Long-Term Chlorpyrifos Exposure Linked to Increased Parkinson's Risk

UCLA study finds over 2.5x higher likelihood of Parkinson's disease in those with residential pesticide exposure

Mar. 16, 2026 at 10:51pm

Got story updates? Submit your updates here. ›

A new UCLA Health study suggests that long-term exposure to the pesticide chlorpyrifos may dramatically raise the risk of Parkinson's disease. Researchers found that people living in areas with ongoing exposure had more than a 2.5 times greater likelihood of developing the condition. The study combined large-scale human data with laboratory experiments showing how the pesticide harms dopamine-producing brain cells, providing biological evidence supporting a connection between chlorpyrifos exposure and Parkinson's disease.

Why it matters

Identifying specific pesticides that increase Parkinson's risk could help guide prevention efforts and make it easier to identify individuals who might benefit from earlier monitoring or future protective therapies. While chlorpyrifos use has declined in the US, many people experienced exposure in the past and similar pesticides are still widely used globally.

The details

The research team estimated each participant's exposure to chlorpyrifos over time by combining California pesticide use records with the locations of participants' homes and workplaces. Mice exposed to aerosolized chlorpyrifos for 11 weeks developed movement problems and lost dopamine-producing neurons, the same type of brain cells that gradually die in Parkinson's disease. Experiments in zebrafish showed that chlorpyrifos disrupts autophagy, the cellular system responsible for clearing damaged proteins from cells.

  • The study was published in the journal Molecular Neurodegeneration in March 2026.
  • Chlorpyrifos' residential use was banned in the US in 2001, and restrictions on agricultural applications were introduced in 2021.

The players

UCLA Health

A leading academic medical center and research institution in Los Angeles, California.

Dr. Jeff Bronstein

Professor of Neurology at UCLA Health and the senior author of the study.

Parkinson's Environment and Genes study

A long-running research study at UCLA examining environmental and genetic factors related to Parkinson's disease.

Chlorpyrifos

A widely used pesticide that has been linked to increased Parkinson's disease risk in this study.

Got photos? Submit your photos here. ›

What they’re saying

“This study establishes chlorpyrifos as a specific environmental risk factor for Parkinson's disease, not just pesticides as a general class. By showing the biological mechanism in animal models, we've demonstrated that this association is likely causal. The discovery that autophagy dysfunction drives the neurotoxicity also points us toward potential therapeutic strategies to protect vulnerable brain cells.”

— Dr. Jeff Bronstein, Professor of Neurology at UCLA Health

What’s next

Future research may examine whether other commonly used pesticides affect the brain in similar ways. Scientists also hope to determine whether treatments that enhance the cell's natural protein cleanup systems could lower Parkinson's risk in exposed populations.

The takeaway

This study provides strong evidence linking long-term exposure to the pesticide chlorpyrifos to a significantly increased risk of developing Parkinson's disease. The findings underscore the importance of understanding environmental risk factors for neurological conditions and could help guide efforts to protect vulnerable populations from pesticide-related brain damage.