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Sylvia Karlsson Swedish Chemicals Inspectorate

FOCUS Degradation Kinetics Training course 26-27 January 2005 Regulatory use of degradation endpoints. Sylvia Karlsson Swedish Chemicals Inspectorate. Parent compounds, soil: DT 50 , DT 90 or rate constant, kinetic model

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Sylvia Karlsson Swedish Chemicals Inspectorate

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  1. FOCUS Degradation KineticsTraining course 26-27 January 2005Regulatory use of degradation endpoints Sylvia Karlsson Swedish Chemicals Inspectorate

  2. Parent compounds, soil: DT50, DT90 or rate constant, kinetic model Metabolites, soil: DT50, DT90 or rate constant, kinetic model, formation fraction Parent and metabolites, water/sediment: DT50, DT90 or rate constant, kinetic model, (formation fraction) – for overall system, water column and sediment What are the kinetic endpoints?

  3. To compare with criteria, triggers for further studies, as provided in Annex II, III and VI of Dir. 91/414/EEC and in Guidance Documents on Aquatic and Terrestrial Ecotoxicology As input to calculations of PECsoil, PECgw, PECsw and PECsed What are the kinetic endpoints used for?

  4. Use against triggers (parents & metabolites): DT50 and DT90 derived by best-fit kinetics (unless deviation from first order kinetics can be attributed to experimental artefact!)Degradation or dissipation endpoints?- Mainly left to users to decide. What endpoints are used for different purposes (triggers/PEC)?

  5. PECgw, PECsw and PECsed – calculated e.g. by FOCUS simulation tools: DT50 or rate constant, for metabolites also formation fraction, derived by first order kinetics (1st tier).Data from lab or field studies.Endpoints from field studies must be normalised.

  6. PECsoil calculated by spreadsheets or parameter estimation software: DT50 or rate constant, for metabolites also formation fraction, Endpoints derived by best-fit kinetics. Data from lab or field studies.

  7. For use against triggers and to calculate PECsoil:Values not averaged (normally!) To calculate PECgw, PECsw and PECsed:Averaged values (normally!) Average or representative worst-case values?

  8. Rate constants and DT50s: Geometric – pragmatic reason: produces equal results Other parameters (e.g., formation fractions): Arithmetic Geometric or arithmetic mean?

  9. DT50 and DT90 obtained by different kinetic models can be averaged. Specific recommendations are provided for metabolite endpoints and for use of endpoints for calculation of PECgw, PECsw and PECsed when first order kinetics does not provide an adequate fit. Finally,

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