Paraquat Parkinson's Disease Lawsuit

What Is the Paraquat Lawsuit?

The paraquat lawsuit is a mass tort action alleging that exposure to the herbicide paraquat dichloride significantly increases the risk of developing Parkinson's disease. Thousands of agricultural workers, farm residents, and others exposed to paraquat have filed claims against the herbicide's manufacturer, Syngenta, and its primary U.S. distributor, Chevron.

These cases have been consolidated into MDL 3004 in the Southern District of Illinois. More than 5,000 cases are currently pending. Plaintiffs allege that Syngenta and Chevron knew about the link between paraquat and Parkinson's disease for decades but failed to warn users about this risk.

Scientific research, including a comprehensive 2011 meta-analysis, has found that paraquat exposure approximately doubles the risk of developing Parkinson's disease. Despite this evidence, paraquat remains on the U.S. market as an EPA-restricted use pesticide, though it has been banned in more than 50 countries worldwide.

The paraquat lawsuit shares similarities with the Roundup weed killer lawsuit, which also involves an herbicide linked to serious health consequences. Both cases involve allegations that manufacturers prioritized profits over public safety. To understand how these cases are handled, see our guide on how mass tort lawsuits work.

What Is Paraquat?

Paraquat dichloride is one of the most widely used herbicides in the world. It is a non-selective contact herbicide, meaning it kills virtually all green plant tissue it contacts. Paraquat is used on a wide variety of crops, including soybeans, corn, cotton, wheat, and fruit orchards, as well as for weed control on non-agricultural land.

Paraquat is classified as an EPA Restricted Use Pesticide (RUP), which means only certified, licensed applicators can purchase and apply it. This restriction exists because paraquat is extremely toxic — a single sip can be fatal to humans. Despite this restriction, many people beyond licensed applicators are exposed to paraquat through drift, contaminated water, and proximity to treated areas.

The chemical structure of paraquat is notable because it closely resembles MPP+, the toxic metabolite of MPTP — a compound known to cause Parkinson's-like symptoms in humans. This structural similarity is one of the biological mechanisms cited by researchers to explain how paraquat damages the dopamine-producing neurons in the brain that are affected in Parkinson's disease.

Paraquat has been banned in over 50 countries, including the entire European Union, China, Brazil, South Korea, and many others. The U.S. EPA has re-evaluated paraquat multiple times but has not banned it, though it has imposed additional safety requirements. The continued U.S. registration despite international bans is a significant issue in the litigation.

Paraquat Exposure Pathways

While paraquat is restricted to licensed applicators, exposure extends far beyond the person spraying the chemical. Multiple pathways of exposure have been documented:

All of these exposure pathways are relevant to the lawsuit. You do not need to have been the person who directly applied paraquat to qualify for a claim. If you lived near agricultural operations, worked on farms, or otherwise had proximity to paraquat application and were diagnosed with Parkinson's disease, you may have grounds for a claim. This is similar to how the Camp Lejeune lawsuit and AFFF foam lawsuit cover environmental exposure beyond direct use.

Products & Brands Named

Several paraquat formulations are sold in the United States. Syngenta's Gramoxone is by far the most widely used, but other formulations manufactured or distributed by various companies are also implicated in the litigation.

Who Qualifies for the Paraquat Lawsuit?

Eligibility for the paraquat Parkinson's disease lawsuit requires documenting both exposure to paraquat and a diagnosis of Parkinson's disease. The key challenge in many cases is establishing the exposure connection, especially for residents who were not the direct applicators.

If you are uncertain about whether your exposure history qualifies, request a free case evaluation. An attorney can investigate your work history and residential proximity to paraquat application areas.

Lawsuit Timeline

The paraquat Parkinson's disease litigation is built on decades of scientific research, with formal legal proceedings beginning in 2017 and intensifying after the MDL was established in 2021.

Settlement Amounts & Projections

As of early 2025, no global settlement has been reached in MDL 3004. The litigation is still in the bellwether trial phase, with outcomes of early trials expected to heavily influence settlement negotiations. Parkinson's disease is a progressive, incurable condition that significantly impacts quality of life, which is reflected in the projected settlement ranges.

For more information about how mass tort settlements are structured, see our guide on mass tort settlement amounts.

How to File a Claim

Filing a paraquat Parkinson's disease claim involves documenting your exposure history and medical diagnosis. An attorney experienced in the paraquat MDL can help build your case and navigate the complex litigation process. As with most mass tort cases, attorneys work on a contingency fee basis.

Named Defendants

The paraquat Parkinson's disease lawsuits primarily target the manufacturer and primary U.S. distributor of paraquat:

• Syngenta AG — The world's largest manufacturer of paraquat, based in Switzerland (now owned by ChemChina/Sinochem). Syngenta manufactures the Gramoxone brand, which is the most widely used paraquat product globally and in the United States. Plaintiffs allege that Syngenta has known about the paraquat-Parkinson's link for decades through its own internal research.
• Chevron U.S.A., Inc. — The primary U.S. distributor of paraquat products. While Chevron did not manufacture paraquat, it played a key role in marketing and distributing the herbicide throughout the United States. Plaintiffs allege Chevron also knew of the neurological risks and failed to warn end users.

Additional defendants in some cases include Helm Agro, Drexel Chemical, and other companies that manufactured or distributed generic paraquat products in the U.S.

Scientific & Medical Evidence

The scientific case linking paraquat to Parkinson's disease is supported by decades of research spanning animal studies, epidemiological studies, and mechanistic biological research. Key findings include:

• A 2011 meta-analysis reviewed multiple epidemiological studies and concluded that paraquat exposure is associated with an approximately 2-fold increase in the risk of Parkinson's disease.
• The Agricultural Health Study (2009), one of the largest long-term studies of pesticide applicators in the United States, found a significant association between paraquat use and Parkinson's disease.
• Biological mechanism: Paraquat's chemical structure closely resembles MPP+, the toxic metabolite of MPTP, which is known to selectively destroy dopamine-producing neurons in the substantia nigra region of the brain — the same neurons affected in Parkinson's disease.
• Animal studies have demonstrated that paraquat exposure causes degeneration of dopaminergic neurons, formation of Lewy body-like structures, and Parkinson's-like motor deficits in laboratory animals.
• A 2019 study in the International Journal of Epidemiology found that paraquat exposure was associated with Parkinson's disease even after controlling for other pesticide exposures.
• Internal company documents obtained through litigation discovery have revealed that Syngenta was aware of research linking paraquat to neurotoxicity and Parkinson's disease risk but did not adequately disclose these findings.

The combination of epidemiological evidence, biological mechanism, and animal study data provides a strong scientific foundation for the paraquat litigation. Unlike some mass tort cases where the science is debated, the paraquat-Parkinson's link is well-established in the medical literature.