A new study from the University of California - Los Angeles Health Sciences has linked long-term residential exposure to the agricultural pesticide chlorpyrifos with a more than 2.5-fold increase in the risk of developing Parkinson's disease.
Published in Molecular Neurodegeneration, the research combined data from 829 Parkinson's patients and 824 unexposed individuals with laboratory experiments on mice and zebrafish.
Biological Mechanism Identified
Lab tests showed that chlorpyrifos directly damages dopamine-producing neurons, induces brain inflammation, and causes abnormal buildup of alpha-synuclein protein.
The pesticide also disrupts autophagy, the cellular cleanup process that removes toxic waste.
"This study establishes chlorpyrifos as a specific environmental risk factor for Parkinson's disease, not just pesticides as a general class," said Dr. Jeff Bronstein, professor of Neurology at UCLA Health and senior author.
Dr. Bronstein noted that identifying autophagy dysfunction as the driver behind this neurotoxicity provides a clear target for developing future protective therapies.
"By showing the biological mechanism in animal models, we've demonstrated that this association is likely causal," he added.
The discovery coincides with expanding litigation in the United States, including a lawsuit filed by former pest control worker Alexander Ramos against Dow Chemical, Corteva, and FMC Corp.
The legal claim accuses the companies of designing and distributing chlorpyrifos while hiding its known links to neurological damage.
"The discovery that autophagy dysfunction drives the neurotoxicity also points us toward potential therapeutic strategies to protect vulnerable brain cells," said Dr. Bronstein.
The lawsuit represents a new legal shift connecting the pesticide to adult neurological disorders, separate from previous mass torts involving childhood developmental harms from prenatal exposure.
Dr. Bronstein described the science associating Parkinson's with chlorpyrifos as "very robust," including "strong epidemiological evidence."
The Environmental Protection Agency currently allows limited agricultural applications of chlorpyrifos despite a phased ban on residential uses that began in 2001.
"If we want to create a world where diseases like Parkinson's are increasingly rare instead of common, we need to reduce or eliminate our use of chemicals tied to the disease," said Ray Dorsey, a neurologist at Atria Health and Research Institute.
Public health advocates continue to push for a total ban due to the chemical's long-term persistence and regulatory failures.
"Stopping use of chlorpyrifos would be a great place to start," Dorsey said.
