How Paraquat Exposure May Increase the Risk of Parkinson’s Disease
Research suggests that exposure to paraquat can cause changes in your brain that may increase your risk of getting Parkinson’s disease. Thousands of paraquat lawsuits have been filed by people exposed to paraquat, claiming that the herbicide caused them to develop Parkinson’s.
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Can Paraquat Cause Parkinson's Disease?
Some studies suggest that people who used the herbicide paraquat are roughly 2.5 times more likely to develop Parkinson’s. Research indicates a link between paraquat and harmful changes in the brain associated with the disease.
- Studies found that people living or working near paraquat-treated fields face an increased risk of developing Parkinson’s. A study in the International Journal of Epidemiology suggested that the risk was higher for people exposed for longer periods. The strongest association was seen in those diagnosed before age 60.
- Research indicates that paraquat can cross the blood-brain barrier and damage dopamine neurons, which are cells that are lost in Parkinson’s disease. This can adversely impact the brain and may increase the risk of Parkinson’s.
How Paraquat Harms the Brain
Paraquat can damage your brain by causing oxidative stress and mitochondrial dysfunction. 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 is 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.
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.
- Farmworkers and those who worked near applicators face the highest risk.
- Residents near spraying zones may experience chronic low-dose exposure via drift or contamination.
- Your risk depends on the dose you receive and the duration of your exposure to paraquat. More prolonged exposure and higher doses increase your risk
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
- You may experience issues like anxiety, depression, fatigue and trouble sleeping.
- 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.
Regulatory Actions Over Paraquat
The U.S. Environmental Protection Agency (EPA) allows the use of paraquat in the United States, but has implemented strict regulations about application, storage and usage to help protect people from exposure.
- Bans and restrictions on specific application methods
- Can only be used by certified pesticide applicators
- Cannot be transferred to other containers
- Creation of safe zones around homes
- Label instructions must be followed
- Limitations on how paraquat can be sprayed
- Must be kept secure to prevent access from unauthorized individuals
- Protective gear is required for applicators
- Use around gardens, homes, parks, schools, golf courses and playgrounds is prohibited
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.
Paraquat Lawsuits
Thousands of people have filed lawsuits against Syngenta, paraquat’s manufacturer, alleging the herbicide causes Parkinson’s disease. Many of these lawsuits were combined into a multidistrict litigation (MDL) to streamline the legal process.
According to a court document dated April 14, 2025, lawyers representing Syngenta and the people suing them agreed to a plan intended to settle many of these cases. In July 2025, Syngenta settled the first paraquat lawsuit pertaining to the MDL.
The announcement came days before the first paraquat bellwether trial was set to start. Other lawsuits are scheduled to go to trial in October 2025 and January 2026, but it’s expected that Syngenta will also settle those cases.
There were over 6,300 lawsuits in the MDL awaiting resolution at the time of the paraquat settlement. Details about the payout amount were not made public.
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