UCLA Health researchers report that long-term residential exposure to chlorpyrifos was associated with more than 2.5 times the risk of Parkinson's disease, and that the pesticide disrupts a cellular clean-up process in animal models.
Researchers at UCLA Health report that people with long-term residential exposure to chlorpyrifos, a widely used agricultural pesticide, had more than 2.5 times the risk of developing Parkinson's disease compared with people who were not exposed. The study, published in Molecular Neurodegeneration, drew on 829 people with Parkinson's and 824 people without it, all enrolled in the university's Parkinson's Environment and Genes study. The team combined California's detailed pesticide application records with participants' home and workplace address histories to estimate how much chlorpyrifos each person may have encountered over the years.
To test whether the chemical could cause the kind of damage seen in the disease, the scientists exposed mice to chlorpyrifos in aerosol form for 11 weeks. The animals developed movement difficulties, lost dopamine-producing neurons, and showed brain inflammation and abnormal build-up of the protein alpha-synuclein. Experiments in zebrafish then pointed to a disruption of autophagy, the cell's recycling system for damaged proteins, and restoring that process or removing synuclein protected neurons in the lab. Senior author Dr. Jeff Bronstein said the work establishes chlorpyrifos as a specific environmental risk factor and that the association is likely causal.
Several caveats apply. The population analysis shows an association and cannot on its own prove that the pesticide directly causes Parkinson's, and the mechanism and the protective effect have so far been shown only in animal and laboratory models, so it is not yet known whether boosting autophagy would help people. Chlorpyrifos was banned for residential use in the United States in 2001 and faced further agricultural restrictions in 2021, but it is still used on many crops there and remains widely applied elsewhere. This report relies on the university's account of its findings as relayed by ScienceDaily, and the results have not been independently replicated.
