"In this paper, the authors have assessed the incidence and determinants of pesticide poisoning among rice farmers in Vietnam's Mekong Delta. Blood cholinesterase tests suggest that the incidence of poisoning from exposure to organophosphates and carbamates is quite high in Vietnam. Using the medical test results as benchmarks, the authors find that farmers' self-reported symptoms have very weak associations with actual poisoning. Regression analysis of blood tests reveals a lower incidence of poisoning for farmers who avoid the most toxic pesticides and use protective items. The authors also find very large provincial differences in poisoning incidence after they control for individual factors. The results highlight the potential importance of negative externalities, and suggest that future research on pesticide-related damage should include information on local water, air, and soil contamination. "--World Bank web site.