Parkinson's risk increases with exposure to common chemical, study suggests

A pesticide commonly used in America’s food supply has been linked to Parkinson’s disease, new research suggests.

A UCLA study published in the journal Springer Nature Link suggests that exposure to chlorpyrifos could increase the risk of the neurological disease.

The chemical is often used on agricultural products like soybeans, fruit and nut trees, broccoli, cauliflower and other row crops, according to the U.S. Environmental Protection Agency.

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The study compared 829 people with Parkinson’s to 824 people without the disease over a 45-year period, focusing on their proximity to chlorpyrifos.

The researchers also conducted mouse experiments, where mice inhaled the pesticide as humans would for 11 weeks. Experiments were also carried out on zebrafish to study cell-level brain damage.

In humans, the study revealed that long-term exposure to chlorpyrifos led to more than a 2.5 times higher risk of Parkinson’s.

In mice, exposure to the pesticide caused movement problems similar to Parkinson’s symptoms, loss of dopamine-producing neurons, increased brain inflammation and build-up of harmful proteins.

Zebrafish suffered brain cell death and damage linked to failure in the cell’s "cleanup system," according to the study press release.

Dr. Jeff Bronstein, director of the Movement Disorders Program at UCLA and professor of neurology and molecular toxicology, noted that previous human studies also suggested an association between chlorpyrifos exposure and Parkinson's.

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"[We were] surprised that the mechanism of toxicity was apparent in both mice and zebrafish," he said. "We rarely find such consistent results in different animal models."

The researcher emphasized that the association between pesticide exposure and Parkinson's was "very strong," and the longer someone was exposed, the higher the risk became.

"People should avoid exposure to CPF and similar pesticides (organophosphates) by not using them in their home, eating organics, and washing fruits and vegetables before eating them," Bronstein advised.

The study did have some limitations, the researchers acknowledged, primarily that it was observational, meaning it shows an association but cannot prove causation.

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It also estimated exposure based on participants’ locations, and did not measure diet, indoor exposure or personal lifestyle behaviors. Additionally, the results of the animal models can't be translated directly to humans.

There was also the possibility that chlorpyrifos was used along with other chemicals, which means it could be difficult to measure its specific impact, the study noted.

Chlorpyrifos is used to control different kinds of pests, like termites, mosquitoes and roundworms, among crops, according to the National Pesticide Information Center (NPIC) at Oregon State University.

People can be exposed to the pesticide by breathing it in or by consuming contaminated food or water.

In 2021, the EPA banned the use of chlorpyrifos on food crops, but a federal appeals court overturned that decision in 2023, allowing its use to resume on some crops while regulators revisit the rule.

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In January 2026, the EPA issued an update outlining plans to move forward with a rule that would ban most uses of chlorpyrifos.

"Chlorpyrifos is subject to registration review, a process required under FIFRA (the Federal Insecticide, Fungicide, and Rodenticide Act) in which registered pesticides are comprehensively evaluated every 15 years against current safety standards and the latest scientific evidence," the EPA said in a statement sent to Fox News Digital.

"EPA is currently developing a revised human health risk assessment for chlorpyrifos as part of that review, and will consider this study alongside any other relevant submissions. Where the science calls for stronger protections or tolerance revocations, EPA will act without hesitation and without delay."

Fox News Digital reached out to several manufacturers of the chemical for comment.

Corteva, an Indiana agrichemical company formed in 2019 through the merger of Dow Chemical and DuPont, announced in 2020 that it would end production of chlorpyrifos within the year, citing declining sales.

In April 2022, the German chemical company BASF requested the cancellation of its pesticide registrations for products containing chlorpyrifos. 

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"BASF does not manufacture chlorpyrifos and does not have any pesticide registrations issued by the U.S. EPA for chlorpyrifos-containing products," the company told Fox News Digital. 

No products from Corteva or BASF were included in the study linking chlorpyrifos to Parkinson’s disease.