Parkinson’s lawsuits mount as Syngenta ends paraquat production worldwide
Approximately 3,700 pages of internal Syngenta records unsealed through litigation in a Pennsylvania state court, where plaintiffs allege they developed Parkinson’s disease from paraquat exposure, show the company did not share multiple categories of safety data on its paraquat weedkiller with the US Environmental Protection Agency as it defended the chemical’s commercial use in the American market, according to a joint Guardian and New Lede investigation published September 25, 2026. The underlying Pennsylvania case was dismissed earlier this month after the judge found the plaintiff did not have sufficient proof of paraquat exposure, but thousands of additional active Parkinson’s-disease lawsuits against Syngenta and other paraquat sellers are pending around the country.
Syngenta has already paid at least $187 million in a 2021 settlement and an undisclosed further amount in settlements since then, the Guardian and New Lede reported; the settlements include no admission of liability. Earlier in 2026, the company announced it would stop all global production of paraquat. Asked about the newly disclosed US court documents, Syngenta said it has never knowingly failed to provide regulators with any relevant and required information. The company has long maintained that there is no actual link between paraquat and Parkinson’s disease and that its decision to stop selling was based on market factors.
Syngenta’s corporate roots trace back to Imperial Chemical Industries (ICI), a British chemical company formed in 1926. ICI transferred several businesses into a new company called Zeneca in 1993, which later merged with the Swedish pharmaceutical firm Astra AB to form AstraZeneca. In 2000, AstraZeneca and the Swiss pharmaceutical company Novartis spun off and merged certain business lines to create Syngenta AG. China National Chemical Corporation (ChemChina) purchased Syngenta in 2017.
Under the Federal Insecticide, Fungicide and Rodenticide Act (Fifra), companies holding a pesticide registration must submit “factual information regarding unreasonable adverse effects” to the EPA even after a pesticide has been approved and is on the market. EPA guidance states the information must be submitted if “the registrant knows, or should reasonably know, that the information, alone or in conjunction with other information, might raise concerns about the continued registration of a pesticide or about the appropriate terms and conditions of registration of a pesticide.” The agency told the Guardian and New Lede that companies must submit information “regarding any unexpected or unreasonable adverse effects resulting from their product’s use to EPA,” and that “failure to comply is a direct violation of federal law.” Syngenta acknowledged in court discovery that as of January 2025 it had no record of providing the EPA with a long list of reports and research it possessed pertaining to paraquat and potential health impacts. Asked about the court records, Syngenta said none of the information was relevant to the US market or to EPA oversight and would not have changed the regulatory view of paraquat, and that it has never “deliberately withheld pertinent information from the US EPA, or any other regulatory authority around the world.”
The court records detail specific categories of information Syngenta developed or accessed but did not share with the EPA. Among them: information, dating to at least the 1970s, that paraquat mixed with surfactants could become more toxic. US product labels have long recommended that applicators add surfactants before spraying paraquat to make the chemical more effective. Internal company files included studies showing the potential for increased absorption through skin and nasal membranes, and deposition testimony indicates Syngenta did not share at least some of those findings with the EPA. In court filings, Syngenta denied that surfactants will “normally increase the absorption of paraquat and hence increase its toxicity.” A company spokesperson said Syngenta conducted many studies that found no harmful nervous-system effects and that the surfactant in its Gramoxone product was “specifically selected not to accelerate epidermal penetration.”
Other withheld records include a 1985 study showing Syngenta’s Gramoxone product “almost immediately” penetrated cotton and Tyvek materials commonly used in protective clothing, though US labels continued to recommend that applicators wear only “a long-sleeved shirt and long pants.” Syngenta told the Guardian and New Lede the 1985 study involved a product not registered in the US. The records also describe a 1988 analysis of paraquat absorption in the urine and blood of workers spraying the pesticide over three days, which found “an unexpected number” of positive urine tests and paraquat in the plasma of several workers. Company notes stated the detection of paraquat in plasma “was the first time it had been observed” and could relate to “a problem that may arise with the EPA.” Syngenta said the situation was not relevant to US paraquat use because the US required personal protective equipment.
A 2007 evaluation of paraquat in the urine of workers spraying the chemical brought what company scientists called “bad news.” Two sprayers in a small group showed levels that vastly exceeded “acceptable operator exposure levels” (AOEL), according to email correspondence included in the court filings. “This is bad news whichever way you look at it,” a Syngenta scientist wrote in an internal email in June 2007. Syngenta told the Guardian and New Lede that most absorbed paraquat is rapidly excreted through urine and so is not a “regulatory or toxicological concern,” and said the operators in the 2007 study were not complying with paraquat safety measures.
In the United States, paraquat is used by farmers to control weeds before planting crops and to dry out crops for harvest, and is applied in orchards, wheat fields, pastures where livestock graze, cotton fields, and elsewhere. Syngenta, which brought paraquat to the US market in the 1960s through a corporate predecessor, has long assured farmers that there is no credible evidence of a connection between paraquat and Parkinson’s disease. But numerous scientific studies have found that paraquat damages cells in the brain in ways that can lead to Parkinson’s, and concerns accelerated in the 2000s as several researchers published studies supporting such a link.
The records also describe an internal corporate campaign to defend paraquat. In contrast to the withheld data, the company focused on developing and promoting science showing paraquat safety that it could share with regulators, including a study published in 2016 that company insiders noted would be “invaluable in supporting our work.” By 2003, the company was noting rising external pressure on the chemical and set a goal to “raise the level of proactive regulatory defence of paraquat globally,” while identifying the United States as a leading market for its Gramoxone brand. In an email attached to the court filing, a Syngenta scientist wrote to a colleague: “what we want to do is brush aside 10 years of research by others and replace it with our own.” The company would “employ the best people to help us” and would need “impeccable data” as well as “a lot of luck,” the email said, and the research had to be “dead solid airtight and self-contained” to be credible with both the scientific community and “the judge and jurors.” Syngenta told the Guardian and New Lede that research at the time was largely based on mouse studies of limited relevance to human exposure and that the company was seeking a more comprehensive analysis.
According to the records, secrecy was a recurring theme in internal communications. In a 2007 email, company officials discussed a need to minimize written communication about an analysis of paraquat and Parkinson’s data, with one message saying the discussion should not be shared in writing but communicated “verbally” to staff. In a 2008 email, company scientists were warned against written discussions about conducting certain studies and chided for writing that “a major objective of this programme is to reduce the risk” that Syngenta might lose Parkinson’s lawsuits. “Please can we call a halt to this correspondence,” a Syngenta executive wrote to the colleagues.
Outside the United States, paraquat has been banned in more than 70 countries. Sweden called for a ban in 2004, and the European Union followed with a bloc-wide ban in 2007. Many African countries, including Senegal and Côte d’Ivoire, banned the chemical in 2011. Brazil cited risks of Parkinson’s and concerns that paraquat may be mutagenic, meaning it could cause permanent mutations in DNA. The World Health Organization’s 2022 report on reducing Parkinson’s risks called for banning certain pesticides, including paraquat. At the US state level, Vermont and California have banned paraquat, citing risks that include an association between paraquat and Parkinson’s disease shown in years of scientific research, and California regulators announced in August 2026 that makers had voluntarily agreed to stop selling the chemical in the state after the state identified health concerns in connection with its use in new research. Several federal lawmakers have pushed for a nationwide ban.
China, the home of Syngenta’s owner ChemChina and a major manufacturing hub for paraquat exported to the United States and elsewhere, banned the chemical domestically in 2016 after commissioning its own independent dermal and inhalation toxicity study at a Chinese lab. Deposition testimony included in the recent court filings shows Syngenta was caught off guard by the Chinese testing; the fact that the Chinese government undertook the study without Syngenta’s knowledge was “alarming,” according to an internal company email confirmed by Syngenta scientist Phil Botham in a 2024 deposition. The EPA did not commission its own such studies, Botham testified. China began a phase-out of paraquat in 2012 and ultimately banned the chemical domestically in 2016 after finding “extreme toxicity risks through both routes of exposure and other health risks.”
The US EPA, which largely relies on safety data submitted by the companies selling pesticides, continues to greenlight paraquat use on millions of acres and has downplayed scientific findings linking paraquat to Parkinson’s, an incurable brain disease. In its 2021 decision, the agency said there was insufficient evidence of links between paraquat and Parkinson’s and that the “human health database for paraquat is considered complete.” Several health advocacy groups challenged that decision in court, and the EPA said it needed time to “further consider substantive issues.” In November 2025, the agency asked paraquat manufacturers to provide additional data on paraquat volatilization to help understand exposure risks to people living beyond areas where the chemical is sprayed. The agency said in June 2026 it would hold a roundtable over the summer to re-examine the “safety challenges” associated with paraquat; no such event has yet been held or scheduled.
Other suppliers continue to sell paraquat in the United States as the EPA maintains there is no “clear link” between paraquat exposure from regular use and “adverse health outcomes such as Parkinson’s disease and cancer.” EPA Administrator Lee Zeldin said in a January 2026 social-media post that the agency was making a decision to “freshly reassess” the safety of paraquat as part of an effort to recognize the “Make America healthy again” (Maha) movement. An EPA spokesperson contradicted Zeldin at the time, saying the administrator had been referring to the volatilization data request rather than a new safety review. Asked about the disclosures, the EPA said in a statement that it “cannot speculate on how this additional information would impact EPA’s assessment,” but noted it has based its paraquat assessments on an “extensive database of information.” The agency added: “If information exists that has not been submitted to EPA, EPA wants it so that any protections developed are rooted in gold standard science and reflective of the full universe of data.”
Critics of the EPA’s pesticide-approval regime called the new disclosures a case study in the failures and frailties of the agency and of a system that they said does more to protect corporate profits than consumer health. They noted that the revelations are particularly concerning in the wake of a US Supreme Court ruling declaring the EPA as the pre-emptive authority for determining when a pesticide product needs to include a particular health warning. Even some large food companies moved against paraquat long before most regulators: Dole, the Irish multinational fruit and vegetable producer, began eradicating paraquat from its fields 19 years ago, and a 2007 email between Syngenta executives about Dole’s decision noted a need to try to “influence” Dole’s press release on the matter “to ensure its not too damaging.”
Public-health researchers said the new disclosures raise broader questions about how pesticide safety is evaluated in the United States. “When the pesticides companies know from their own studies that their pesticides are harmful and don’t tell the public or regulators, then they are knowingly contributing to people getting sick and dying,” said Tracey Woodruff, a professor of epidemiology and population health at Stanford University School of Medicine. Syngenta rejected Woodruff’s claims and said it takes the safety of its products very seriously. Ted Schettler, a former physician who serves as science director for the Science and Environmental Health Network, said paraquat was a prime example of weaknesses in the current regulatory system. “[This situation] illustrates the public health risks of allowing the US EPA to be the sole arbiter of pesticide safety,” he said. “Untold numbers of people could have been prevented from developing Parkinson’s disease, not to mention other illnesses, if the agency had done its job of protecting public health.”
In court filings, Syngenta said claims that it did not provide regulators with proper information are “inaccurate and misleading,” and noted the EPA has “never cited or sanctioned Syngenta for failing to comply” with its disclosure obligations with respect to paraquat. The company said for each instance of not sharing information with the agency, there were other factors and findings that reduced the significance of the information, and that EPA guidance regarding company obligations under Fifra had “evolved” and the company had followed “processes designed to comply with its evolving obligations.” The 2026 disclosure follows prior reporting from 2022 and 2023 in which the New Lede and the Guardian obtained and revealed a set of internal corporate records showing that Syngenta and its predecessor corporate entities used an array of tactics for decades to downplay and discredit science linking what the company called its “blockbuster” weedkiller to Parkinson’s and other chronic health issues.