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5B a - RA: Ranking and Chemical Specific (TU6/6) Maximising the use of existing and new degradation data in overall persistence assessments. Snape, Jason1, Marie-Libre, Jean2, van Wijk, Dolf3, Douben, Peter4, Murray-Smith, Richard1, Whelan, Mick4, Cowan, Christina5, Mackay, Donald6, Holt, Martin7, 1 AstraZeneca Global SHE, Brixham, Devon, UK2 AtoFina, Paris, France3 EuroChlor, Brussels, Belgium4 Unilever, Sharnbrook, Bedfordshire, UK5 The Procter & Gamble Company, Cincinnati, OH, US6 Trent University, Peterborough, ON, Canada7 ECETOC, Brussels, Belgium ABSTRACT- A persistent chemical can be defined as a substance that is resistant to abiotic and or biotic degradation under both aerobic and anaerobic conditions. Unlike toxicity, persistence cannot be directly measured it can only be inferred from laboratory data demonstrating no degradation, or robust monitoring data demonstrating the continued presence of a chemical substance in the environment. However, at present there is no pragmatic laboratory testing regime or regulatory structure, in which these data can be used to accurately infer the persistence of chemicals in the environment. Such a regime is required to allow the effective prioritisation of chemical substances based on the P criterion of PBT (such that subsequent whole organism-based tests may be reduced). In order to address these issues ECETOC commissioned a Task Force to review the use of laboratory data and multi-media modelling within a broader regulatory framework to assess persistence. In order to recommend an improved framework to assess persistence the Task Force reviewed all publicly available laboratory and field degradation data, and laboratory-based tests systems for assessing degradation. A four-tiered framework was proposed designating persistence categories P1 to P4, where P1 describes a highly persistence chemical substance and P4 describes a substance that will undergo rapid degradation in all environmental compartment. The final persistence category assigned (P1 to P4) reflects the power of the degradation test system used and the probability that degradation will occur in the environment or environmental compartment of concern. The overall persistence of chemical substances were described by a distribution of T1/2 values. This presentation will compare laboratory and field degradation data for standard and non-standard test protocols, identify improved testing protocols and describe the four-tiered framework for assessing persistence. Key words: fate, degradation, persistence, exposure assessment |
