Photo: Field Bindweed, Fredericksburg, Texas. © 2022 Amber Leung
Glyphosate (Roundup) Herbicide
Summaries of the research and commentary by Dr. Delena Norris-Tull, Professor Emerita of Science Education, University of Montana Western, October 2020, updated April 2022, and November 2024.
In use in the US since 1974, Roundup and other glyphosate derivatives have been widely viewed as the latest savior of agricultural products worldwide. It is a broad-spectrum herbicide, and can be used on a variety of broadleaf and grass weeds.
Glyphosate (Roundup) has become an herbicide of particular concern recently because of the development of a number of crop seeds that have been genetically modified to be resistant to the herbicide. The invention of Roundup-ready seed has been touted as one of the most important improvements to agriculture in recent decades. Prior to the development of these GMO seeds, farmers were not able to broadcast spray the herbicides, because that would kill off the broadleaf crop species, as well as the noxious weeds. With the development of Roundup Ready alfalfa seed, for example, farmers can now broadcast herbicides, to kill off broadleaf weeds. That means that the entire crop of alfalfa can be sprayed with herbicides (personal interview with Katy McKee, 2016). This has raised concerns about the herbicide making it into the food supply in larger amounts.
Schulz & Segobye, 2016, found that “Glyphosate, which came to dominate world herbicide markets after the introduction of transgenic glyphosate-resistant crops in the US from 1996 to 1998 (soybean, maize and cotton) became the epicenter of a rampant resistance epidemic due to overreliance and repeated use.”
Schulz & Segobye, 2016, reported that the rapid development of herbicide resistance in crops treated with glyphosate “prompted farmers and the agricultural industry to search for alternative weed-control strategies. Two herbicide producers [Dow AgroSciences and Monsanto] developed 2,4-D- and dicamba-resistant crops using bacterial resistance genes… However, concerns have already been voiced that this might also lead to an increase in 2,4-D resistance in weeds... It can only be hoped that lessons from the rapid spread of glyphosate resistance have been learned and a similar scenario can be avoided with the use of these new herbicide tolerant crops.” The information on dicamba, above, proves that these hopes have now been dashed, as dicamba resistant weeds have since evolved.
Within this website, refer to the section, Herbicide resistance for further information on glyphosate resistant noxious weeds.
Glyphosate impacts on the environment and human health
In 2016, a group of 14 scientists from a wide array of fields, including environmental health, medical genetics, endocrinology, preventive medicine, biomedicine, and pediatrics, published a statement titled, “Concerns over use of glyphosate-based herbicides and risks associated with exposures” (Myers, et al., 2016). In their statement, they point out that “(1) GBHs [Glyphosate-based herbicides] are the most heavily applied herbicide in the world and usage continues to rise; (2) Worldwide, GBHs often contaminate drinking water sources, precipitation, and air, especially in agricultural regions; (3) The half-life of glyphosate in water and soil is longer than previously recognized; (4) Glyphosate and its metabolites are widely present in the global soybean supply; (5) Human exposures to GBHs are rising; (6) Glyphosate is now authoritatively classified as a probable human carcinogen; (7) Regulatory estimates of tolerable daily intakes for glyphosate in the United States and European Union are based on outdated science.” They recommend increased biomonitoring, epidemiological studies, and toxicology studies, to establish the effects of glyphosate and ascertain the causes of those effects on the environment and health.
Labad, et al., 2020, conducted a study of a barley crop in India. Under field conditions, they tested the impacts of different dosages of glyphosate. They found that use of the herbicide was critical to cereal production. While glyphosate use in small doses did decrease weeds, the use of high herbicide doses was necessary to adequately enhance cereal productivity. Higher doses of glyphosate left high residues in the soil surface that transferred into deeper soil layers and accumulated in cereal seeds. They found that, although glyphosate in the soil “can be degraded biologically, transfer and accumulation phenomena persisted.”
For many invasive plants, repeated doses of glyphosate or other herbicides are needed to impact the weedy species. The University of California Integrated Pest Management Program recommends various treatments to control field bindweed and points out that herbicide treatment alone will not eradicate the plant.
There have been concerns expressed in recent years by various agencies and countries about the potential carcinogenic effects of glyphosate. The International Agency for Research on Cancer (2015), part of the World Health Organization, declared glyphosate, possibly the most widely used herbicide worldwide, a probable carcinogen. In the United States, California has declared it a carcinogen.
In May 2016, a World Health Organization (WHO) committee that reviewed the research on genotoxic effects of glyphosate concluded that “glyphosate is unlikely to pose a carcinogenic risk to humans from exposure through the diet” (WHO, May 16, 2016). However, exposure through the diet is different from exposure to agricultural workers through spraying of glyphosate on crops.
After heated debate, the European Union voted in November 2017 to extend its authorization for use of the herbicide glyphosate for five more years. The EU stated that there is not sufficient evidence to warrant labeling it as a carcinogen. 18 member nations voted in favor of extending the use of the herbicide, but nine members voted against it. The French President is pushing to ban the herbicide within France. The agrochemical industry was disappointed at the EU’s decision, as they expected the EU to reauthorize the herbicide for 10-15 years.
In March 2019, in the second U.S. trial related to the possible link between glyphosate and cancer, specifically non-Hodgkin’s lymphoma, the jury concluded that glyphosate was a substantial factor in the development of the disease in the plaintiff. This was the first case held in a federal court, and the second case that awarded tens of millions of dollars to the plaintiffs. A second phase of that federal trial addressed the question of the extent to which Monsanto (now Bayer) is liable. The jury concluded that, although the company had hired external researchers to conduct studies on the safety of Roundup, there was evidence that suggested that Monsanto had influenced the results of those scientific studies and attempted to hide negative information. In addition, internal memos revealed questionable public relations tactics used by the company to convince the public of the safety of glyphosate, and questionable communications with individuals at the EPA, that hinted at a possible cover-up.
Thousands of similar cases are waiting in the wings. In April 2019, a federal judge overseeing approximately 800 of these cases ordered Bayer and the plaintiffs’ attorneys to use mediation to come to settlements in the remaining cases.
Monsanto was purchased by the German chemical company Bayer AG in 2018, just before the first trial was set. The acquisition was set up such that Bayer, not Monsanto, bears the liability to pay out the millions of dollars in case settlements.
Several scientists, including an epidemiologist and a pathologist, testified at the first three trials, that, in examining the research, they concluded that there is a credible link between glyphosate and human cancers.
In response to the lawsuits, Bayer has made 107 safety studies available to the public. In 2018, teams of scientists with the European Food Safety Authority and the U.S. EPA reviewed the corporation-funded research. Both organizations concluded that the research supports Monsanto’s claim that glyphosate does not pose a harm to human health. In 2019, the EPA (EPA, April 2019) stated that, “The EPA conducted an independent evaluation of the carcinogenic potential of glyphosate and has determined that glyphosate is ‘not likely to be carcinogenic to humans.’”
However, in 2021, an analysis of 53 of these corporate-funded studies found that all but two of the studies were flawed by today’s standards, and many were decades old. Gillam, 2021, reported that researchers at the Institute of Cancer Research at the Medical University of Vienna, concluded that “most do not comply with modern international standards for scientific rigor, and lack the types of tests most able to detect cancer risks.” Siegfried Knasmueller, the lead author of the analysis, told The Guardian that, “The health authorities… accepted some of these very poor studies as informative and acceptable, which is not justified from a scientific point of view.”
It is worthwhile noting that, while Monsanto allegedly funded hundreds of studies on glyphosate safety, they did not fund any long-term studies on safety. Unfortunately, when the industry is paying for the research itself, rather than the research funding coming from Federal organizations such as the National Institutes of Health, the temptation for the industry to interfere with the results may be too great.
In June 2020, Bayer agreed to pay out $10.9 billion to cover the nearly 100,000 lawsuits in the USA (Burger & Bellon, June 24, 2020). By March 2022, Bayer had paid out $80 million to $2 billion in lawsuits brought forward by individuals claiming that glyphosate caused their lymphomas. Bayer is appealing some of these cases to the US Supreme Court.
In December, 2021, Wollrab, et al., reported that about 320 investors have sued Bayer for $2.5 billion, in a class action lawsuit claiming that Bayer “deceived shareholders about the risks of consumer lawsuits pending in the United States.”
And in July 2021, Bayer announced it will remove glyphosate from retail stores by 2023, due to the many pending lawsuits (Renda, 2021). However, they plan to continue making it available to professionals, such as in large-scale agricultural operations. And they plan to eventually replace glyphosate with alternative chemicals.
Bayer maintains a website with updates on the legal cases against them, Managing the Roundup litigation. A number of cases have gone to trial, with some juries deciding in favor of Bayer (the defendant), and some juries deciding in favor of the individuals (the plaintiffs) who have filed the lawsuits.
For additional research on the impacts of glyphosate, within this website, refer to the section on environmental impacts of herbicides.
References:
Next sections on the most widely used modern herbicides:
Links to additional information on herbicides and other pesticides:
Glyphosate (Roundup) Herbicide
Summaries of the research and commentary by Dr. Delena Norris-Tull, Professor Emerita of Science Education, University of Montana Western, October 2020, updated April 2022, and November 2024.
In use in the US since 1974, Roundup and other glyphosate derivatives have been widely viewed as the latest savior of agricultural products worldwide. It is a broad-spectrum herbicide, and can be used on a variety of broadleaf and grass weeds.
Glyphosate (Roundup) has become an herbicide of particular concern recently because of the development of a number of crop seeds that have been genetically modified to be resistant to the herbicide. The invention of Roundup-ready seed has been touted as one of the most important improvements to agriculture in recent decades. Prior to the development of these GMO seeds, farmers were not able to broadcast spray the herbicides, because that would kill off the broadleaf crop species, as well as the noxious weeds. With the development of Roundup Ready alfalfa seed, for example, farmers can now broadcast herbicides, to kill off broadleaf weeds. That means that the entire crop of alfalfa can be sprayed with herbicides (personal interview with Katy McKee, 2016). This has raised concerns about the herbicide making it into the food supply in larger amounts.
Schulz & Segobye, 2016, found that “Glyphosate, which came to dominate world herbicide markets after the introduction of transgenic glyphosate-resistant crops in the US from 1996 to 1998 (soybean, maize and cotton) became the epicenter of a rampant resistance epidemic due to overreliance and repeated use.”
Schulz & Segobye, 2016, reported that the rapid development of herbicide resistance in crops treated with glyphosate “prompted farmers and the agricultural industry to search for alternative weed-control strategies. Two herbicide producers [Dow AgroSciences and Monsanto] developed 2,4-D- and dicamba-resistant crops using bacterial resistance genes… However, concerns have already been voiced that this might also lead to an increase in 2,4-D resistance in weeds... It can only be hoped that lessons from the rapid spread of glyphosate resistance have been learned and a similar scenario can be avoided with the use of these new herbicide tolerant crops.” The information on dicamba, above, proves that these hopes have now been dashed, as dicamba resistant weeds have since evolved.
Within this website, refer to the section, Herbicide resistance for further information on glyphosate resistant noxious weeds.
Glyphosate impacts on the environment and human health
In 2016, a group of 14 scientists from a wide array of fields, including environmental health, medical genetics, endocrinology, preventive medicine, biomedicine, and pediatrics, published a statement titled, “Concerns over use of glyphosate-based herbicides and risks associated with exposures” (Myers, et al., 2016). In their statement, they point out that “(1) GBHs [Glyphosate-based herbicides] are the most heavily applied herbicide in the world and usage continues to rise; (2) Worldwide, GBHs often contaminate drinking water sources, precipitation, and air, especially in agricultural regions; (3) The half-life of glyphosate in water and soil is longer than previously recognized; (4) Glyphosate and its metabolites are widely present in the global soybean supply; (5) Human exposures to GBHs are rising; (6) Glyphosate is now authoritatively classified as a probable human carcinogen; (7) Regulatory estimates of tolerable daily intakes for glyphosate in the United States and European Union are based on outdated science.” They recommend increased biomonitoring, epidemiological studies, and toxicology studies, to establish the effects of glyphosate and ascertain the causes of those effects on the environment and health.
Labad, et al., 2020, conducted a study of a barley crop in India. Under field conditions, they tested the impacts of different dosages of glyphosate. They found that use of the herbicide was critical to cereal production. While glyphosate use in small doses did decrease weeds, the use of high herbicide doses was necessary to adequately enhance cereal productivity. Higher doses of glyphosate left high residues in the soil surface that transferred into deeper soil layers and accumulated in cereal seeds. They found that, although glyphosate in the soil “can be degraded biologically, transfer and accumulation phenomena persisted.”
For many invasive plants, repeated doses of glyphosate or other herbicides are needed to impact the weedy species. The University of California Integrated Pest Management Program recommends various treatments to control field bindweed and points out that herbicide treatment alone will not eradicate the plant.
There have been concerns expressed in recent years by various agencies and countries about the potential carcinogenic effects of glyphosate. The International Agency for Research on Cancer (2015), part of the World Health Organization, declared glyphosate, possibly the most widely used herbicide worldwide, a probable carcinogen. In the United States, California has declared it a carcinogen.
In May 2016, a World Health Organization (WHO) committee that reviewed the research on genotoxic effects of glyphosate concluded that “glyphosate is unlikely to pose a carcinogenic risk to humans from exposure through the diet” (WHO, May 16, 2016). However, exposure through the diet is different from exposure to agricultural workers through spraying of glyphosate on crops.
After heated debate, the European Union voted in November 2017 to extend its authorization for use of the herbicide glyphosate for five more years. The EU stated that there is not sufficient evidence to warrant labeling it as a carcinogen. 18 member nations voted in favor of extending the use of the herbicide, but nine members voted against it. The French President is pushing to ban the herbicide within France. The agrochemical industry was disappointed at the EU’s decision, as they expected the EU to reauthorize the herbicide for 10-15 years.
In March 2019, in the second U.S. trial related to the possible link between glyphosate and cancer, specifically non-Hodgkin’s lymphoma, the jury concluded that glyphosate was a substantial factor in the development of the disease in the plaintiff. This was the first case held in a federal court, and the second case that awarded tens of millions of dollars to the plaintiffs. A second phase of that federal trial addressed the question of the extent to which Monsanto (now Bayer) is liable. The jury concluded that, although the company had hired external researchers to conduct studies on the safety of Roundup, there was evidence that suggested that Monsanto had influenced the results of those scientific studies and attempted to hide negative information. In addition, internal memos revealed questionable public relations tactics used by the company to convince the public of the safety of glyphosate, and questionable communications with individuals at the EPA, that hinted at a possible cover-up.
Thousands of similar cases are waiting in the wings. In April 2019, a federal judge overseeing approximately 800 of these cases ordered Bayer and the plaintiffs’ attorneys to use mediation to come to settlements in the remaining cases.
Monsanto was purchased by the German chemical company Bayer AG in 2018, just before the first trial was set. The acquisition was set up such that Bayer, not Monsanto, bears the liability to pay out the millions of dollars in case settlements.
Several scientists, including an epidemiologist and a pathologist, testified at the first three trials, that, in examining the research, they concluded that there is a credible link between glyphosate and human cancers.
In response to the lawsuits, Bayer has made 107 safety studies available to the public. In 2018, teams of scientists with the European Food Safety Authority and the U.S. EPA reviewed the corporation-funded research. Both organizations concluded that the research supports Monsanto’s claim that glyphosate does not pose a harm to human health. In 2019, the EPA (EPA, April 2019) stated that, “The EPA conducted an independent evaluation of the carcinogenic potential of glyphosate and has determined that glyphosate is ‘not likely to be carcinogenic to humans.’”
However, in 2021, an analysis of 53 of these corporate-funded studies found that all but two of the studies were flawed by today’s standards, and many were decades old. Gillam, 2021, reported that researchers at the Institute of Cancer Research at the Medical University of Vienna, concluded that “most do not comply with modern international standards for scientific rigor, and lack the types of tests most able to detect cancer risks.” Siegfried Knasmueller, the lead author of the analysis, told The Guardian that, “The health authorities… accepted some of these very poor studies as informative and acceptable, which is not justified from a scientific point of view.”
It is worthwhile noting that, while Monsanto allegedly funded hundreds of studies on glyphosate safety, they did not fund any long-term studies on safety. Unfortunately, when the industry is paying for the research itself, rather than the research funding coming from Federal organizations such as the National Institutes of Health, the temptation for the industry to interfere with the results may be too great.
In June 2020, Bayer agreed to pay out $10.9 billion to cover the nearly 100,000 lawsuits in the USA (Burger & Bellon, June 24, 2020). By March 2022, Bayer had paid out $80 million to $2 billion in lawsuits brought forward by individuals claiming that glyphosate caused their lymphomas. Bayer is appealing some of these cases to the US Supreme Court.
In December, 2021, Wollrab, et al., reported that about 320 investors have sued Bayer for $2.5 billion, in a class action lawsuit claiming that Bayer “deceived shareholders about the risks of consumer lawsuits pending in the United States.”
And in July 2021, Bayer announced it will remove glyphosate from retail stores by 2023, due to the many pending lawsuits (Renda, 2021). However, they plan to continue making it available to professionals, such as in large-scale agricultural operations. And they plan to eventually replace glyphosate with alternative chemicals.
Bayer maintains a website with updates on the legal cases against them, Managing the Roundup litigation. A number of cases have gone to trial, with some juries deciding in favor of Bayer (the defendant), and some juries deciding in favor of the individuals (the plaintiffs) who have filed the lawsuits.
For additional research on the impacts of glyphosate, within this website, refer to the section on environmental impacts of herbicides.
References:
- Burger, L., & Bellon, T. (June 24, 2020). Bayer to pay up to $10.9 billion to settle bulk of Roundup weedkiller cancer lawsuits. Reuters: Frankfurt/New York.
- Gillam, C. (July 2, 2021). Corporate studies asserting herbicide safety show many flaws, new analysis finds. The Guardian: NY.
- International Agency for Research on Cancer. (March 20, 2015). IARC Monographs Volume 112: Evaluation of five organophosphate insecticides and herbicides. World Health Organization.
- Labad, R., Hartani, T., & Shinde, G.U. (2020). Effect of weed treatment on cereal yield in direct seeding: A challenge between soil pollution and seeds quality. Indian Journal of Agricultural Research, 54(1): 101-106.
- Myers, J.P., Antoniou, M.N., Blumberg, B., Carroll, L., Colborn, T., Everett, L.G.,Hansen, M., Landrigan, P.J., Lanphear, B.P., Mesnage, R., Vandenberg, L.N., vom Saal, F.S., Wade V. Welshons, W.V., & Charles M. Benbrook, C.M. (Feb.17, 2016). Concerns over use of glyphosate-based herbicides and risks associated with exposures: A consensus statement. Environmental Health: A Global Access Science Source, 15:1013.
- Renda, M. (July 29, 2021). Bayer to pull glyphosate from stores due to cancer lawsuits. Courthouse News Service.
- Schulz, B., & Segobye, K. (2016). 2,4-D transport and herbicide resistance in weeds. Journal of Experimental Botany, 67 (11):3177-3179.
- US EPA (January, 2020). Glyphosate: Interim registration review decision, Case number 0178. US EPA: Washington, D.C.
- Wollrab, S., Weiss, P., Inverardi, M., Schwartz, J., Chambers, M., & Lewis, B. (Dec. 15, 2021). Bayer faces class action suit over Monsanto takeover in Germany, law firm says. Reuters: Frankfurt/New York.
- Food and Agriculture Organization of the United Nations. (May 16, 2016.). Summary Report: Joint FAO/WHO meeting on pesticide residues. Geneva. WHO.
Next sections on the most widely used modern herbicides:
Links to additional information on herbicides and other pesticides: