ChileanJAR

A standardized ecotoxicological evaluation of soil pesticides such as lindane, chlorpyrifos and metamidofos was realized at Federico Villarreal University, Lima, Peru, employing the freshwater snail Physa venustula as a tool for environmental risk assessment. The values determined for mean lethal concentration (LC₅₀) for the lethal effect of the pesticides evaluated were at 24, 48 and 96 h of exposure respectively: lindane 811.89, 715.30 and 415 m g L^-1; chlorpyrifos 379.13, 154 and 66.01 m g L^-1 and metamidofos 1 791, 391.33 and 194 m g L^-1. Sublethal effects were observed with chlorpyrifos and metamidofos. The CE₅₀ values determined for disadherence at 24, 48 and 96 h respectively were chlorpyrifos 197.14, 89.14 and 36.23 m g L^-1, and metamidofos 600.81, 361.69 and 150.75 m g L^-1. The values for cephalic detachment at 24, 48 and 96 h of exposure respectively were chlorpyrifos 323.69, 109.02 and 60.01m g L^-1, and metamidofos 738.4, 314.4 and 155.93 m g L^-1. Of the three evaluated pesticides, the decreasing order of ecotoxicity for the lethal effects, at 24 h of exposure was chlorpyrifos > lindane > metamidofos; and at 48 h and 96 h was chlorpyrifos> metamidofos > lindane. For sub-lethal effects the decreasing order of ecotoxicity at 24, 48 and 96 h was chlorpyrifos > metamidofos. This protocol of ecotoxicological assays using P. venustula is proposed as a tool for the evaluation of environmental risks of soil pesticides.