Parkinsonism and occupational exposure to pesticides

Objective-To examine the risk of parkinsonism related to lifetime occupatio nal exposure to pesticides among a cohort of men, mostly orchardists, in Wa shington State. Methods-All 310 subjects in this study had previously participated in a coh ort study of men occupationally exposed to pesticides. Subjects were given a structured neurological examination and completed a self administered que stionnaire which elicited detailed information on pesticide (insecticide, h erbicide, and fungicide) use throughout their working careers. Demographic characteristics were also sought. Subjects had a mean age of 69.6 years (ra nge 49-96, SD 8.1). There were 238 (76.8%) subjects who reported some occup ational exposure to pesticides, whereas 72 (23.2%) reported none. Parkinson ism was defined by the presence of two or more of rest tremor, rigidity, br adykinesia, and impairment of postural reflexes in subjects not on antipark insonian medication, or the presence of at least one sign if they were on s uch medication. Parkinson's disease was not studied explicitly because of t he difficulty in distinguishing it from other parkinsonian syndromes. A gen eralised linear model was used to estimate prevalence ratios (PRs) for park insonism relative to history of farming, pesticide use, and use of well wat er. Results-A PR of 2.0 (95% confidence interval (95% CI) 1.0 to 4.2) was found for subjects in the highest tertile of years of exposure to pesticides; a similarly increased, non-significant, PR was found for the middle tertile ( 1.9 (95% CI 0.9 to 4.0)), although a trend test did not show a significant exposure-response relation. No increased risks were found associated with s pecific pesticides or pesticide classes, nor with a history of farming or u se of well water. Conclusion-Parkinsonism may be associated with long term occupational expos ure to pesticides, although no associations with specific pesticides could be detected. This finding is consistent with most of the publications on th is topic.