Review 585: Glyphosate – Latest Findings

Glyphosate is the most widely – and the most heavily – used pesticide in the world, including on at least 80% of all GM crops. This scale of use, which is likely to skyrocket still further given the current drive to deregulate GMOs, is leading to widespread human exposure, including via contaminated food, water and air. This is confirmed by urine samples, with glyphosate showing up even in urban children far from where glyphosate is most heavily applied. All of which makes glyphosate’s regulation of planetary importance.

Yet when the European Union re-approved glyphosate use for a further ten years at the end of 2023, it ignored not just the concerns of the WHO’s International Agency for Research on Cancer (IARC), but the warnings of many independent scientists who consider glyphosate a serious threat to human and animal health, not to mention global biodiversity. And among those raising the alarm were a group of researchers who had embarked on an extensive long-term cancer study that was already throwing up disturbing results in animals exposed to even low doses of glyphosate.

The final results of that study have now been published, making it still harder for regulators to ignore its finding that glyphosate and glyphosate-based weedkillers cause multiple types of cancer, not least leukaemia, at doses that regulators claim are safe. The results also show that the other ingredients in pesticides containing glyphosate “may increase the risk of cancer, particularly in the case of leukaemia” still further.

The first section of our Review focuses in on this critically important study and the impact of its publication. But the bad news for glyphosate defenders doesn’t stop with this groundbreaking study. That’s because our second section (OTHER RECENT FINDINGS) shows how exposure to realistic levels of glyphosate herbicides also seems to lead to babies being born earlier and underweight, gut microbiome dysfunction, kidney injury in children, a liver disease epidemic, and increased all-cause deaths. Meanwhile, the primary metabolite of glyphosate has been found at very high levels in menstrual products, like tampons, that provide a perfect conduit for direct entry to women’s bloodstreams, so bypassing the body’s detoxification systems.

These extremely worrying findings come at the same time as Bayer is busy campaigning in the US for legal immunity for itself and other pesticide manufacturers – a campaign we will be looking at in detail in our next Review, which zeroes in on the bitter political and legal battles currently being waged over glyphosate.

GLYPHOSATE-CANCER LINK FURTHER STRENGTHENED BY GROUNDBREAKING STUDY

International study reveals glyphosate weedkillers cause multiple types of cancer
A just-published comprehensive two-year-long carcinogenicity study on the world’s most widely used herbicide, glyphosate, involving 27 co-authors from multiple institutions in Europe and the US, has found that low doses of the weedkiller cause multiple types of cancer in rats. In this long-term study on over 1000 rats, glyphosate alone and two commercial glyphosate-based formulations were administered to rats beginning in prenatal life, at doses of 0.5, 5, and 50 mg/kg body weight/day for 2 years. These doses are currently considered safe by regulatory agencies. In all groups of animals given these small daily doses of the herbicide, the researchers write, “we observed a statistically significant dose-dependent increase in the tendency to develop benign or malignant tumours in several tissues”. Most of the observed cancers are rare in Sprague-Dawley rats, with 40% of leukaemia deaths in treated groups occurring in early life. Increased early deaths were also observed for other solid tumours. The leukaemia findings are especially strong and may provide important support for plaintiffs in court cases who allege that exposure to Roundup caused their Non-Hodgkin lymphoma, another type of blood cancer. Glyphosate is used on over 80% of GM crops.

Evidence was ignored in EU reapproval
Despite early warnings of their cancer findings being shared with EU authorities by the Ramazzini Institute overseeing the glyphosate study, this critical evidence was ignored during glyphosate’s reapproval process, resulting in its reapproval for a further ten years. PAN Europe warns that these findings directly contradict EU risk assessors’ conclusions and raise serious concerns about the adequacy of current safety standards and compliance with EU law. Dr Angeliki Lysimachou, head of science and policy at PAN Europe says, “This peer-reviewed publication removes any excuse for inaction. Regulators knowingly excluded critical evidence from the risk assessment. Glyphosate clearly fails to meet the safety requirements of EU law.”

Dutch farmers’ union says if findings are correct, glyphosate should be withdrawn immediately
Responding to the glyphosate study, the main Dutch farmers union, LTO Netherlands, urged a quick assessment by the independent scientific institutes Ctgb (Dutch Board for the Authorisation of Plant Protection Products and Biocides) and EFSA (European Food Safety Authority). “Scientific insights should always be leading in the authorisation of plant protection products,” the advocacy group believes. “Should their analysis show that the research results are correct and there is actually an increased risk of cancer for humans and animals, it is crystal clear to us that the authorisation of glyphosate should be withdrawn with immediate effect,” LTO argues. According to LTO, protecting public health and preventing human suffering must always come first. “On the other hand, we also call for no hasty conclusions to be drawn ahead of the judgement of the scientific institutes appointed to that end.”

Independent scientists praise the new cancer study
Dutch scientists not involved in the newly published glyphosate study have called it “groundbreaking and alarming”, while French researchers called it “well-crafted”. It shows “a clear pattern, very consistent,” says Ad Ragas, professor of risk assessment of chemical substances at Radboud University, a leading university in the Netherlands. Ragas was not involved in the study but confirmed that it was done meticulously. The French toxicologist Laurence Huc, research director at the French National Institute for Agricultural, Food and Environmental Research (INRAE), who was also not involved in the research, praised “a well-designed study with impressive statistical power, which highlights several characteristics of glyphosate toxicity”. She told Le Monde that its results obtained on rodents in the laboratory “are consistent with the available epidemiological studies [on humans]” that indicate a link between occupational exposure to glyphosate and certain blood diseases, notably lymphomas and myelomas. The German epidemiologist Kurt Straif, former head of the carcinogen classification program at the WHO’s International Agency for Research on Cancer (IARC), which classified glyphosate as a “probable human carcinogen” in March 2015, told Le Monde that the new study makes IARC’s conclusion that available animal studies constituted “sufficient evidence” of glyphosate’s carcinogenicity in animals “even stronger”. He also said the finding of an increase in leukaemia at a relatively young age in rodents exposed to very low doses during pregnancy “adds additional concerns” to those already raised by IARC.

ECHA risk assessment expert commends the study
Leading toxicologist Alberto Mantovani, a member of the ECHA (European Chemicals Agency) Risk Assessment Committee, commended the study on his LinkedIn page as a “new and robust multi-centre study” which “uses a protocol encompassing pre- and post-natal development and fulfils the need for sound experimental evidence. The results highlight the tumorigenic potential of glyphosate and glyphosate-based products at dose levels considered as ‘safe’. This new evidence has to be carefully considered by the regulatory authorities globally.” His positive review has attracted a few desperate attempts to discredit the study by various defenders of glyphosate in the comments thread, but it’s clear they are floundering.

Glyphosate’s permitted exposure level must be lowered at least 100-fold – expert
Co-author of the glyphosate study Prof Michael Antoniou of King’s College London commented on the mechanisms by which glyphosate herbicides cause cancer: “Previous work in laboratory rats conducted by my own group in collaboration with the Ramazzini Institute has shown that exposure to glyphosate herbicides results in DNA damage, which appears to be caused by oxidative stress. Given that DNA damage is a major risk factor in cancer formation, I am not surprised with the finding in the Global Glyphosate Study that long-term exposure to glyphosate and commercial glyphosate herbicide formulations, even at low levels that government regulators stipulate as perfectly safe, results in a wide range of different cancers, including leukaemia. When one considers that glyphosate herbicide exposure has also been found to be associated with oxidative stress and leukaemia in human populations, the findings of the Global Glyphosate Study take on even greater significance. These observations suggest that if glyphosate is not outright banned, the permitted daily exposure level needs to be lowered, in my view by at least 100-fold.” (No link in header)

Bayer attacks the new study
Bayer responded to the new glyphosate study by attacking it. It claimed the study exhibits “significant methodological deficiencies”. But according to the German newspaper Taz, when it asked Bayer to be more specific about the study’s failings, “the company did not provide any justification for this accusation”. However, Taz says, “probably in an attempt to undermine the credibility of the study’s authors, the Leverkusen-based company criticised the Ramazzini Institute for having ‘made misleading claims about the safety of various products’ in the past”. Bayer said that some studies the institute had conducted on other substances had not been accepted by the US Environmental Protection Agency (EPA). But Daniele Mandrioli, director of the institute's cancer research centre, told Taz that “the substances identified as carcinogenic in our laboratories sooner or later (sometimes decades later) turned out to be carcinogenic to humans, for example vinyl chloride, benzene, formaldehyde, and asbestos”. He said in the institute’s 50-year history, its studies on more than 200 chemical compounds had been “routinely used worldwide for hazard and risk assessment”.

OTHER RECENT FINDINGS

Prof Michael Antoniou’s inaugural lecture on glyphosate available online
Michael Antoniou’s inaugural lecture as professor of molecular genetics and toxicology at King’s College London is now available online. It’s called “Glyphosate herbicides: safer than table salt or deceptively toxic?” Using cutting-edge molecular profiling methods, Antoniou’s group has shown that exposure to realistic levels of glyphosate herbicides can cause gut microbiome dysfunction, compromised gut integrity, and fatty liver disease – a modern epidemic. Their work also shows that the daily intake levels of glyphosate permitted by regulators need to be drastically lowered to better protect public health.

Glyphosate-based weedkillers may be harming infants
Babies in rural counties of the US that liberally use glyphosate-based weedkillers are born earlier and underweight, a study finds. These changes could result in learning disabilities and an increased risk of infection, researchers reported, resulting in more than $1 billion in health care costs nationwide each year. For the most vulnerable infants, in historically disadvantaged groups, the effect was significantly greater. Low birthweight is an important predictor of health problems, such as delayed cognitive development, and raises the risk of infection and diseases such as diabetes and cardiovascular disease. The study links increase in glyphosate exposure to the rollout of GM glyphosate-tolerant seeds. See also Beyond Pesticides' article on the study.

Glyphosate may be linked to liver disease epidemic, study warns

Glyphosate herbicide exposure may significantly raise the risk of an increasingly common chronic liver disease – metabolic dysfunction-associated steatotic liver disease (MASLD) – even at low exposure levels, according to a new review of more than 40 scientific studies published over the past 17 years. MASLD is a serious type of fatty liver disease. It’s another name for non-alcoholic fatty liver disease (NAFLD). See also this article on a study showing that glyphosate herbicide exposure causes NAFLD.

Higher urinary glyphosate levels linked to all-cause deaths
Higher urinary glyphosate may be associated with more all-cause death, a new study by Chinese scientists finds. The correlation is more pronounced in females. Additionally, glyphosate may have a higher effect on cancer mortality in patients without hypertension.

Glyphosate exposure increases early kidney injury biomarker in children
Previous studies have associated glyphosate exposure with both acute and chronic kidney damage. A newly published study by Mexican researchers focuses on glyphosate’s potential renal impact on children by looking at a specific biomarker – kidney injury molecule-1 (KIM-1) – used in the diagnosis and detection of early kidney damage. They looked for glyphosate in urine samples from urban children and found higher levels of the kidney injury molecule-1 (KIM-1) in individuals with higher levels of glyphosate exposure. KIM-1 concentration rose by 52% on average per unit increase in glyphosate. Glyphosate exposure accounted for about 51% of KIM-1 variability, linking exposure to early kidney changes. The researchers say these signs of pediatric kidney injury “underscore the importance of monitoring glyphosate exposure and its potential renal impact in children”.

Hypothesis: Glyphosate-based herbicides can increase risk of blood cancers through extended persistence in bone
Glyphosate levels detected in the urine of herbicide applicators and the public are relatively stable across space (urban vs rural) and time (weed spray season, not spray season). A scientific paper explores a novel two-part hypothesis: first, the likely reason for the lack of variability in glyphosate levels in urine is that glyphosate stored in bone is excreted gradually over days to weeks, and augments the stable and modest levels of dietary exposure to glyphosate; and second, the prolonged systemic movement of glyphosate into bone marrow and bone extends contact between glyphosate and blood-producing stem cells, increasing the risk of glyphosate-induced breaks and rearrangements in the DNA in these cells, potentially giving rise to blood cancers.

Glyphosate found at very high levels in menstrual products in the UK
AMPA, the main metabolite of glyphosate, has been found in menstrual products at levels 40 times higher than the legal limit for drinking water, according to a report by Pesticide Action Network UK (PAN UK), Women’s Environmental Network and Pesticide Collaboration. This is concerning, according to the authors, because chemicals absorbed through the vagina directly enter the bloodstream, bypassing the body’s detoxification systems. Josie Cohen, interim director at PAN UK, said: “We were genuinely shocked to find glyphosate in tampons sitting on UK shelves. This harmful chemical is already impossible to avoid since it’s sprayed by councils in streets and parks and contaminates much of our food and water due to its overuse in farming. We urgently need to reduce our overall toxic load and shouldn’t have to worry about glyphosate and other highly hazardous pesticides in our period products. This is a blatant gap in health and safety regulation that the government urgently needs to address.” If you’re in the UK, take action to keep pesticides out of period products.

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