Deriving bioconcentration factors and somatic biotransformation rates from dietary bioaccumulation and depuration tests

Gobas, Frank A.P.C.; Lo, Justin C.

doi:10.1002/etc.3481

Cited by 14 publications

(27 citation statements)

References 25 publications

(64 reference statements)

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“…Respiratory uptake rate constants ( k 1 ) and BCFs were generated from the dietary bioaccumulation tests according to Gobas and Lo ()

k_{1} = (\frac{1}{ω}) \times (\frac{ϕ_{BL}}{d_{L}})

where 1/ ω is the slope term derived from Equation , d L is the density of the fish lipids (assumed to be 0.90 kg L –1 ), and ϕ BL is the measured lipid content of fish (kg lipid kg fish –1 ). A detailed derivation of Equation is provided in Gobas and Lo () and is based on the assumptions that it applies to test chemicals with log K OW ≥ 3 and that chemical partitioning between the fish and water (i.e., k 1 / k 2 ) is represented by K OW × ϕ BL .…”

Section: Methodsmentioning

confidence: 99%

Dietary Bioaccumulation and Biotransformation of Hydrophobic Organic Sunscreen Agents in Rainbow Trout

Saunders

Hoffman

Nichols

et al. 2020

Enviro Toxic and Chemistry

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The present study investigated the dietary bioaccumulation and biotransformation of hydrophobic organic sunscreen agents, 2‐ethylhexyl‐4‐methoxycinnamate (EHMC) and octocrylene (OCT), in rainbow trout using a modified Organisation for Economic Co‐operation and Development 305 dietary bioaccumulation test that incorporated nonbiotransformed reference chemicals. Trout were exposed to 3 dietary concentrations of each chemical to investigate the relationship between dietary exposure concentration and observed accumulation and depuration. Both EHMC and OCT were significantly biotransformed, resulting in mean in vivo whole‐body biotransformation rate constants (kMET) of 0.54 ± 0.06 and 0.09 ± 0.01 d–1, respectively. The kMET values generated for both chemicals did not differ between dietary exposure concentrations, indicating that chemical concentrations in the fish were not high enough to saturate biotransformation enzymes. Both somatic and luminal biotransformation substantially reduce EHMC and OCT bioaccumulation potential in trout. Biomagnification factors (BMFs) and bioconcentration factors (BCFs) of EHMC averaged 0.0035 kg lipid kg lipid–1 and 396 L kg–1, respectively, whereas those of OCT averaged 0.0084 kg lipid kg lipid–1 and 1267 L kg–1. These values are 1 to 2 orders of magnitude lower than the BMFs and BCFs generated for reference chemicals of similar log KOW. In addition, for both chemicals, derived BMFs and BCFs fell below established bioaccumulation criteria (1.0 kg lipid kg lipid–1 and 2000 L kg–1, respectively), suggesting that EHMC ad OCT are unlikely to bioaccumulate to a high degree in aquatic biota. Environ Toxicol Chem 2020;39:574–586. © 2019 SETAC

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“…Respiratory uptake rate constants ( k 1 ) and BCFs were generated from the dietary bioaccumulation tests according to Gobas and Lo ()

k_{1} = (\frac{1}{ω}) \times (\frac{ϕ_{BL}}{d_{L}})

Section: Methodsmentioning

confidence: 99%

Dietary Bioaccumulation and Biotransformation of Hydrophobic Organic Sunscreen Agents in Rainbow Trout

Saunders

Hoffman

Nichols

et al. 2020

Enviro Toxic and Chemistry

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“…However, a range of nonbiotransformable reference chemicals with varying K OW , encompassing the K OW of the test chemical, can be used to develop a quantitative relationship between k BT,R and K OW for nonbiotransformable chemicals that can then be used to derive the k BT,R for the test chemical. For example, a simple linear relationship between k BT,R and 1/K OW (Equation 14in Table 1) may be adequate (Gobas and Lo 2016). Other relationships, such as log k BT,R versus log K OW , may also be useful.…”

Section: Somatic Biotransformation Rate Constantmentioning

confidence: 99%

“…For substances with high K OW , k B2 is often small and of little relevance in dietary bioaccumulation tests except for its relationship with the respiratory uptake clearance rate k B1 and the BCF. If the dietary bioaccumulation test involves multiple nonbiotransformable reference chemicals, it is possible to determine k B2 from the slope of the relationship of the depuration rate constants of the reference chemicals (k BT,R ) and K OW following Gobas and Lo (2016;Equation 31 in Table 1). If the dietary bioaccumulation test did not include reference chemicals, then the ADME-B calculator uses the model in Arnot and Gobas (2004) for deriving the uptake clearance rate (k B1 ) and the elimination rate constant (k B2 ; Equation 32 in Table 1).…”

Section: Rate Constant For Chemical Elimination From the Fish Body To...mentioning

confidence: 99%

“…In these tests, the removal of intestinal content is not expected to have a significant effect on the determination of the BCF and BMF. The use of nonbiotransforming reference chemicals in the dietary bioaccumulation test can enhance the determination of biotransformation rates (Lo et al 2015) and BCFs (Gobas and Lo 2016). Another modification that is useful when administering diets is the inclusion of chromic oxide in the diet.…”

Section: Merits and Limitationsmentioning

confidence: 99%

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A Toxicokinetic Framework and Analysis Tool for Interpreting Organisation for Economic Co‐operation and Development Guideline 305 Dietary Bioaccumulation Tests

Gobas

Lee

et al. 2019

Enviro Toxic and Chemistry

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The Organisation for Economic Co-operation and Development guideline 305 for bioaccumulation testing in fish includes the option to conduct a dietary test for assessing a chemical's bioaccumulation behavior. However, the onecompartment toxicokinetic model that is used in the guidelines to analyze the results from dietary bioaccumulation tests is not consistent with the current state of the science, experimental practices, and information needs for bioaccumulation and risk assessment. The present study presents 1) a 2-compartment toxicokinetic modeling framework for describing the bioaccumulation of neutral hydrophobic organic chemicals in fish and 2) an associated toxicokinetic analysis tool (absorption, distribution, metabolism, and excretion [ADME] B calculator) for the analysis and interpretation of dietary bioaccumulation test data from OECD-305 dietary tests. The model framework and ADME-B calculator are illustrated by analysis of fish dietary bioaccumulation test data for 238 substances representing different structural classes and susceptibilities to biotransformation. The ADME of the chemicals is determined from dietary bioaccumulation tests and bioconcentration factors, biomagnification factors, and somatic and intestinal biotransformation rates. The 2-compartment fish toxicokinetic model can account for the effect of the exposure pathway on bioaccumulation, which the one-compartment model cannot. This insight is important for applying a weight-of-evidence approach to bioaccumulation assessment where information from aqueous and dietary test endpoints can be integrated to improve the evaluation of a chemical's bioaccumulation potential. Environ Toxicol Chem 2020;39:171-188.The depuration rate constant of the test (k BT ) and nonmetabolizable reference (k BT,R ) chemicals is the sum of the rate constants for respiratory elimination (k B2 ), fecal excretion (k BE ), somatic biotransformation (k BM , with k BM = 0 for k BT,R ) and growth dilution (k GD ; Equation 5 in Table 1). It can be derived wileyonlinelibrary.com/ETC © 2019 SETAC Interpreting OECD-305 dietary bioaccumulation tests-Environmental Toxicology and Chemistry, 2020;39:171-188 173 © 2019 SETAC wileyonlinelibrary.com/ETC Application and evaluation of the ADME-B calculatorThe results of the application of the ADME-B calculator to the dietary bioaccumulation test data of 238 test chemicals in wileyonlinelibrary.com/ETC

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“…Considerable literature exists on these factors and especially BMFs and TMFs that may yield the highest concentrations and exposures. [8][9][10][11][12] In the terminology of MacDonald et al, 13 a BCF represents solvent switching from water to lipid at a constant fugacity, while BAF, BMF and TMF represent additional solvent depletion as the ingested lipid solvent is hydrolysed causing an increase in fugacity.…”

Section: Introductionmentioning

confidence: 99%

Bioconcentration, bioaccumulation, biomagnification and trophic magnification: a modelling perspective

Mackay

Celsie

Powell

et al. 2018

Environ. Sci.: Processes Impacts

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We present a modelling perspective on quantifying metrics of bio-uptake of organic chemicals in fish. The models can be in concentration, partition ratio, rate constant (CKk) format or fugacity, Z and D value (fZD) format that are shown to be exactly equivalent, each having it merits. For most purposes a simple, parameter-parsimonious one compartment steady-state model containing some 13 parameters is adequate for obtaining an appreciation of the uptake equilibria and kinetics for scientific and regulatory purposes. Such a model is first applied to the bioaccumulation of a series of hypothetical, non-biotransforming chemicals with log K (octanol-water partition ratio) values of 4 to 8 in 10 g fish ranging in lipid contents to deduce wet-weight and lipid normalized concentrations, bioaccumulation and biomagnification factors. The sensitivity of biomagnification factors to relative lipid contents is discussed. Second, a hypothetical 5 species linear food chain is simulated to evaluate trophic magnification factors (TMFs) showing the critical roles of K and biotransformation rate. It is shown that lipid normalization of concentrations is most insightful for less hydrophobic chemicals (log K < 5) when bio-uptake is largely controlled by respiratory intake and equilibrium (equi-fugacity) is approached. For more hydrophobic chemicals when dietary uptake kinetics dominate, wet weight concentrations and BMFs are more insightful. Finally, a preferred strategy is proposed to advance the science of bioaccumulation using a combination of well-designed ecosystem monitoring, laboratory determinations and modelling to confirm that the perceived state of the science contained in the models is consistent with observations.

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Deriving bioconcentration factors and somatic biotransformation rates from dietary bioaccumulation and depuration tests

Cited by 14 publications

References 25 publications

Dietary Bioaccumulation and Biotransformation of Hydrophobic Organic Sunscreen Agents in Rainbow Trout

Dietary Bioaccumulation and Biotransformation of Hydrophobic Organic Sunscreen Agents in Rainbow Trout

A Toxicokinetic Framework and Analysis Tool for Interpreting Organisation for Economic Co‐operation and Development Guideline 305 Dietary Bioaccumulation Tests

Bioconcentration, bioaccumulation, biomagnification and trophic magnification: a modelling perspective

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