Bioaccumulation Tests For Hydrophobic Chemicals (2017-2018) Frank - PowerPoint PPT Presentation

ECO33: Use & Interpretation Of Dietary Bioaccumulation Tests For Hydrophobic Chemicals (2017-2018) Frank Gobas, Yung-Shan Lee and Justin Lo Simon Fraser University, Vancouver, British Columbia, Canada E-mail contact: gobas@sfu.ca

Regulatory ry 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 Bioaccumulation in other species TMF High (eco)toxicity Monitoring data

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

Regulatory ry 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 Bioaccumulation in other species TMF High (eco)toxicity Monitoring data

BMF : : Dietary ry Bioaccumulation Tests OECD 305 Guidelines for Bioaccumulation Testing Lab Test 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

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.

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.

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.

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.

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

Development of a Toxicokinetic Modeling Framework Gill Elimination Somatic Metabolism k 1 k G Dietary Uptake k M Lier k D 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 k BG W B C B Digesta k GM W G C G G I C D G GE C G Diet

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

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 k BG W B C B Digesta k GM W G C G G I C D G GE C G Diet

Fish Bioaccumulation ADME Calculator Output Secondary Data Symbol Action Value Standard Error Rate constant for respiratory uptake k B1 Calculated 306.01 32.34 Rate constant for respiratory elimination k B2 Calculated 0.0239 0.0025 Rate constant for chemical transfer from fish body to GI content k BG Calculated 0.0218 0.0024 Rate constant for somatic biotransformation k BM Calculated 0.2334 0.0374 Rate constant for chemical transfer from GI content to fish body k GB Calculated 0.8809 0.0974 Rate constant for fecal egestion k GE Calculated 0.7944 0.0000 Rate constant for biotransformation in the GI content k GM Calculated 1.3329 0.4188 Biomagnification factor BMF Calculated 0.0305 0.0052 Biomagnification factor (lipid equivalent) BMF L Calculated 0.1550 0.0263 Biomagnification factor (lipid equivalent, growth corrected) BMF L,g Calculated 0.1736 0.0251 Bioconcentration factor (wet weight, freely dissolved) BCF ww,fd Calculated 1061.7 176.5 Bioconcentration factor (lipid equivalent, freely dissolved) BCF L,fd Calculated 28084.8 4669.6 Bioconcentration factor (wet weight, freely dissolved, 5% lipid content) BCF 5%,fd Calculated 1404.2 233.5 Bioconcentration factor (wet weight, total) BCF ww,t Calculated 1035.9 172.2 Bioconcentration factor (lipid equivalent, total) BCF L,t Calculated 27404.1 4556.5 Bioconcentration factor (wet weight, total, 5% lipid content) BCF 5 %,t Calculated 1370.2 227.8 Bioconcentration factor (wet weight, total, growth corrected) BCF ww,t,g Calculated 1160.5 208.3

Fish Bioaccumulation ADME Calculator Output 5-ethyl-1-nonene BCF 1061.7 L/kg ww 2.30% 0% 2.98% 0.00% 0.00% 22.51% 2.30% 0.00% 22.51% 2.10% 2.10% 29.90% 0.61% 0.93% 29.28% 45.24% 0.55% 44.31% 26.41% 100% 26.96%

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 4.11. • Compared derived & independent BCF and k M data

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

BCF ww,t Derived from OECD 305 Dietary Tests # Tests 10 3100  520 (SE) Minimum BCF 7200  2500 (SE) Maximum BCF Geometric mean BCF 4300 Lower 95% confidence limit 2600 Upper 95% confidence limit 7000 Hexachlorobenzene

BCF ww,t Derived from Bioconcentration Tests # Tests 178 Minimum BCF 65 Maximum BCF 181000 Geometric mean BCF 7500 Lower 95% confidence limit 230 Upper 95% confidence limit 25000 Hexachlorobenzene

Comparison of BCFs from Aqueous & Dietary Tests # Comparisons 2040 Minimum BCF D /BCF Aq 0.004 BCF Diet Maximum BCF D /BCF Aq 192 R = BCF Aqueous Geometric mean BCF D /BCF Aq 1.088 Lower 95% confidence limit 0.028 Upper 95% confidence limit 39 All Test Chemicals

Comparison of Biotransformation Rate Constants in Dietary ry & Aqueous Tests 100 Aqueous test: k M (1/d) 10 1 Episuite 0.1 0.01 0.001 0.0001 0.0001 0.001 0.01 0.1 1 10 100 this study Dietary test : k BM (1/d)

Exposure Pathways BAF BCF L/kg ww 1063.2 L/kg ww 1061.7 7.84% 99.50% 2.30% 0% 10.15% 2.98% 7.67% 0.00% 74.91% 0.00% 76.60% 0.17% 22.51% 6.99% 2.30% 0.00% 1.69% 22.51% 0.16% 2.10% 7.15% 2.24% 2.10% 29.90% 2.09% 0.61% 3.17% 0.93% 0.15% 3.39% 45.24% 1.89% 29.28% 0.55% 0.22% 44.31% 0.13% 26.41% 0.50% 2.02% 100% 26.96% OECD 305 Dietary Bioaccumulation Test Field Exposure 5-ethyl-1-nonene 5-ethyl-1-nonene Concentration in Water : 0 g/L water Concentration in Water : 0.01 mg/L water Concentration in Diet : 1 mg/kg food Concentration in Diet : 0.5 mg/kg food

Potential for “adverse” Perturbations Delayed Narcosis Developm ent 0 Concentration

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