Researchers combine human data and lab experiments to investigate possible brain effects
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Long-term exposure to the pesticide chlorpyrifos was associated with more than a 2.5-fold higher risk of Parkinsons disease.
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The study combined human population data with experiments in mice and zebrafish to examine how the chemical affects brain cells.
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Researchers found the pesticide may damage dopamine-producing neurons by disrupting the brains natural protein-cleanup process.
A widely used agricultural pesticide may be linked to a significantly higher risk of Parkinsons disease, according to a new study from researchers at UCLA Health published in the journal Molecular Neurodegeneration.
The research focused on chlorpyrifos, a pesticide that has been used on crops for decades. While residential uses were banned in the United States in 2001 and agricultural uses have been restricted more recently, the chemical is still used on some crops domestically and remains widely used in other countries.
Parkinsons disease is a progressive neurological disorder that affects movement and can cause symptoms such as tremors, stiffness, and difficulty with coordination. Scientists have long suspected that environmental exposures including pesticides may contribute to the condition in some cases, alongside genetic factors.
The new research aimed to identify whether a specific pesticide might play a role and to better understand the biological mechanisms that could connect exposure to Parkinsons disease.
The study
To explore the potential link, the researchers analyzed health data from 829 people diagnosed with Parkinsons disease and 824 people without the condition. All participants were part of UCLAs long-running Parkinsons Environment and Genes (PEG) study.
The team estimated participants exposure to chlorpyrifos by combining residential and workplace address histories with detailed pesticide-use records from California. This allowed them to determine whether people had lived or worked near areas where the pesticide was applied over time.
The researchers also carried out laboratory experiments to examine how chlorpyrifos might affect the brain. In one set of tests, mice were exposed to aerosolized chlorpyrifos for 11 weeks using inhalation methods designed to mimic how people could encounter the pesticide in real life.
Additional experiments were conducted in zebrafish, which scientists often use to study neurological processes, to investigate the biological pathways that might be involved in the chemicals effects on nerve cells.
The results
The analysis showed that people with long-term residential exposure to chlorpyrifos had more than a 2.5-times higher risk of developing Parkinsons disease compared with people who were not exposed.
Results from the laboratory experiments provided clues about why this association might occur.
Mice exposed to the pesticide developed movement problems and lost dopamine-producing neurons the same type of brain cells that are damaged in Parkinsons disease. The exposed mice also showed brain inflammation and abnormal buildup of alpha-synuclein, a protein known to accumulate in Parkinsons disease.
Experiments in zebrafish suggested the pesticide disrupts autophagy, a cellular process that normally helps clear damaged proteins from cells. When this cleanup process was restored or when the problematic protein was removed, researchers observed that neurons were protected from damage.
Together, the findings suggest that chlorpyrifos exposure may contribute to Parkinsons disease risk and point to specific biological pathways that scientists could study further in future research.
This study establishes chlorpyrifos as a specific environmental risk factor for Parkinson's disease, not just pesticides as a general class, researcher Dr. Jeff Bronstein said in a news release.
By showing the biological mechanism in animal models, we've demonstrated that this association is likely causal. The discovery that autophagy dysfunction drives the neurotoxicity also points us toward potential therapeutic strategies to protect vulnerable brain cells.
Posted: 2026-03-16 17:18:16

















