There have been dozens of studies on the possible harmful effects of glyphosate. There are many well-funded organizations and tons of lawyers who would like nothing better than to sue Monsanto/Bayer into bankruptcy for promoting Roundup® and there are many environmental and health organizations who claim that glyphosate is harmful to humans.
The claims that glyphosate causes cancer and other ill effects in humans fall into three main categories.
Studies showing a link between glyphosate exposure and cancer: These are mostly studies on animals (rats and mice) that are exposed to large amounts of a certain chemical. Lots of chemicals are associated with cancer in such studies; for example, digesting huge amounts of salt results in cancer and so does ingesting large amounts of alcohol. In the case of glyphosate, most of the studies are not reproducible and in those that are, the effect (cancer) is small and the dosage of glyphosate is equivalent to drinking many liters of Roundup® every day for years. If you are stupid enough to do that then cancer is the least of your problems.
Juries have awarded millions to "victims" of glyphosate: Juries are notoriously bad at evaluating scientific controversies. Smart lawyers can always find scientists or pseudoscientists who are willing to support non-scientific claims. Juries can't recognize a scientific consensus as long as opponents get equal time on the witness stand. Besides, juries are usually very sympathetic to people who have suffered from cancer or any other disease and they are more than willing to award a large cash settlement from a company who they perceive as being able to afford it. Cases that have been decided by judges do not usually find that glyphosate is to blame. (For reasons that aren't clear to me, lawyer scam is a serious problem in the United States but less of a problem in other countries.)
Some agencies err on the side of caution: Some government agencies have at times published reports claiming that glyphosate may cause, or probably causes, cancer in humans. In some cases these agencies are cherry-picking a few animal studies that show an association between glyphosate and cancer and ignoring the majority that don't. In others, they are focusing on studies showing that megadoses of glyphosate cause problems while downplaying the fact that so do other chemicals like salt.
In discussing the possible harmful effects of glyphosate it's also important to recognize that establishing a true causal link between two things requires a mechanism that explains the linkage. For example, if glyphosate really causes cancer in humans then how does it do that? There is no known mechanism whereby a simple chemical like glyphosate can induce mutations in DNA.
Hasn't happened. The vast majority of the scientific studies find no harmful effects of Roundup® on humans.
You may not like Monsanto/Bayer and genetically-modified food for ethical reasons or because the company exploits third-world farmers. These are valid, if controversial, reasons for opposing the spread of genetically-modified crops. Personally I don't have a problem with genetically modified foods, but I do have a problem with the power of large international for-profit companies.
Express your opposition, if it's rational and scientifically based, but don't fall into the trap of opposing GM foods because you think glyphosate is dangerous.
Here's the link to an article from 2018 where he is responding to a court decision: Stop worrying and trust the evidence: it’s very unlikely Roundup causes cancer.
Here's a more recent article (2024) that was also prompted by a court decision where a judge found no evidence that Roundup causes cancer: Federal Court finds insufficient evidence Roundup weedkiller causes cancer. What does the science say?. It's a good read because it points out that there is a controversy within the scientific/medical community but it summarizes the reasons why we should be skeptical of claims about the harmful effects of glyphosate.
He discusses all the points I make at the top of this post.
Those who believe glyphosate causes cancer often refer to the International Agency for Research on Cancer’s (IARC) 2015 report that classified the herbicide as “probably carcinogenic to humans”. This was based on "convincing evidence that these agents cause cancer in laboratory animals."
However, IARC arrived at its conclusion using a narrower base of evidence than other peer-reviewed papers and governmental reviews. Also, unlike other regulatory bodies, it flags any possibility of causing cancer, rather than risk from plausible exposures.
The Food and Agriculture Organization/World Health Organization joint meeting on pesticide residues report in 2016 concluded that glyphosate was unlikely to pose a carcinogenic risk to humans from exposure through the diet.
... Australia’s regulator, the Australian Pesticides and Veterinary Medicines Authority, reviewed the safety of glyphosate after IARC’s determination and concluded, "there is no reliable evidence that products containing glyphosate pose a risk of causing cancer in humans."
Ian Mugrave is implying that most knowledgeable experts think that glyphosate is safe and I agree with him. This point of view needs to be covered in the media.
- How glyphosate (Roundup®) works
- How Roundup® Works
- Roundup Ready® Transgenic Plants
- The Molecular Basis of Roundup® Resistance
- Glyphosate-resistant Weeds
- Roundup® Is Safe
- Test Your Scientific Skepticism
1. He's also passionately interested in observational astronomy.
I heard something a couple of months ago to the effect that some study demonstrating the safety of glyphosate had undisclosed conflicts of interest (something like that; sorry I didn't pay it that much attention and don't recall the details). I assume that's what kicked off the current media interest. I'm assuming for the present that it was just one study called into question, and doesn't affect the overall picture.
ReplyDeleteMeh. Analyzing the evidence studying glyphosate and cancer and concluding the negative hardly repudiates all possible harmful effects of glyphosate in the food chain (e.g. trace metal chelation). It seems speculative to conclude that "Glyphosate (Roundup) is safe". This is akin to saying that my seat belt works and thus my car is safe.
ReplyDeleteWater is safe but you may die from it if you drink too much.
Delete-César
@Anonymous: There's a sense in which your criticism is valid. If there is solid evidence that glyphosate is harmful then it's okay to say that glyphosate is harmful.
ReplyDeleteHowever, in order to claim the negative, i.e. glyphosate is NOT harmful, one would have to rule out all possible causes and speculations and that's impossible. When I say that glyphosate is safe, I am effectively affirming the negative and that's, strictly speaking, not logical.
But we live in the real world where such quibbles don't make a lot of sense. What we are trying to do is refute misinformation and that requires a more realistic expression of the facts. In this case, I'm not saying that there's no evidence that glyphosate causes cancer but it may be harmful for other reasons. I'm saying that there's no evidence that glyphosate poses any significant harm to humans for any reason.
I don't think it's unreasonable to express this view by saying that glyphosate is safe in order to make the point to the general public.
This is related to the concept of a null hypothesis. Is the null hypothesis the idea that an approved medical/industrial chemical is safe if used appropriately? If so, then the burden of proof is one those who want to prove that it is harmful.
The null hypothesis cannot be that every approved chemical is harmful and the burden of proof is on those who have to prove that it is safe under all conceivable circumstances. The fact that it has already been approved means that it has passed the major hurdle where it's safety was evaluated.
What we are seeing in action here is called ad hoc rescue. Some people desperately want to ban glyphosate so if it doesn't cause cancer then they will come up with some other ad hoc excuse such as chelating trace minerals.
It that's debunked then they will find another excuse such as killing off beneficial intestinal bacteria.
"However, in order to claim the negative, i.e. glyphosate is NOT harmful, one would have to rule out all possible causes and speculations and that's impossible. When I say that glyphosate is safe, I am effectively affirming the negative and that's, strictly speaking, not logical."
ReplyDeleteI second this point. Once we start going down this road of splitting hairs, then there is practically nothing that we can call safe. To borrow the example in the post, is salt "safe"? It's possible for it to be harmful, and almost everyone has enough of the stuff in their kitchen to kill themselves a dozen times over. Can we really call it "safe"? And that's not to mention all the other stuff we tend to have nearby; alcohol, bleach, 120 volts AC outlets... the water that comes out of our taps (water intoxication kills a few dozen people each year in the U.S.).
What truly matters risk: the hazard (the potential to cause harm) combined with the likelihood of exposure to hazardous amounts.
For consumers, glyphosate is a non risk issue. The residues found in food are simply far too low. For farmers, it could pose an occupational hazard... but then again the evidence that it causes cancer specifically is very poor at best.