Glyphosate Fact Sheet: Cancer and Other Health Concerns

Print Email Share Tweet

Glyphosate, a synthetic herbicide patented in 1974 by the Monsanto Company and now manufactured and sold by many companies in hundreds of products, has been associated with cancer and other health concerns. Glyphosate is best known as the active ingredient in Roundup-branded herbicides, and the herbicide used with “Roundup Ready” genetically modified organisms (GMOs).

Herbicide tolerance is the most prevalent GMO trait engineered into food crops, with some 90% of corn and 94% of soybeans in the U.S. engineered to tolerate herbicides, according to USDA data. A 2017 study found that Americans’ exposure to glyphosate increased approximately 500 percent since Roundup Ready GMO crops were introduced in the U.S in 1996. Here are some key facts about glyphosate:

Consumer market withdrawal planned 

In July 2021, Monsanto owner Bayer AG said it would remove glyphosate-based herbicides from the U.S. consumer market by 2023 due to tens of thousands of lawsuits brought by people alleging they developed non-Hodgkin lymphoma from exposure to the company’s glyphosate herbicides, such as Roundup.

Most widely used pesticide

According to a February 2016 study, glyphosate is the most widely used pesticide: “In the U.S., no pesticide has come remotely close to such intensive and widespread use.” Findings include:

  • Americans have applied 1.8 million tons of glyphosate (or 1.6 billion kilograms) since its introduction in 1974 to 2014. 
  • Worldwide 9.5 million tons (or 8.6 billion kilograms) of the chemical has been sprayed on fields – enough to spray nearly half a pound of Roundup on every cultivated acre of land in the world, according to an examination of data from 1994-2014.
  • Globally, glyphosate use has risen almost 15-fold since Roundup Ready GMO crops were introduced. 
  • Approximately 281 million pounds of glyphosate was applied to 298 million acres annually in U.S. agricultural settings, on average, from 2012 to 2016, according to the Environmental Protection Agency. Most glyphosate was applied to soybean (117.4 million lbs applied annually), corn (94.9 million lbs applied annually), and cotton (20 million lbs applied annually). Many citrus fruits, including grapefruit, oranges, and lemons, and field crops such as soybeans, corn, and cotton have  high percentages of their acres treated with glyphosate. Approximately 24 million pounds of glyphosate are applied to non-agricultural sites annually, on average, from 2012 through 2016, according to EPA.  The majority of non-agricultural use is in the homeowner market. About 5 million lbs is applied annually for residential use.

Statements from scientists and health care providers 

  • Statement by the International Federation of Gynecology and Obstetrics (FIGO) Reproductive and Environmental Health Committee: “We recommend that glyphosate exposure to populations should end with a full global phase out.” (7.2019) 
  • Essay in Journal of Epidemiology and Community Health: “Is it time to reassess safety standards for glyphosate based herbicides?” (6.2017)
  • Consensus statement in Environmental Health Journal: “Concerns over use of glyphosate-based herbicides and risks associated with exposures: a consensus statement” (2.2016)
  • Monsanto owner Bayer AG maintains that glyphosate and glyphosate-based herbicides are safe when used as directed and do not cause cancer.  “Glyphosate is one of the most studied herbicides in the world – and, like all crop protection products, it is subject to rigorous testing and oversight by regulatory authorities,” Bayer states on its website. “There is an extensive body of research on glyphosate and glyphosate-based herbicides…  that confirm that glyphosate and our glyphosate-based formulated products can be used safely and do not cause cancer.”  

Concerns with corporate studies

Regulators in Europe and the United States, Canada and elsewhere have repeatedly affirmed the corporate assertions of glyphosate safety. In coming to determinations about safety these regulators have relied in part on tests that are conducted by or for the companies that have not been published or peer reviewed.  

The corporate studies have long been kept secret, even by regulators. But in Europe, litigation by a group of European Parliament lawmakers led to the release of dozens of such studies. More than 50 of those corporate studies were analyzed in 2021 by two independent scientists – Armen Nersesyan and Siegfried Knasmueller, both from the Institute of Cancer Research, Department of Medicine at the Medical University of Vienna.

The goal of the analysis was to determine if the industry studies examined comply with current international guidelines for chemical testing. 

The resulting analysis was released July 2, 2021 and concluded that the bulk of the industry studies were outdated and did not meet current guidelines. An array of shortcomings and flaws were found in the studies, rendering most of them unreliable, according to the analysis.

In fact, of the 53 studies submitted to regulators by the companies, only two were acceptable under current internationally recognized scientific standards, said Knasmueller. See more details here. 

Cancer concerns

The scientific literature and regulatory conclusions regarding glyphosate and glyphosate-based herbicides show a mix of findings, making the safety of the herbicide a hotly debated subject. 

In 2015, the World Health Organization’s International Agency for Research on Cancer (IARC) classified glyphosate as “probably carcinogenic to humans” after reviewing years of published and peer-reviewed scientific studies. The team of international scientists found there was a particular association between glyphosate and non-Hodgkin lymphoma.

U.S. agencies: At the time of the IARC classification, the Environmental Protection Agency (EPA) was conducting a registration review. The EPA’s Cancer Assessment Review Committee (CARC) issued a report in September 2016 concluding that glyphosate was “not likely to be carcinogenic to humans” at doses relevant to human health. In December 2016, the EPA convened a Scientific Advisory Panel to review the report; members were divided in their assessment of EPA’s work, with some finding the EPA erred in how it evaluated certain research. Additionally, the EPA’s Office of Research and Development determined that EPA’s Office of Pesticide Programs had not followed proper protocols in its evaluation of glyphosate, and said the evidence could be deemed to support a “likely” carcinogenic or “suggestive” evidence of carcinogenicity classification. Nevertheless the EPA issued a draft report on glyphosate in December 2017 continuing to hold that the chemical is not likely to be carcinogenic. In April 2019, the EPA reaffirmed its position that glyphosate poses no risk to public health. But earlier that same month, the U.S. Agency for Toxic Substances and Disease Registry (ATSDR) reported that there are links between glyphosate and cancer. According to the draft report from ATSDR, “numerous studies reported risk ratios greater than one for associations between glyphosate exposure and risk of non-Hodgkin’s lymphoma or multiple myeloma.” 

The EPA issued an Interim Registration Review Decision in January 2020 with updated information about its position on glyphosate, continuing to hold the position that glyphosate is unlikely to cause cancer. 

European Union: The European Food Safety Authority and the European Chemicals Agency have said glyphosate is not likely to be carcinogenic to humans. A March 2017 report by environmental and consumer groups argued that regulators relied improperly on research that was directed and manipulated by the chemical industry. A 2019 study found that Germany’s Federal Institute for Risk Assessment report on glyphosate, which found no cancer risk, included sections of text that had been plagiarized from Monsanto studies.  In February 2020, reports surfaced that 24 scientific studies submitted to the German regulators to prove the safety of glyphosate came from a large German laboratory that has been accused of fraud and other wrongdoing.

In June 2021, the European Union’s (EU) Assessment Group on Glyphosate (AGG) issued an 11,000-page draft report concluding that glyphosate is safe when used as directed and does not cause cancer. The finding is based in part on a dossier of roughly 1,500 studies submitted to European regulators by the “Glyphosate Renewal Group (GRG),” a collection of companies that includes Monsanto owner Bayer AG. The companies are seeking the renewal of the EU authorization of glyphosate. Current authorization in Europe expires in December 2022. The companies say they also gave regulators a “literature review” of around 12,000 published scientific articles on glyphosate.

WHO/FAO Joint Meeting on Pesticide Residues determined in 2016 that glyphosate was unlikely to pose a carcinogenic risk to humans from exposure through the diet, but this finding was tarnished by conflict of interest concerns after it came to light that the chair and co-chair of the group also held leadership positions with the International Life Sciences Institute, a group funded in part by Monsanto and one of its lobbying organizations.

California OEHHA: On March 28, 2017, the California Environmental Protection Agency’s Office of Environmental Health Hazard Assessment confirmed it would add glyphosate to California’s Proposition 65 list of chemicals known to cause cancer. Monsanto sued to block the action but the case was dismissed. In a separate case, the court found that California could not require cancer warnings for products containing glyphosate. On June 12, 2018, a U.S. District Court denied the California Attorney General’s request for the court to reconsider the decision. The court found that California could only require commercial speech that disclosed “purely factual and uncontroversial information,” and the science surrounding glyphosate carcinogenicity was not proven.

Agricultural Health Study: A long-running U.S. government-backed prospective cohort study of farm families in Iowa and North Carolina has not found any connections between glyphosate use and non-Hodgkin lymphoma, but the researchers reported that “among applicators in the highest exposure quartile, there was an increased risk of acute myeloid leukemia (AML) compared with never users…” The most recent published update to the study was made public in late 2017.

Recent studies linking glyphosate to cancer and other health concerns 

Cancer

Endocrine disruption, fertility and reproductive concerns 

Liver disease 

  • A 2017 study associated chronic, very low-level glyphosate exposures to non-alcoholic fatty liver disease in rats. According to the researchers, the results “imply that chronic consumption of extremely low levels of a GBH formulation (Roundup), at admissible glyphosate-equivalent concentrations, are associated with marked alterations of the liver proteome and metabolome,” the biomarkers for NAFLD.

Microbiome disruption

  • November 2020 paper in the Journal of Hazardous Materials reports that approximately 54 percent of species in the core of the human gut microbiome are “potentially sensitive” to glyphosate. With a “large proportion” of bacteria in the gut microbiome susceptible to glyphosate, the intake of glyphosate “may severely affect the composition of the human gut microbiome,” the authors said in their paper. 
  • A 2020 literature review of glyphosate’s effects on the gut microbiome concludes that, “glyphosate residues on food could cause dysbiosis, given that opportunistic pathogens are more resistant to glyphosate compared to commensal bacteria.” The paper continues, “Glyphosate may be a critical environmental trigger in the etiology of several disease states associated with dysbiosis, including celiac disease, inflammatory bowel disease and irritable bowel syndrome. Glyphosate exposure may also have consequences for mental health, including anxiety and depression, through alterations in the gut microbiome.”
  • A 2018 rat study conducted by the Ramazzini Institute reported that low-dose exposures to Roundup at levels considered safe significantly altered the gut microbiota in some of the rat pups.
  • Another 2018 study reported that higher levels of glyphosate administered to mice disrupted the gut microbiota and caused anxiety and depression-like behaviors.

Neurotoxicity

  • A large nationwide study published in the journal NeuroToxicology (December 2021) reports that “several neurotoxic pesticide exposures estimated using residential location were associated with statistically significant increased risk of ALS (amyotrophic lateral sclerosis). These include the herbicides 2,4-D and glyphosate, and the insecticides carbaryl and chlorpyrifos.” ALS is a progressive nervous system disease that affects nerve cells in the brain and spinal cord, causing loss of muscle control. 

Harmful impacts bees and monarch butterflies

Cancer lawsuits

More than 42,000 people have filed suit against Monsanto Company (now Bayer) alleging that exposure to Roundup herbicide caused them or their loved ones to develop non-Hodgkin lymphoma (NHL), and that Monsanto covered up the risks. As part of the discovery process, Monsanto has had to turn over millions of pages of internal records. We are posting these Monsanto Papers as they become available. For news and tips about the ongoing legislation, see Carey Gillam’s Roundup Trial Tracker. The first three trials ended in large awards to plaintiffs for liability and damages, with juries ruling that Monsanto’s weed killer was a substantial contributing factor in causing them to develop NHL. Bayer is appealing the rulings. 

Monsanto influence in research: In March 2017, the federal court judge unsealed some internal Monsanto documents that raised new questions about Monsanto’s influence on the EPA process and about the research regulators rely on. The documents suggest that Monsanto’s long-standing claims about the safety of glyphosate and Roundup do not necessarily rely on sound science as the company asserts, but on efforts to manipulate the science

More information about scientific interference

Sri Lankan scientists awarded AAAS freedom award for kidney disease research

The AAAS has awarded two Sri Lankan scientists, Drs. Channa Jayasumana and Sarath Gunatilake, the 2019 Award for Scientific Freedom and Responsibility for their work to “investigate a possible connection between glyphosate and chronic kidney disease under challenging circumstances.” The scientists have reported that glyphosate plays a key role in transporting heavy metals to the kidneys of those drinking contaminated water, leading to high rates of chronic kidney disease in farming communities. See papers in  SpringerPlus (2015), BMC Nephrology (2015), Environmental Health (2015), International Journal of Environmental Research and Public Health (2014). The AAAS award had been suspended amidst a fierce opposition campaign by pesticide industry allies to undermine the work of the scientists. After a review, the AAAS reinstated the award

Desiccation: another source of dietary exposures 

Some farmers use glyphosate on non-GMO crops such as wheat, barley, oats, and lentils to dry down the crop ahead of harvest in order to accelerate the harvest. This practice, known as desiccation, may be a significant source of dietary exposure to glyphosate.

Glyphosate in food: U.S. drags its feet on testing

Despite having annual pesticide residue testing programs for more than 30 years, the U.D. Department of Agriculture (USDA) and U.S. Food and Drug Administration (FDA) mostly skipped testing food for glyphosate until after criticism from the Government Accountability Office in 2014. The USDA said it would start testing but then dropped the plan in 2017. Internal agency documents obtained by U.S. Right to Know show the agency had planned to start testing over 300 samples of corn syrup for glyphosate in April 2017. But the agency killed the project before it started. The U.S. Food and Drug Administration began a limited testing program in 2016, but the effort was fraught with controversy and internal difficulties and the program was suspended in September 2016. The FDA did later resume limited testing. 

One FDA chemist found alarming levels of glyphosate in many samples of U.S. honey, levels that were technically illegal because there have been no allowable levels established for honey by the EPA. Here is a recap of news about glyphosate found in food:

Residues of glyphosate and other pesticides in food

USDA data from 2016 shows detectable pesticide levels in 85% of more than 10,000 foods sampled, everything from mushrooms to grapes to green beans. The government says there are little to no health risks, but some scientists say there is little to no data to back up that claim. See “Chemicals on our food: When “safe” may not really be safe: Scientific scrutiny of pesticide residue in food grows; regulatory protections questioned.”

In 2020, a group of FDA scientists published a research paper  examining pesticide residue data collected from 2009-2017. The scientists said this: “In this study, results for over 56,000 human food samples collected and analyzed under the FDA pesticide residue monitoring program between fiscal years (FY) 2009 to 2017 were reviewed to identify trends not apparent in annual reports. The overwhelming majority of these samples, 98.0% of domestic and 90.9% of import human foods, were compliant with federal standards. Although herbicides may be more widely used, the 10 most frequently detected residues were insecticides and fungicides. On a yearly basis, the violation rate for imported samples is 3-5 times higher than the rate for domestic samples. The import violation rate increased over time, as did the number of residues detected. Targeted sampling of foods with higher commodity-specific violation rates appears to be a major contributor to the increased violation rate. Mismatches between US tolerances and international MRLs can lead to violations; this was especially marked for rice. Overall, the majority of violations are due to residues of pesticides not authorized for use in the US (lack of tolerances). While DDT continues to persist in the environment and was found in 2.2% of domestic samples and 0.6% of imported samples, 42.3% of DDT-positive samples were below the limit of quantitation. The trends and analyses identified in this paper may help FDA plan future sampling and continue to protect the food supply.”

Monsanto owner Bayer AG maintains that residues of glyphosate in food are not harmful at levels approved by the Environmental Protection Agency.  A 2021 paper written by longtime Bayer (former Monsanto) scientist John Vicini and published in Comprehensive Reviews in Food Science and Food Safety states that  “dietary exposures to glyphosate are within established safe limits.” 

For a complete history of the use of glyphosate, including regulatory action and inaction, scientific controversies, human and environmental impact data, read Whitewash – The Story of a Weed Killer, Cancer and the Corruption of Science, winner of the 2018 Rachel Carson Book Award from the Society of Environmental Journalists.

New glyphosate papers point to “urgency” for more research on chemical impact to human health

Print Email Share Tweet

Newly published scientific papers illustrate the ubiquitous nature of the weed killing chemical glyphosate and a need to better understand the impact exposure to the popular pesticide may be having on human health, including the health of the gut microbiome.

In one of the new papers, researchers from the University of Turku in Finland said that they were able to determine, in a “conservative estimate,” that approximately 54 percent of species in the core of the human gut microbiome are “potentially sensitive” to glyphosate. The researchers said they used a new bioinformatics method to make the finding.

With a “large proportion” of bacteria in the gut microbiome susceptible to glyphosate, the intake of glyphosate “may severely affect the composition of the human gut microbiome,” the authors said in their paper, which was published this month in the Journal of Hazardous Materials.

The microbes in the human gut include a variety of bacteria and fungi and are believed to impact immune functions and other important processes. Unhealthy gut microbiomes are believed by some scientists to contribute to a range of diseases.

“Although data on glyphosate residues in human gut systems are still lacking, our results suggest that glyphosate residues decrease bacterial diversity and modulate bacterial species composition in the gut,” the authors said. “We may assume that long-term exposure to glyphosate residues leads to the dominance of resistant strains in the bacterial community.”

The concerns about glyphosate’s impact on the human gut microbiome stem from the fact that glyphosate works by targeting an enzyme known as 5-enolpyruvylshikimate-3-phosphate synthase (EPSPS.) This enzyme is critical to the synthesizing of essential amino acids.

“To determine the actual impact of glyphosate on the human gut microbiota and other organisms, further empirical studies are needed to reveal glyphosate residues in food, to determine the effects of pure glyphosate and commercial formulations on microbiomes and to assess the extent to which our EPSPS amino acid markers predict bacterial susceptibility to glyphosate in in vitro and real-world scenarios,” the authors of the new paper concluded.

In addition to the six researchers from Finland, one of the authors of the paper is affiliated with the department of biochemistry and biotechnology at Rovira i Virgili University, Tarragona, Catalonia, in Spain.

“The consequences for human health are not determined in our study. However, based on previous studies… we know that alterations in the human gut microbiome may be connected to several diseases,” University of Turku researcher Pere Puigbo said in an interview.

“I hope that our research study opens the door to further experiments, in-vitro and in the field, as well as population-based studies to quantify the effect the use of glyphosate has on human populations and other organisms,” Puigbo said.

Introduced in 1974

Glyphosate is the active ingredient in Roundup herbicides and hundreds of other weed killing products sold around the world. It was introduced as a weed killer by Monsanto in 1974 and grew to become the most widely used herbicide after Monsanto’s introduction in the 1990s of crops genetically engineered to tolerate the chemical. Residues of glyphosate are commonly found on food and in water. Consequently, residues are also often detected in the urine of people exposed to glyphosate through either diet and/or application.

U.S. regulators and Monsanto owner Bayer AG maintain there are no human health concerns with glyphosate exposure when the products are used as intended, including from residues in the diet.

The body of research contradicting those claims is growing, however. The research on the potential impacts of glyphosate on the gut microbiome is not nearly as robust as the literature associating glyphosate to cancer, but is an area many scientists are probing.

In a somewhat related paper published this month, a team of researchers from Washington State University and Duke University said that they had found a correlation between the levels of bacteria and fungi in the gastrointestinal tracts of children and the chemicals found in their homes. The researchers did not look at glyphosate specifically, but were alarmed to find that children with higher levels of common household chemicals in their bloodstream showed a reduction in the amount and diversity of important bacteria in their gut.

Glyphosate in urine

An additional scientific paper published this month underscored a need for better and more data when it comes to glyphosate exposure and children.

The paper, published in the journal Environmental Health by researchers from the Institute for Translational Epidemiology at the Icahn School of Medicine at Mount Sinai in New York, is the outcome of a literature review of multiple studies reporting actual values of glyphosate in people.

The authors said they analyzed five studies published in the last two years reporting glyphosate levels measured in people, including one study in which urinary glyphosate levels were measured in children living in rural Mexico. Of 192 children living in the Agua Caliente area, 72.91 percent had detectable levels of glyphosate in their urine, and all of the 89 children living in Ahuacapán, Mexico, had detectable levels of the pesticide in their urine.

Even when including additional studies, overall, there is sparse data regarding glyphosate levels in people. Studies globally total only 4,299 people, including 520 children, the researchers said.

The authors concluded that it is not currently possible to understand the “potential relationship” between glyphosate exposure and disease, especially in children, because data collection on exposure levels in people is limited and not standardized.

They noted that despite the lack of solid data about the impacts of glyphosate on children, the amount of glyphosate residues legally allowed by U.S. regulators on food has increased dramatically over the years.

“There are gaps in the literature on glyphosate, and these gaps should be filled with some urgency, given the large use of this product and its ubiquitous presence,” said author Emanuela Taioli.

Children are especially vulnerable to environmental carcinogens and tracking exposure to products such as glyphosate in children is “a pressing public health priority,” according to the authors of the paper.

“As with any chemical, there are multiple steps involved in evaluating risk, which include gathering information about human exposures, so that the levels that produce harm in one population or animal species can be compared to typical exposure levels,” the authors wrote.

“However, we have previously shown that data on human exposure in workers and the general population are very limited. Several other gaps in knowledge exist around this product, for example results on its genotoxicity in humans are limited. The continued debate regarding the effects of glyphosate exposure makes establishing exposure levels in the general public a pressing public health issue, especially for the most vulnerable.”

The authors said monitoring of urinary glyphosate levels should be conducted in the general population.

“We continue to suggest that inclusion of glyphosate as a measured exposure in nationally representative studies like the National Health and Nutrition Examination Survey will allow for a better understanding of the risks that glyphosate may pose and allow for better monitoring of those who are most likely to be exposed and those who are more susceptible to the exposure,” they wrote.