Common Pesticide Linked to Over 2.5 Times Parkinson's Risk, UCLA Study Finds

A recent study by UCLA Health has established a significant link between long-term residential exposure to chlorpyrifos, a common pesticide, and a more than 2.5 times increased risk of developing Parkinson's disease. Researchers not only identified this strong association but also uncovered a biological mechanism explaining how the chemical damages brain cells, alongside a promising avenue for protecting them. The findings were published in the journal *Molecular Neurodegeneration*.

Parkinson's disease affects nearly one million Americans, presenting as a progressive neurological condition that gradually damages brain cells involved in movement, causing tremors, muscle stiffness, and coordination difficulties. A defining feature is the loss of dopamine-producing neurons, essential for nerve cell communication and coordinated movements. While genetic factors contribute, environmental exposures, notably pesticides, are increasingly investigated. Chlorpyrifos, used extensively in agriculture for decades, saw its residential use banned in the U.S. in 2001 and agricultural restrictions added in 2021, yet it remains in use on many crops domestically and is widely applied internationally. Understanding its long-term effects is crucial, as exposure can precede symptoms by years, potentially informing prevention strategies and neurological monitoring for at-risk individuals.

The UCLA investigation involved 829 people with Parkinson's and 824 without, all enrolled in the Parkinson's Environment and Genes study. Scientists correlated California's detailed pesticide application records with participants' residential and workplace histories to estimate chlorpyrifos exposure. This population analysis revealed that individuals with prolonged residential exposure faced over 2.5 times the risk of Parkinson's. To strengthen this, the team conducted laboratory experiments: mice exposed to aerosol chlorpyrifos for 11 weeks, mimicking environmental exposure, developed movement difficulties and lost dopamine-producing neurons—a central characteristic of Parkinson's. Brain inflammation and abnormal accumulations of alpha-synuclein protein, known for forming clumps linked to the disease, were also observed in the animals.

Further insights into the precise cellular damage mechanism came from experiments with zebrafish. These studies pointed to a disruption in autophagy, a natural cellular maintenance process that acts as an internal recycling system, clearing damaged proteins and unwanted material. This process is vital for neurons to maintain functionality throughout a lifetime. When chlorpyrifos interfered with autophagy, damaged material accumulated within neurons, contributing to their deterioration. Crucially, researchers made an encouraging discovery: restoring the cellular cleanup process or removing synuclein protein in their experiments offered protection to the neurons. These findings collectively provide robust biological evidence linking chlorpyrifos to Parkinson's and highlight potential therapeutic targets.

What to watch: Future research may focus on therapies that restore cellular cleanup processes or target synuclein protein to protect neurons from damage.

Editor's note: Comprehensive coverage of the study's findings, methodology, and biological mechanisms described in the source.