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:
Most Widely Used Pesticide
- Americans have applied 1.8 million tons of glyphosate since its introduction in 1974.
- Worldwide 9.4 million tons 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.
- Globally, glyphosate use has risen almost 15-fold since Roundup Ready GMO crops were introduced.
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.
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 publishing the CARC report, the EPA said that it was beginning work with the National Toxicology Program to investigate the mechanisms and toxic effects of glyphosate formulations. The agency then convened a Scientific Advisory Panel (SAP) in December 2016 to review the CARC report conclusion that glyphosate was not likely to be carcinogenic. The scientific advisory panel 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 the agency’s Office of Pesticide Programs had not followed proper protocols in its evaluation of glyphosate. An ORD memo stated that the government scientists agreed in part with IARC and believed EPA was not properly following guidelines in coming to the conclusion that glyphosate was not likely to be carcinogenic. ORD 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.
EFSA, ECA, WHO/FAO JMPR: The European Food Safety Authority and the European Chemicals Agency have said glyphosate is not likely to be carcinogenic to humans. But 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.
The WHO/FAO Joint Meeting on Pesticide Residues determined that glyphosate was unlikely to pose a carcinogenic risk to humans from exposure through the diet, though the finding was tarnished by conflict of interest concerns after it was revealed that certain members of the group, including its chair, worked for 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 that 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, the United States District Court for the Eastern District of California 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.
New studies in 2019 report cancer links and concerns about the validity of the EPA classification:
- April 2019: the U.S. Agency for Toxic Substances and Disease Registry issued its draft toxicological profile for glyphosate. The report confirms increased cancer risk from glyphosate exposures. (Emails released via court proceedings show officials at EPA and Monsanto trying to stop the ATSDR report; read the emails here.)
- March 2019 study published in the International Journal of Epidemiology analyzed data from more than 30,000 farmers and agricultural workers from studies done in France, Norway and the U.S., and reported links between glyphosate and diffuse large B-cell lymphoma.
- February 2019: A new meta-analysis published in Mutation Research/Reviews in Mutation Research reported a “compelling link” between glyphosate-based herbicides and non-Hodgkin lymphoma. Three of the study authors were members of the EPA’s scientific advisory panel on glyphosate who have stated publicly that the EPA failed to follow proper scientific practices in its glyphosate assessment.
- January 2019: An analysis published in Environmental Sciences Europe argues that the U.S. EPA’s classification of glyphosate disregarded substantial scientific evidence of genotoxicity (the negative impact on a cell’s genetic material) associated with weed killing products such as Roundup.
More than 11,000 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, and that Monsanto covered up the risks. As part of the discovery process, Monsanto has had to turn over millions of pages of its internal records. We are posting these Monsanto Papers as they become available here. For news and tips about the ongoing legislation, see Carey Gillam’s Roundup Trial Tracker. The first two trials ended with juries ruling that Monsanto’s weed killer was a substantial contributing factor in causing the plaintiffs to develop non-Hodgkin lymphoma, and giving large awards for liability and damages.
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.
A study for the European Parliament published January 2019 asserts that the EU approval of glyphosate was based on plagiarized text from Monsanto. The study found plagiarism in 50.1 percent of chapters dealing with the assessment of published studies on health risks related to glyphosate in Germany’s Federal Institute for Risk Assessment, including whole paragraphs and entire pages of plagiarized text.
More information about scientific interference:
- “The Monsanto Papers: Poisoning the Scientific Well,” by Leemon McHenry (2018)
- “Roundup litigation discovery documents: implications for public health and journal ethics,” by Sheldon Krimsky and Carey Gillam (June 2018)
- Letter to Nature by Stéphane Horel and Stéphane Foucart (March 2018)
Endocrine Disruption and Other Health Concerns
Some research suggests that glyphosate may be an endocrine disruptor. It has also been linked to liver disease, birth defects and reproductive problems in laboratory animals; and may kill beneficial gut bacteria and damage the DNA in human embryonic, placental and umbilical cord cells. A 2019 study in a Nature journal reported increases in obesity, reproductive and kidney diseases, and other problems in the second- and third-generation offspring of rats exposed to glyphosate. See the study and Washington State University press release.
Many scientists have raised concerns about the health risks of glyphosate. See:
- Is it time to reassess current safety standards for glyphosate-based herbicides? – Journal of Epidemiology and Community Health
- Concerns over use of glyphosate-based herbicides and risks associated with exposure: a consensus statement – Environmental Health Journal
Recent studies have shown adverse biological effects from low-dose exposures to glyphosate at levels to which people are routinely exposed.
- A birth cohort study in Indiana published in 2017 – the first study of glyphosate exposure in US pregnant women using urine specimens as a direct measure of exposure – found detectable levels of glyphosate in more than 90% of the pregnant women tested and found the levels were significantly correlated with shortened pregnancy lengths.
- A 2018 ecological and population study conducted in Argentina found high concentrations of glyphosate in the soil and dust in agricultural areas that also reported higher rates of spontaneous abortion and congenital abnormalities in children, suggesting a link between environmental exposure to glyphosate and reproductive problems. No other relevant sources of pollution were identified.
- 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.
- 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.
- A 2018 rat study by Argentinian researchers linked low-level perinatal glyphosate exposures to impaired female reproductive performance and congenital anomalies in the next generation of offspring.
Glyphosate has also been linked by recent studies to harmful impacts on bees and monarch butterflies.
- A 2018 study reported that glyphosate damaged the beneficial gut bacteria in honeybees and made them more prone to deadly infections. This followed research from China showing that honeybee larvae grew more slowly and died more often when exposed to glyphosate, and a 2015 study that found field-levels of exposure impaired the cognitive capacities of honeybees.
- Research from 2017 correlated glyphosate use with reduced populations of monarch butterflies, possibly due to reductions in milkweed, the main food source for monarch butterflies.
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 Found in Food: U.S. Drags Its Feet on Testing
The USDA quietly dropped a plan to start testing food for residues of glyphosate 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. Both agencies have programs that annually test foods for pesticide residues but both have routinely skipped testing for glyphosate.
Before the suspension, 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:
- October 2018: FDA issued its first-ever report showing the results of its glyphosate residue in food testing. The FDA said no residues of glyphosate were found in milk or eggs, but residues were found in 63.1 percent of corn samples and 67 percent of soybean samples, according to FDA data. The agency did not disclose in that report the findings of glyphosate in oatmeal or honey products.
- April 2018: internal FDA emails indicated the agency had trouble finding food sample without traces of glyphosate.
- Sept. 2016: FDA found glyphosate in US honey at double the levels allowed in the EU, and FDA tests confirm oatmeal and baby foods contain glyphosate.
- Nov. 2016: FDA chemist found glyphosate in honey in Iowa at 10X higher levels than allowed in EU. Also in November, independent testing by consumer group Food Democracy Now found glyphosate in Cheerios, oatmeal cookies, Ritz crackers and other popular brands at high levels.
Pesticides in Our Food: Where’s the Safety Data?
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,” by Carey Gillam (11/2018).