UCLA Study Links Chlorpyrifos Exposure to Higher Parkinson’s Risk

Why It Matters

A new study from UCLA Health, published in Molecular Neurodegeneration, has found that long‑term residential exposure to the pesticide chlorpyrifos is associated with more than a 2.5‑fold increased risk of developing Parkinson’s disease. Nearly one million Americans live with Parkinson’s, a progressive neurological disorder marked by tremors, stiffness, and difficulty with movement. While genetics plays a role, environmental factors such as pesticide exposure are increasingly recognized as critical contributors.

Chlorpyrifos has been widely used in agriculture for decades. Though residential use was banned in 2001 and agricultural use restricted in 2021, the chemical remains in use on many crops in the U.S. and abroad. Identifying pesticides that elevate Parkinson’s risk could inform prevention strategies and help target early monitoring or protective treatments.

What the Study Did

Researchers analyzed data from 829 people with Parkinson’s disease and 824 without the condition, all participants in UCLA’s long‑running Parkinson’s Environment and Genes study. Using California’s pesticide use reports and participants’ residential and work addresses, the team estimated individual exposure to chlorpyrifos over time.

To explore biological mechanisms, scientists exposed mice to aerosolized chlorpyrifos for 11 weeks, mimicking typical human inhalation exposure. They also conducted experiments in zebrafish to pinpoint how the pesticide damages brain cells.

What They Found

• People with long‑term chlorpyrifos exposure had 2.5 times the risk of Parkinson’s.
• Mice developed movement problems and lost dopamine‑producing neurons, the same cells that die in Parkinson’s patients.
• Exposed mice showed brain inflammation and abnormal accumulation of alpha‑synuclein, a protein that clumps in Parkinson’s disease.
• Zebrafish studies revealed chlorpyrifos disrupts autophagy, the cellular process that clears damaged proteins. Restoring autophagy or removing synuclein protected neurons from damage.

Outlook

The findings provide strong biological evidence linking chlorpyrifos to Parkinson’s, underscoring the need for stricter pesticide regulation and proactive monitoring of at‑risk populations.?