Agrochemical Giants Face Explosive Paraquat Parkinson's Disease Allegations as Wisner Baum Trial Date is Set in California

California's first paraquat Parkinson's trial is set for March 1, 2027, as litigation against Syngenta and Chevron progresses. The case alleges manufacturers knew or should have known about paraquat's neurotoxic properties and failed to adequately warn consumers about risks. 

LOS ANGELES, June 9, 2026 /PRNewswire/ -- Nationwide paraquat litigation moved one step closer to trial when the first California case was scheduled for March 1, 2027, in Contra Costa County Superior Court. The plaintiff alleges that exposure to the pesticide paraquat caused his Parkinson's disease. Anderson v. Syngenta AG, et al. is expected to become a landmark proceeding that will shape future litigation for thousands of other farmers and agricultural workers with Parkinson's across the country.

Wisner Baum LLP, a nationally recognized plaintiffs' law firm, is representing the Anderson family alongside co-counsel R. Allen Smith Jr. of The Smith Law Firm. Attorneys Brent Wisner, Conor Kennedy and Harrison E. James will serve on the plaintiffs' trial team for the case. The firm is representing farmers, pesticide applicators, landscapers, and others who sprayed Gramoxone^® and other paraquat-containing products and later developed Parkinson's disease or Parkinsonism.

"This will be the first time a California jury will hear the evidence about what paraquat manufacturers knew regarding the herbicide's connection to Parkinson's disease," said Brent Wisner, lead trial attorney and managing partner of Wisner Baum. "These cases reveal a disturbing reality: Syngenta and Chevron knew for decades that paraquat destroyed the dopamine-creating cells in the brain—the very cells that, when dead, cause Parkinson's. It's reprehensible, and when a jury sees this evidence, most of which is still sealed from public scrutiny, there will be a reckoning."

A Progressive Disease with Life-Altering Consequences

Parkinson's disease is a progressive neurological disorder that affects movement, coordination, and cognitive functioning. Symptoms include tremors, rigidity, slowed movement, balance impairment, and other debilitating complications. As the disease advances into its later stages, patients face compounding medical crises that often prove fatal.

Nearly one million Americans are currently living with the disease, according to the Parkinson's Foundation. Some studies have found increased risk among populations who live in rural areas or drink well water, findings that may ultimately be linked to pesticide runoff.

Decades of Exposure, Known Toxic Properties

Plaintiffs Keith and Cheryl Anderson allege that prolonged paraquat exposure on their California walnut farm caused Mr. Anderson to develop Parkinson's disease.

According to the complaint, Mr. Anderson was repeatedly exposed to paraquat from approximately 1994 through 2022, via mixing, loading, spraying, and otherwise handling paraquat products, including Gramoxone^®.

The complaint alleges the neurotoxin entered his body through inhalation, skin absorption, and ingestion during routine agricultural use, and—as a result—Mr. Anderson developed Parkinson's disease and was diagnosed in 2021.

The lawsuit further alleges that manufacturers Syngenta and Chevron knew, or should have known, about paraquat's neurotoxic properties for decades, yet failed to adequately warn users. "Keith Anderson represents thousands of people who used these products, unaware of the risk, and now face devastating neurological injuries allegedly linked to years of exposure," James said.

Scientific Evidence Has Mounted for Years

More than a decade ago, laboratory studies found that paraquat can cause oxidative stress and damage to dopamine-producing neurons. Several other epidemiological and laboratory studies have likewise linked paraquat exposure to elevated Parkinson's disease risk.

Research from the Agricultural Health Study (AHS), a large, federally funded cohort of pesticide applicators, reported that exposure to paraquat was associated with an elevated risk of Parkinson's disease among agricultural workers.

A related, more targeted study published soon after confirmed AHS's findings. Top Parkinson's disease researchers concluded that with respect to paraquat being associated with Parkinson's disease, "[t]he data is overwhelming." A lead investigator at the National Institutes of Health described it as "about as persuasive as these things can get."

"Thanks to independent scientists, we're now aware of the danger, but the public should have known decades ago," said Kennedy. "This trial will be a critical opportunity to give agricultural workers and their families their day in court and to demand accountability from companies that have profited from a dangerous product for decades."

Scrutiny Amidst Restrictions

The case comes amid growing scrutiny over paraquat, which remains widely used in U.S. agriculture despite bans or restrictions in dozens of countries.

"When you see a chemical banned across large parts of the world but still widely used in American agriculture, you have to wonder whether the system designed to protect public health is working the way it's supposed to," Wisner said.

Plaintiffs' attorneys contend that internal corporate documents obtained through discovery may show longstanding knowledge of paraquat's toxicity and potential connection to neurological injury. "Syngenta explicitly said that its stewardship of paraquat would involve the 'placing of economics before safety,'" Kennedy said.

"For years, these issues largely remained buried in scientific literature and internal corporate records," James said. "Now, jurors will have the opportunity to evaluate the evidence that these companies acted recklessly."

About Wisner Baum 

Wisner Baum is a nationally recognized plaintiffs' law firm with offices across the United States. For decades, the firm has represented individuals harmed by corporate misconduct, dangerous products, environmental exposure, and systemic failures. Wisner Baum is known for its trial experience, investigative rigor, and leadership in complex, high-impact litigation involving some of the world's largest companies. For more information, visit www.wisnerbaum.com 

References

• Anderson, K., & Anderson, C. (2022, August 5). Complaint for damages (Case No. C22-01622). Superior Court of the State of California, County of Contra Costa, Judicial Council Coordinated Proceeding No. 5031, California Paraquat Cases. 
• Baltazar, M. T., Dinis-Oliveira, R. J., de Lourdes Bastos, M., Tsatsakis, A. M., Duarte, J. A., & Carvalho, F. (2014). Pesticides exposure as etiological factors of Parkinson's disease and other neurodegenerative diseases—A mechanistic approach. Toxicology Letters, 230(2), 85–103. 
• Parkinson's Foundation. (2024). Statistics on Parkinson's disease. 
• Tanner, C. M., Kamel, F., Ross, G. W., Hoppin, J. A., Goldman, S. M., Korell, M., Marras, C., Bhudhikanok, G. S., Kasten, M., Chade, A. R., Comyns, K., Richards, M. B., Meng, C., Priestley, B., Fernandez, H. H., Cambi, F., Umbach, D. M., Blair, A., Sandler, D. P., & Langston, J. W. (2011). Rotenone, paraquat, and Parkinson's disease. Environmental Health Perspectives, 119(6), 866–872. 

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SOURCE Wisner Baum