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Study Supports Link Between Pesticides and Parkinsonís

Exposure to pesticides or solvents may increase a person’s risk of developing Parkinson’s disease (PD), according to a new analysis of combined data from more than 100 studies. In particular, the researchers associated exposure to the weed killer paraquat and the fungicides maneb and mancozeb with doubling the risk of PD.  The results appear in the May 28 issue of Neurology.

In recent years, increasing evidence has shown that people who work with pesticides, herbicides and chemical solvents, or are exposed to them elsewhere, develop PD at higher rates than people who do not. Even so, PD is not very common and most studies gather data on relatively small numbers of people, making it difficult to prove a connection.

With a statistical technique called meta-analysis, researchers can combine the results of many small studies to understand overall patterns in the data and draw stronger conclusions about them.  Emanuele Cereda, M.D., Ph.D., with the IRCCS University Hospital San Matteo Foundation in Pavia, Italy, and Gianni Pezzoli, M.D., with the Parkinson Institute-ICP, Milan, used this method to analyze data from 104 previous reports investigating the risk of PD associated with exposure to pesticides and solvents. They also accounted for the fact that these earlier studies were not all carried out in the same way, or according to the same protocols.


  • Exposure to some types of pesticides, herbicides, insecticides or solvents was associated with 1.3-1.8-fold increased risk of PD. To put this in context, in the general population, the average risk of PD is .6 percent; this changes one’s risk to 1.1.
  • PD risk doubled with exposure to the herbicide paraquat or the fungicides maneb and mancozeb.
  • Risk may increase with longer exposures and higher doses.

What Does It Mean?

The study authors found that research to date supports the idea that exposure to pesticides or solvents is a risk factor for PD. Understanding and demonstrating this risk in detail is important to making policy regulating use of these products; for instance while many of the compounds are no longer permitted in the United States, they are still used in other countries.

It is important to understand that the studies reviewed here are epidemiological studies, which report on associations between different compounds and PD. These studies are not designed to prove definitive cause and effect between the compounds and the development of PD. Further research is needed to understand the mechanism of the connection between pesticides and PD. Furthermore, the strength of association between pesticides and PD (two-fold at most) suggests that even among those who are chronically exposed to pesticides, PD is rare.

Additionally, PD is a complex disease and most cases have no known cause. It is likely that a combination of genetic and environmental factors, which varies from person to person, and can include pesticide exposure, contribute to PD. Much research is under way to investigate, for example, the interaction of exposures to different products, the role of genes linked to PD in a person’s risk from pesticide exposure and the molecular mechanisms by which these products may contribute to PD.

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Do you have more questions about environmental factors and Parkinson's? Contact us at (800) 457-6676 or or use our free resources below.

View the Article: Environmental Factors and PD: What Have We Learned?

Reference: Pezzoli G, Cereda E (2013) Exposure to pesticides or solvents and risk of Parkinson disease. Neurology 80:2035–2041. DOI: 10.1212/WNL.0b013e318294b3c8

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Source Date: Jun 14 2013