Biomarkers of pesticide exposure predict Depressive Symptoms in rural and urban workers of the Maule Region, Chile

BackgroundAgricultural workers are routinely exposed to pesticides, which are associated with a range of adverse health outcomes, including potential impacts on mental health such as depressive symptoms. In the Maule region of Chile, an area characterized by intensive pesticide use, this study investigates the association between exposure to organophosphate (OP) pesticides and the prevalence of depressive symptoms among agricultural workers. MethodsWe conducted a longitudinal study with 78 participants, comprising agricultural workers occupationally exposed to pesticides and nearby urban non-agricultural workers. Pesticide exposure was assessed through six dialkyl phosphate (DAP) metabolites in four repeated urine samples over two years. Depressive symptoms were evaluated using the CES-D scale and affect using the PANAS scale. Sociodemographic, health, and exposure-related variables were included as covariates. Generalized Estimating Equations (GEE) were employed to investigate dose-response relationships between pesticide exposure and depressive symptoms. ResultsNo reliable differences in urinary DAP, DEAP, and DMP metabolite concentrations were observed directly when testing between rural and urban workers, however, dose-response analyses revealed that cumulative exposure to diethyl alkyl phosphates (DEAPs) was associated with depressive symptoms (CI=0.0003-0.0127, p = 0.040). Over time, positive affect increased among rural workers, whereas urban workers reported significantly lower negative affect in 2023. Further analyses showed problematic alcohol consumption (CI=0.018-3.707, p = 0.048) as a predictor of depressive symptoms. ConclusionsPesticide exposure extends beyond occupational settings to include environmental sources or food residues, as shown by comparable exposure levels in rural and urban participants and consistent measurements over two years. Chronic exposure to DEAPs was predictive of depressive symptoms, emphasizing the importance of biomarkers for assessing cumulative exposure. Public health interventions, stricter regulations, and awareness programs are needed to address the mental health risks of pesticide exposure. Further research should explore genetic and environmental factors influencing susceptibility to mental health.