Long-term exposure to the widely used pesticide chlorpyrifos may more than double the risk of developing Parkinson’s disease, according to a new study by researchers at the University of California, Los Angeles (UCLA). The findings, published in Molecular Neurodegeneration, also reveal how the chemical damages brain cells involved in movement.
The researchers analyzed data from 829 people diagnosed with Parkinson’s disease and 824 individuals without the condition who participated in UCLA’s Parkinson’s Environment and Genes study. Using California pesticide application records and participants’ residential and workplace addresses, the team estimated long-term exposure to chlorpyrifos.
The analysis showed that people living near areas where chlorpyrifos had been used over extended periods were more than 2.5 times more likely to develop Parkinson’s disease than those without such exposure.
To understand the biological mechanism behind this association, the scientists conducted laboratory experiments in mice and zebrafish. Mice exposed to chlorpyrifos through inhalation for 11 weeks developed movement impairments and experienced the loss of dopamine-producing neurons—the same type of brain cells that progressively degenerate in Parkinson’s disease.
The researchers also observed increased brain inflammation and abnormal accumulation of alpha-synuclein, a protein closely linked to Parkinson’s disease. Additional experiments showed that chlorpyrifos disrupts autophagy, the cell’s natural system for removing damaged proteins and cellular waste. When this process was impaired, toxic proteins accumulated and neurons became more vulnerable to damage.
Importantly, restoring autophagy or eliminating excess alpha-synuclein protected nerve cells from injury, suggesting that impaired cellular cleanup may be a key mechanism through which chlorpyrifos contributes to Parkinson’s disease.
Although residential use of chlorpyrifos was banned in the United States in 2001 and agricultural use has been restricted since 2021, the pesticide is still used on some crops in the U.S. and remains widely applied in many countries. Researchers note that millions of people may have experienced exposure before these restrictions were introduced.
The study highlights autophagy as a promising target for future therapies aimed at protecting the brain from pesticide-related damage. The researchers also plan to investigate whether other commonly used pesticides affect the brain through similar mechanisms.
The authors suggest that individuals with known past exposure to chlorpyrifos may benefit from closer neurological monitoring as scientists continue to study the long-term consequences of pesticide exposure.
Follow NEWS.am Medicine on Facebook and Twitter