How Paraquat Exposure May Increase the Risk of Parkinson’s Disease
According to the National Institutes of Health (NIH) FAME study, people who used paraquat had a 2.5 times greater chance of developing Parkinson's disease. Researchers think this increased risk is due to oxidative stress. Now, thousands of lawsuits claim paraquat exposure is linked to Parkinson's.
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- Medically reviewed by Rajesh Burela, D.O.
- Last update: September 3, 2026
- Est. Read Time: 7 min read
- A 2.5 times higher risk of Parkinson’s was linked to paraquat use in the NIH FAME study.
- More than 70 countries have banned or heavily restricted paraquat. The U.S. still allows restricted use.
- 6,666 Parkinson’s-related paraquat lawsuits are pending in a Southern Illinois federal court as of September 2026.
Can Paraquat Cause Parkinson's Disease?
Some studies suggest that people who use paraquat are roughly 2.5 times more likely to develop Parkinson’s disease. Research has also linked paraquat to harmful changes in the brain that are associated with Parkinson’s.
- 2024 International Journal of Epidemiology study:
- People who live or work near fields where paraquat is used may have up to twice the risk of Parkinson’s disease. The risk increases if they are exposed for longer times or to larger amounts.
- 2019 meta-analysis:
- An analysis of 13 studies found that people exposed to paraquat had a 64% higher chance of developing Parkinson’s.
- 2011 NIH FAME study:
- People who used paraquat or rotenone were 2.5 times more likely to develop Parkinson's disease.
Studies Linking Paraquat to Parkinson’s Disease
A 2024 study in the International Journal of Epidemiology looked at 829 Parkinson’s patients in California’s Central Valley. It found that people who lived or worked within 500 meters of fields where applicators sprayed paraquat had up to twice the risk of developing Parkinson’s. The risk increased with longer or more intense exposure.
Another 2024 study in Open Medicine found that paraquat can cross the blood-brain barrier and harm dopamine neurons, the cells that are lost due to Parkinson’s disease. This can affect the brain and may raise the risk of Parkinson’s.
How Paraquat Harms the Brain
Paraquat can damage your brain by causing oxidative stress, mitochondrial dysfunction, neuroinflammation and altered lipid metabolism. These issues are implicated as mechanisms involved in the progression of Parkinson’s disease.
Oxidative stress occurs when there is an imbalance of antioxidants and reactive, unstable oxygen molecules in the body. Mitochondrial dysfunction occurs when energy production in your cells is adversely impacted.
Both oxidative stress and mitochondrial dysfunction can cause the loss of nigral dopaminergic neurons that are responsible for dopamine in your nervous system. The loss of these neurons is linked to Parkinson’s.
Certain brain cells that help control movement, called dopaminergic neurons, are especially at risk of damage. These neurons expend energy quickly, rely on mitochondria and are exposed to the natural breakdown products of dopamine itself. This makes them more likely to be harmed by paraquat than other kinds of brain cells.
When paraquat causes oxidative stress in dopaminergic neurons, it may also lead to the misfolding and clumping of a protein called alpha-synuclein. Studies have found that these clumps, called Lewy bodies, are a sign of Parkinson’s and can be found in the brains of people with the disease.
How Long After Paraquat Exposure Can Parkinson’s Develop?
Parkinson’s disease often appears years or decades after someone is exposed to paraquat. Some studies have found the strongest links when paraquat exposure happened 11 to 30 years before diagnosis. This makes it more difficult to recognize the connection between a Parkinson’s diagnosis and past paraquat usage.
Many people filing paraquat lawsuits now were exposed to paraquat in the 1970s, 1980s or 1990s, but did not receive a Parkinson’s diagnosis until the 2000s or later. During this time, the disease developed slowly in the body before specific symptoms appeared.
Since Parkinson’s symptoms usually show up long after exposure, most states follow a “discovery rule” for filing deadlines. This means the time limit to file a claim usually starts when you are diagnosed, not when you were exposed. A paraquat attorney can explain the deadline for your state.
Who Is Most at Risk?
Your risk for developing Parkinson’s from paraquat exposure depends on several factors. These include your proximity to paraquat, how long you were exposed and your level of exposure.
Licensed Applicators and Farmworkers
People who mix, load or spray paraquat, including farm owners, licensed pesticide applicators and hired agricultural workers, face the highest documented risk. This is because they often have repeated and direct contact with the chemical.
People may be exposed through skin contact, inhaling spray mist during application or reentering treated fields. The longer and more intense the exposure, the greater the risk.
People Living Near Treated Fields
People living near treated fields may also face increased risk. Residents near spraying zones may experience chronic low-dose paraquat exposure via drift or contamination.
The 2024 UCLA study found that people living or working within 500 meters of paraquat-treated fields had up to twice the risk of Parkinson’s. Exposure can happen through spray drift, runoff and soil residue. People can also be exposed to Paraquat after its initial application because it can remain in soil for years.
Family Members of Applicators
When someone who applies paraquat brings pesticide residue home on contaminated clothing, shoes or equipment, they may unintentionally expose their family members. Experts call this take-home or para-occupational exposure.
Studies, including one in the International Journal of Environmental Research and Public Health, have shown that secondary exposure can affect households even if family members never handle paraquat themselves. However, this risk is not addressed by standard PPE mandates, which are only used during application.
Parkinson's Symptoms After Paraquat Exposure
Parkinson’s disease affects everyone differently. Early symptoms after paraquat exposure can be subtle and easy to miss. Symptoms may start on one side of your body and then spread, usually being more pronounced on the first side.
Some signs of Parkinson’s can resemble those of other conditions, making it challenging to identify.
- Balance and Posture Issues
- You may experience balance issues. Poor posture may also develop, increasing your risk of falling.
- Loss of Automatic Movements
- Actions like blinking or swinging your arms while walking may stop occurring automatically and require thought instead.
- Non-Motor Symptoms
- Non-motor changes often come before the movement problems most people associate with Parkinson’s disease. These can include anxiety, depression, fatigue, trouble sleeping, loss of smell and constipation. Some of these symptoms may show up years before any movement issues appear.
- Slowed Movement
- Everyday tasks, like showering or getting dressed, may become difficult. You might also show fewer facial expressions.
- Speech Changes
- You may speak more softly or quickly and notice changes in speech rhythm.
- Stiff Muscles
- Your muscles may feel tight and painful, leading to jerky movements.
- Tremors
- You may experience shaking, typically starting in your hands or fingers. This may also occur in your feet or jaw and can lessen with movement.
- Writing Changes
- Your handwriting may become small and cramped. Writing may also become more difficult.
According to the Parkinson’s Foundation, you must experience bradykinesia, or slow movement, to be diagnosed with the disease. Along with this slowness, you must also have one or more of the following symptoms:
- A shaking or tremor in a limb when it's not being used
- Difficulty with balance, which can lead to falls
- Stiffness in your arms, body or legs
These signs can help doctors understand if Parkinson’s disease could be the cause of your symptoms.
Early Non-Motor Warning Signs of Parkinson’s Disease
Non-motor symptoms can show up years before the tremors and movement problems usually linked to Parkinson’s disease begin. If you were previously exposed to paraquat, noticing these early signs could be important.
- Digestive Changes:
- People often report ongoing constipation early in Parkinson’s disease. A 2025 study in Movement Disorders found that this symptom may trigger an immune response in the brain and spinal cord, which researchers call neuroinflammation.
- Loss of Smell (Anosmia):
- Many people notice a weaker or missing sense of smell as one of the first signs of Parkinson’s disease. This symptom can begin ten years or more before movement problems appear.
- Mood and Cognitive Changes:
- Feeling depressed, anxious or uninterested before movement symptoms start may be due to changes in brain chemistry, not just emotions.
- REM Sleep Behavior Disorder:
- Physically acting out dreams while asleep, such as talking, moving or thrashing, is linked to Parkinson’s. This warning sign can appear years before movement symptoms start.
If you have been exposed to paraquat and notice any of these changes, it may help to talk with a neurologist who understands environmental risks for Parkinson’s disease.
Regulatory Actions Over Paraquat
More than 70 countries have completely banned the herbicide, but the U.S. still allows its use under certain rules. The U.S. Environmental Protection Agency (EPA) has strict mandates for how paraquat can be applied, stored and used to help keep people safe.
- Certain ways of applying paraquat are either limited or not allowed.
- Only certified pesticide applicators can use paraquat.
- Paraquat cannot be used near homes, schools, parks, golf courses or playgrounds.
- There must be spray buffer zones around residential areas.
- Workers must use enclosed cabs or wear respirators for larger applications.
Although the EPA has implemented these safety measures, the agency has stated that it hasn’t found strong evidence linking paraquat exposure to Parkinson’s disease. Despite the EPA’s actions, more than 70 other countries have banned paraquat.
In January 2026, EPA Administrator Lee Zeldin said the agency would reassess paraquat’s safety, reopening a long-running regulatory debate. In June 2026, Vermont became the first state to ban paraquat. At least nine other U.S. states, including New York, Illinois and Virginia, introduced bills or proposals to restrict or ban paraquat as of 2026.
The international outlook is much stricter. The European Union banned paraquat in 2007. China and Brazil followed with domestic bans in 2017 and 2020.
Paraquat Lawsuits
Thousands of people have sued Syngenta, the company that makes paraquat, claiming the herbicide causes Parkinson’s disease. Many of these lawsuits were grouped together in a multidistrict litigation (MDL) to streamline the legal process.
In April 2025, lawyers for Syngenta and the plaintiffs agreed on a tentative settlement. In July 2025, Syngenta settled the first paraquat lawsuit in the MDL. It settled another lawsuit in January 2026, just before the start of a paraquat bellwether trial — a kind of test case in the MDL.
In March 2026, the MDL judge approved a qualified settlement fund (QSF). The court also appointed an administrator to oversee the money in the QSF based on the terms of a paraquat settlement agreement.
As of September 2026, there were 6,666 paraquat lawsuits still active in the MDL.
Syngenta stopped making paraquat at the end of June 2026. It promised to stop sales on December 31, 2026, or when supplies ran out, whichever came first. The company said its decision was due to competition from generic producers worldwide. Syngenta did not connect this decision to the lawsuits or to any health concerns about the herbicide.
If you developed Parkinson’s disease after confirmed or likely exposure to paraquat, you may be able to file a claim. A lawyer can help you determine whether you qualify for a paraquat lawsuit and explain the deadline for your state.
FAQs About Paraquat and Parkinson’s
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