Environmental determinants of Parkinson's disease.

Increasing toxicologic and epidemiologic evidence suggests that pesticides and other environmental exposures are associated with idiopathic Parkinson's disease. Using a case-control study, the authors examined the impact of farming, pesticide use, rural residence, and well water use (including critical periods of childhood exposure) on the risk of Parkinson's disease. After adjustment for confounding, > or = 40 years of well-water exposure (compared to no well water use) was associated with an increased risk of Parkinson's disease (OR = 7.1; 95% CI: 2.3-22.1). The authors found an increased risk of Parkinson's disease (OR = 2.1; 95% Cl: 0.7-6.4) for well water use during the first 20 years of life (compared with <20 years of exposure) and saw some suggestion of an exposure-response relationship with increasing childhood exposure. Farming and pesticide use (occupational or residential) was not associated with Parkinson's disease but exposure assessment limitations warrant further investigation.