Toxic effect and bioavailability of malathion spiked in natural sediments from the Ignacio Ramirez dam on the snail Stagnicola sp

Malathion (MA) is a widely used insecticide in Mexico. The snail Stagnicola sp is a native species of the Ignacio Ramirez dam (IRD). This work aimed to evaluate the bioavailability and toxicity of MA in sediments of the IRD from the Stagnicola sp snail, taking into account the physicochemical properties of the IRD sediment. The toxic effect of MA on the snail Stagnicola sp was evaluated by biochemical tests of acetylcholinesterase (AchE) activity, protein concentration, lipid peroxidation level (LPL), and lipid content; a toxicokinetic study was also carried out. An increment in all biochemical parameters was observed at the beginning of exposure, while at 48 and 72 h a decrement in AchE activity, LPL, and lipid content was observed. The kinetics study showed gradual uptake and rapid elimination of the insecticide in the test organism. The bioconcentration factor and the absorption and elimination constants led to the conclusion that this compound is not being stored in snails. However, at the end of the experiment, the snails without MA exhibited a lack of recovery in AchE activity, which indicates that there is no correlation between the inhibitory pattern of AchE activity and snail MA concentration. (C) 2002 Elsevier Science (USA).