LOS ANGELES — Researchers from UCLA Health have found that long-term exposure to the pesticide chlorpyrifos significantly increases the risk of Parkinson’s disease. According to the study, high levels of exposure more than doubled the chance of developing the brain disorder.
Parkinson’s disease is a brain condition that gets worse over time. It causes muscle stiffness, shaking, and trouble moving, and it currently affects about one million people in the United States.
Researchers compared 829 people with Parkinson’s to 824 healthy people. They did this by matching California pesticide records with the places where the participants lived and worked. The study, published in the medical journal Molecular Neurodegeneration, found the risk was highest for people exposed to the pesticide at work over many years.
Long-term Risk
For people with high exposure at work, the chance of a Parkinson’s diagnosis was up to 2.74 times higher than for those with no exposure. The research also found that the risk rose significantly when people were exposed to the chemical more than 10 years before their physical symptoms began.
The research team used laboratory tests to understand how the chemical harms the brain. Experiments on zebrafish showed that chlorpyrifos stops a natural cleaning process in brain cells called autophagy. This process clears away damaged proteins. When the cleaning process fails, brain cells can die.
Biological Impact
Further tests on mice over an 11-week period showed that breathing in the pesticide spray caused movement problems and brain inflammation. The exposure also destroyed brain cells that produce dopamine, a chemical that helps the body control movement.
Dr. Jeff Bronstein, the senior study author and a neurology professor at UCLA, said the research suggests the chemical is a direct cause of the disease. Bronstein noted that understanding why cellular waste disposal fails could lead to new treatments to protect brain cells.
Pesticide Regulation
Government regulators have looked more closely at the use of chlorpyrifos over the last 20 years. The chemical was banned for home use in 2001, and new rules restricted its use on farms in 2021. However, the pesticide is still used on several types of food crops in the United States.
By contrast, chlorpyrifos is currently banned in the United Kingdom and the European Union. Researchers hope that identifying things in the environment that cause the disease, like this pesticide, will help health officials better prevent and treat the condition.
