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Current regulatory approaches to short-term and longer-term avian risk assessment of pesticides are primarily limited to an initial screening level evaluation. This evaluation is based on a product's maximum application rate and the maximum estimated residues for avian feed item categories described in the Hoerger and Kenaga nomograph. A more refined evaluation, including an uncertainty component, is needed if the screening procedure indicates a potential for adverse effects from labeled uses of a product. We describe a tiered approach to avian risk assessment that represents an integration of use pattern information, nature and magnitude of the residue data, soil metabolism data, and appropriate toxicological data. One example assessment focuses on longer-term evaluations for an acutely toxic insecticide; a second example assesses the potential risk from a toxic fungicide degradate. The screening level evaluation indicated unacceptable acute and longer-term risk for both products. Higher tier evaluation of the insecticide indicated a substantial reduction in potential risk because of rapid foliar degradation. Higher-tier analysis of the fungicide degradate indicate low risk because of metabolism patterns. The analyses compare estimated residues to actual residue data, and explore the limitations of estimating degradate concentrations on feed items from estimates of parentcompound.
avian risk methodology, tiered evaluation procedure, feed item residues, field data, uncertainty
Deputy director of toxicology, Jellinek, Schwartz & Connolly, Inc., Arlington, VA
Program manager, Environmental and Metabolic Fate, Ricerca, Inc., Painesville, OH