rss-bridge 2026-02-25T13:20:48+00:00

Glyphosate Remains Controversial

Glyphosate is the most used herbicide in the world, with farmers applying about 750 million kg per year. The US is the heaviest user, responsible for 19% of global use. The chemical is popular among industrial farmers because it is safe and effective, and yet it also remains highly controversial. It is also back in the news, and so an update on […]

The post Glyphosate Remains Controversial first appeared on Science-Based Medicine.

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Glyphosate is a non-specific herbicide, meaning it kills most plants. It works by blocking the shikimic acid pathway, which is necessary for the production of important proteins in plants and some microorganisms. It does not affect animals, which is part of the reason it is considered safe for crops. It is currently approved, and has been reapproved, by regulatory agencies in the US, Canada, Europe and Australia.

It is also safer, and this is important, than any other viable alternative herbicide. Its widespread use has arguably reduced human exposure to other chemicals which do not have as good a safety profile. However, there are other alternatives, specifically farming without the use of herbicides, and the use of organic herbicides. However, manually pulling weeds is not practical on industrial scales.

Organic herbicides are considered safer by some because they break down more quickly and do not persist in the environment. But this also means they need to be applied more frequently and at higher doses. So they are considered to have more acute but less chronic toxicity; however, they are not as well studied. Often the “appeal to nature” fallacy is invoked to argue for their safety, but this is not a valid point.

Currently, therefore, there is no perfect solution, which is why glyphosate remains highly used. It remains controversial for several reasons. First, it was originally produced by Monsanto (now owned by Bayer), which is itself a controversial company. Monsanto marketed “Roundup Ready” GMO crops, which could tolerate glyphosate and increased its use, so the herbicide became wrapped up in the anti-GMO messaging.

But there is also a legitimate scientific controversy fueling the public controversy, and it mainly revolves around how best to approach the question of toxicity. As I have discussed previously, we can frame this as a difference between hazard and risk. Hazard is the potential to cause harm, while risk is the actual chance of harm at a given level of exposure. There is no question glyphosate is a potential hazard. It has the potential to be carcinogenic and to be an endocrine disruptor. There is also some potential that, because it affects some microorganisms, it can affect the gut flora of humans and other animals. But is it a risk at actual levels of exposure?

This difference is why the International Agency for Research on Cancer (IARC) designated glyphosate a “probable carcinogen” using their hazard-based approach. But regulatory agencies, using a risk-based approach, have repeatedly found glyphosate to be safe.

Regarding risk, there are two populations to consider—farm workers with potentially heavy exposure to glyphosate, and everyone else exposed only through crops that have been treated with glyphosate. Here is some recent evidence since the last time I wrote about it.

A 2022 systematic reviewof glyphosate and neurological outcomes found no association. Here is a good recent summary of how the regulatory agencies determine safety levels. The EPA, for example, determines a maximum daily exposure “based on amounts that are 1/100th (for sensitive populations) to 1/1,000th (for children) the no observed adverse effects level (NOAEL) identified through a comprehensive battery of animal toxicology studies.”

Research on actual levels of glyphosate in crops and livestock are variable, by country and crop, are mixed. Many crops have no residue or slight residue below regulatory limits, but some do exceed those limits. However, because of the two orders of magnitude margin of safety, none exceed safety limits, even if they exceed the regulatory limits. But you can focus on different parts of this information to either make a case for or against the safety of glyphosate.

The bottom line for consumers has not changed—while there is a potential hazard, consumer exposure levels remain far below a level that plausibly causes any risk. Where the scientific controversy remains heated is over the question of an association with non-Hodgkin lymphoma (NHL), especially for workers with the highest exposure.

These two reviews come to the conclusion that there is a persistent signal in the research for an association between high levels of glyphosate exposure and non-Hodgkin lymphoma. However, this 2023 review aligns more with the opinion of regulatory agencies. It finds that most of the epidemiological studies looking at this question are highly flawed, mainly because they do not control for exposure to other pesticides. Meanwhile, the best epidemiological study found no association between glyphosate exposure, even at the highest levels, and NHL.

While I personally find the evidence overall supports the safety of glyphosate (I feel a risk-based approach is better than a hazard-based approach, there is a wide margin of safety levels, and the best evidence is negative), there is a lot of data that legitimately can be seen as concerning. There is also the question of industry influence in the research. A study from 2000showing glyphosate is safe was recently retracted because of undisclosed industry funding. It is therefore no wonder that the public remains confused and divided on the safety of glyphosate.

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