Nothing engenders fear in our modern society quite like the thought that we are being slowly poisoned en masse by pollutants in our food and water. From fluoride in the taps to pesticides in our fruit and vegetables, there’s nothing quite so scary as being told that you might be at risk of disease from something you can’t see and can do nothing about.
Which is where we get the glyphosate controversy.
Glyphosate, commercially sold as the weedkiller RoundUp, is one of the most common products used in the world today. Because of this, it has been researched extensively — virtually everyone in our society is exposed to some amount of it, so we are really interested in whether it is bad for our health.
After decades of research, we can safely say that glyphosate is not harmful to the average person. Despite the recent research, it’s unlikely that glyphosate poses any significant harm.
The first thing we always check is whether something is acutely harmful. This means that we want to know whether it will cause problems in the short term.
Initial studies found that, in this acute phase, even very high doses of glyphosate are safe. The toxicity — whether it will kill you in the next ~24 hours if you drink the stuff — is about as problematic as table salt.
So glyphosate is safe in the short term. But that’s often only a minor concern. Most people who are in contact with glyphosate have only tiny amounts — 1 or 2 milligrams a month — but over their entire lives. This is what’s known as chronic exposure, and it’s a different beast entirely.
For chronic exposure, we often first look at rodent studies to see whether there’s an issue. This is because it’s unethical and impossible to expose people to potentially hazardous substances for their entire lives, so we do it to rats instead.
If you look at the rodent studies, the research is a bit equivocal. There are a few studies that show that may be a risk of cancer at very high doses, but there are an equal number of studies showing the exact opposite. There is also no evidence that glyphosate causes any other health issues in rodents, again except potentially at the very highest doses.
And when I say “high doses”, I mean really high. One study that found potential carcinogenic effects for glyphosate used a dose equivalent to more than 100 grams per day for an adult human.
That’s somewhere around 30,000x the average intake for a person. Not really that useful.
So animal research is a bit of a mixed bag. There might be some risk, but equally there might not.
What about research in people?
The Real Deal
As I said, there has been quite a lot of research into glyphosate in people. Numerous trials have looked at whether it is related to a whole slew of cancers.
Using this combined evidence, from dozens of studies, we can pretty conclusively say: there is no evidence that glyphosate causes most cancers in human beings.
The biggest study done on glyphosate risk is a good example of this — researchers looked at 55,000 people, followed them for decades, and found that there was no increased risk in people who were exposed to higher levels of glyphosate. It showed fairly conclusively that there is no reason to think that glyphosate has any relationship with most cancer at all.
So where are the terrifying headlines coming from?
Well, researchers recently did what’s known as a meta-analysis to look at glyphosate risk for a specific type of cancer — Non-Hodgkin’s Lymphoma. What this means is that they combined all of the studies that have been done looking at this specific cancer, and reanalyzed the data to see if there was a risk. They found that being exposed to the highest levels of glyphosate for long periods of time was associated with a 41% increased risk of developing the cancer.
The problem is, this study had issues. It collected a diverse range of observational studies into one place, and then combined the results into one statistical analysis. To see the problem with combining studies in this way, we can take a look at two of the included studies — one of them measured glyphosate exposure via a single yes/no question, while the other used a detailed interview that looked at a wide variety of exposures. Are those two studies measuring the same thing? It’s hard to know.
And remember, this was only apparent in people who had been exposed to very high levels of glyphosate for long periods of time. These people are likely to be very different to people who are exposed to lower levels of the chemical, and given the nature of this study it’s hard to know whether glyphosate causes cancer, or whether these people were simply unhealthy in other ways.
Overall, even if we accept the results on face value, the study isn’t that meaningful to individuals. The increased risk, in absolute terms, was only about 0.5%, which is much lower than the scary-sounding 41% that’s been in most headlines. It was also for people who have been exposed to very high levels of glyphosate, often for decades. This is very different to the tiny exposure that most people would get from eating fruit and vegetables grown using glyphosate.
Glyphosate might not be so scary after all.
International Cancer Concerns
So why are so many people concerned that glyphosate might give them cancer?
A lot of this comes from a decision from the International Agency for Research on Cancer (IARC), that concluded that glyphosate was a category 2A carcinogen — classified as “probably carcinogenic to humans”.
This sounds scary. It is absolutely not.
The thing about IARC classifications is that they do not define the magnitude of the risk. Both smoking and cured meats are category 1 carcinogens — “carcinogenic to humans” — but one raises your risk of cancer by more than 3000%, the other less than 20%.
IARC classifications may sound scary, but they often aren’t very meaningful to your life.
And all of this is compounded by a recent Californian court decision, which awarded a large penalty against Monsanto, the company that makes RoundUp, for causing a man’s cancer. The problem here is that courts are not arbiters of truth, and scientific fact does not rest on juries. Convincing 12 Californians that something is true is not the same as demonstrating it in a scientific manner, and when we look at the scientific research the answer is very different.
Ultimately, the evidence is clear: glyphosate doesn’t cause most cancers. People who use glyphosate every day for most of their lives might be at an increased risk of a single, rare, type of cancer, but even this hasn’t been well demonstrated. If you’re a farmer spraying glyphosate daily, it’s possible that there’s an increased risk of Non-Hodgkin’s Lymphoma, but even then the absolute risk only increases by about 0.5%.
But for you and me? Average people eating food we brought at the supermarket?
There is no good reason to think that glyphosate causes harm.
There is definitely no evidence that it causes cancer.