Parkinson’s and Pesticides: The Risks

Summary
It is important to look at the toxic effects of increasingly used pesticides, especially on nerves and the brain. This study conducted in California examined the effects of these pesticides on the incidence of Parkinson’s disease. It was found from this study that exposure to pesticides such as ziram, maneb and paraquat raised the risk of Parkinson’s disease substantially. Authors concluded that, “Those exposed to ziram, maneb, and paraquat together experienced the greatest increase in Parkinson’s disease risk.” They speculate that these pesticides kill certain important nerve pathways such as the dopaminergic pathway of nerves in the brain leading to Parkinson’s disease.

Introduction
Parkinson’s disease is a common disorder of nerves and the brain that leads to progressive tremors and immobility. It is diagnosed in 17 of 100,000 people each year and the incidence is on the rise. Recent animal experiments have revealed that some pesticides such as paraquat act by damaging and killing certain nerve pathways in the brain — notably dopaminergic pathway — that leads to the development of Parkinson’s disease. Apart from paraquat, there are other pesticides such as maneb and ziram that may cause similar damage to neurons. In spite of these reports, there have been no studies that explore the effects of these chemicals on humans. It is known that those working in the farms as well as those residing in the neighborhood are exposed to high amount of sprayed pesticides. This study attempted to test the association between Parkinson’s disease and specific pesticides.

Methodology
* This study spanned the years between 2001 and 2007. A total of 362 newly diagnosed patients with Parkinson’s disease were included in the study. To compare with these patients, a further 341 healthy individuals residing in the Central Valley of California were included.
* The researchers employed specific geographical test models to assess the exposure to the pesticides maneb, ziram and paraquat.
* All the patients were checked for these chemical exposures at their homes and occupational sites between 1974 and 1999.
* Stratified analyses were also conducted by exposure time window and by age of the patients.

Data/Results/Key Findings
* Results showed that at places of work, the three tested pesticides — ziram, paraquat and maneb — increased the risk of acquiring Parkinson’s disease by three times.
* The results also showed that when there was a combined exposure to paraquat and ziram, without exposure to maneb, there was an 80 percent rise in the risk of Parkinson’s disease.
* The risk of exposure and developing Parkinson’s disease was higher when exposed at place of work rather than at homes, especially in patients who suffered from Parkinson’s disease at a younger age. The risk was greatest in those who were exposed to the chemicals both at home and at workplace.

Next steps/Shortcomings
Authors admit that while using geographical testing for pesticide exposure over a particular period, they had to trust the accuracy of the reported home and work addresses of the people. It was noted that 26 percent each of the patients and healthy volunteers, who served as control, did not provide accurate occupational addresses. This could have skewed the results of the study. Further studies to eliminate these shortcomings are warranted.

Conclusion
This is the first study of its kind that shows that ziram, paraquat and maneb may be implicated in raising the risk of developing Parkinson’s disease in humans. This study concludes that their combination may pose a higher risk than each of the chemicals alone and this could be due to different methods by which they kill the brain nerve pathways. This study also shows that exposure to the chemicals at the workplace is more important than those exposed at homes and this is especially so in those who are diagnosed with PD at a younger age. It is also seen that those who are exposed to the pesticides both at home and at workplace are at the greatest risk of developing Parkinson’s disease.

For More Information:
Parkinson’s Disease Risk from Ambient Exposure to Pesticides
Publication Journal: European Journal of Epidemiology, 2011
By Anthony Wang; Sadie Costello; UCLA School of Public Health, Los Angeles, CA; UC Berkeley School of Public Health, Berkeley, CA

*FYI Living Lab Reports Are Summaries of the Original Research.

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