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5F - Probabilistic approaches (MOP/202) Tiered Probabilistic Risk Assessment of Deltamethrin in Aquatic Environments. Giddings, Jeffrey1, Feyerabend, Martin2, Romijn, Kees2, Schaefer, Dieter2, Sowig, Peter2, 1 The Cadmus Group, Inc., Massachusetts, USA, USA2 Bayer CropScience, Frankfurt, Germany, Germany ABSTRACT- A tiered approach was used to assess the potential risk to fish, invertebrates, and algae inhabiting ecosystems adjacent to crops treated with plant protection products containing the active ingredient deltamethrin. A conceptual model identified sources of variability and uncertainty in the analysis, and resulted in a stepwise plan for addressing them (e.g., using simplifying assumptions at lower tiers, and parameter distributions or advanced testing methods at higher tiers). Algae were eliminated from consideration after Tier 1 indicated negligible risk under all exposure scenarios. Risk to standard fish species was found to be low in Tier 2, and negligible risk to fish was confirmed in Tier 3 through analysis of species sensitivity distributions. Tier 4 therefore focused on risk to invertebrates, and incorporated specialized studies including sediment-water toxicity tests and an outdoor microcosm study to better define the potential ecological effects of deltamethrin. Multiple lines of evidence, including a review of data on other pyrethroid insecticides, were used to determine an ecologically acceptable concentration for deltamethrin of 10 ng/L. The assessment concluded that safe use of deltamethrin is possible in a variety of arable crops at distances of 10 m from water bodies without any further risk mitigation measures. If drift-reducing nozzles are used, distances as low as 1 to 5 m are sufficient to protect aquatic life. Key words: probabilistic risk assessment, pesticides, deltamethrin, aquatic |
