Wisner Baum is evaluating cases for farmworkers, agricultural employees, pesticide applicators, and others who were exposed to chlorpyrifos-based pesticides and subsequently developed Parkinson’s disease.
A 2026 study from UCLA Health found that long-term residential exposure to chlorpyrifos is associated with a more than 2.5-fold increased risk of developing Parkinson’s disease. Attorneys believe this is the strongest evidence to date linking this widely used pesticide to serious, irreversible neurological harm.
Millions of Americans have lived and worked in areas where chlorpyrifos was heavily sprayed on crops, absorbed into soil, and carried by wind and water into surrounding communities. Many of these individuals are only now learning of the connection between Parkinson’s and chlorpyrifos exposure. Our toxic tort attorneys are actively filing chlorpyrifos Parkinson’s lawsuits on behalf of people harmed by this pesticide and are prepared to hold the manufacturers accountable.
We are currently offering free chlorpyrifos Parkinson’s disease lawsuit consultations. To discuss your potential case, please contact us or call (310) 207-3233 to start your free case evaluation.
What Is Chlorpyrifos?
Chlorpyrifos is a broad-spectrum organophosphate insecticide that has been used in the U.S. since 1965. Originally patented by Dow Chemical Company (now Corteva Agriscience), the chemical was designed to kill insects by disrupting the function of acetylcholinesterase, an enzyme critical to the proper function of the nervous system. While effective at killing pests, this same mechanism of action poses serious risks to the human nervous system, particularly for those with chronic exposure.
For decades, chlorpyrifos was one of the most heavily used insecticides in American agriculture. EPA estimates that between 1987 and 1998, approximately 21-24 million pounds of chlorpyrifos were applied annually in the United States. The chemical was used extensively on a wide range of crops, as well as in residential pest control, golf course maintenance, and structural termite treatment.
Common crops treated with chlorpyrifos include:
- Corn
- Soybeans
- Almonds and walnuts
- Citrus (oranges, lemons, grapefruit)
- Apples, peaches, and cherries
- Cotton
- Strawberries
- Sugar beets and wheat
Which Products Contain Chlorpyrifos?
Chlorpyrifos has been sold under several brand names, including:
- Dursban
- Lorsban
- Cobalt
- Lock-On
- Nufos
- Warhawk
In February 2020, Corteva Agriscience announced it would stop producing chlorpyrifos, citing declining market demand. However, existing stocks continued to be used, and the chemical remains available for certain agricultural applications in the U.S. today.
How Are People Exposed to Chlorpyrifos?
Chlorpyrifos exposure occurs primarily through inhalation and skin contact, though ingestion of contaminated food and water is also a recognized exposure pathway. Farmworkers and other workers who mixed, loaded, and applied the pesticide face the highest levels of direct exposure. However, exposure was not limited to those who handled the chemical directly.
Chlorpyrifos is volatile and can drift significant distances from application sites. It leaches into groundwater and contaminates surface water through agricultural runoff. Residents of communities near treated farmland, including California’s Central Valley, were chronically exposed through the air they breathed and the water they drank — often without any warning.
People who may have been exposed to chlorpyrifos include:
- Farmers and farmworkers who applied or worked near chlorpyrifos
- Licensed pesticide applicators
- Crop dusters and aerial applicators
- Workers at pesticide mixing and loading facilities
- Landscapers and groundskeepers
- Golf course maintenance workers
- Residents living near agricultural fields where chlorpyrifos was sprayed
- People who consumed food or water contaminated with chlorpyrifos residue
Chlorpyrifos and Parkinson’s Disease
Scientists have long suspected a connection between organophosphate pesticide exposure and Parkinson’s disease. A groundbreaking 2026 study from UCLA Health provided the most compelling evidence to date that chlorpyrifos increases the risk of developing Parkinson’s. Researchers also demonstrated the biological mechanism by which the pesticide can damage the brain.
The 2026 UCLA Health Study
Published in the journal Molecular Neurodegeneration, the UCLA study combined large-scale human population data with controlled laboratory experiments to investigate the relationship between chlorpyrifos exposure and Parkinson’s disease. The research team, led by Dr. Jeff Bronstein, professor of Neurology at UCLA Health, analyzed data from 829 individuals diagnosed with Parkinson’s disease and 824 individuals without the condition. All participants were enrolled in UCLA’s long-running Parkinson’s Environment and Genes (PEG) study.
Using California’s detailed pesticide use reports and participants’ residential and workplace addresses, the researchers estimated individual chlorpyrifos exposure over time.
The results were striking: people with long-term residential chlorpyrifos exposure had more than 2.5 times the risk of developing Parkinson’s disease compared to those without such exposure.
To investigate how chlorpyrifos can damage the brain, researchers conducted parallel laboratory experiments. Mice exposed to aerosolized chlorpyrifos for 11 weeks using inhalation methods designed to mimic real-world human exposure developed movement problems, lost dopamine-producing neurons, exhibited brain inflammation, and showed abnormal accumulation of alpha-synuclein, the protein that forms the toxic clumps (Lewy bodies) that define Parkinson's pathology.
Additional experiments in zebrafish revealed the specific biological mechanism: chlorpyrifos disrupts autophagy, the cellular process responsible for clearing damaged proteins from the brain. When researchers restored this cleanup process or removed the synuclein protein, the neurons were protected from damage.
How Chlorpyrifos Causes Parkinson’s Disease
Parkinson’s disease is characterized by the progressive loss of dopamine-producing neurons in the brain. The UCLA study demonstrated that chlorpyrifos damages these neurons through a specific pathway: by disrupting autophagy, the cellular mechanism that removes damaged and misfolded proteins. When this cleanup system fails, toxic proteins (particularly alpha-synuclein) accumulate in the brain, triggering inflammation and neuronal death.
This finding is particularly significant because it establishes biological plausibility for the epidemiological association between chlorpyrifos exposure and Parkinson’s disease. As Dr. Bronstein stated in the UCLA press release: “This study establishes chlorpyrifos as a specific environmental risk factor for Parkinson’s disease, not just pesticides as a general class. By showing the biological mechanism in animal models, we’ve demonstrated that this association is likely causal.”
What Is Parkinson’s Disease?
Parkinson’s disease is a progressive neurodegenerative disorder that affects nearly one million Americans. The disease involves the gradual degeneration and death of dopamine-producing neurons in the brain. As dopamine levels decline, patients experience worsening motor symptoms and, in many cases, cognitive and emotional impairment. There is currently no cure for Parkinson’s disease, and available treatments become progressively less effective over time.
According to the Michael J. Fox Foundation, a person diagnosed with Parkinson’s disease spends an estimated $26,400 per year on care. The disease’s total annual economic burden in the United States is estimated at $19.8 to $26.4 billion.
Common Parkinson’s Symptoms
The primary motor symptoms of Parkinson’s disease include:
- Resting tremor – Involuntary shaking when the muscles are relaxed
- Bradykinesia – Slowness in voluntary movement and reflexes
- Rigidity – Stiffness and resistance to passive movement
- Postural instability – Impaired balance and coordination
Additional symptoms may include:
- Freezing of gait
- Slurred or quiet speech
- Difficulty swallowing
- Mask-like facial expression
- Depression, anxiety, and sleep disorders
- Cognitive impairment and memory problems
EPA Chlorpyrifos Regulatory History
The regulatory history of chlorpyrifos in the U.S. shares similarities to other pesticides that lacked safety enforcement actions despite mounting scientific evidence of harm. For more than two decades, federal regulators have grappled with the chemical’s risks while the pesticide industry pushed to keep it on the market.
1965: Dow Chemical introduces chlorpyrifos. It becomes one of the most widely used insecticides in the U.S.
2000: Under pressure from health advocates, chlorpyrifos manufacturers voluntarily agree to eliminate most residential and household uses of the pesticide.
2007: The Pesticide Action Network and the Natural Resources Defense Council petition the EPA to ban all food uses of chlorpyrifos, citing evidence of neurodevelopmental harm.
2015–2016: The EPA concludes that chlorpyrifos residues on food and in drinking water are unsafe and proposes a ban on all food uses.
2017: The first Trump administration reverses course, blocking the proposed ban and claiming more study is needed.
2019–2020: California, Hawaii, New York, Maryland, and Oregon take independent action to ban or restrict chlorpyrifos. Corteva Agriscience, the primary manufacturer, announces it will stop producing the chemical. The European Union bans chlorpyrifos.
2021: The Biden EPA issues a final rule revoking all chlorpyrifos food tolerances, effectively banning the pesticide’s use on food crops.
2023: The U.S. Court of Appeals for the Eighth Circuit vacates the EPA’s ban, reinstating chlorpyrifos tolerances and sending the matter back to the agency.
2024–Present: EPA formally proposed revoking all tolerances except for those 11 specific crops. The 11 crops are alfalfa, apple, asparagus, tart cherry, citrus, cotton, peach, soybean, strawberry, sugar beet, and spring/winter wheat. As of July 1, 2025, EPA confirmed that no one in the U.S. is allowed to legally use chlorpyrifos on any crops other than the 11.
Despite the patchwork regulatory landscape, the core scientific finding remains: chlorpyrifos is a neurotoxin that can harm the human brain. Millions of Americans were exposed during the decades when the pesticide was widely and freely used, and many are now living with the consequences.
Do I Qualify for a Chlorpyrifos Parkinson’s Lawsuit?
You may qualify for a chlorpyrifos Parkinson’s lawsuit if you were exposed to chlorpyrifos and have been diagnosed with Parkinson’s disease. While every case is evaluated individually, the following criteria are generally what attorneys assess when determining eligibility.
Exposure to chlorpyrifos. You may have been exposed through your occupation or through living near areas where the pesticide was applied. Occupations and circumstances associated with chlorpyrifos exposure include:
- Farmers who used chlorpyrifos on their crops
- Licensed pesticide applicators
- Farmworkers who worked in or near treated fields
- Landscapers and groundskeepers
- Golf course maintenance workers
- Workers at facilities where chlorpyrifos was mixed, loaded, or stored
- Residents who lived near farms or orchards where chlorpyrifos was regularly applied
A qualifying medical diagnosis. Chlorpyrifos lawsuits involve a diagnosis of Parkinson’s disease. Other neurological conditions that may be associated with organophosphate exposure, such as atypical Parkinsonism or progressive supranuclear palsy, may also form the basis of a claim.
Timing. Chlorpyrifos exposure may have occurred years or even decades before a Parkinson’s diagnosis. Research shows that Parkinson’s disease begins developing long before symptoms become apparent, meaning that historical exposure during the decades when chlorpyrifos was most widely used is relevant to claims being filed today.
If you are unsure whether you qualify, we encourage you to contact Wisner Baum for a free evaluation. There is no cost or obligation. Give us a call today at (310) 207-3233 or fill out our contact form.
Wisner Baum’s Track Record in Pesticide Litigation
Wisner Baum has extensive experience litigating toxic tort claims against major agrochemical companies. Our attorneys served as co-lead trial counsel in the first three Monsanto Roundup cancer trials, securing landmark jury verdicts that changed the trajectory of pesticide litigation in the United States.
Our results include a $2 billion jury verdict in Pilliod v. Monsanto and a $289 million verdict in Johnson v. Monsanto, the first Roundup case to reach a jury. These verdicts, along with the subsequent Roundup settlements totaling roughly $10.9 billion, demonstrated that agrochemical companies can be held accountable if their products are found to cause serious harm.
Wisner Baum is also deeply involved in the paraquat Parkinson’s disease litigation, where managing partner R. Brent Wisner is scheduled to serve as trial counsel in an upcoming bellwether trial. Our firm brings the same scientific rigor, trial preparation, and commitment to accountability to chlorpyrifos lawsuits.
While every case is different and past results do not guarantee future outcomes, our track record demonstrates our commitment to fighting for people harmed by dangerous pesticides.
