Searles_2014_Environ.Res_136C_75

Epidemiologic studies suggest that occupational exposure to pesticides might increase Parkinson disease risk. Some pesticides, such as the organophosphorus insecticide chlorpyrifos, appear to increase the expression of alpha-synuclein, a protein critically involved in Parkinson disease. Therefore, we assessed total blood cell alpha-synuclein in 90 specimens from 63 agricultural pesticide handlers, mainly Hispanic men from central Washington State, who participated in the state's cholinesterase monitoring program in 2007-2010. Additionally, in age-adjusted linear regression models for repeated measures, we assessed whether alpha-synuclein levels were associated with butyrylcholinesterase-chlorpyrifos adducts or cholinesterase inhibition measured in peripheral blood, or with self-reported pesticide exposure or paraoxonase (PON1) genotype. There was no evidence by any of those indicators that exposure to chlorpyrifos was associated with greater blood alpha-synuclein. We observed somewhat greater alpha-synuclein with the PON1-108T (lower paraoxonase enzyme) allele, and with >/=10h of exposure to cholinesterase inhibiting insecticides in the preceding 30 days, but neither of these associations followed a clear dose-response pattern. These results suggest that selected genetic and environmental factors may affect alpha-synuclein blood levels. However, longitudinal studies with larger numbers of pesticide handlers will be required to confirm and elucidate the possible associations observed in this exploratory cross-sectional study.