Parkinson’s disease risk from ambient exposure to pesticides

Abstract

Due to the heavy and expanding agricultural use of neurotoxic pesticides suspected to affect dopaminergic neurons, it is imperative
to closely examine the role of pesticides in the development of Parkinson’s disease (PD). We focus our investigation on pesticide
use in California’s heavily agricultural central valley by utilizing a unique pesticide use reporting system. From 2001 to
2007, we enrolled 362 incident PD cases and 341 controls living in the Central Valley of California. Employing our geographic
information system model, we estimated ambient exposures to the pesticides ziram, maneb, and paraquat at work places and residences
from 1974 to 1999. At workplaces, combined exposure to ziram, maneb, and paraquat increased risk of PD three-fold (OR: 3.09;
95% CI: 1.69, 5.64) and combined exposure to ziram and paraquat, excluding maneb exposure, was associated with a 80% increase
in risk (OR:1.82; 95% CI: 1.03, 3.21). Risk estimates for ambient workplace exposure were greater than for exposures at residences
and were especially high for younger onset PD patients and when exposed in both locations. Our study is the first to implicate
ziram in PD etiology. Combined ambient exposure to ziram and paraquat as well as combined ambient exposure to maneb and paraquat
at both workplaces and residences increased PD risk substantially. Those exposed to ziram, maneb, and paraquat together experienced
the greatest increase in PD risk. Our results suggest that pesticides affecting different mechanisms that contribute to dopaminergic
neuron death may act together to increase the risk of PD considerably.

KeywordsCase–control study–Geographic information systems (GIS)–Paraquat–Parkinson’s disease–Pesticide–Ziram