Biomonitoring of acetylcholinesterase inhibition among agricultural workers exposed to pesticides in Tanzania: a cross-sectional study.

BACKGROUND

Agricultural workers in Tanzania face substantial occupational health risks associated with pesticide exposure, yet national biomonitoring data remain limited. Organophosphate and carbamate pesticides inhibit acetylcholinesterase (AChE), an established biomarker of pesticide exposure and early biological effect. This study evaluated erythrocyte AChE inhibition among agricultural workers across multiple farming systems and geographic regions in Tanzania.

METHODS

A cross-sectional study was conducted between January 2020 and December 2025 within the framework of occupational safety assessments coordinated by the Tanzania Plant Health and Pesticides Authority (TPHPA). A total of 1,387 agricultural workers from Arusha, Kilimanjaro, Morogoro, Mbeya/Songwe, and Coastal regions were recruited using multistage stratified sampling. Participants were classified as pesticide-exposed workers if they directly handled pesticides during agricultural activities and as apparently unexposed workers if they had no direct occupational pesticide handling responsibilities. Erythrocyte AChE activity was measured using the Test-mate ChE Cholinesterase Test System (Model 400). Statistical analyses included independent-samples t-tests, one-way and two-way analysis of variance (ANOVA), mixed-effects regression models, Pearson correlation analyses, and Tukey's Honest Significant Difference post-hoc tests.

RESULTS

Pesticide-exposed workers had significantly lower AChE levels compared with apparently unexposed workers (21.52 ± 2.41 vs. 28.47 ± 6.93 U/g Hb; mean difference = 6.95 U/g Hb; 95% CI: 6.54-7.36; p < 0.001). Regional differences were observed, with Morogoro recording the lowest mean AChE level and the highest proportion of exposed workers. Sugarcane workers demonstrated lower mean AChE levels than other agricultural sectors. Mixed-effects modeling confirmed that occupational pesticide exposure remained significantly associated with reduced AChE activity after adjustment for farm-level clustering and covariates.

CONCLUSIONS

This study demonstrates a strong association between occupational pesticide exposure and reduced erythrocyte AChE activity among agricultural workers across diverse farming systems in Tanzania. The findings support the integration of routine cholinesterase biomonitoring into occupational health surveillance programs.