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(621) Tiered Probabilistic Risk Assessment of Deltamethrin in Aquatic Environments.
Giddings, Jeffrey*,1, Feyerabend, Martin2, Romijn, Kees2, Schäfer, Dieter2, Sowig, Peter2, 1 The Cadmus Group, Marion, MA, USA2 Aventis Crop Science, Frankfurt, 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. The initial problem formulation phase of the assessment 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. Tiers 3 and 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: deltamethrin, probabilistic risk assessment, pesticide, aquatic
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