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 α-
synuclein, a
protein critically involved in
Parkinson disease. Therefore, we assessed total blood cell α-
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 α-
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 α-
synuclein. We observed somewhat greater α-
synuclein with the PON1-108T (lower
paraoxonase enzyme) allele, and with ≥ 10 h 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 α-
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.