Biomonitoring of Acetylcholinesterase Inhibition among Agricultural Workers Exposed to Pesticides in Tanzania: A Cross-Sectional Study

Background: Agricultural workers in Tanzania face significant health risks from pesticide exposure, yet national biomonitoring data remain limited. This study evaluated acetylcholinesterase (AChE) inhibition as a biomarker of pesticide exposure among agricultural workers across diverse farming systems. Methods: A cross-sectional study was conducted from January 2020 to December 2025 within a safety assessment framework by the Tanzania Plant Health and Pesticides Authority. A total of 1,387 agricultural workers from five regions (Arusha, Kilimanjaro, Morogoro, Mbeya/Songwe, and Coastal areas) were recruited using multistage stratified sampling. Participants were classified as exposed (direct pesticide handlers) or apparently unexposed (reference). AChE levels were measured using the Test-mate ChE Cholinesterase Test System (Model 400). Statistical analyses included t-tests, ANOVA, mixed effects models, and correlation analyses, with adjustment for age, sex, and years of exposure where available. Results: Exposed individuals had significantly lower AChE levels than the reference group (21.5 ± 2.4 vs. 28.5 ± 6.9 U/g Hb; mean difference 7.0 U/g Hb; 95% CI: 6.5–7.5; p < 0.001; Cohen's d = 1.34). Regional variations were observed, with Morogoro showing the lowest levels (22.5 U/g Hb). Sugarcane and flower farming sectors were associated with greater enzyme inhibition. Age showed a small positive correlation with AChE levels (r = 0.06, p = 0.039). Mixed effects modeling confirmed that exposure status remained predictive after accounting for farm-level clustering (β = 6.51, p < 0.001). Conclusions: Despite the lack of detailed health information, this study provides critical biomonitoring data demonstrating significant AChE inhibition among pesticide-exposed agricultural workers in Tanzania. Routine cholinesterase biomonitoring should be incorporated into national occupational health programs.