Thousands of U.S. farmers have Parkinson’s

Lead

Hundreds of U.S. farmers and farmworkers — including longtime peach grower Paul Friday of Coloma, Michigan — say years of working with the herbicide paraquat contributed to their diagnoses of Parkinson’s disease. Dozens of lawsuits now accuse manufacturers and sellers of failing to warn about neurological risks, while federal regulators continue to weigh the chemical’s risks and benefits. More than 6,400 cases are consolidated in a federal multidistrict litigation in Southern Illinois and state suits are active in Pennsylvania and California. Meanwhile, paraquat remains legal in the United States even as more than 70 countries have banned it.

Key takeaways

More than 6,400 lawsuits alleging paraquat–Parkinson’s links are pending in the U.S. District Court for the Southern District of Illinois; another roughly 1,300 are in Pennsylvania and about 450 in California.
U.S. farmers apply an estimated 11 million to 17 million pounds of paraquat annually, according to the U.S. Geological Survey (USGS).
Paraquat has been prohibited in 70+ countries, including the U.K. and China (where much commercial production occurs), but the EPA reauthorized its use in the U.S. in 2021 under strict conditions.
National Poison Data System recorded 114 paraquat exposure reports and one death in 2023; the system logged 1,151 calls from 2014–2023.
Epidemiological and lab studies have shown associations or biological plausibility between paraquat exposure and Parkinson’s-like neuron damage, but regulators and manufacturers dispute a settled causal link.
Syngenta and other sellers have disputed liability and maintained paraquat is safe when used as labeled; some internal historical documents show early company concern about central nervous system effects.
State-level efforts to restrict or ban paraquat are under way; California expedited a safety reassessment and Pennsylvania lawmakers introduced prohibition legislation in 2024–2025.

Background

Paraquat, first sold commercially in the early 1960s under brand names such as Gramoxone, is a fast-acting, nonselective herbicide used as a pre-plant burn-down to clear fields of weeds. Its speed and effectiveness made it a staple for producers of cotton, soybeans, corn and other commodity crops, and the USGS estimates annual U.S. use at 11–17 million pounds in recent years. Because the chemical destroys plant tissue rapidly, it is also highly toxic to humans; labels include skull-and-crossbones warnings, a blue dye, and emetic agents intended to reduce fatal ingestion.

International responses diverged: Norway banned paraquat in 1981; the European Union adopted a full ban in 2007; China phased out domestic use and tightened controls in the 2010s. Despite those moves, major portions of the global supply have continued to originate in Chinese manufacturing and multinational firms that sell to countries where it remains registered. In the United States the EPA completed a scheduled review and in 2021 concluded paraquat could remain on the market with strengthened protections, a decision that has been litigated and remains under further agency review.

Main event

Individual farmer accounts and clustered legal filings have brought the paraquat controversy into focus. Paul Friday, diagnosed with Parkinson’s in 2017 after decades spraying paraquat on his Michigan peach orchard, is one of many plaintiffs who say occupational exposure explains otherwise unexplained disease. Other plaintiffs named in ongoing litigation include California stone-fruit grower Jim Krause (diagnosed 2019, died 2024), Ohio winemaker Dave Jilbert (diagnosed 2020), and Alabama farmer Mac Barlow — each alleging long-term paraquat use preceded Parkinson’s symptoms.

The legal campaign has followed a multidistrict litigation (MDL) model in Southern Illinois that consolidates federal claims for pretrial handling. Plaintiffs allege manufacturers and distributors failed to warn about neurological risks despite decades of studies and, plaintiffs say, internal company documents suggesting central nervous system concerns. Defendants — including Syngenta and Chevron (a past seller) — deny paraquat causes Parkinson’s and contend litigation is unfounded; Chevron says it has not manufactured paraquat since 1986 and disputes liability.

Negotiations toward a broad settlement advanced in April 2025 but remained incomplete in court records; if no deal finalizes, bellwether trials could proceed to test scientific evidence and company conduct. Parallel state actions and proposed legislation in several states — and federal petitions and lawsuits challenging the EPA’s 2021 reapproval — keep pressure on regulators while paraquat stays in commercial use for now.

Analysis & implications

Scientific assessment of paraquat and Parkinson’s involves multiple evidence streams: toxicology showing paraquat can damage dopamine-producing neurons in animal models, epidemiological studies reporting elevated Parkinson’s risk among exposed farmworkers or residents near treated fields, and company and regulatory dossiers reviewing decades of data. Laboratory work from several groups found paraquat concentrates in brain tissue in animal inhalation and systemic-exposure models, creating biological plausibility for neurotoxicity. Still, proving causation in people is difficult because Parkinson’s typically appears years or decades after exposure and has mixed genetic and environmental causes.

Regulatory choices turn on risk–benefit calculations. The EPA’s 2021 reapproval weighed paraquat’s agricultural utility — including as a resistance-management tool in settings with few alternatives — against occupational and bystander exposure risks, and implemented labeling and buffer-zone restrictions. Critics argue those mitigations cannot remove the long-term, low-level exposure risks implicated in recent studies and that reauthorization contradicts international trends. A full ban in the U.S. would force growers to switch practices or substitute other herbicides, with potential economic impacts and possible unintended consequences such as increased use of other chemicals.

Litigation outcomes could reshape incentives for manufacturers and regulators. Large settlements or adverse trial verdicts might accelerate reformulations, tighter controls, or market withdrawal; conversely, rulings favoring defendants or equivocal science could prolong use and litigation. For public health, the central question remains whether regulatory action should prioritize precaution given the disease burden: roughly 90,000 Americans are diagnosed with Parkinson’s each year and global cases are projected to double by 2050, partly due to aging populations.

Comparison & data

Metric	Recent value
Estimated U.S. paraquat use annually	11–17 million pounds (USGS)
MDL cases in Southern Illinois	more than 6,400 pending
NPDS paraquat reports (2023)	114 exposures; 1 death
NPDS paraquat calls (2014–2023)	1,151 calls

The table above places the scale of agricultural use beside measured acute exposures and the volume of litigation. High annual tonnage underscores why occupational and drift exposures are plausible; at the same time, acute poisonings (reflected in NPDS data) differ from the low-dose, long-latency exposures implicated by Parkinson’s studies. The MDL count indicates many plaintiffs alleging chronic harm, but case numbers are not a direct measure of causation—rather, they reflect the scope of personal injury claims tied to life-long agricultural practices.

Reactions & quotes

Advocates, clinicians and industry spokespeople have offered sharply different interpretations of the same data. Below are representative statements with context.

“What we’ve seen over the course of decades is a systemic failure to protect farmworkers and the agricultural community from pesticides.”

Jonathan Kalmuss-Katz, Earthjustice (environmental law group)

Earthjustice, which has sued the EPA over its reauthorization decision, frames the dispute as regulatory failure and emphasizes worker protections. The organization has pressed for an approach grounded in the precautionary principle given mounting epidemiology and toxicology evidence.

“For the vast majority of Americans, the cause of Parkinson’s disease lies not within us, but outside of us, in our environment.”

Ray Dorsey, neurologist and Parkinson’s researcher

Dorsey underscores the role of environmental exposures in most Parkinson’s cases and argues that prevention through environmental controls could reduce incidence. His comments are drawn from clinical and research perspectives linking non-genetic risks to disease trends.

“The scientific evidence simply does not support a causal link between paraquat and Parkinson’s disease, and paraquat is safe when used as directed.”

Syngenta spokesperson (company statement)

Syngenta and other industry actors continue to deny a causal relationship and emphasize compliance with label directions and regulatory approvals. The company also notes settlements in past litigation do not constitute admissions of liability.

Unconfirmed

Whether paraquat exposure alone, in isolation from other pesticides or genetic factors, is sufficient to cause Parkinson’s in individual patients remains scientifically unresolved.
Interpretations of internal company documents vary: some lines suggest awareness of CNS effects, but they do not establish company belief in a causal link to Parkinson’s.
The precise number of U.S. residents who developed Parkinson’s because of paraquat exposure cannot be determined from current public datasets.

Bottom line

The paraquat dispute sits at the intersection of occupational health, agricultural economics and scientific uncertainty. Tens of thousands of pounds remain in U.S. fields annually, and thousands of plaintiffs claim that long-term exposure contributed to degenerative neurological disease. Regulators must weigh the chemical’s agronomic utility and lack of ready substitutes against epidemiological signals and laboratory findings that support biological plausibility for neurotoxicity.

Litigation and state actions are likely to accelerate regulatory scrutiny and could lead to settlement, further restrictions, or, conversely, continued use if courts and agencies find the evidence inconclusive. For now, paraquat’s fate in the United States will depend on how regulators synthesize decades of studies, the trajectory of high-stakes litigation, and public and legislative pressure to reduce occupational and community exposure.

Thousands of U.S. farmers have Parkinson’s. They blame a deadly pesticide.