Scientists have identified 10 pesticides that significantly damaged neurons implicated in the development of Parkinson’s disease.
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Backstory
While pesticides have been suspected by scientists for quite awhile now as being linked to Parkinson’s Disease, efforts to identify the specific offending ingredients and pesticides has been daunting. The reason? There are tens of thousands of pesticides with over 1,000 active ingredients currently registered and in use in the U.S.
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Study overview
Scientists in the current study took advantage of California’s extensive pesticide use database and then used novel pairing of epidemiology and toxicity screening to identify 10 pesticides that were directly toxic to dopaminergic neurons. These neurons play a key role in voluntary movement, and the death of these neurons is a hallmark of Parkinson’s. Additionally, the researchers uncovered co-exposure of pesticides that are typically used in combinations in certain types of agriculture like cotton farming were more toxic than any single pesticide in that group.
The researchers examined exposure history going back decades for 288 pesticides among patients with Parkinson’s disease who had participated in previous studies. They were able to determine long-term exposure for each person and then, using what they labeled a pesticide-wide association analysis, tested each pesticide individually for association with Parkinson’s. From this untargeted screen, researchers identified 53 pesticides that appeared to be implicated in Parkinson’s – most of which had not been previously studied for a potential link and are still in use.
Next, they had the pesticides under suspicion for a link with Parkinson’s tested for toxicity. This was done in dopaminergic neurons that had been derived from Parkinson’s patients through what’s known as ‘induced pluripotent’ stem cells, which are a type of “blank slate” cell that can be reprogrammed into neurons that closely resemble those lost in Parkinson’s disease.
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Results overview
The 10 pesticides identified as directly toxic to these neurons included: four insecticides (dicofol, endosulfan, naled, propargite), three herbicides (diquat, endothall, trifluralin), and three fungicides (copper sulfate [basic and pentahydrate] and folpet). Most of the pesticides are still in use today in the United States.
Combinations involving trifluralin, one of the most commonly used herbicides in California, produced the most toxicity.
Journal reference: Paul, K.C., et al. A pesticide and iPSC dopaminergic neuron screen identifies and classifies Parkinson-relevant pesticides. Nature Communications Journal, 14, 2803 (2023). https://doi.org/10.1038/s41467-023-38215-z
Dr. Scott
Chemical Free Life 