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.
Thank you for this post.
You knew this article would be controversial but you gave us the information anyway.
I learn more every time I read one of your articles.
I am a scientist with years of experience (BS, MS Marine Biology Univ. West Florida1974, 78). In graduate school I was employed by the university’s laboratory co-located on EPA’s Sabine Island toxicity laboratory, near Pensacola Florida. EPA’s research at the time was partially targeted toward “sublethal” affects on aquatic organisms (they were using juvenile Mysid shrimps originally caught in our experimental ponds). The key word being “sublethal”, not the typical LD 50 of adult organisms. Behavioral and fecundity changes were apparent in adults, behavioral changes juveniles and especially affects on larval Mysids. Other aquatic organisms were also evaluated. What they determined about glyphosate was:
Sublethal Effects on Mysid Shrimp
Research indicates that glyphosate exposure can lead to various sublethal effects on mysid shrimp, which are important indicators of aquatic ecosystem health. The following table summarizes key findings regarding these effects:
Effect Description
Behavioral Changes Exposure can alter swimming patterns and feeding behavior, impacting survival.
Physiological Stress Glyphosate can induce stress responses, affecting growth and reproduction rates.
Biochemical Alterations Changes in enzyme activity and metabolic processes have been observed.
Mortality Rates While sublethal concentrations do not cause immediate death, they can increase vulnerability to other stressors.
Implications for Ecosystems
The sublethal effects of glyphosate on mysid shrimp can have broader implications for aquatic ecosystems. As these shrimp serve as a food source for various fish and other wildlife, their health directly influences the entire food web. Additionally, changes in their behavior and physiology can disrupt ecological balance and biodiversity.
Understanding these effects is crucial for assessing the environmental risks associated with glyphosate use and for developing strategies to mitigate its impact on aquatic life.
While I agree with the research the impacts of glyphosate to adult humans is low, I should think all of us need to use caution when applying any herbicide or pesticide.
A good overview on Roundup and its effects, I learned a lot, thanks you for putting the facts out there to clear up a number of issues. I will go back to using Roundup again.
Bill R
How are these ‘facts’ rather than discussions? Use Roundup all you like but not because of any facts in the article.
Show me the studies that prove glyphosate has not effect on the available nutrients in plants and the residue has no impact on the availability of those same nutrients in soil where it has been applied. I know that dairy farmers are recommended to add certain minerals as supplements to overcome the deficiency of dairy feed.
“studies that prove glyphosate has not effect on the available nutrients in plants and the residue has no impact on the availability of those same nutrients in soil”
1) I never said that was true.
2) “no” effect on nutrients is a very strong statement.
The question you need to ask, is there a significant effect? You can search for that.
“dairy farmers are recommended to add certain minerals as supplements to overcome the deficiency of dairy feed” – That may be true, but you do not indicate what kind of deficiency or why there is a deficiency.
The very fact that you admit to the ability of science to measure glyphosate admits the lies that were originally told, that glyphosate is inert immediately upon mineralization. My understanding is that glyphosate breaks down into two separate chemicals which have a half life of 18 months. Farmers are now applying it several times a season because weeds have developed a resistance to it. And the microbes population which breaks it down increases to crowd out other beneficial microbes which are critical to healthy plants. And isn’t it true that since glyphosate is less effective now that Dicamba is now recommended to be added to the application of glyphosate?
You are confusing things:
“that glyphosate is inert immediately upon mineralization.” Inert means it is not reactive, ie it does not affect chemicals or organisms in soil. It does NOT mean it can’t be detected.
You didn’t mention how it kills broadleaf plants like what is in your garden…so if you use horse manure or anything else containing it to fertilize your garden your plants wither and die…
no they don’t. Glyphosate added to soil won’t harm plants. It needs to be absorbed by leaves. Here is some proof.
https://youtu.be/YX8g16R4iws
This attitude to herbicides troubles me. You say elsewhere that vinegar is more toxic than Roundup, but is vinegar used by farmers, gardeners, anyone who has land, around the globe? You say yourself, too much of anything is toxic, even water, which is correct. So too much vinegar, like salt or anything else imbibed by humans and the earth would be toxic. Like a virus which the body can fight, but is overcome by excessive viral load. The body is like the earth, needs balance to thrive and survive. So it’s the ‘too much’ of roundup that is toxic to all of us, earth being the carrier. I feel it’s irresponsible and dangerous to say anything used in massive quantities is ‘safe’. Who knows for sure about anything except statements such as ‘rain is wet’, but there is plenty of evidence to show that risks ARE present; not because of any [or most, some elements are highly toxic in small quantities] single element, but because of the cumulative rate of all the toxins we are chucking into the earth, and ourselves, and others.
You are trying to stretch what I say to use as an agreement. You can’t win a debate that way.
I say vinegar is more toxic then glyphosate – that is a known and accepted fact.
how much is use in the world does not change the fact.
If you want to argue that more glyphosate is used than vinegar – OK. So what.
There have been several legitimate studies regarding glyphosate toxicity in fish.
https://pmc.ncbi.nlm.nih.gov/articles/PMC8146734/
https://pubmed.ncbi.nlm.nih.gov/36103761/
https://link.springer.com/article/10.1007/s00244-023-01015-z
and others.
Of course, some will argue:
https://extension.rwfm.tamu.edu/wp-content/uploads/sites/8/2013/09/Safe-Use-of-Glyphosate-containing-Products-in-Aquatic-and-Upland-Natural-Areas.pdf
Let’s have a look at your first study. In table, there was no effect at 25 mg/L. An effect was seen at 50, 100 and 150 mg/L, but the effect was not concentration dependent.
What is the natural level in lakes and rivers? 0-5mg/L. The very highest level is 1/5 th the level that had no effect on the fish.
What is a normal range for glyphosate? A study in Ontario found “A small percentage of samples exhibited glyphosate concentrations greater than the analytical limit of quantitation (17 microg a.e./L), and the maximum concentration of glyphosate measured was 40.8 microg/L.” 40 ug/L is 0.04 mg/L. This is 0.16% of the safe level found in the study.
It is common for research to use high doses to see an effect. It does not mean the chemical found in normal amounts is harmful.
Great logical revie. Nice job. Stop the fear-mongers!!!
I try – but we’ll never stop them all 🙂
Unfortunately, the Genetic Literacy Project is owned by a PR firm supported by Monsanto and Bayer. https://usrtk.org/our-investigations/jon-entine-genetic-literacy-project/
1) I had a look at the article. It tries to say a lot but says almost nothing. A lot of “he said” and “there were plans”. Then they do the usually indirect arguments to convince the casual reader they are right. They did not present any evidence to support their claim. The best they have is “Bayer paid the Genetic Literacy Project $100,000 from July 2020 to June 2021 for its work “to prevent legislative overreach in genetic engineering,” according to the group’s IRS form 990.” That does not mean GLP is a front for the chemical industry. It just means they are a subject expert and got paid for their knowledge. It also means they understand the value of genetic engineering and think the government should stay out of its development. I agree, and I am not a front for the chemical industry. It proves nothing.
2) Who is USRTK? I had a quick look at their GMO piece. That is a very one sided opinion against GMOs – they clearly don’t want to present the facts. And they go on to link in Roundup – which has nothing to do with the safety of GMOs but it is a common tactic used by groups that have very little science to use to support their opinion.
Clearly USRTK is a vey biased group – so I put no value in their report.
Maybe this article in Bloomberg will help: https://www.bloomberg.com/news/articles/2015-10-02/how-monsanto-mobilized-academics-to-pen-articles-supporting-gmos
You need a subscription to read it.
https://paywallbuster.com/ is quite useful – it didn’t work on Bloomberg but a search of the title of the article revealed many other sources – which it invariably does – most are free or limited to one or more articles. I tried the paywall buster on NY Times and it worked – https://archive.is/20211220012755/https://www.nytimes.com/2015/09/06/us/food-industry-enlisted-academics-in-gmo-lobbying-war-emails-show.html
But perhaps you will have to access it via paywallbuster – https://www.nytimes.com/2015/09/06/us/food-industry-enlisted-academics-in-gmo-lobbying-war-emails-show.html
I have one comment to add to the points you make – and don’t doubt for a second that I more than appreciate efforts to find and share an objective, well-researched, non-biased viewpoint. But humans may not be aware of personal bias. My main question, overall, is whether research accounts for the accumulative effect of human attempts to subvert nature for their own needs. Some use the rationale that population growth means that people will starve and we need to develop more and more methods to increase production. But it has been calculated that the entire global population could fit shoulder-to-shoulder onto the Isle of Wight, a small island off the south coast of Britain. Whether that’s true I cannot confirm – is it a myth? But is it a myth that food production cannot keep up with population growth given that even if the global population fitted shoulder-to-shoulder in England? Given, say half of the globe isn’t currently able to support agriculture, in some respects due to commercial efforts to extract as much as is possible form the earth’s resources, eg dams for water then sold to water bottling companies – as in Australia where whole creeks have dried up, cattle farms die along with the cattle, vets out of business – a town will die. And does.
I ask – what is the accumulative effect of man-made influence on the earth – one isolated instance may not have much effect, so cannot be said to cause caner or whatever on its own, but with many other assaults on human, flora and fauna, saturation point has been reached and disease proliferates, does it not?