Epidemiologists from the UCLA School of Public Health conducted a study of Central Valley residents diagnosed with Parkinson's disease. Their findings provided clear evidence that years of exposure to the fungicide maneb and the herbicide paraquat increases the risk of Parkinson's by 75 percent - and the increase is even greater in people 60 and under.

The researchers enrolled 368 longtime residents of the Central Valley who were diagnosed with Parkinson's, as well as 341 others as a control group. Senior Study Author Beate Ritz, professor of epidemiology at the UCLA School of Public Health, First Author Sadie Costello from the University of California, Berkeley, and their colleagues found that Central Valley residents who lived within 500 meters of fields sprayed between 1974 and 1999 were at a 75 percent greater risk for getting the disease. Furthermore, younger Parkinson's sufferers - those 60 or under - were found to be at a four- to six-fold increase due to their having been exposed to the pesticides between 1974 and 1989, when they would have been children, teens or young adults.

This is the first time that definitive evidence has been shown linking longtime pesticide exposure to Parkinson's. "Because pesticides applied from the air or ground may drift from their intended treatment sites - with measurable concentrations subsequently detected in the air, in plants and in animals up to several hundred meters from application sites - accurate methods of estimating environmental exposures in rural communities have long been sorely needed," writes Ritz in a recent issue of the American Journal of Epidemiology.

To conduct the study, the researchers developed a geographic information system tool with the ability to estimate human exposure to pesticides applied to agricultural crops. In addition, telephone interviews were conducted to secure demographic and exposure information. Ritz noted that "this is the first epidemiological study to provide strong evidence that maneb and paraquat act synergistically to become neurotoxic and strongly increase the risk of Parkinson's disease in humans."  She also reported that the data "suggests that the critical window of exposure to toxicants may have occurred years before the onset of motor symptoms when a diagnosis of Parkinson's is made."

A degenerative disorder of the central nervous system that typically affects motor skills, speech and other functions, Parkinson's disease has been shown to occur at high rates among farmers and in rural populations. This reinforces the hypothesis that agricultural pesticides may be partially responsible.

News Release: Pesticide exposure found to increase risk of Parkinson's disease  http://www.newswise.com/articles/view/551453/    April 21, 2009