Glyphosate and cancer : buying science

How industry strategized (and regulators colluded) in an attempt to save the world’s most widely used herbicide from a ban


In this report we show how Europe’s pesticide regulation, introduced in 2009, threatened the survival of glyphosate herbicides, the most widely used in the world, and how industry fought back to save its chemical from a ban.

Chapter 1 describes the challenges that confronted manufacturers of glyphosate-based herbicides in 2012 when they had to apply for re-approval in the EU of their active ingredient, glyphosate. Under the 2009 law, pesticide active ingredients are not allowed to be marketed if they have the potential to cause cancer, damage DNA, or have toxic effects on reproduction. This is known as a hazard-based approach. It means that if the pesticide has these effects, in principle, it must be banned. The inherent properties of the chemical are crucial, rather than the – often difficult to predict – risk to humans under certain exposure scenarios. The reasoning that if the pesticide is properly used, people would only be exposed to “safe” doses – the “risk-based approach” – is not permitted for such substances.

This change in law posed a problem for Monsanto and other companies that manufacture or market glyphosate herbicides, because several of the industry’s own animal studies show statistically significant and dose-dependent carcinogenic effects from glyphosate.

Another aspect of the 2009 regulation also posed a problem for industry. In the past, the regulatory assessment of pesticide active ingredients has been based on industry-sponsored studies. These are generally unpublished and are kept hidden from the public and independent scientists on the grounds that they are commercial secrets. But the regulation mandated for the first time that studies from the peer-reviewed open scientific literature must be included in the dossier of documents that the industry submits to regulators in support of the approval of a pesticide.

The challenge to the pesticide companies lay in the fact that while industry studies generally conclude that glyphosate is safe for its proposed uses, many studies conducted independently of the industry disagree. In recent years, a growing number of peer-reviewed studies in the published scientific literature have pointed to the harmful effects of glyphosate and its commercial formulations. Notably, while most industry studies indicate that glyphosate is not genotoxic (damaging to DNA), the majority of independent studies find the opposite.

In 2015 a severe blow hit the industry when the World Health Organization’s cancer research agency IARC published its verdict that glyphosate was probably carcinogenic to humans and that there was strong evidence that it was genotoxic. Glyphosate products represent a lucrative global market that is expected to cross US$ 10 billion by 2021. So the industry had to come up with a strategy to save its chemical.

Monsanto and other glyphosate companies responded to these cumulative threats to their business by sponsoring scientific reviews, published in peer-reviewed journals, which conclude that glyphosate and its commercial formulations are not harmful to health.

In 2016 a series of reviews with favourable conclusions on glyphosate’s safety (we call them the “Intertek papers”) were published in a peer-reviewed journal. The authors were members of the Glyphosate Expert Panel, convened by the commercial consultancy firm Intertek under commission from Monsanto. Monsanto had paid Intertek to convene and facilitate the panel’s work. The specific and stated aim of the Intertek papers was to counter IARC’s evaluation of glyphosate. They unanimously conclude that glyphosate in humans does not harm genetic material or trigger cancer.

In Chapter 2 we identify nine major scientific flaws in the Intertek papers and other industry-sponsored and -supported review articles on glyphosate’s health risks. Specifically, they utilize manipulations such as apparently calculated omissions and the introduction of irrelevant data, confusing the picture and denying the scientific evidence of glyphosate’s harmful effects.

Most importantly, the authors claim to have used a “weight of evidence” approach to assess whether glyphosate is carcinogenic or not, yet in reality, they avoided such an approach.

A weight of evidence approach takes a holistic view of the different lines of evidence, namely:

  • Animal studies
  • Epidemiological data
  • Possible mechanisms of carcinogenesis.

In the case of glyphosate, the different lines of evidence complement each other. For instance, the finding of a significantly increased incidence of malignant lymphoma in three mouse studies is complementary to the association between glyphosate exposure and non-Hodgkin lymphoma in humans. These lines of evidence are in turn supported by convincing evidence for genotoxicity and oxidative stress as possible underlying mechanisms for cancer development.

Altogether evidence exists in all three areas of consideration. A holistic consideration of this evidence inevitably leads to the conclusion that glyphosate is carcinogenic. Instead, the Monsanto-sponsored authors considered the different lines of evidence separately, used false arguments, and concealed or distorted the facts, concluding that glyphosate is not carcinogenic.

One episode that is not objectively addressed in the Intertek papers took place in 1985, when the US EPA classified glyphosate as a possible human carcinogen. The EPA had based its verdict on a significant and dose-dependent increased incidence of a rare kidney tumour in a mouse study submitted by Monsanto. But Marvin Kuschner, a consultant pathologist who was reportedly a member of Monsanto’s Biohazards Commission, re-evaluated the data and claimed to find such a tumour in a control mouse (which did not receive glyphosate), thus removing the statistically significant increase in the incidence of this tumour in glyphosate-treated animals. This finding, if confirmed, would have exonerated glyphosate from suspicion of causing kidney cancer.

Pathologists tasked by the EPA with re-examining the original kidney sections and new sections of the same organs were unable to identify the alleged new tumour. However, four consultants commissioned by Monsanto stated that they were able to confirm Kuschner’s extra tumour. After a long back-and-forth discussion, the EPA moved glyphosate from class C (possible human carcinogen) into class D (not classified for carcinogenicity) in 1988.

In addition to the fact that the Intertek papers themselves were commissioned by Monsanto, many of the authors of these and other industry-sponsored or industry-supported reviews have conflicts of interest with the pesticide and chemical industries. This is shown in Chapter 3. Twelve of the 16 members of the Glyphosate Expert Panel have served as consultants to Monsanto and/or have been employed by the company. Others have different conflicts of interest with industry or industry-linked bodies, notably the International Life Sciences Institute (ILSI), an organization funded by (among others) companies that manufacture and/or market glyphosate products, including Monsanto, Dow, and BASF. These conflicts of interest have often not been made clear to members of the public and media.

Only in the case of one panel member were we unable to find any conflicts of interest, apart from her participation in the Intertek papers. In spite of all this, members of the Glyphosate Expert Panel were claimed in the Intertek papers to be independent.

The notion that glyphosate is not carcinogenic has found backing in the verdicts of several regulatory agencies and expert bodies, including BfR (Germany’s Federal Institute for Risk Assessment), the European Food Safety Authority (EFSA), the Joint Food and Agriculture Organization/World Health Organization (FAO/WHO) Meeting on Pesticide Residues (JMPR), and the US Environmental Protection Agency (EPA).

However, the assessments of BfR and EFSA suffer from fundamental scientific weaknesses and the JMPR’s conclusions are marred by a severe lack of transparency and scientific clarity, as shown in Chapter 4.

As an example of the problems with BfR’s assessment, after the cancer research agency IARC found “sufficient” evidence of a carcinogenic effect of glyphosate in the same four industry studies (two studies with rats and two with mice) in which BfR had previously not been able to detect any evidence of cancer activity, the German authority had to evaluate the assessments of the IARC. As a result, BfR was forced to confirm the statistically significant tumour findings noted by IARC in all four studies. Also, in the remaining three mouse studies of the manufacturers, BfR had to admit the existence of statistically significant and dose-dependent increases in tumours, which it had previously overlooked. As an explanation for its colossal error, the BfR admitted that “initially”, it had “relied on the statistical evaluation provided [by the glyphosate manufacturers] with the study reports”.

This failure of the German authority is particularly explosive because the hazard-based approach in the EU pesticide regulation forbids the authorization of an active substance as soon as there are positive cancer findings in at least two independent animal studies.

In addition, BfR repeatedly confused hazard with risk, apparently deliberately. Our presumption is that this was intended to divert attention from the hazard-based approach of EU law, which, in light of the positive cancer findings in mice and rats in the industry cancer studies, would require a ban for glyphosate.

The whole of the evidence on glyphosate, taken together – animal studies, human epidemiological evidence, and mechanistic evidence – provides ample confirmation of glyphosate’s carcinogenicity. Yet in a similar fashion to the Intertek papers, rather than evaluating the evidence as a whole, BfR separated out the various lines of evidence of glyphosate’s carcinogenicity in order to deny them individually, and finally to discard the isolated evidence as a single random result. It concluded that glyphosate does not warrant a carcinogenic classification.

In parallel with these scientific shortcomings, the regulatory and expert agencies’ reports on glyphosate are also compromised by conflicts of interest, as detailed in Chapter 5. For example, the same people who were involved in the European evaluation of glyphosate in Germany in the 1990s are also involved in the current re-evaluation. Some have evaluated glyphosate for national agencies and then re-evaluated their own previous decisions at the EU and international level, in different positions. This is a problem because if individuals are asked to assess their own earlier assessment, they will not be inclined to admit any mistakes – particularly regarding a politically and economically sensitive issue like the re-approval of glyphosate.

Some people who have evaluated glyphosate for regulatory and expert bodies also have conflicts of interest with industry. For instance, the chairman of the JMPR for glyphosate, Alan Boobis, was also the vice-president of ILSI Europe. In 2012 – the year Monsanto submitted the dossier for the re-approval of glyphosate – the ILSI group received a $500,000 (£344,234) donation from Monsanto and a $528,500 donation from the industry group Croplife International, which represents Monsanto, Dow, Syngenta, and others. The co-chair of the JMPR glyphosate sessions was Professor Angelo Moretto, a board member of the ILSI Health and Environmental Sciences Institute (HESI), and of its Risk21 steering group, which Boobis also co-chairs.

Even the EPA’s forthcoming report on glyphosate – which was widely expected to give the chemical a clean bill of health – has become mired in controversy. According to court filings by people who believe that their cancer was caused by exposure to glyphosate herbicides, a former long-time EPA scientist, Marion Copley, accused former top-ranking EPA official Jess Rowland of colluding with Monsanto to protect the company’s interests and deny that glyphosate was carcinogenic. Copley cited evidence from animal studies and wrote to Rowland: “It is essentially certain that glyphosate causes cancer.” Rowland left the EPA in 2016, shortly after the agency’s favourable report on glyphosate was leaked.

In sum, attempts by agencies and individuals to defend glyphosate and its formulations against evidence that they cause cancer and damage DNA are scientifically unsound and undermined by serious conflicts of interest.

In the light of our findings, we recommend that the evaluations of glyphosate and its formulations by individuals and institutions compromised by conflicts of interest are set aside. If these institutions and individuals wish to address their flawed evaluations, they must openly address the scientific points and evidence raised in this report. For the sake of transparency, they should use only studies available in the public domain. In the meantime, glyphosate-based formulations should be phased out as a precautionary measure. The continuation of the European authorization of glyphosate would lead to an unacceptable risk of cancer, which would be avoided by correctly observing the laws and respecting scientific integrity.

  • Read the full report, Glyphosate and cancer: Buying science, How industry strategized (and regulators colluded) in an attempt to save the world’s most widely used herbicide from a ban, global2000, March 2017.
  • Read Green NGOs blame Monsanto for ‘buying science’ to save glyphosate, euractiv, Mar 24, 2017.

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