For a while now it's known that exposure to pesticides is associated with developing Parkinson's Disease. But which pesticides? This is an important question because millions of pounds of pesticides are applied in the US each year. A recent study provides some answers.
The Harvard and UCLA Health researchers looked at 288 pesticides. They found that 53 pesticides were associated with Parkinson's disease, but 10 were directly toxic to dopaminergic neurons. Dopaminergic neurons are cells in the brain, and their degeneration and death play a key role in Parkinson's disease.
The 10 most toxic pesticides included four insecticides (dicofol, endosulfan, naled, propargite), three herbicides (diquat, endothall, trifluralin), and three fungicides (copper sulfate [basic and pentahydrate] and folpet). Some are commonly used even by homeowners, such as Preen (contains trifluralin) and Ortho Groundclear (contains diquat).
They also found that co-exposure to several pesticides (which typically happens) have a greater negative effect than just 1 pesticide.
Bottom line: There is much we don't know about pesticides, but studies are finding more health harms each year. Avoid using pesticides in your home, lawn, and garden if you can - especially unnecessary "cosmetic" lawn pesticides. Best and safest is to use nontoxic Integrated Pest Management (IPM) or organic.
Think of it this way: pesticides can give you cancer and damage your health, but clover and crabgrass can't.
From Science Daily: 10 pesticides toxic to neurons involved in Parkinson's
Researchers at UCLA Health and Harvard have identified 10 pesticides that significantly damaged neurons implicated in the development of Parkinson's disease, providing new clues about environmental toxins' role in the disease.
While environmental factors such as pesticide exposure have long been linked to Parkinson's, it has been harder to pinpoint which pesticides may raise risk for the neurodegenerative disorder. Just in California, the nation's largest agricultural producer and exporter, there are nearly 14,000 pesticide products with over 1,000 active ingredients registered for use.
Through a novel pairing of epidemiology and toxicity screening that leveraged California's extensive pesticide use database, UCLA and Harvard researchers were able to identify 10 pesticides that were directly toxic to dopaminergic neurons. The neurons play a key role in voluntary movement, and the death of these neurons is a hallmark of Parkinson's.
Further, the researchers found that co-exposure of pesticides that are typically used in combinations in cotton farming were more toxic than any single pesticide in that group.
For this study, published May 16 in Nature Communications, UCLA researchers examined exposure history going back decades for 288 pesticides among Central Valley patients with Parkinson's disease who had participated in previous studies. The researchers 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.
Those results were shared for lab analysis led by Richard Krolewski, MD, PhD, an instructor of neurology at Harvard and neurologist at Brigham and Women's Hospital. He tested the toxicity for most of those pesticides 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.
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.
Aside from their toxicity in dopaminergic neurons, there is little that unifies these pesticides. They have a range of use types, are structurally distinct, and do not share a prior toxicity classification.
Researchers also tested the toxicity of multiple pesticides that are commonly applied in cotton fields around the same time, according to California's pesticide database. Combinations involving trifluralin, one of the most commonly used herbicides in California, produced the most toxicity. Previous research in the Agricultural Health Study, a large research project involving pesticide applicators,had also implicated trifluralin in Parkinson's.