Paraquat Parkinson’s Lawsuit: MDL, Settlements, and Causation Ruling

The paraquat Parkinson’s lawsuit is a mass tort brought by thousands of people diagnosed with Parkinson’s disease after exposure to the herbicide paraquat, alleging that Syngenta and Chevron knew for decades the chemical could damage the brain and hid that risk. More than 8,200 cases were pending across federal and state courts as of late 2025,¹ and in April 2025 the parties signed a settlement framework intended to resolve much of the federal multidistrict litigation.²

Who Can File a Paraquat Lawsuit

People diagnosed with Parkinson’s disease after exposure to paraquat may be eligible to file. The occupational groups most commonly affected are farmers and farmworkers, licensed applicators, landscapers, and golf course groundskeepers. Rural residents who lived near sprayed fields and were exposed through chemical drift may also qualify.¹ Exposure can date back to any point after 1966.

Deadlines vary by state. Statutes of limitations typically run one to three years from either the Parkinson’s diagnosis or from when the person discovered the potential link between their illness and paraquat.¹ Useful evidence includes employment records, medical records, applicator licenses, purchase receipts for paraquat products, and coworker testimony.

One caution about the current settlement framework: attorneys outside the MDL leadership have reported that the deal imposes strict diagnostic and exposure-proof requirements that would exclude some claimants.³ Whether a given case fits inside or outside those terms is worth clarifying early with counsel.

Where the Cases Stand in 2026

The federal multidistrict litigation, MDL No. 3004, sits in the U.S. District Court for the Southern District of Illinois under Chief Judge Nancy J. Rosenstengel, where cases were consolidated in June 2021.⁴ As of mid-2026, the MDL includes roughly 6,580 pending cases and remains under an extended stay while the global settlement framework is finalized.⁵ A February 2026 order addressed voluntary dismissals, suggesting some plaintiffs are beginning to accept settlement offers. There are no upcoming federal trial dates, and the January 2026 status conference was canceled.

State litigation is a separate track. Philadelphia’s Court of Common Pleas held 1,843 cases in early 2026, up from 728 in mid-2024. In October 2025, the U.S. Supreme Court declined to hear Syngenta’s challenge to Pennsylvania’s consent-by-registration jurisdiction, clearing the way for those cases.⁶ The first Philadelphia bellwether was set to begin January 28, 2026, on behalf of a 77-year-old retired landscaper diagnosed in 2021; Syngenta settled the night before opening statements on confidential terms.⁷ No paraquat case has reached a jury verdict.

The 2025 Settlement Framework

On April 26, 2025, the parties told the court they had signed a settlement framework covering much of the federal MDL, which at that point included more than 5,800 active cases.² Plaintiffs’ co-lead counsel Khaldoun Baghdadi told the court terms should be finalized within 30 days. Dollar figures have not been publicly disclosed. One legal source estimated individual payouts would range from tens of thousands to over $1 million depending on injury severity and duration of exposure.¹

Syngenta framed the deal narrowly. The company said there is “no merit” to the claims and that entering settlement negotiations “in no way implies that paraquat causes Parkinson’s Disease or that Syngenta has done anything wrong.”² Some attorneys with cases outside the MDL leadership have complained they were excluded from negotiations and that opt-out rates among certain plaintiffs’ groups remained an ongoing issue for the settlement’s viability into early 2026.⁸

The 2021 Illinois Settlements

An earlier round of resolutions came from the original Illinois state court cases. In June 2021, Syngenta agreed to pay $187.5 million to settle several of those claims, including the first-filed Hoffmann case.⁹ Terms were confidential and Syngenta admitted no wrongdoing. A subsequent court order required defendants to share the Hoffmann discovery with attorneys in the MDL and in California proceedings, giving the broader plaintiff pool access to internal documents that would become central to later cases.

What the Lawsuits Allege

The principal defendants are Syngenta (and its predecessor, Imperial Chemical Industries) and Chevron USA. ICI introduced paraquat commercially in 1962 and manufactured it for Chevron, which held exclusive U.S. distribution rights from roughly 1964 until 1986.¹⁰ Syngenta’s U.S. subsidiary took over sales after 1986. Wilbur-Ellis Company and Growmark appear as defendants in individual cases.

The complaints generally raise three theories:

Design defect: paraquat was unreasonably dangerous because exposure through inhalation, skin absorption, or ingestion caused permanent neurological damage, and safer alternatives existed.
Failure to warn: defendants did not adequately warn users about the risk of irreversible brain damage and Parkinson’s disease from chronic, low-dose exposure.
Negligence: defendants failed to conduct adequate research and testing on paraquat’s long-term neurodegenerative effects and negligently labeled their products.

What Internal Documents Showed

Thousands of internal corporate records disclosed during the litigation clash with the defendants’ public position. Reporting by The Guardian and The New Lede showed that ICI’s own 1960s animal studies documented weakness, incoordination, and tremors, and that by 1968 autopsies of people who ingested paraquat confirmed the chemical accumulated in human brain tissue.¹¹

Mid-1970s communications show ICI and Chevron staff discussing “permanent CNS effects” and legal exposure. One ICI scientist called the potential for chronic health effects “a quite terrible problem” in a 1975 letter to a Chevron toxicologist.¹¹ A 1985 Chevron memo noted a high correlation between paraquat exposure and Parkinson’s cases and acknowledged the chemical’s structural similarity to MPP+, a substance known to destroy dopamine neurons.¹²

Internal Syngenta research conducted in 2003 by company scientist Louise Marks found statistically significant loss of dopamine neurons in mice. According to The Guardian, this data was not disclosed to the EPA until 2019, while Syngenta’s public website stated that paraquat did not cross the blood-brain barrier.¹¹ A company official later admitted in deposition testimony that these public communications contained “inaccuracies.” Additional documents describe an internal Syngenta “SWAT” team assembled to influence scientific research, public opinion, and regulatory proceedings, and efforts through CropLife America to discredit researcher Dr. Deborah Cory-Slechta and block her from EPA advisory panels.¹³

The Causation Ruling That Nearly Ended the Federal Case

On April 17, 2024, Judge Rosenstengel excluded the testimony of Dr. Martin Wells, the plaintiffs’ sole general-causation expert. Applying the amended Federal Rule of Evidence 702, the court found “numerous methodological red flags,” including inconsistent definitions, a non-systematic approach to selecting studies for his meta-analysis, and what the court described as “results-driven analysis.”¹⁴ The same day, the court granted summary judgment for the defendants in the first four bellwether cases and dismissed them with prejudice.¹⁵

Plaintiffs appealed to the Seventh Circuit. In April 2025, after the parties signed the settlement framework, they moved to hold the appeal in abeyance, and it may be mooted if the settlement takes effect.¹⁶ A second-round bellwether preparation Judge Rosenstengel had ordered was stayed in May 2025 to allow settlement talks to proceed.¹⁷

Regulatory Status and Why Paraquat Is Still in Use

Paraquat, first sold commercially in 1962 under the brand name Gramoxone,¹⁰ is a restricted-use pesticide in the United States, meaning only licensed applicators can handle it.¹⁸ More than 74 countries have banned it, including China, Brazil, and every EU member state.¹⁹

The EPA has moved unevenly. Its 2021 interim registration decision added safety requirements such as limits on aerial spraying, restrictions on pressurized sprayers, and a respirator mandate, but concluded there was “insufficient” evidence linking paraquat to Parkinson’s disease.²⁰ Health advocacy groups challenged that decision in the Ninth Circuit. In January 2025, the EPA asked the appeals court to let it withdraw the 2021 decision entirely so it could investigate further, citing concerns about volatilization and inhalation risks to bystanders.²¹ As of 2026, the EPA’s reassessment is incomplete, and paraquat continues to be used legally on American farms.¹⁸

States have begun to move on their own. Vermont became the first to enact a paraquat ban when Governor Phil Scott signed H. 739 on May 26, 2026; the law takes effect November 1, 2026, requires permits during a transition period, and prohibits all sale and use after 2030.²² Separately, Syngenta announced on March 3, 2026, that it would cease global paraquat production by the end of June 2026 and close its sole manufacturing facility in Huddersfield, England, attributing the decision to competition from generic manufacturers.²³ The Michael J. Fox Foundation said the announcement “does not solve the problem” and called for a federal ban, warning that generic producers will fill the void as long as paraquat remains legal in the United States.²⁴

1
Sokolove Law. Paraquat Lawsuit
2
The New Lede. Syngenta Moving to Settle Thousands of Lawsuits
3
The New Lede. Paraquat MDL Hearing Transcript
4
U.S. District Court, Southern District of Illinois. Paraquat Products Liability Litigation
5
Wisner Baum. Paraquat Parkinsons Lawsuit
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Motley Rice. Paraquat Lawsuit
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The New Lede. Syngenta Settles Bellwether Trial
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Law.com. Aimee Wagstaff Ordered Into Court, Denies Attacking Paraquat Settlement
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Seeger Weiss. Paraquat Lawsuit
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U.S. Right to Know. Isaak v. Syngenta Complaint
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The Guardian. Syngenta Weedkiller Pesticide Parkinsons Disease Paraquat Documents
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Washington Legal Foundation. In re Paraquat: Studious Gatekeeping Exposes and Excludes Made-for-Litigation Testimony
15
GovInfo. In re Paraquat Products Liability Litigation, Summary Judgment Order
16
Miller & Zois. Paraquat Lawsuit
17
U.S. District Court, Southern District of Illinois. Paraquat MDL Order
18
Michael J. Fox Foundation. Vermont Passes First-in-Nation Ban of Paraquat
19
WUFT. The Global Paraquat Trail
20
The Washington Post. Paraquat EPA Pesticide Parkinsons
21
The New Lede. EPA Moves to Withdraw Decision on Paraquat
22
Safety and Health Magazine. Vermont Finalizes Landmark Ban of Paraquat
23
Syngenta. Syngenta to Cease Paraquat Production
24
Michael J. Fox Foundation. What Syngenta’s Decision to End Paraquat Production Means for Parkinsons Risk