Differential risk assessment for an acetylcholine esterase inhibitor (carbaryl)

Objectives of the investigation - to derive a reliable "Ecologically Acceptable Concentration" (EAC) for freshwater invertebrates with lowest possible residual uncertainty; - to evaluate the validity of the decisive risk assessment data from the literature using well documented (GLP) studies; - to study how exposure of the test organisms is influenced by the presence of sediment; - to identify the most sensitive groups of organisms; - to derive the risk potential for the most sensitive group(s) in relation to the duration of exposure. The properties of the substance allow highly comparable test results to be obtained, regardless of the GLP study design, the concentration checking, or the presence of sediment. The sensitivity of the test organisms is determined by ecophysiological characteristics. Our Hypothesis: The rate of absorption is determined by the rate of water exchange at the respiratory membranes. The three most sensitive groups are 1. insect larvae from high-current habitats 2. ladocerans as planktonic high-volume filter feeders 3. insect larvae and crustaceans from considerable current habitats. EAC summary, additional safety margins: Risk Group 1, High-current habitats NOEC after 1 h exposure - 20 µg/L; Risk Group 2, planktonic high-volume filter feeders Complete population recovery after 3 w: 10 µg/L; Risk Group 3, considerable current habitats NOEC-based HC5: 13 µg/L Overall EAC (conservative): 10 µg/L.