Acute Toxicity of Chlorpyrifos to Hyalella curvispina: Comparison of Species Sensitivity and Assessment of Environmental Risk

The objective of the work reported here was to determine the acute toxicity of chlorpyrifosthe most commonly used pesticide in Argentinato the amphipod Hyalella curvispina, with that species being widely distributed in South America. The 50% lethal concentration (LC 50) of chlorpyrifos to H. curvispina was determined and compared to that of other crustacean species by means of the species-sensitivity distribution (SSD). The ecological risk was assessed as the Hazard Quotient (HQ). The mean 48-h LC50 recorded in this study was 0.38 +/- 0.04g/L. Hyalella curvispina was considerably sensitive compared to other crustacean species reported in the literature. The HQ values calculated from the LC50s estimated here and the chlorpyrifos concentrations reported in previous studies in the Argentine Pampas ranged within 0.6-46. The chlorpyrifos concentrations in those stream waters were often above the H. curvispina 48-h LC50, indicating that acute toxicity of chlorpyrifos to H. curvispina is predicted to be occurring in these streams. The present results suggest that H. curvispina represents a suitable sentinel species for water-quality assessment and that H. curvispina along with similarly sensitive macroinvertebrate species in intensively cultivated areas in South America are likely to be affected by the application of chlorpyrifos to the neighboring crops.