Quick Facts

• Long-term chlorpyrifos exposure increases Parkinson’s disease risk by 2.74 times according to UCLA research
• The pesticide damages brain cells by disrupting autophagy, the cellular cleanup process that removes damaged proteins
• Nearly 90,000 Americans are diagnosed with Parkinson’s annually, a 50% increase over previous estimates

A groundbreaking UCLA study has identified the pesticide chlorpyrifos as a major environmental risk factor for Parkinson’s disease. Researchers found that people with the highest workplace exposure had 2.74 times higher odds of developing the neurological disorder.

The research analyzed 829 people with Parkinson’s disease and 824 without the condition. Scientists used California’s pesticide reports and participants’ addresses to track individual chlorpyrifos exposure over time.

“This study establishes chlorpyrifos as a specific environmental risk factor for Parkinson’s disease, not just pesticides as a general class,” said Dr. Jeff Bronstein, professor of Neurology at UCLA Health and the study’s senior author.

How the Pesticide Damages the Brain

Laboratory experiments revealed the biological mechanism behind the increased risk. Chlorpyrifos disrupts autophagy, the cellular process that clears damaged proteins from brain cells.

Zebrafish exposed to the pesticide showed damaged neurons. When researchers restored the cleanup process, the neurons were protected from harm. Mice exposed to chlorpyrifos developed movement problems and lost dopamine-producing neurons, the same cells that die in Parkinson’s patients.

The strongest disease associations occurred when exposure happened 10 to 20 years before diagnosis. This delayed effect aligns with Parkinson’s slow progression.

Current Regulatory Status

The EPA has moved to restrict chlorpyrifos use but faces legal challenges. As of July 2025, the pesticide is banned on most crops in the United States. However, it remains approved for use on 11 crops including apples, citrus, wheat, and strawberries in specific states.

The EPA plans to issue an updated decision on chlorpyrifos in 2026. The World Health Organization has recommended banning the chemical due to health concerns.

Nearly One Million Americans Affected

Parkinson’s disease affects nearly one million Americans. The Parkinson’s Foundation found that about 90,000 people receive a Parkinson’s diagnosis each year, a 50% increase over previous estimates.

The disease causes tremors, stiffness, and difficulty with movement. It progressively worsens over time as brain cells continue to die.

Therapeutic Implications

The discovery of autophagy disruption opens new treatment possibilities. “Knowing which pathways are causing someone’s Parkinson’s allows doctors to potentially slow or stop the progression,” Bronstein said.

Future treatments might include medicines that stimulate autophagy. When researchers enhanced this process in fish, it made them resistant to chlorpyrifos effects.

The research suggests people with known chlorpyrifos exposure should receive closer neurological monitoring. Scientists are now investigating whether other common pesticides cause similar brain damage.

Read more: This Widely Used Chemical Doubles Parkinson’s Risk — How To Reduce Exposure