Bioaccumulation Tests For Hydrophobic

Transcription

1 ECO33: Use & Interpretation Of Dietary Bioaccumulation Tests For Hydrophobic Chemicals ( ) Frank Gobas, Yung-Shan Lee and Justin Lo Simon Fraser University, Vancouver, British Columbia, Canada contact:

2 Regulatory Bioaccumulation Assessment End Points Canada US REACH Japan UN K ow K ow K ow K ow BCF BCF BCF BCF BCF BAF BAF BMF TMF Bioaccumulation in other species High (eco)toxicity Monitoring data

3 BCF : Aqueous Bioconcentration Tests Lab Test OECD 305 Guidelines for Bioaccumulation Testing But: Time consuming Expensive Use many animals Technically difficult Water often not main exposure route in field Informs on fish, not air-respiring species

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5 Regulatory Bioaccumulation Assessment End Points Canada US REACH Japan UN K ow K ow K ow K ow BCF BCF BCF BCF BCF BAF BAF BMF TMF Bioaccumulation in other species High (eco)toxicity Monitoring data

6 BMF : Dietary Bioaccumulation Tests Lab Test OECD 305 Guidelines for Bioaccumulation Testing Less time consuming Less expensive Less animals Less difficult Informs on main exposure route for many chemicals Easier to extrapolate to other consumer organisms Does not generate a BCF for regulatory use

7 Objectives Develop a toxicokinetic modelling framework for the interpretation of OECD 305 dietary bioaccumulation test results. Apply & test methods for deriving bioaccumulation metrics (including the BCF) from the results of OECD 305 dietary bioaccumulation tests. Develop methods for assessing bioaccumulation exposure pathways for aquatic and terrestrial biota from the results of dietary bioaccumulation tests and field studies. Investigate whether dietary bioaccumulation tests can inform on the potential of substances to cause adverse perturbations on individuals and populations resulting from uptake and storage of the chemical regardless of trophic magnification.

8 Objectives Develop a toxicokinetic modelling framework for the interpretation of OECD 305 dietary bioaccumulation test results. Apply & test methods for deriving bioaccumulation metrics (including the BCF) from the results of OECD 305 dietary bioaccumulation tests. Develop methods for assessing bioaccumulation exposure pathways for aquatic and terrestrial biota from the results of dietary bioaccumulation tests and field studies. Investigate whether dietary bioaccumulation tests can inform on the potential of substances to cause adverse perturbations on individuals and populations resulting from uptake and storage of the chemical regardless of trophic magnification.

9 Objectives Develop a toxicokinetic modelling framework for the interpretation of OECD 305 dietary bioaccumulation test results. Apply & test methods for deriving bioaccumulation metrics (including the BCF) from the results of OECD 305 dietary bioaccumulation tests. Develop methods for assessing bioaccumulation exposure pathways for aquatic and terrestrial biota from the results of dietary bioaccumulation tests and field studies. Investigate whether dietary bioaccumulation tests can inform on the potential of substances to cause adverse perturbations on individuals and populations resulting from uptake and storage of the chemical regardless of trophic magnification.

10 Objectives Develop a toxicokinetic modelling framework for the interpretation of OECD 305 dietary bioaccumulation test results. Apply & test methods for deriving bioaccumulation metrics (including the BCF) from the results of OECD 305 dietary bioaccumulation tests. Develop methods for assessing bioaccumulation exposure pathways for aquatic and terrestrial biota from the results of dietary bioaccumulation tests and field studies. Investigate whether dietary bioaccumulation tests can inform on the potential of substances to cause adverse perturbations in individuals and populations resulting from uptake and storage of the chemical regardless of trophic magnification.

11 Constraints Framework should be applicable to OECD 305 type tests Framework should not require significant extra effort and/or costs Framework should not require additional data Framework should support regulatory efforts Framework should support B assessment in industry

12 Development of a Toxicokinetic Modeling Framework k 1 k G Gill Elimination Somatic Metabolism k D k M Dietary Uptake Lier Growth Dietary Uptake k 2 k E Gill Uptake Fecal Excretion Intestinal Metabolism Water k B2 W B C B k B1 W B C W Fish body k GD W B C B k BM W B C B k GB W G C G Digesta k BG W B C B k GM W G C G G I C D Diet G GE C G

13 Rationale More realistic, not overly complex Derives more information from test results without modifying the test Requirements: i. remove guts from fish (option included in OECD 305) ii. Use non-metabolizable reference chemicals (included in OECD 305) No additional data are needed. Derives both somatic and intestinal biotransformation rates Better insights into the internal dynamics of the substance in the fish Can derive a BCF

14 Toxicokinetic Modeling Framework Water k B2 W B C B k B1 W B C W Fish body k GD W B C B k BM W B C B k GB W G C G Digesta k BG W B C B k GM W G C G G I C D Diet G GE C G

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17 Fish Bioaccumulation ADME Calculator Output Secondary Data Symbol Action Value Standard Error Rate constant for respiratory uptake k B1 Calculated Rate constant for respiratory elimination k B2 Calculated Rate constant for chemical transfer from fish body to GI content k BG Calculated Rate constant for somatic biotransformation k BM Calculated Rate constant for chemical transfer from GI content to fish body k GB Calculated Rate constant for fecal egestion k GE Calculated Rate constant for biotransformation in the GI content k GM Calculated Biomagnification factor BMF Calculated Biomagnification factor (lipid equivalent) BMF L Calculated Biomagnification factor (lipid equivalent, growth corrected) BMF L,g Calculated Bioconcentration factor (wet weight, freely dissolved) BCF ww,fd Calculated Bioconcentration factor (lipid equivalent, freely dissolved) BCF L,fd Calculated Bioconcentration factor (wet weight, freely dissolved, 5% lipid content) BCF 5%,fd Calculated Bioconcentration factor (wet weight, total) BCF ww,t Calculated Bioconcentration factor (lipid equivalent, total) BCF L,t Calculated Bioconcentration factor (wet weight, total, 5% lipid content) BCF 5%,t Calculated Bioconcentration factor (wet weight, total, growth corrected) BCF ww,t,g Calculated

18 Fish Bioaccumulation ADME Calculator Output 5-ethyl-1-nonene BCF L/kg ww 2.30% 0% 0.00% 2.98% 0.00% 2.30% 22.51% 0.00% 22.51% 2.10% 29.90% 2.10% 0.61% 0.93% 29.28% 45.24% 0.55% 44.31% 100% 26.41% 26.96%

19 Testing of the Toxicokinetic Modelling Framework Methodology Compiled OECD 305 (2012) dietary bioaccumulation test results for 186 test chemicals Analyzed data using the ADME Calculator Derived all rate constants with associated error, including k M (k BM ) & BCF Compiled independent data on the BCF and k M of the test chemicals in fish using Arnot & Gobas (2006) data base and Episuite Compared derived & independent BCF and k M data

20 Aqueous Test: BCF (L/kg ww) Comparison of BCFs in Dietary & Aqueous Tests 100,000 10,000 1, ,000 10, ,000 Dietary Test: BCF (L/kg ww)

21 BCF ww,t Derived from OECD 305 Dietary Tests Hexachlorobenzene # Tests 10 Minimum BCF (SE) Maximum BCF (SE) Geometric mean BCF 4300 Lower 95% confidence limit 2600 Upper 95% confidence limit 7000

22 BCF ww,t Derived from Bioconcentration Tests Hexachlorobenzene # Tests 178 Minimum BCF 65 Maximum BCF Geometric mean BCF 7500 Lower 95% confidence limit 230 Upper 95% confidence limit 25000

23 Comparison of BCFs from Aqueous & Dietary Tests R = BCF Diet BCF Aqueous All Test Chemicals # Comparisons 2040 Minimum BCF D /BCF Aq Maximum BCF D /BCF Aq 192 Geometric mean BCF D /BCF Aq Lower 95% confidence limit Upper 95% confidence limit 39

24 Aqueous test: k M (1/d) Comparison of Biotransformation Rate Constants in Dietary & Aqueous Tests Episuite Dietary test : k BM (1/d) this study

25 Exposure Pathways 2.30% 2.30% 29.90% 22.51% BCF L/kg ww 0.00% 22.51% 2.10% 0.00% 0% 0.00% 2.10% 2.98% 7.84% 0.17% 2.24% 1.69% BAF L/kg ww 7.67% 76.60% 0.16% 74.91% 99.50% 6.99% 7.15% 10.15% 29.28% 100% 44.31% 0.61% 45.24% 26.41% 0.93% 0.55% 26.96% 0.15% 0.50% 0.22% 2.09% 3.39% 0.13% 3.17% 1.89% 2.02% OECD 305 Dietary Bioaccumulation Test 5-ethyl-1-nonene Concentration in Water : 0 g/l water Concentration in Diet : 1 mg/kg food Field Exposure 5-ethyl-1-nonene Concentration in Water : 0.01 mg/l water Concentration in Diet : 0.5 mg/kg food

26 Potential for adverse Perturbations Delayed Developm ent Narcosis 0 Concentration

27 Potential for adverse Perturbations: 5-ethyl-1-nonene Narcosis 0 Concentration

28 Potential for adverse Perturbations: 5-ethyl-1-nonene Narcosis 0 Concentration

29 Conclusions/Output 1.Developed a toxicokinetic modeling framework for OECD 305 dietary bioaccumulation tests 2. ADME calculator for OECD 305 dietary bioaccumulation tests (Excel Spreadsheet) 3. Included improved error analysis (ADME calculator) 4. Applied modeling framework to 186 substances 5. Data base for BMF and somatic and gastro-intestinal biotransformation rate constants 6. Tested modeling framework with satisfactory results. 7. Included exposure pathway analysis in ADME calculator 8. Included assessment for potential of adverse perturbations in ADME calculator 9. Paper on the toxicokinetic framework, including testing, is in preparation

30 Where to go from here. 1. Add terrestrial exposure pathway assessment to ADME calculator 2. Develop QSARs for BMF and somatic and gastro-intestinal biotransformation rate constants 3. Include in-vitro biotransformation assay results in the ADME calculator 4. Develop a toxicokinetic framework that can use and interpret results from in-vivo bioconcentration and dietary bioaccumulation tests, in-vitro bioassays, field observations (e.g. TMF) and phys-chemical properties (e.g. Kow) to develop an internally consistent bioaccumulation profile with outputs in terms of BCF, BMF, TMF, exposure pathways, potential for adverse outcomes.

31 Individual Lines of Evidence K ow BCF BMF In-Vitro TMF

32 BCF K ow BMF In-Vitro TMF

33 Information Toxicokinetic Framework B-Profile Phys-Chem Properties: Kow Solubility In-vitro Bioassays: K dep hepatic K dep intestinal In-vivo Lab Tests: Bioconcentration Dietary Bioaccumulation Field Studies: TMF BMF BCF BAF BMF TMF Elimination rate Biotransformation rate Exposure Pathways Potential for adverse outcomes

34 Thank You

35 Development of a Toxicokinetic Modeling Framework k 1 k G Gill Elimination Somatic Metabolism k D k M Dietary Uptake Lier Growth Dietary Uptake k 2 k E Gill Uptake Fecal Excretion Intestinal Metabolism Water k B2 W B C B k B1 W B C W Fish body k GD W B C B k BM W B C B k GB W G C G Digesta k BG W B C B k GM W G C G G I C D Diet G GE C G

36 Potential for adverse Perturbations: Hexachlorobenzene Narcosis 0 Concentration

37 Development of a Toxicokinetic Modeling Framework k 1 k G Gill Elimination Somatic Metabolism k D k M Dietary Uptake Lier Growth Dietary Uptake k 2 k E Gill Uptake Intestinal Metabolism Fecal Excretion