Carbofuran Presence in Soil Leachate, Groundwater, and Surface Water in the Potato Growing Area in

Carbofuran (2,3-dihydro-2,2-dimethyl-7-benzofuranyl methylcarbamate) is a toxic insecticide widely used on potato (Solanum tuberosum L.) crops in Carchi Province, Ecuador. Carbofuran can leach to groundwater and become a threat for both human health and the environment. To determine the extent of carbofuran presence in the area, we sampled soil leachate, groundwater, and surface water from within 14 hydrologic units (each 2.5–20 ha) where potato was being grown from September to November 1999. Carbofuran was found in all hydrologic units except one, at concentrations that were in-versely proportional to the organic matter content of the predominant soil type. A simulation study showed that the Leaching Estimation and Chemistry Model (LEACHM) could be a valuable tool for evaluating carbofuran fate, because it was shown to correctly identify soil types with the greatest risk for leaching. Concerns about the adverse effects of carbofuran on human health and the environment led to an analysis of farmer practices and pesticide use in two Carchi watersheds during the early 1990s (Crissman et al., 1998a). This analysis showed that most of the negative impacts of pesticide use on human health were due to pesticide exposure following unsafe storage, handling, and application. Although the fate of carbofuran in the environment was not measured and monitored directly, modeling studies indicated that leaching of carbofuran would be minimal because of the high organic matter (OM) content of soils in the region; sorption of the pesticide increases with increasing OM content (Ducrot et al., 1998). These results, however, do not suggest that carbofuran poses no adverse environmental risks in the potato-growing areas of Carchi. Rather, they have pro-vided the impetus for several mor