Pesticide exposure tied to higher Parkinson’s risk in UCLA study
UCLA Health researchers linked long-term chlorpyrifos exposure near homes to higher Parkinson’s risk and found signs of neuron damage in lab tests.
By Priya Raghavan · Science Reporter
3 min read
Long-term exposure to the pesticide chlorpyrifos near the home was associated with a sharply higher chance of developing Parkinson’s disease, UCLA Health researchers reported. The study matters because it ties a specific agricultural chemical to both human disease risk and lab evidence of damage to dopamine-producing brain cells.
The research, published in Molecular Neurodegeneration, examined data from UCLA’s Parkinson’s Environment and Genes study and paired that analysis with experiments in animals. UCLA Health said the work points to a possible biological route by which chlorpyrifos could contribute to Parkinson’s disease.
Exposure near homes
The UCLA team analyzed 829 people with Parkinson’s disease and 824 people without the disorder. Researchers estimated long-term chlorpyrifos exposure by matching California pesticide-use records with participants’ home and workplace addresses, according to UCLA Health.
People with long-term residential exposure to chlorpyrifos had more than 2.5 times the risk of Parkinson’s disease compared with people who were not exposed, the researchers reported. UCLA Health described chlorpyrifos as a pesticide used on agricultural crops for decades.
Residential uses of chlorpyrifos were banned in 2001, and agricultural applications faced restrictions in 2021, according to UCLA Health. The chemical still has been used on multiple crops in the United States and remains common in many other countries, the university said.
Damage seen in brain cells
Parkinson’s disease is a progressive neurological disorder that affects nearly one million Americans, according to UCLA Health. The disease develops as dopamine-producing neurons die, reducing a brain chemical involved in movement, coordination and balance.
UCLA Health said symptoms can include tremors, stiffness, slower movement and balance problems. Although genes can affect risk, the researchers said environmental exposures, including pesticides, have become a focus of Parkinson’s research.
To test how chlorpyrifos might affect the brain, researchers exposed mice to aerosolized chlorpyrifos for 11 weeks using inhalation methods meant to resemble environmental exposure, UCLA Health reported. The exposed mice developed movement problems and lost dopamine-producing neurons, the researchers found.
The team also reported brain inflammation and unusual accumulation of alpha-synuclein, a protein linked to Parkinson’s disease. In people with Parkinson’s, alpha-synuclein can form clumps that interfere with normal brain function, according to UCLA Health.
Cell cleanup process implicated
Additional experiments in zebrafish suggested that chlorpyrifos disrupts autophagy, the process cells use to clear damaged proteins and other waste, UCLA Health said. When that system was impaired, neurons were more susceptible to injury.
The researchers reported that restoring autophagy or removing synuclein protein protected nerve cells from damage in the experiments. UCLA Health said those findings suggest the pesticide may allow harmful proteins to accumulate by weakening the cell’s cleanup system.
Dr. Jeff Bronstein, a UCLA Health neurology professor and senior author of the study, said the results identify chlorpyrifos as a specific environmental risk factor rather than treating pesticides only as a broad category. UCLA Health said future work will examine whether other pesticides affect autophagy and whether boosting that process could help protect vulnerable brain cells.
This story draws on original reporting from ScienceDaily.