Neuropsychological effects of long-term low-level organophosphate exposure in orchard sprayers in England.

The health effects from prolonged low-level organophosphate exposure are unknown. We hypothesized that exposed individuals would show neuropsychological decrements when compared with unexposed individuals, and that cumulative organophosphate exposure would be correlated with neuropsychological performance. We used a quasiexperimental cross-sectional design to compare neuropsychological test scores among three groups: orchard sprayers exposed to organophosphates, and construction worker and pig farm workers who were not exposed. Relative to construction workers, orchard sprayers were significantly slower on negative statements of the syntactic reasoning test. However, we found no relationship between cumulative exposure and test response. The slower response of the orchard sprayers was apparently exposure-related, but we could not identify an underlying neurotoxic mechanism. Therefore, we are unable to conclude whether this is a specific cognitive effect, or a decrement arising on the most sensitive test employed.