Researchers found that long-term residential exposure to the pesticide was associated with more than 2.5 times the risk of Parkinson’s disease and identified a possible mechanism for brain damage.
By yourNEWS Media Newsroom
Long-term exposure to the pesticide chlorpyrifos may significantly increase the risk of Parkinson’s disease, according to a UCLA Health study that combined human population data with laboratory research in animals.
The study, published in January 2026 in Molecular Neurodegeneration, found that people with the highest levels of residential exposure to chlorpyrifos faced more than 2.5 times the risk of developing Parkinson’s disease compared with people who had little or no exposure.
Researchers said the findings strengthen evidence that certain agricultural chemicals may contribute to Parkinson’s, a progressive neurological disorder that affects nearly one million Americans.
The UCLA team also identified a biological pathway by which chlorpyrifos may damage the brain. Laboratory experiments showed the pesticide can harm dopamine-producing neurons, trigger brain inflammation and disrupt autophagy, the cellular process that removes damaged proteins and waste.
Dopamine-producing neurons are the brain cells that degenerate in Parkinson’s disease.
Chlorpyrifos is an organophosphate pesticide that has been used for decades on agricultural crops. The U.S. Environmental Protection Agency banned residential uses of chlorpyrifos in 2001 and restricted agricultural applications in 2021, but the chemical remains in use on some U.S. crops and continues to be widely applied in other countries.
The UCLA study focused on California’s Central Valley, a major agricultural region with high pesticide use.
Researchers examined data from 829 people diagnosed with Parkinson’s disease and 824 people without the condition. Participants were enrolled in UCLA’s Parkinson’s Environment and Genes study.
The team used California pesticide use records together with participants’ residential and workplace addresses to estimate long-term chlorpyrifos exposure.
The strongest risk was seen among people with the highest residential exposure levels. Those individuals had more than 2.5 times the risk of developing Parkinson’s disease compared with those who had little or no exposure.
To explore whether the association reflected a true biological effect, researchers conducted laboratory experiments in mice and zebrafish.
Male mice were exposed to aerosolized chlorpyrifos for 11 weeks using inhalation methods intended to resemble real-world exposure. The exposed mice developed movement problems and showed significant loss of dopamine-producing neurons.
Researchers also observed brain inflammation and abnormal buildup of alpha-synuclein, a protein associated with Parkinson’s disease. In Parkinson’s, alpha-synuclein can accumulate into toxic clumps that interfere with normal brain function.
Experiments in zebrafish helped identify what researchers described as a critical mechanism. Chlorpyrifos appeared to interfere with autophagy, the body’s internal cellular cleanup and recycling process.
Autophagy helps remove damaged proteins and cellular debris before they build up and cause injury. When chlorpyrifos disrupted that process, neurons became more vulnerable to damage.
When scientists restored autophagy function or removed synuclein protein, nerve cells were protected from injury. Researchers said that finding suggests autophagy disruption plays a central role in chlorpyrifos-related neurotoxicity.
The discovery may point to future treatment strategies. If therapies can be developed to enhance autophagy or improve the brain’s ability to clear toxic proteins, researchers may be able to better protect neurons from pesticide-related damage.
Dr. Jeff Bronstein, the study’s senior author, said the research identifies chlorpyrifos as a specific environmental risk factor for Parkinson’s disease rather than only part of a broader category of pesticide exposure. By showing a biological mechanism in animal models, the study provides evidence that the link may be causal.
The findings come as Parkinson’s disease rates continue rising globally. Genetics account for only a portion of cases, and researchers have long suspected that environmental factors, including pesticide exposure, contribute to the disease.
While chlorpyrifos use has declined in the United States, many people were exposed for decades before restrictions took effect. Other organophosphate pesticides remain in use worldwide, raising questions about whether similar chemicals may damage the brain through the same autophagy-related pathway.
The study suggests people with known past exposure to chlorpyrifos may benefit from closer neurological monitoring. Researchers are also expected to examine whether interventions that support cellular cleanup systems could reduce Parkinson’s risk among exposed populations.
Because Parkinson’s disease has no cure, identifying preventable environmental risks remains a major public health priority. The UCLA findings point to one pesticide and one possible mechanism that may help explain how environmental toxins contribute to the loss of dopamine-producing neurons.
Source: Natural News
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