More Pesticides = More Parkinson's Disease

Pesticide exposure is linked to Parkinson's disease. Image courtesy of santiago nicolau.

Over the past five years several studies have linked pesticide exposure to a greater risk of Parkinson's disease. Now new research confirms and extends these findings demonstrating that more exposure, as well as exposure to additional chemicals, increases risk even further.

Parkinson's disease is a neurodegenerative disorder that attacks a group of dopamine neurons in a small part of the brain called the substantia nigra. As the neurons degenerate, the patient loses the ability to initiate motion and can eventually become “frozen” within the body. Other symptoms include shaking, slow movement and other cognitive problems. Both actor Michael J. Fox and boxing champion Muhammad Ali have the disease.

Until recently the cause of Parkinson's was unknown. Recently, however, UCLA professor of epidemiology Dr. Beate Ritz found an increased risk of the disease among people living near farms where pesticides are used. Specifically the research found a link to the pesticides maneb and paraquat.

The latest study, which took place in a rural farming community in the California Central Valley, confirmed the link between these pesticides and also an additional fungicide called ziram. Additionally, people who were exposed to all three chemicals had a greater risk than those exposed to any of the pesticides in isolation.

Ritz's team also examined the effect of risk based on occupation. They found that while being near farms increases risk, working within the fields themselves poses an even greater risk, providing an independent measure of the dangers of exposure.

To try and elucidate the mechanism by which ziram may be damaging neurons, Ritz collaborated with UCLA neurologist Jeff Bronstein, who used a cell culture model to show that ziram inhibits the breakdown of protein alpha-synuclein in dopaminergic neurons. When alpha-synuclein accumulates, it causes selective cell death in these neurons. When administered to rodents in the lab, ziram created symptoms similar to Parkinson's disease.

The case is getting stronger that working with or around pesticides directly increases risk of Parkinson's disease. The obvious next question is what happens when we eat food from farms where these pesticides are used.

This study is published in the current online issue of the European Journal of Epidemiology.

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