UCLA Health researchers reported that long-term pesticide exposure to chlorpyrifos near the home was associated with a more than 2.5-fold increase in Parkinson's disease risk. The study, published in Molecular Neurodegeneration, paired data from 829 people with Parkinson's disease and 824 without the condition with laboratory work in mice.
UCLA Health Study Data
The team drew all participants from UCLA's ongoing Parkinson's Environment and Genes study. It estimated each person's long-term exposure by combining California pesticide use records with residential and workplace addresses, then compared people diagnosed with Parkinson's disease with those who were not.
The numbers point in the same direction. Among the 829 people with Parkinson's disease and 824 individuals without it, higher residential exposure to chlorpyrifos tracked with the larger risk estimate. The finding adds to research looking at environmental factors that may contribute to the disease, which affects nearly one million Americans.
Mice Exposed For 11 Weeks
The laboratory part of the study gave the epidemiology a biological test. Mice exposed to aerosolized chlorpyrifos for 11 weeks developed movement problems, lost dopamine-producing neurons, and showed inflammation in the brain along with an abnormal buildup of alpha-synuclein.
That pattern matters because Parkinson's disease is tied to movement problems and neuron loss, and alpha-synuclein is one of the proteins implicated in the disease process. The mouse results do not replace the human data, but they show a plausible route from exposure to the brain changes seen in Parkinson's disease.
Chlorpyrifos In United States Crops
Residential uses of chlorpyrifos were banned in 2001, and agricultural applications faced restrictions in 2021. Even so, chlorpyrifos continues to be used on a variety of crops in the United States, leaving a gap between the study's near-home exposure finding and current crop use.
For readers who live near treated fields or have lived near them for years, the practical takeaway is narrow but direct: this study points to long-term nearby exposure as the risk condition, not a one-time contact. How much current United States crop exposure to chlorpyrifos still exists is not answered here, but the study gives a stronger reason to pay attention to where and how the pesticide is used.
