Monsanto engaged in high-profile lawsuits, as both plaintiff and defendant. It defended lawsuits mostly over its products' health and environmental effects. Monsanto used the courts to enforce its patents, particularly in agricultural
biotechnology, an approach similar to that of other companies in the field, such as
Dupont Pioneer and
Syngenta. Monsanto also became one of the most controversial large corporations in the world, over a range of issues involving its industrial and agricultural chemical products, and GM seed. In April 2018, just prior to Bayer's acquisition, Bayer indicated that improving Monsanto's reputation represented a major challenge. That June, Bayer announced it would drop the Monsanto name as part of a campaign to regain consumer trust. The consolidation led to a decrease in production of many staples such as
milk,
rice,
maize,
potatoes and
lentils. As of 2004, about 150,000 small farmers had left the countryside; as of 2009, 50% in the Chaco region.
The Guardian reported that a Monsanto representative had said, "any problems with GM soya were to do with use of the crop as a monoculture, not because it was GM. If you grow any crop to the exclusion of any other you are bound to get problems." In 2013, environmentalist groups objected to a Monsanto corn seed conditioning facility in
Malvinas Argentinas, Córdoba. Neighbours objected to the risk of environmental impact. Court rulings supported the project, but environmentalist groups organised demonstrations and opened an online petition for the subject to be decided in a popular
referendum. The court rulings stipulated that while construction could continue, the facility could not begin operating until the
environmental impact report required by law had been duly presented. In 2016, Monsanto reached an agreement with Argentina's government on soybean seed royalty payments. Monsanto agreed to give the Argentine Seed Institute (Inase) oversight over crops grown from Monsanto's Intacta genetically modified soybean seeds. Before the agreement, Argentine farmers generally avoided royalties by using seeds from previous harvests or purchased from non-registered suppliers. Inase agreed to delegate testing to grain exchanges. About 6 million sample tests were to be conducted annually. Seeds that appear to be GMOs may be tested again using a
polymerase chain reaction test.
Brazil Brazil is the second largest producer of GMO soy. In 2003, GM soy was found in fields planted in the state of
Rio Grande do Sul. This was a controversial decision, and in response, the
Landless Workers' Movement protested by invading and occupying several Monsanto farm plots used for research, training and seed-processing. In 2005, Brazil passed a law creating a regulatory pathway for GM crops.
China Monsanto was criticized by
Chinese economist
Larry Lang for controlling the Chinese soybean market, and for trying to do the same to Chinese corn and cotton.
India In the late 1990s and early 2000s, public attention was drawn to suicides by indebted farmers following crop failures. For example, in the early 2000s, farmers in
Andhra Pradesh (AP) were in economic crisis due to high-interest rates and crop failures, leading to widespread unrest and farmer suicides. Monsanto was one focus of protests with respect to the price and yields of Bt seed. In 2005, the Genetic Engineering Approval Committee, the Indian regulatory authority, released a study on field tests of certain Bt cotton strains in AP and ruled that Monsanto could not market those strains in AP because of poor yields. At about the same time, the state agriculture minister barred the company from selling Bt cotton seed, because Monsanto refused a request by the state government to provide pay about Rs 4.5 crore (about one million US$) to indebted farmers in some districts, and because the government blamed Monsanto's seeds for crop failures. The order was later lifted. In 2006, AP tried to convince Monsanto to reduce the price of Bt seeds. Unsatisfied, the state filed several cases against Monsanto and its
Mumbai-based licensee, Maharashtra Hybrid Seeds. Research by
International Food Policy Research Institute found no evidence supporting an increased suicide rate following the introduction of Bt cotton and that Bt cotton. The report stated that farmer suicides predated commercial introduction in 2002 (and unofficial introduction in 2001) and that such suicides had made up a fairly constant portion of the overall national suicide rate since 1997. The report concluded that while Bt cotton may have been a factor in specific suicides, the contribution was likely marginal compared to
socio-economic factors. Critics including
Vandana Shiva said that the crop failures could "often be traced to" Monsanto's Bt cotton, that the seeds increased farmer indebtedness and argued that Monsanto misrepresented the profitability of their Bt Cotton, causing losses leading to debt. In 2009, Shiva wrote that Indian farmers who had previously spent as little as ₹7 (
rupees) per kilogram were now paying up to ₹17,000 per kilo per year for Bt cotton. In 2012, the
Indian Council of Agricultural Research (ICAR) and the Central Cotton Research Institute (CCRI) stated that for the first time farmer suicides could be linked to a decline in the performance of Bt cotton, and advised, "cotton farmers are in a deep crisis since shifting to Bt cotton. The spate of farmer suicides in 2011–12 has been particularly severe among Bt cotton farmers." The survey cited "government apathy, the absence of a safety net for farmers, and lack of access to information related to agriculture as the chief causes for the desperate condition of farmers in the state." ICAR and CCRI stated that the cost of cotton cultivation had jumped as a consequence of rising pesticide costs, while total Bt cotton production in the five years from 2007 to 2012 had declined.
United Kingdom Brofiscin Quarry was used as a waste site from about 1965 to 1972 and accepted waste from
BP,
Veolia and Monsanto. A 2005 report by
Environment Agency Wales (EAW) found that the quarry contained up to 75 toxic substances, including
heavy metals,
Agent Orange and PCBs. In February 2011, Monsanto agreed to help with the costs of remediation, but did not accept responsibility for the pollution. In 2011, EAW and the Rhondda Cynon Taf council announced that they had decided to place an engineered cap over the waste mass, and stated that the cost would be £1.5 million; previous estimates had been as high as £100 million.
United States PCBs In the late 1960s, the Monsanto plant in
Sauget, Illinois, was the nation's largest producer of
polychlorinated biphenyl (PCB) compounds, which remained in the water along Dead Creek there. An EPA official referred to Sauget as "one of the most polluted communities in the region" and "a soup of different chemicals". In
Anniston, Alabama, plaintiffs in a 2002 lawsuit provided documentation showing that the local Monsanto factory knowingly discharged both
mercury and PCB-laden waste into local creeks for over 40 years. In 1969 Monsanto dumped 45 tons of PCBs into Snow Creek, a feeder for
Choccolocco Creek, which supplies much of the area's drinking water, and buried millions of pounds of PCB in open-pit landfills located on hillsides above the plant and surrounding neighborhoods. In August 2003,
Solutia and Monsanto agreed to pay plaintiffs $700 million to settle claims by over 20,000 Anniston residents. In June 2020, Bayer proposed paying $650 million to settle local PCB lawsuits, and $170 million to the attorneys-general of New Mexico, Washington and the District of Columbia. In January 2025, Monsanto was ordered to pay $100 million to four people who say they were sickened by PCBs at a school in
Monroe, Washington.
Polluted sites As of November 2013, Monsanto was associated with nine "active"
Superfund sites and 32 "archived" sites in the US, in the EPA's Superfund database. Monsanto was sued and settled multiple times for damaging the health of its employees or residents near its Superfund sites through pollution and poisoning.
GM wheat In 2013, a Monsanto-developed transgenic cultivar of
glyphosate-resistant
wheat was discovered on a farm in Oregon, growing as a weed or
"volunteer plant". The final Oregon field test had occurred in 2001. As of May 2013, the GMO seed source was unknown. Volunteer wheat from a former test field two miles away was tested and was not found to be glyphosate-tolerant. Monsanto faced penalties up to $1 million over potential violations of the
Plant Protection Act. The discovery threatened world-leading US wheat exports, which totaled $8.1 billion in 2012. This wheat variety was rarely exported to Europe and was more likely destined for Asia. Monsanto said it had destroyed all the material it held after completing trials in 2004 and it was "mystified" by its appearance. On June 14, 2013, the USDA announced: "As of today, USDA has neither found nor been informed of anything that would indicate that this incident amounts to more than a single isolated incident in a single field on a single farm. All information collected so far shows no indication of the presence of GE wheat in commerce." As of August 30, 2013, while the source of the GM wheat remained unknown, Japan, South Korea and Taiwan had all resumed placing orders.
Cancer risks of Roundup Monsanto has faced controversy in the United States over claims that its herbicide products might be carcinogens. There is limited evidence that human cancer risk might increase as a result of occupational exposure to large amounts of glyphosate, as in agricultural work, but no good evidence of such a risk from home use, such as in domestic gardening. The
consensus among national pesticide regulatory agencies and scientific organizations is that labeled uses of glyphosate have demonstrated no evidence of human carcinogenicity. Organizations such as the
World Health Organization (WHO), the
Food and Agriculture Organization,
European Commission, Canadian
Pest Management Regulatory Agency, and the German
Federal Institute for Risk Assessment have concluded that there is no evidence that glyphosate poses a carcinogenic or
genotoxic risk to humans. However, one international scientific organization, the
International Agency for Research on Cancer (IARC), affiliated with the WHO, has made claims of carcinogenicity in research reviews; in 2015 the IARC declared glyphosate "probably carcinogenic". As of October 30, 2019, there were 42,700 plaintiffs who said that glyphosate herbicides caused their cancer after the IARC report in 2015 linking glyphosate to cancer in humans. Monsanto denies that Roundup is carcinogenic. In March 2017, 40 plaintiffs filed a lawsuit at the
Alameda County Superior Court, a branch of the California Superior Court, asking for damages caused by the company's glyphosate-based weed-killers, including Roundup, and demanding a jury trial. On August 10, 2018, Monsanto lost the first decided case. Dewayne Johnson, who has
non-Hodgkin's lymphoma, was initially awarded $289 million in damages after a jury in San Francisco said that Monsanto had failed to adequately warn consumers of cancer risks posed by the herbicide. Pending appeal, the award was later reduced to $78.5 million. In November 2018, Monsanto appealed the judgement, asking an appellate court to consider a motion for a new trial. On March 27, 2019, Monsanto was found liable in a federal court for Edwin Hardeman's non-Hodgkin's lymphoma and ordered to pay $80 million in damages. A spokesperson for Bayer, by this time the parent company of Monsanto, said the company would appeal the verdict. On May 13, 2019, a jury in California ordered Bayer to pay $2 billion in damages after finding that the company had failed to adequately inform consumers of the possible carcinogenicity of Roundup. On July 26, 2019, an Alameda County judge cut the settlement to $86.7 million, stating that the judgement by the jury exceeded legal precedent. In June 2020, Monsanto acquisitor Bayer agreed to settle over a hundred thousand Roundup cancer lawsuits, agreeing to pay $8.8 to $9.6 billion to settle those claims, and $1.5 billion for any future claims. The settlement does not include three cases that have already gone to jury trials and are being appealed.
Dicamba lawsuits Following a lawsuit by a
peach farmer alleging that Dicamba used as a weed killer drifted in the wind from adjacent crops to destroy his peach orchards, a
Missouri trial jury found in February 2020 that Monsanto and codefendant
BASF were negligent in design of Dicamba and failed to warn farmers about the product, awarding $15 million for losses and $250 million in
punitive damages. On February 14, 2020, the jury involved in a Missouri lawsuit involving tree damage caused by dicamba drift ruled against Bayer and its co-defendant BASF and found in favor of Bader Farms owner Bill Bader. In June 2020, Bayer agreed to a settlement of up to $400 million for all 2015–2020 crop year dicamba claims, not including the $250 million judgement which was issued to Bader.
Improper accounting for incentive rebates From 2009 to 2011, Monsanto improperly accounted for incentive rebates. The actions inflated Monsanto's reported profit by $31 million over the two years. Monsanto paid $80 million in penalties pursuant to a subsequent settlement with the
US Securities and Exchange Commission. Monsanto materially misstated its consolidated earnings in response to losing market share of Roundup to generic producers. Monsanto overhauled its internal controls. Two of their top CPAs were suspended and Monsanto was required to hire, at their expense, an independent ethics/compliance consultant for two years.
Ghostwriting In 2000 three scientists, who were not Monsanto employees, published a review evaluating the safety in humans of glyphosate and Roundup, concluding that it posed no health risks. The paper, in
Regulatory Toxicology and Pharmacology, was retracted on November 28, 2025 by the editor-in-chief, citing "lack of authorial independence", "misrepresentation of contributions", "questions of financial compensation", and a variety of concerns over whether the conclusions presented were adequately supported by the scientific data. A review of glyphosate's carcinogenic potential by four independent expert panels, disputing the conclusions of the
IARC assessment and finding that glyphosate was unlikely to cause cancer, was published in 2016. That paper was co-written by panels of academic authors, some of whom were recruited by a Canadian company hired by Monsanto. According to the journal: In 2017,
The New York Times reported that a 2015 article attributed to researcher and columnist
Henry I. Miller had been drafted by Monsanto. According to the report, Monsanto asked Miller to write an article rebutting the findings of the
International Agency for Research on Cancer, and he indicated willingness to do it if he "could start from a high-quality draft". ==Government relations==