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

Kow BCF BAF Kow BCF BMF TMF Kow BCF Kow BCF Bioaccumulation in other species High (eco)toxicity Monitoring data BCF BAF

BCF : : Aqueous Bioconcentration Tests

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 Lab Test

Regulatory ry Bioaccumulation Assessment End Points

Canada US REACH Japan UN

Kow BCF BAF Kow BCF BMF TMF Kow BCF Kow BCF Bioaccumulation in other species High (eco)toxicity Monitoring data BCF BAF

BMF : : Dietary ry Bioaccumulation Tests

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 Lab Test

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

Dietary Uptake Lier

Gill Elimination Somatic Metabolism Fecal Excretion Growth Dietary Uptake Gill Uptake

kD k1 k2 kM kE kG

Development of a Toxicokinetic Modeling Framework

Fish body Digesta Water Diet

kBMWBCB kGMWGCG kB1WBCW kB2WBCB kGDWBCB GICD GGECG kGBWGCG kBGWBCB

Intestinal Metabolism

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

Fish body Digesta Water Diet

kBMWBCB kGMWGCG kB1WBCW kB2WBCB kGDWBCB GICD GGECG kGBWGCG kBGWBCB

Toxicokinetic Modeling Framework

Secondary Data Symbol Action Value Standard Error Rate constant for respiratory uptake kB1 Calculated 306.01 32.34 Rate constant for respiratory elimination kB2 Calculated 0.0239 0.0025 Rate constant for chemical transfer from fish body to GI content kBG Calculated 0.0218 0.0024 Rate constant for somatic biotransformation kBM Calculated 0.2334 0.0374 Rate constant for chemical transfer from GI content to fish body kGB Calculated 0.8809 0.0974 Rate constant for fecal egestion kGE Calculated 0.7944 0.0000 Rate constant for biotransformation in the GI content kGM Calculated 1.3329 0.4188 Biomagnification factor BMF Calculated 0.0305 0.0052 Biomagnification factor (lipid equivalent) BMFL Calculated 0.1550 0.0263 Biomagnification factor (lipid equivalent, growth corrected) BMFL,g Calculated 0.1736 0.0251 Bioconcentration factor (wet weight, freely dissolved) BCFww,fd Calculated 1061.7 176.5 Bioconcentration factor (lipid equivalent, freely dissolved) BCFL,fd Calculated 28084.8 4669.6 Bioconcentration factor (wet weight, freely dissolved, 5% lipid content) BCF5%,fd Calculated 1404.2 233.5 Bioconcentration factor (wet weight, total) BCFww,t Calculated 1035.9 172.2 Bioconcentration factor (lipid equivalent, total) BCFL,t Calculated 27404.1 4556.5 Bioconcentration factor (wet weight, total, 5% lipid content) BCF5%,t Calculated 1370.2 227.8 Bioconcentration factor (wet weight, total, growth corrected) BCFww,t,g Calculated 1160.5 208.3

Fish Bioaccumulation ADME Calculator Output

100% 29.90% 45.24% 26.96% 22.51% 2.30% 2.98% 2.10% 0% 0.00% 0.00% 0.00% 2.30% 2.10% 22.51% 29.28% 44.31% 26.41% 0.61% 0.93% 0.55%

BCF 1061.7 L/kg ww

Fish Bioaccumulation ADME Calculator Output 5-ethyl-1-nonene

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 kM (kBM) & BCF
• Compiled independent data on the BCF and kM of the test chemicals in

fish using Arnot & Gobas (2006) data base and Episuite 4.11.

• Compared derived & independent BCF and kM data

Comparison of f BCFs in Dietary ry & Aqueous Tests

1 10 100 1,000 10,000 100,000 1 10 100 1,000 10,000 100,000

Aqueous Test: BCF (L/kg ww) Dietary Test: BCF (L/kg ww)

BCFww,t Derived from OECD 305 Dietary Tests

# Tests 10 Minimum BCF 3100 520 (SE) Maximum BCF 7200  2500 (SE) Geometric mean BCF 4300 Lower 95% confidence limit 2600 Upper 95% confidence limit 7000

Hexachlorobenzene

BCFww,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 BCFD/BCFAq 0.004 Maximum BCFD/BCFAq 192 Geometric mean BCFD/BCFAq 1.088 Lower 95% confidence limit 0.028 Upper 95% confidence limit 39

All Test Chemicals

BCFDiet BCFAqueous R =

Comparison of Biotransformation Rate Constants in Dietary ry & Aqueous Tests

0.0001 0.001 0.01 0.1 1 10 100 0.0001 0.001 0.01 0.1 1 10 100

Aqueous test: kM (1/d) Dietary test : kBM (1/d)

this study Episuite

Exposure Pathways

0.50% 2.24% 3.39% 2.02% 76.60% 7.84% 10.15% 7.15% 99.50% 7.67% 6.99% 74.91% 0.17% 0.16% 1.69% 0.15% 0.22% 0.13% 2.09% 3.17% 1.89%

BAF

1063.2 L/kg ww 100% 29.90% 45.24% 26.96% 22.51% 2.30% 2.98% 2.10% 0% 0.00% 0.00% 0.00% 2.30% 2.10% 22.51% 29.28% 44.31% 26.41% 0.61% 0.93% 0.55%

BCF

1061.7 L/kg ww

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

Concentration

Narcosis

Potential for “adverse” Perturbations

Delayed Developm ent

Concentration

Narcosis

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

Concentration

Narcosis

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

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

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.

Individual Lines of Evidence

Kow BCF BMF In-Vitro TMF

Kow BCF BMF In-Vitro TMF

Information B-Profile Toxicokinetic Framework

Phys-Chem Properties: Kow Solubility In-vitro Bioassays: Kdep hepatic Kdep 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

• utcomes

Thank You

Dietary Uptake Lier

Gill Elimination Somatic Metabolism Fecal Excretion Growth Dietary Uptake Gill Uptake

kD k1 k2 kM kE kG

Development of a Toxicokinetic Modeling Framework

Fish body Digesta Water Diet

kBMWBCB kGMWGCG kB1WBCW kB2WBCB kGDWBCB GICD GGECG kGBWGCG kBGWBCB

Intestinal Metabolism

Concentration

Narcosis

Potential for “adverse” Perturbations: Hexachlorobenzene

Dietary Uptake Lier

Gill Elimination Somatic Metabolism Fecal Excretion Growth Dietary Uptake Gill Uptake

kD k1 k2 kM kE kG

Development of a Toxicokinetic Modeling Framework

Intestinal Metabolism