on frequent discussions on social media, the message is still not getting through to the gardening community.
My goal in this post is not to do my usual deep dive into Roundup, but instead I want to give readers a summary overview of the facts along with references containing more details. I hope that putting all of the information in one spot will make it a useful tool for discussions in gardening social media groups.
Roundup vs Glyphosate
Roundup was originally produced by Monsanto and it contained glyphosate as its active ingredient. Most people recognize and use the name Roundup. Unfortunately, Monsanto (now Bayer) has decided that since this brand name is so well known, they could use it to promote other products, some of which don’t even contain glyphosate.
One Roundup product marketed in Europe is vinegar with no glyphosate, and some products contain both glyphosate and another herbicide.
We really should be talking about glyphosate and not Roundup.
Roundup and Monsanto
Conversations that go something like this, “Roundup is toxic because I hate Monsanto” are illogical.
If you hate Monsanto – that is fine. But your love or hate of the company does not change the chemical properties of glyphosate. One has nothing to do with the other.
Does Glyphosate (Roundup) Cause Cancer?
The general public is more convinced than ever that glyphosate (Roundup) causes cancer because of the recent court cases. I’ve discussed this in detail in Roundup (Glyphosate), Cancer and the Courts.
The result of a court case is the sum opinion of the jury, and it does not represent the scientific facts. There is no doubt that the majority of general public hate Monsanto and Roundup, and they truly believe Roundup causes cancer. But that belief does not make it true.
One of the largest agricultural human heath studies has been following workers using glyphosate, for 20 years, and reported, “Overall rates of cancer in the study remain lower than in the general population, especially cancers of the oral cavity, pancreas and lung.”
The science is quite clear on this, there is no evidence that glyphosate causes cancer and most global health and safety organisations agree. The following infographic was prepared by the Genetic Literacy Project, a group promoting truth in science.
The EU Joins the Group
Update: July 26, 2021. I just saw a report from the EU (European Community) that reviewed the science on glyphosate. This 11,000 page report, looking at over 20,000 studies, concluded that glyphosate is safe and does not cause cancer. The only danger they found was that glyphosate “causes serious eye damage”.
Why is this significant? The EU has banned glyphosate in many applications, on a purely political basis, but the average person used this as “evidence” that glyphosate was harmful and caused cancer. It is good to see that the EU scientific community has finally done a proper review. Hopefully, governments will now catch up with the science.
Glyphosate (Roundup) and GMO
A common argument agaisnt GMO plants is that it encourages the use of Roundup. These two issues are unrelated to one another.
Yes, there are some Roundup-ready GMO crops. But the majority of GMO plants have nothing to do with Roundup and they are not Roundup-ready. See GMO Myths – Understand the Truth About GMO Plants for more details.
You can be against Roundup and be for GMO.
Glyphosate (Roundup) Found in Drinking Water and Babies Milk
Studies have found glyphosate in drinking water and in mothers breast milk. The headlines claimed that this was a huge problem, but when you look at the details you realize that it’s a non-issue.
It’s all about the dose.
Our scientific instruments are so good these days that we can find just about any chemical in water and milk. I reviewed the report that found glyphosate in Spain’s drinking water and calculated that you would need to drink the equivalent of 1,000,000,000 bottles of beer, on a daily basis, in order to reach an unsafe level.
The levels found in the environment and in mothers milk are extremely low and of no health concern.
Glyphosate (Roundup) and Chronic Diseases
Some claim that glyphosate causes all kinds of diseases including, diabetes, neuropathies, obesity, asthma, infections, osteoporosis, infertility, birth defects and non-celiac gluten sensitivity. Many of these claims have been made by Samsel and Seneff.
Anyone who has followed the Roundup debate will recognize the name of Dr. Stephanie Seneff. She has made numerous claims about glyphosate which are quickly discounted by the scientific community “as outrageous use of science”. Dr. Seneff is a computer programmer with no experience in chemistry, plant science or health science. Her most recent claim is that glyphosate is a contributing factor of COVID-19.
Unfortunately, the general public eats up her publicity stunts.
A recent review of the claim that glyphosate causes chronic diseases found no support for the claim and went on to say “Our critical analysis of the commentaries published by Samsel and Seneff reveals that their conclusions are not substantiated by experimental evidence but are based on a type of failed logic known as syllogism fallacies. As Nobel Prize-winning theoretical physicist Richard Feynman famously said, “It doesn’t matter how beautiful your theory is, it doesn’t matter how smart you are. If it doesn’t agree with experiment, it’s wrong.””
Glyphosate (Roundup) and Soil Microbes
It is commonly believed that glyphosate harms soil microbes. When glyphosate was added to soil it was found that “it was rapidly degraded by microbes, even at high application rates, without adversely affecting microbial activity.”
Glyphosate (Roundup) and Gut Bacteria
Numerous recent reports in the media and online claim that science has demonstrated glyphosate affects our gut bacteria, and if true could have serious health implications.
One of the reasons glyphosate is so safe is that it only affects a well understood biochemical pathway called shikimate, which is found in plants but not animals. This is the reason it is not toxic to animals. The shikimate pathway is found in some bacteria that live in our gut.
A recent study claims to have shown that glyphosate can affect these bacteria.
Marc Brazeau is the editor of Food and Farm Discussion Lab and is the Genetic Literacy project’s senior contributing writer. He has done a thorough review of the report claiming a link between glyphosate and gut bacteria and found that the data did not support the conclusions.
The study itself does say, “more studies will be needed to ascertain if there are health implications arising from glyphosate inhibition of the shikimate pathway in the gut microbiome”. The study did not reach any conclusions about glyphosates effect on our health, even though the news reported it with sensational headlines.
Another study found that even levels 50 times larger than the Accepted Daily Intake (ADI) set by European food safety agencies had very limited effect on gut bacteria.
Glyphosate (Roundup) and Bees
A study sprayed honeybees with a normal concentration of glyphosate and found no harm to the bees.
Some studies have looked at bee behavior after exposure to glyphosate, and have reported some learning disabilities in bees. The number of bees studied was very low, and 1/4 of those were lost during the study. Other studies have looked at exposure to very high levels of glyphosate.
Bees certainly have environmental and pest problems, but glyphosate has not been shown to be one of them.
Facts About Glyphosate
Here are some important facts about glyphosate.
- our skins absorb very little
- it undergoes very little metabolism in the body and is mostly excreted
- it has a very low toxicity; the oral LD50 in rats is 4320 mg/kg, significantly less than vinegar
- it quickly adsorbs to soil and becomes inactive
- it has a soil half-life of 50 days, which is short for a pesticide
- plant uptake from soil is minimal
Not Enough Testing!
The anti-Roundup movement is quick to claim that there has not been enough testing, and that the existing testing was done by labs hired by Monsanto. That is nonsense. Over the last 45 years there have been thousands of studies by labs all around the world.
At some point you have to accept the results.
The EPA assessment concludes that there is risk to honeybees and aquatic life. Look on regulations.gov and search for glyphosate.
You expect me to go out and find the information you were reading????
Post the link to your evidence!
From the comprehensive european study you cited. Yes, one can try to keep round-up away from water areas, but even so there’s some possibility that it will leach (or be carried) to nearby ‘aquatic life.’ No?
“The AGG has also compared the outcome of the evaluation with the criteria for classification as provided in Regulation (EC) No 1272/2008. Based on this comparison, AGG proposes that glyphosate fulfils the criteria for classification for Eye Damage Category 1 (H318) “causes serious eye damage” and Aquatic Chronic 2 (H411) “toxic to aquatic life with long lasting effects”.”
” AGG proposes that glyphosate fulfils the criteria for classification for Eye Damage Category” – at what does? Nobody suggests you should spray it in your eyes!!!
Why did you comment on the ‘eye damage’ part of the sentence, yet entirely ignore the part that states “toxic to aquatic life with long lasting effects”?
I don’t have time to check them both.
Ah. Right.
My concern is that over-use of a comparatively safe chemical (and misuse) is causing concentrations beyond the environmental carrying capacity and exposure above safe limits to those with direct frequent contact.
The dose makes the poison.
It’s use should be better regulated and restricted to control for invasive weeds and careful agricultural use (i.e. by season, by weather) to benefit from the good without abusing it with unnecessary applications. (Like our Nitrogen overuse is polluting the gulf of Mexico.)
Also, there is broadcast use of glyphosate in forestry that ought to be scaled back where possible.
I’ve used it carefully gloves, mask, eye protection and covered skin for spot control for a few agressive invasive weeds, and spray based on the plant life cycle. I control benign weeds naturally (with your lawn care tips for healthy grass!)
Like antibiotics, we should use it more wisely.
“concern is that over-use of a comparatively safe chemical (and misuse) is causing concentrations beyond the environmental carrying capacity” – that supported by science.
Use in agriculture has resulted in a large drop in the use of much more toxic pesticides – in North America. In Europe that banned glyphosate in some agriculture it resulted in farmers going back to the older, more toxic technology – and people were happy about it because were only biased against Roundup.
Yes. In Australia the chemicals permitted for pre-harvest crop desiccation include paraquat, diquat, metsulfuron, saflufenacil as well as glyphosate. The government regulator is encouraging a variety of chemicals to minimise the evolution of Roundup-resistant weeds. The old chemicals paraquat and diquat have high acute toxicity to humans (unlike Roundup).
In general crop desiccation results in significantly higher herbicide residues in food than their traditional use directly on weeds. Mostly the public know nothing about this practice which has been around for over a decade, but everybody “knows” that Roundup is the supreme evil.
https://www.pulseaus.com.au/blog/post/broadleaf-crop-desiccation
https://en.wikipedia.org/wiki/Crop_desiccation
It is really nice to see a reasonable response that is not all FOR or AGAINST. Compromise is a lost word in our vocabulary. Thanks.
Soil microbes eat glyphosate for dinner and eventually convert it to CO2 and H2O
Despite all the lawsuits, Bayer/Monsanto is still going strong and show no sign of decline. Furthermore, the public does trust that Round Up/ glyphosate is safe since people still buy it from big box stores and use it to spray their yards. Just look at what welcomes you the moment you set foot in one of these big box stores: gallons upon gallons of Round Up. In fact, public schools use Round Up on their grounds.
And all this for what? Heaven forbid…weeds.
I personally do not use Round Up and definitely do not trust that it is safe.
Many people do not trust it – many people do not believe science.
If you look at the facts – they are clear – it is one of the safest chemicals – its even less toxic than vinegar.
You mean this one?
Cancer Incidence in the Agricultural Health Study
Overall rates of cancer in the AHS remain lower than in the general population, especially cancers of the oral cavity, pancreas and lung. Lower rates of smoking may partly explain decreased smoking-related cancers such as lung cancer. Beyond smoking, AHS farmers who reported raising animals and handling stored grain were observed to have lower rates of lung cancer, which may be due to endotoxin exposure [see below]. [ In contrast, higher rates were seen for prostate, lip, thyroid, testicular, and peritoneal cancers, and multiple myeloma and acute myeloid leukemia. ] We continue to investigate the reasons for these excesses.
Please note the HIGHER incidence and that it is still being investigated. I too am skeptical of studies funded by the industry that is producing the product. Science doesn’t mean they use the scientific method. No one should believe the science, they should be convinced by the quality of the study. Controls are the Achilles Heel of most glyphosate studies I have read.
“You mean this one?” – not sure what you are referring to?
no link ?
2nd last bullet point in the article says “short for a pesticide” – do you mean for a herbicide?
No. A herbicide is a pesticide and the half life is short for all pesticides.
Robert, I loved this article! I grew up on a farm and I am currently a Athletic Field Manager. Everyone is missing on the Real science behind this! No one listens! You need to create a movie documentary on this issue. I have been sharing for year how the LF 50 of common house hold kitchen ingredients are more deadly than glyphosate. Please keep up the great work. Hell try to get on Joe Rogan podcast to help spead the word.
Robert- firstly, thanks for this interesting and rigorous site. Secondly, your reply to the point about the effects of the loss of weeds is simply wrong. Modern, intensive farms are almost entirely and truly monocultural in the sense of being almost devoid of ‘weeds’. This was never the case in the past, and is not on organic farms.
Now, you can argue that this is progress, that it has lead to increased yields, but there is no doubt that this has lead to a massive reduction in all wildlife, as on intensive farms there is almost no food or habitat. To pretend otherwise, or that herbicides have no part in that, is disingenuous.
Since you did not include mu comments, I have no idea what your referring to?
I agree, modern farming has resulted in loss of wildlife. You can’t blame that on Roundup. It is mostly do to using large tracks of land and not leaving wild areas.
The same happens on large organic farms.
“You can’t blame that on Roundup”.
Well, not specifically. But it’s partly the result of intensive general herbicide and pesticide use. Farms in the past rarely included “wild areas”, as you put it; they didn’t need to, food sources in the form of field weeds were endemic.
Insect numbers have declined catastrophically in recent years in Europe and the US- this is due to several factors, but the ability of farmers to now exclude all plants except their crop is surely one of them. The ultimate result of this loss of insects is obviously unknown (though the situation of Californian almond growers and the destruction of local bee populations by this intensive technique is instructive), but it will surely mitigate to a significant degree the increase in yields provided by such monocultures.
As to direct effects on humans, I don’t doubt the results of your quoted studies – but I do, like many now, wonder to what extent the currently still standard scientific method of isolating each chemical or product and quantifying its effects outside of the environment as a whole, with its vast sum of interactions and relationships, involving an ever-increasing soup of novel materials and chemical combinations, can make truly meaningful statements about ‘safe’ concentrations of any individual product in the world we are creating.
Having said that, I admire anyone writing a horticulture blog who is always pictured in full dinner dress.
A couple of years ago, there was a lot of literature that was anti-glyphosate. I did a search the other day, it was back the other direction. Upon looking at the research closely, I saw the results were conditional. Often the results were contingent on “proper use”. As you pointed out, it has a short half life, so if it is used in the spring, it should not be a problem. It was never intended to be used as a desiccant three days before harvest. I read your critique of the Spanish water study, “The average glyphosate in the 41% of positive samples, was 200 ng/L.” and describing how much beer that you would need to drink to reach unsafe levels (I assume LD50). That is the wrong measure to use because it isn’t the short term poisoning that is the problem, it is the long-term exposure to something that causes genetic change. Only 50 ng/L glyphosate equivalent dilution is necessary to cause liver disease in rats. https://www.nature.com/articles/srep39328
It is like DDT. It isn’t the single dose that will kill you, it is the accumulation within the entire ecosystem that is the problem. It might not even be the chemical by itself, but a synergy with other things in the environment:
https://pubmed.ncbi.nlm.nih.gov/23756170/
“Glyphosate exerted proliferative effects only in human hormone-dependent breast cancer, T47D cells, but not in hormone-independent breast cancer, MDA-MB231 cells…” Since there is an increased pseudo-estrogen load due to micro-plastics and phyto-estrogen load due to an increased consumption of soybeans, we must not exclude issues that Glyphosate may contribute to if not be solely responsible for.
This has been studied by many global organizations and they now all agree that glyphosate is extremely safe – even from cumulative effects.
Is there any number of scientific studies to the contrary that will convince you? I illustrated how the conclusions based on the Spanish Study were flawed. “Global Organizations” are just individuals sitting in offices around the world. Just read this publication: “Glyphosate induces human breast cancer cells growth via estrogen receptors” – https://pubmed.ncbi.nlm.nih.gov/23756170/ – and look at the sections of “similar articles” and “cited by”. Those scientists are global as well. They either have corroborative research have just accepted the premise that there is a problem is true.
Who has better authority?
“Is there any number of scientific studies to the contrary that will convince you?” You don’t need to convince – I am not a glyphosate expert. I am convinced by the fact that the global scientific community is not convinced, and I believe in science.
““Global Organizations” are just individuals sitting in offices around the world.” – no they are not. They are a large group of scientists, who are experts in this field. They read all of these studies and evaluate them – then reach a conclusion based on the data. They have now studied some 20,000 papers to reach this conclusion.
Low yield organic farming requires more land for the same production and therefore leads to more habitat loss.
Thanks for sharing the information
Two things: (1) There is a risk that stopping the use of glyphosate will lead to more toxic substances being used. (2) I personally will not touch the stuff nor advocate its use, (a) out of an abundance of caution, (b) because I don’t want to pay for it; there are other methods available to the home gardener, and (c) because no study to my knowledge has looked at the effects of multiple agents when combined, even in the recommended dosages – for example, all of the additives in food may be safe at the levels prescribed individually, but what happens when they are mixed over time? No one knows.
Hi, I’m not scientist, I don’t use round up, in terms of glyphosate, all I know is that ut was WIDELY used in my country, if I’m not wrong due to the “Plan Colombia”, probably even before, but back then I, like millions of people, wasn’t paying attention in the way I should have, the thing is, this stuff was being “Sprayed” by plane in a vast area of my country. The results? We still have coke fields, (No, my whole country is not a coke plantation, nor a jungle either ) the level of health problems for the people living in those areas is terrible, kids born with deformities, people sick. I know is difficult to fathom the idea of so many organizations being bought to turn their faces away, but I believe it was done. We do nothing by disregarding the suffering of our fellow humans in the name of science. Scientists can get it wrong and now about it, for some reason, I don’t know if motivated by feeling God like, or if for lack of morals, scientists will sell their soul to the companies they work for, or simply have to because they feel their voices won’t be heard(and it won’t, there’s too much money and power behind them) I won’t unsuscribe, because in general I take everything with a grain of salt. I have my position and respect yours. Illiterate or no.