Parkinson's Disease Strongly Linked To Pesticide Exposure, New Research Continues To Show

There has been a lot of research done in recent years that has exposed a strong link between pesticide exposure and the development of Parkinson’s disease. And now new research has added to that, showing that a pesticide discontinued from use in the U.S. ten years ago, benomyl, is still having a profound effect on the health of many people in the United States.


“Even more significantly, the research suggests that the damaging series of events set in motion by benomyl may also occur in people with Parkinson’s disease who were never exposed to the pesticide, according to Jeff Bronstein, senior author of the study and a professor of neurology at UCLA, and his colleagues.”

“Benomyl exposure, they say, starts a cascade of cellular events that may lead to Parkinson’s. The pesticide prevents an enzyme called ALDH (aldehyde dehydrogenase) from keeping a lid on DOPAL, a toxin that naturally occurs in the brain. When left unchecked by ALDH, DOPAL accumulates, damages neurons and increases an individual’s risk of developing Parkinson’s.”

Benomyl is only one of many pesticides used in significant quantities over the past century. So far, the pesticides paraquat, maneb and ziram — all very commonly used chemicals in California’s Central Valley and in agricultural areas around the world — have been shown to cause increases in the the prevalence of Parkinson’s disease. And very importantly, this is not just amongst the farmworkers, but anyone who lived or spent significant time near any of the areas where they are used or the wind carries them.

But even if all of the pesticides that are known to cause significant health problems were discontinued, they could still contribute to health problems far into the future, as Benomyl is showing. And that is not even taking into account all of the unknown effects of all of the (largely untested) chemicals and pesticides in use today.

The rapid increases in the prevalence of such neurological diseases, cancers, and developmental diseases during the last century has coincided very clearly with the enormous increase in the use of many chemicals that have never had any real long-term testing done on them.

“Parkinson’s disease is a debilitating neurodegenerative disorder that affects millions worldwide. Its symptoms — including tremor, rigidity, and slowed movements and speech — increase with the progressive degeneration of neurons, primarily in a part of the mid-brain called the substantia nigra. This area normally produces dopamine, a neurotransmitter that allows cells to communicate, and damage to the mid-brain has been linked to the disease. Usually, by the time Parkinson’s symptoms manifest themselves, more than half of these neurons, known as dopaminergic neurons, have already been lost.”

“While researchers have identified certain genetic variations that cause an inherited form of Parkinson’s, only a small fraction of the disease can be blamed on genes, said the study’s first author, Arthur G. Fitzmaurice, a postdoctoral scholar in Bronstein’s laboratory.”

“As a result, environmental factors almost certainly play an important role in this disorder,” Fitzmaurice said. “Understanding the relevant mechanisms — particularly what causes the selective loss of dopaminergic neurons — may provide important clues to explain how the disease develops.”

Benomyl itself was used very widely and on a very large-scale in the U.S. for over 30 years, until the evidence finally accumulated showing that it contributes to the development of liver tumors, “brain malformations, reproductive effects and carcinogenesis.” It wasn’t banned until 2001. And has likely been replaced with newer pesticides that have remained largely untested.

“We’ve known that in animal models and cell cultures, agricultural pesticides trigger a neurodegenerative process that leads to Parkinson’s,” said Bronstein, who directs the UCLA Movement Disorders Program. “And epidemiologic studies have consistently shown the disease occurs at high rates among farmers and in rural populations. Our work reinforces the hypothesis that pesticides may be partially responsible, and the discovery of this new pathway may be a new avenue for developing therapeutic drugs.”

The new research was just published in the online edition of Proceedings of the National Academy of Sciences.

Source: University of California – Los Angeles

Image Credits: UCLA

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