Paraquat is a restricted-use herbicide manufactured primarily by Syngenta and distributed by Chevron Phillips Chemical and Growmark. Despite being banned in more than 70 countries including the European Union, China, Brazil, and Thailand, paraquat remains legal in the United States, where approximately 10 million pounds are applied annually. Scientific evidence — including the landmark Farming and Movement Evaluation (FAME) study published in 2011 — demonstrates that paraquat exposure increases the risk of Parkinson’s disease by 2.5 times. The mechanism is well understood: paraquat triggers oxidative stress through redox cycling, inhibits mitochondrial complex I, and selectively kills dopamine-producing neurons in the substantia nigra, leading to the progressive motor and cognitive deterioration characteristic of Parkinson’s disease. MDL 3004 was established in June 2021 in the Southern District of Illinois, with approximately 5,000 cases pending. Bellwether proceedings and settlement negotiations are ongoing, with projected individual settlements ranging from $20,000 to over $1,000,000 depending on disease severity and exposure documentation.
The Mertens v. Syngenta bellwether case settles on the eve of a Philadelphia trial on January 28–29, 2026, with confidential terms. This follows two earlier Philadelphia state court settlements in July and October 2025. A broader framework settlement agreement had been reached in April 2025. The litigation pause has been extended through March 6, 2026, as the parties work toward comprehensive resolution of the remaining approximately 5,000 cases.
settlementJudge Rosenstengel issues a Daubert ruling excluding the testimony of Dr. Martin Wells, a statistician, leading to the dismissal of four bellwether cases on April 17, 2024. Separately, the EPA completes its registration review of paraquat, reaffirming the herbicide’s registration despite submissions of 90 studies by the Michael J. Fox Foundation. The Daubert ruling, while a setback, does not affect the broader scientific evidence available through other expert witnesses.
verdictDr. Ray Dorsey and colleagues publish a landmark paper documenting what they term "agnotology" — the deliberate production of ignorance — by Syngenta regarding the paraquat-Parkinson’s connection. The paper systematically catalogues Syngenta’s "Scientific Influencing Strategy," suppression of the Louise Marks studies, targeting of independent researchers, and use of reputation management firms. The paper draws explicit parallels to the tobacco industry’s decades-long campaign to deny the link between smoking and cancer.
verdictThe Judicial Panel on Multidistrict Litigation consolidates paraquat Parkinson’s cases in the Southern District of Illinois before Judge Nancy J. Rosenstengel (MDL 3004). Syngenta simultaneously announces a $187.5 million initial settlement fund. The MDL consolidation signals the scale and seriousness of the litigation, with thousands of cases from across the country coordinated for pre-trial proceedings.
settlementChina bans all domestic paraquat sales and use, the same year ChemChina acquires Syngenta for $43 billion. The first U.S. lawsuits alleging that paraquat exposure caused Parkinson’s disease are filed in federal courts. The combination of international bans, strong scientific evidence, and newly available internal corporate documents creates the conditions for mass litigation.
filingThe landmark Farming and Movement Evaluation (FAME) study, led by Dr. Caroline Tanner and published in Environmental Health Perspectives, finds that paraquat users have a 2.5-fold (250%) increased risk of developing Parkinson’s disease compared to non-users. The study’s use of detailed pesticide use records rather than self-reported data gives it exceptional methodological rigor. The FAME study becomes the cornerstone of plaintiffs’ causation arguments in the litigation.
filingThe European Commission declines to renew paraquat’s authorization under Directive 91/414/EEC (Decision 2007/442/EC), effectively banning the herbicide throughout the EU. The decision cited unacceptable risks to operators and bystanders, including evidence of neurotoxicity. The EU ban was upheld by the European Court of Justice in 2008 and is frequently cited in the U.S. litigation as evidence that international regulators reached more protective conclusions than the EPA.
regulatoryICI’s agrochemical division (via Zeneca) merges with Novartis’s crop science division to form Syngenta AG, headquartered in Basel, Switzerland. Syngenta inherits ICI’s paraquat product line, manufacturing operations, and accumulated internal research documenting neurotoxicity — including the suppressed Louise Marks studies showing substantia nigra damage.
product-launchThe U.S. Environmental Protection Agency classifies paraquat as a Restricted Use Pesticide (RUP) due to its acute toxicity, limiting purchase and application to licensed certified applicators. The restriction acknowledged paraquat’s danger but focused on acute poisoning risk rather than chronic neurological effects. The RUP classification remains in effect today.
regulatoryImperial Chemical Industries (ICI) begins commercial marketing of paraquat as a broad-spectrum contact herbicide. ICI’s own internal research had already identified neurotoxic properties of the compound as early as 1958 and confirmed that paraquat enters the brain in mice by 1966. Despite this knowledge, ICI marketed paraquat without neurological warnings for decades.
product-launchSyngenta agreed to establish a $187.5 million initial settlement fund at the time of MDL 3004’s formation in June 2021. The fund was created to resolve early-filing paraquat Parkinson’s claims and demonstrated Syngenta’s recognition of significant liability exposure. The settlement marked the first major financial resolution in the paraquat litigation and established a baseline for case valuations.
The Mertens v. Syngenta bellwether case settled on the eve of trial in Philadelphia on January 28–29, 2026, with confidential terms. The case had been selected as a bellwether to test plaintiffs’ causation theory and damages evidence before a jury. The pre-trial settlement signals the defendants’ assessment that trial posed significant risk and provides momentum for resolution of the broader MDL.
While not a paraquat case, the Roundup/glyphosate litigation provides the most directly comparable precedent for pesticide-cancer/neurodegenerative disease mass torts. Bayer agreed to pay approximately $10.9 billion to settle over 100,000 Roundup claims alleging the herbicide caused non-Hodgkin lymphoma. Individual jury verdicts in the Roundup cases ranged from $80 million to $2 billion before reductions. The Roundup litigation demonstrates that pesticide manufacturers face massive liability exposure when scientific evidence, internal corporate documents, and failure-to-warn claims converge — the same combination present in the paraquat litigation.
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