glyphosate; toxicity and risks of exposure

In 2015, the International Agency for Research on Cancer (IARC), an offshoot of the WHO, classified glyphosate as a probable human carcinogen (Group 2A). A few months later, the EFSA (European Food Safety Authority) and the EChA (European Chemicals Agency) published their own expert reports stating that glyphosate is not carcinogenic, mutagenic, or toxic to reproduction in humans. Other non-European agencies issued similar opinions (see some opinions at the bottom of the page).

Why such a difference in assessment?

Group 2A, which includes glyphosate, covers substances with limited evidence of carcinogenicity in humans but sufficient evidence of carcinogenicity in animals. This list focuses primarily on the danger associated with the agents. The IARC itself states that "The classification indicates the weight of evidence as to whether an agent is capable of causing cancer (technically referred to as ‘hazard’), but it does not measure the likelihood that cancer will occur (technically referred to as ‘risk’) following exposure to the agent (1). It is up to health agencies to study the risks associated with the dose of exposure, i.e., the probability of developing cancer given the level of exposure to the carcinogen.

Ignoring the IARC opinion mentioned above, most of those who campaign against the use of glyphosate prefer to discredit health agencies and question the integrity of the experts involved. Health agencies are accused of being influenced by lobbyists from Monsanto-Bayer, the company that produces glyphosate-based products. Other critics question the health agencies' risk assessment system, their lack of transparency, their disregard for data from sources independent of industry, and the selection by manufacturers of studies that are favorable to them. Could this be a vast global conspiracy orchestrated by a multinational corporation that has bribed all the health agencies?

Rather than falling into the trap of conspiracy theories, which have invaded the internet in recent years, let's return to the definition of danger highlighted by the IARC and the exposure risks identified by health agencies in real-world situations. In reality, there is no contradiction, as the analysis criteria and objectives of these different institutions are not the same. To illustrate their different interpretations, it is more meaningful to take as an example another molecule in group 2A that many French people consume every day without knowing it: acrylamide.

Why choose this molecule?

Excerpts from the CIRC nomenclature

The IARC list can be viewed by clicking ici

Acrylamide forms spontaneously when foods rich in carbohydrates and proteins are cooked at high temperatures (above 120°C). This substance is present in coffee following roasting, but also in many other products subjected to high temperatures, such as roasted almonds, French fries, and even certain cooked vegetables.

Since acrylamide belongs to the same classification as glyphosate, why is no one calling for a ban on coffee? Why is so much energy being expended to combat the use of glyphosate, and nothing against coffee, which contains a substance recognized as a probable carcinogen in the IARC nomenclature?

Because there are no scientific studies showing that coffee consumption increases the risk of cancer (there are even studies that show the opposite due to the antioxidant properties of coffee). The amount of acrylamide in coffee is so low that to reach a worrying level of cancer risk, you would have to drink at least 1,000 cups of coffee a day.

Coffee was considered a probable carcinogen by the IARC for about 20 years before it was removed from its list. This was because it had to be admitted that, in everyday life, the carcinogenic risk is zero, as demonstrated by irrefutable epidemiological studies. However, acrylamide is still listed by the IARC alongside glyphosate and other substances used, for example, in cancer treatment, such as adriamycin, and chloramphenicol, an essential antibiotic according to the World Health Organization.

To quote Paracelsus, “Everything is poison and nothing is without poison; only the dose makes something not a poison.” The lower the exposure to the carcinogen, the lower the risk of developing cancer. This risk is virtually zero when exposure is 700 times lower than the dose considered toxic (a).

The IARC has established that glyphosate is carcinogenic in animals at doses much higher than those used to destroy weeds, i.e., approximately 1,000 times the dose recommended for agricultural use (b). It is important to know whether, at the doses used by farmers, there is still a risk of developing cancer, including in the long term. The conclusions of all the health agencies mentioned above are unequivocal: there is no significant risk under normal conditions of use.

It is mainly when handling containers of glyphosate concentrate that the risk of toxicity can become a concern if the necessary precautions are not taken. This situation is sometimes encountered in rural areas where some farmers do not wear personal protective equipment and are exposed to inhalation for years (soluble glyphosate concentrates often reach 450 grams per liter of active ingredient).

EFSA and Monsanto publications

The EFSA is accused of copying word for word the dossier submitted by Monsanto. With regard to independent studies, the vast majority of studies showing a harmful effect of glyphosate have been declared unreliable. On the contrary, the EFSA claims that it has independently evaluated the studies submitted by industry. Rejecting a copy of a text only makes sense if its content is flawed, regardless of its origin. Should we then rely on robust data that contradicts the documents provided by their public or private authors? If experts consider that a study from an industry source is correct, why should it be ignored? In addition, health agencies require manufacturers to fund long-term studies on hundreds of rats, which no university is capable of conducting.

The IARC did not fail to take industrial studies into account. Of the animal carcinogenicity studies on glyphosate and the eight long-term studies selected by the IARC, four were found to provide sufficient evidence. However, these four studies are mandatory regulatory studies funded by industry: three studies funded by Monsanto in 1981, 1983, and 1990, and one study funded by Cheminova in 1993.

As for the research studies that were not taken into account by the health agencies, this was because they did not meet the criteria for confirming the claimed results. To cite one example, this is why the work of INSERM, although taken into account by EFSA, did not change its opinion. A meticulous protocol is imposed and everything must be verified. the origin of the products tested (are the dosages equivalent to those on the market), the measurement methods, the number of trials, the nature and number of participants in the cohorts, any biases, etc. To identify the hazards and risks of exposure to a substance, EFSA conducts an analysis of all scientific publications, but not just any old how. Studies are selected if they meet the rigorous and mandatory criteria defined in particular in European Union Regulation No. 283/2013. As glyphosate is a highly sensitive subject, it is certain that each publication has been scrutinized by EFSA and other health agencies, especially since Monsanto has been ordered to pay compensation to individuals on several occasions.

Glyphosate and non-Hodgkin lymphoma

It is interesting to revisit a topic often raised by anti-glyphosate activists. Meta-analyses would reinforce the presumption of a link between glyphosate and the risk of non-Hodgkin's lymphoma in farming populations (which is still a rare cancer among farmers). Several recent studies, including a cohort analysis (Andreotti et al., 2018) specifically on glyphosate exposure using the most up-to-date follow-up data, show no association and no dose effect has been demonstrated. The Joint Meeting on Pesticide Residues (JMPR) of the World Health Organization has emphasized that the Agricultural Health Study (AHS) is the only prospective study of good quality.

This is also why, in the United States, Mark McCostlin's widely publicized lawsuit against Monsanto ended in failure. Mark McCostlin was convinced that glyphosate was the cause of his non-Hodgkin's lymphoma, but Judge Brian May ruled that there was no evidence to support the plaintiff's army of lawyers. It should be noted that one of Mark McCostlin's lawyers, who participated in the “Monsanto Papers,” was disbarred after serving two years in prison for attempting to blackmail another pesticide manufacturer.

This is also why, in the United States, Mark McCostlin's widely publicized lawsuit against Monsanto ended in failure. Mark McCostlin was convinced that glyphosate was the cause of his non-Hodgkin's lymphoma, but Judge Brian May ruled that there was no evidence to support the plaintiff's army of lawyers. It should be noted that one of Mark McCostlin's lawyers, who participated in the “Monsanto Papers,” was disbarred after serving two years in prison for attempting to blackmail another pesticide manufacturer.

With regard to mortality, French farmers do not show any higher than normal mortality rates for any type of cancer. On the contrary, their mortality rates are significantly lower than those of the general population for most types of tumors, regardless of whether or not farmers use pesticides.

Thus, to date, there is no robust scientific study showing that the dose of glyphosate recommended for agricultural use presents a proven carcinogenic risk as long as the recommended precautions are applied. This is specified in the INRS summary sheet accessible by clicking here.

A very detailed study by the CNRS on the health risks of glyphosate and glyphosate-based formulations is also available here.

a) Endocrine disruptors, which act at very low doses, do not obey this rule, but their effects on organisms are very different (they disrupt hormone action). Although the data in the literature is contradictory, EFSA published a report in 2017 stating that glyphosate was probably not an endocrine disruptor, leaving the debate open.

b) Since October 2020, glyphosate is authorized at 1080 g/ha/year only in situations of no-till or summer-early autumn tillage in hydromorphic soil or in the presence of regulated weeds (ragweed is mainly concerned in certain departments), in the latter case the dose can go up to 2880 g/ha/year.

c) https://www.europeanscientist.com/fr/opinion/pesticides-et-cancers-chez-les-agriculteurs-la-fuite-en-avant-vers-lirrefutabilite-premiere-partie/

The fierce controversy surrounding glyphosate, sparked in recent years by insinuating journalists, a few militant scientists, and NGOs, has had numerous negative effects and led to abuses that prevent the general public from distinguishing truth from falsehood. The confusion between danger and exposure levels is perpetuated either through ignorance on the part of the authors or deliberately to create a climate of fear. It should also be noted that the teaching of food toxicology is limited in many scientific training programs, including medical universities, which explains why some scientists are unable to distinguish between danger and risk.

Critics of glyphosate are on the lookout for any unfavorable scientific publications. Glyphosate could have an impact on the nervous system, causing memory disorders or depressive syndromes, or could alter gene expression, microbiota development, apoptosis of abnormal cells, etc. (The numerous favorable studies, more than 1,500 over the last decade, are ignored by glyphosate critics). But all these unfavorable studies often suffer from the same flaws: methodological biases, lack of rigor, and failure to translate negative effects into real-life exposure situations in humans. Some studies are sponsored by organizations and companies known for their anti-glyphosate activism; lobbying and conflicts of interest are not always the fault of Monsanto-Bayer.

This is the case of a well-known critic of glyphosate, Christopher Portier, former director of US federal research institutions and recruited by a predatory law firm. He sent letters to European and US health authorities expressing his doubts about the assessment of glyphosate. In an article in the AFIS magazine “Science et Speudo-sciences” dated June 4, 2018, it is stated that C. Portier is "a long-time employee of the Environment Defense Fund, an American environmental NGO that has been campaigning against pesticides since the 1960s. In May 2017, Mr. Portier had been paid for at least two years by an American law firm to prepare a class action lawsuit against Monsanto over glyphosate. Documents declassified by the US courts at the end of 2017 (2) show that Christopher Portier received approximately $160,000 in fees over two years (excluding expenses) to collect scientific information on the dangers of glyphosate that could be used against Monsanto."

Here are a few examples of media campaigns aimed at discrediting glyphosate that have made headlines in the media, on TV channels, and on social networks:

Three questionable studies on glyphosate rejected by the scientific community

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In December 2008, a study from the University of Caen, published in the journal Chemical Research in Toxicology, attempted to highlight the impact of various glyphosate-containing formulations on human cell lines. The authors reported various cell damages (necrosis, asphyxia, DNA degradation, etc.) allegedly induced by glyphosate, its degradation product (AMPA), or an adjuvant present in some preparations. This study was heavily criticized by the scientific community. The French Agency for Food, Environmental and Occupational Health & Safety (ANSES, formerly AFSSA) highlighted three methodological errors:

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The cells were subjected to a pH of 5.8 without a buffer solution for 24 hours. This did not allow observation of the effect of glyphosate, but more likely the effect of an acidic, hypotonic solution on cells. Animal cells tolerate a pH between 7.4 and 6.8 and require a precise ionic environment to survive. In the absence of control cells treated under the same conditions, the effect of glyphosate cannot be confirmed.

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Observations of cell death cannot be extrapolated to the behavior of the entire organism. Many substances cause local cell death without being toxic to the whole organism; this is notably the case with certain disinfectants (some components of eye drops, for example).

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The agency believes that "the authors of the study overinterpret their results regarding potential health consequences for humans, particularly based on an unsupported in vitro in vivo extrapolation."

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In 2010, Argentinian scientists attempted to assess the effects of low doses of glyphosate on development by studying vertebrate embryos. Their study, published in the journal Chemical Research Toxicology on August 9, 2010 (1), notably states that the treated embryos are highly abnormal. This is also a questionable experiment, as the solution used contained a concentration of 72 to 192 mg of glyphosate per liter, which is 720,000 to 1,900,000 times higher than the maximum permitted dose for drinking water in France.

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One of the most controversial and widely publicized studies against glyphosate was conducted in 2012 by molecular biology professor Gilles-Éric Séralini on the toxicity of Roundup and Monsanto's NK603 GM corn. This researcher, a co-founder of GRIIGEN, which opposes the cultivation of genetically modified plants, received support from Elise Lucet in a report by Envoyé Spécial and Le Nouvel Observateur on September 20, 2012, which published an article entitled: "YES, GMOs ARE POISON." However, Gilles-Éric Séralini's study was met with almost unanimous criticism from the scientific community before being invalidated by three large-scale European studies. The study was retracted from the prestigious journal Food and Chemical Toxicology, which had initially published it (it was republished in June 2014 in open access in the German journal Environmental Sciences).

None of the investigative journalists corrected Éric Séralini when he claimed in a report that tap water containing a glyphosate dose of 0.1 micrograms per liter (permitted by regulations) is chronically deadly, which is false. The publication of Gilles-Éric Séralini's study was the subject of a media frenzy orchestrated by a communications agency funded by certain major retailers eager to enter the non-GMO market. A confidentiality agreement was even signed between Gilles-Éric Séralini and some members of editorial staff, such as that of Le Nouvel Observateur. To learn more about this affair, click here.

Glyphosate pissers to the rescue

The campaign against glyphosate launched in April 2018 involved recruiting thousands of volunteers to provide urine samples to determine whether they contained traces of this much-maligned herbicide. Stars Jamel Debbouze and Julie Gayet were enlisted by Élise Lucet for a report on Envoyé spécial, even though the test used, the Elisa method, is known to be flawed, generating more than 80% false positives. This analysis procedure had been recommended by the anti-pesticide NGO Générations Futures. The same samples tested using chromatography coupled with mass spectrometry revealed only trace amounts in 15% to 25% of the samples, with no impact on the health of the volunteers.

Everything mixes together in nature in infinitesimal doses that laboratory analyses can now detect. This is how we can find minute doses of radioactive uranium 235 or even arsenic in the human body without it being a cause for concern. Of course, this is rarely disclosed by anti-glyphosate activists, who use these infinitesimal analyses to fuel their conspiracy theories and chemophobia.

Poor studies marred by undisclosed conflicts of interest

The Italian Ramazzini Institute, known for its partisan stance against pesticides, published a study in its journal in the summer of 2025 claiming to provide significant evidence of a dose-related increase in benign and malignant tumors in rats exposed to glyphosate. This study was promoted by a wide range of NGOs, activists, and sensationalist journalists, political organizations, and interest groups in the US litigation sector. This study aimed to contribute significantly to the debate surrounding the health effects of glyphosate, but the scientific weaknesses of this publication did not attract much attention from the newspaper L'Humanité, Europe Ecology, Le Monde, local newspapers such as Ouest-France, and others. The study was critically analyzed by the renowned biostatistician Robert Tarone in "The Firebreak," a summary of which follows:

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The results provided by Ramazzini's researchers suffered from flawed statistical analysis (using incorrect approximate p-values rather than much higher exact p-values), meaning that the number of significant tumor trends was actually very small.

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The funding for the research was tainted by undeclared conflicts of interest (particularly from the American litigation sector).

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The article's publication process was biased (in a journal controlled by Ramazzini and reviewed by an activist from the Pesticide Action Network).

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The researchers drew conclusions despite the lack of statistically significant evidence in their results tables.

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The researchers chose not to cite or discuss an important study on tumors in rodents that contradicts their findings.

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The summarized results of IARC monograph 112 concerned only observed adenomas, with no apparent progression to carcinomas.

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The three groups exposed to glyphosate in the Ramazzini study all showed no evidence of a trend in tumor incidence across all anatomical sites.

A translation of the article containing more details on this critical analysis is available by clicking here.

The background to the retraction of an article 25 years after its publication

More recently, an article published in 2000 by Williams et al. on the safety of glyphosate in the peer-reviewed journal *Regulatory Toxicology and Pharmacology* was retracted on grounds of scientific integrity, 25 years after its publication. This retraction, predictably, triggered a media campaign by anti-glyphosate groups, amplified in the local press and on social media. This article, accepted in 2000 by health agencies, presented evidence of glyphosate's safety and relied on data provided by the industry. Furthermore, a letter leaked during the preparation of legal proceedings against Monsanto allegedly revealed that the company had participated in writing the article.

The retraction of the article is therefore not based on manipulated data or flawed methodology. The EFSA had already reacted two years ago to this article and the evidence presented, stating that industry involvement had been declared and that the way the article was written did not compromise its scientific content. It is interesting to note that the co-editor of the journal that retracted the article (Mr. Martin van den Berg) is known for his activism against industry and gained notoriety in the early 2000s for his rudimentary blood tests to support NGO campaigns against brominated flame retardants. Further details on this case, which contain other interesting information on the reasons for this retraction, are available by clicking here.

Finally, studies have shown that glyphosate is also an antibiotic and that it degrades the soil microbiome. It can chelate calcium and magnesium, reducing their absorption by plants. These concerns have never been confirmed in soil conservation techniques (particularly no-till farming) where glyphosate is used to destroy cover crops. In fact, the opposite is true: the objective of these farming techniques, widely used especially in the USA, is to restore soil biodiversity. Again, these studies have nothing to do with the reality of agricultural practices and the consequences related to the doses used. It is difficult to imagine how such a priority as restoring soil biodiversity could be thwarted by the application of a toxic substance that would poison the microflora.

Dallas dethroned by glyphosate; a saga that is far from over

Will the definitive ban on glyphosate in agriculture be enough to eliminate this molecule from the environment and from the urine of voluntary urine donors? This is doubtful, as researchers have found that most of the glyphosate found in European rivers does not come from agriculture, but from wastewater treatment plants, from additives used in laundry detergents: aminopolyphosphonates. The war on glyphosate is therefore far from over, with washing machines and the cleaning ladies who use them likely to be the next victims....

Disastrous consequences for everyone

The ban on glyphosate in France compromises the availability of an effective tool for farmers, individuals, and local authorities. The economic consequences are catastrophic, both for farmers who face unfair competition from foreign producers and for local authorities who must resort to weeding, most often by hand, which costs taxpayers a fortune. As for amateur gardeners, they no longer have an effective weeding solution, except for elbow grease, as practiced in the Middle Ages. This is a step back more than a century to satisfy an electoral clientele blinded by backward-looking and anti-progressive extremists.

For more information; the glyphosate saga (a library of articles, press releases, etc.); click here

Opinions of some non-European health agencies on the carcinogenicity of glyphosate
• New Zealand Environmental Protection Authority (NZ EPA, August 2016) “It is concluded that the overall weight of evidence indicates that glyphosate is not carcinogenic” (5.
• Australian Pesticides and Veterinary Medicines Authority (APVMA, September 2016): “The APVMA has concluded that glyphosate does not pose a carcinogenic risk to humans” (6).
• Japanese Food Safety Commission (FSCJ, September 30, 2016): “Glyphosate is not neurotoxic, carcinogenic, toxic to reproduction, teratogenic, or genotoxic” (7).
• Canadian Pest Management Regulatory Agency (PMRA, April 28, 2017): “Glyphosate is not genotoxic and is unlikely to pose a cancer risk to humans” (8).
• US Environmental Protection Agency (EPA, December 12, 2017): “The comprehensive evaluation of the data supports the statement ‘not likely to be a human carcinogen’” (9).

1) ARC Monographs Questions and Answers”, OMS, 2015.
https://pediatraselche.files.wordpress.com/2015/10/monographs-qa.pdf
2) Exhibit 2, UNITED STATES DISTRICT COURT NORTHERN DISTRICT OF CALIFORNIA, ROUNDUP PRODUCTS MDL LIABILITY LITIGATION
3) glyphosate-Based Herbicides Produce Teratogenic Effects on Vertebrates by Impairing Retinoic Acid Signaling
4) Water Research 1 10 2024 Université de Tübingen ; Glyphosate contamination in European rivers not from herbicide application? Glyphosate contamination in European rivers not from herbicide application? - ScienceDirect ♦
5) Review of the Evidence Relating to Glyphosate and Carcinogenicity ur epa.govt.nz
6) Glyphosate sur apvma.gov.au
7) Risk Assessment Report : Pesticides, Glyphosate, Food Safety Commission of Japan sur jstage.jst.go.jp
8) Décision de réévaluation RVD2017-01, Glyphosate sur publications.gc.ca
9) Revised Glyphosate Issue Paper : Evaluation of Carcinogenic Potential sur regulations.gov

Glyphosate: toxicity and exposure risks

EFSA and Monsanto publications

Glyphosate and non-Hodgkin lymphoma

Toxicological characteristics of glyphosate are detailed in the INRS summary sheet.

Three questionable studies on glyphosate rejected by the scientific community