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 (LC 50 ) 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 CE 50 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