Publications by authors named "Frank A P C Gobas"

75 Publications

Bioaccumulation of dodecamethylcyclohexasiloxane (D6) in fish.

Chemosphere 2021 Oct 21;281:130948. Epub 2021 May 21.

School of Resource and Environmental Management, Biological Sciences, Simon Fraser University, Burnaby, British Columbia, V5A 1S6, Canada. Electronic address:

To investigate the bioaccumulation behavior of dodecamethylcyclohexasiloxane (D6, CAS number: 540-97-6) in fish, an OECD-305 style dietary bioaccumulation study of D6 in rainbow trout was conducted in the presence of non-metabolizable reference chemicals. The dietary uptake absorption efficiency of D6 was 14 (3 SE) % and lower than that of the reference chemicals which ranged between 22 (2 SE) to 60 (8 SE) %. The concentration of D6 in the body of the fish showed a rapid 40% drop during the first day of the depuration phase, followed by a slower decline during the remainder of the depuration period. The overall depuration rate constant of D6 was 0.016 (0.0026 SE) d and significantly greater than those of PCB153 and PCB209, which were not significantly different from zero. During the depuration phase, when fish body weight did not significantly change over time, depuration of D6 appears to be almost entirely due to biotransformation in the body of the fish. The biomagnification factor of D6 in rainbow trout was 0.38 (0.14 SE) kg-lipid kg-lipid, indicating a lack of biomagnification. The bioconcentration factor (BCF) of D6 in Rainbow trout was estimated at 1909 (483 SE) L kg wet for natural waters of mostly oligotrophic lakes in Northern Canada with an average concentration of total organic carbon of 7.1 mg L. Comparing the bioaccumulation profile of D6 to that of 238 similar profiles for 166 unique chemicals indicates that the bioaccumulation capacity of D6 is markedly less than that of many very hydrophobic organochlorines.
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http://dx.doi.org/10.1016/j.chemosphere.2021.130948DOI Listing
October 2021

Deconvoluting Thermodynamics from Biology in the Aquatic Food Web Model.

Environ Toxicol Chem 2021 Aug 16;40(8):2145-2155. Epub 2021 Jul 16.

Resource and Environment Management, Simon Fraser University, Burnaby, British Columbia, Canada.

Bioaccumulation of hydrophobic pollutants in an aquatic food web is governed by exposure concentrations in sediment and water phases and by complex trophic interactions among the various species. We demonstrate that biological interactions and exposure from the chemical environment can be deconvoluted for aquatic food webs to allow clearer assessments of the role of thermodynamic drivers from the sediment and surface water phases. We first demonstrate the feasibility of this deconvolution mathematically for hypothetical food webs with 3 and 4 interacting species and for more realistic real-world food webs with >10 species of aquatic organisms (i.e., the freshwater lake food web in Western Lake Erie [ON, Canada] and the marine food web in New Bedford Harbor [MA, USA]). Our results show both mathematically (for the simple food webs) and computationally (for the more complex food webs) that a deconvoluted food web model parameterized for site-specific conditions can predict the bioaccumulation of polychlorinated biphenyls in aquatic organisms same as existing complex food web models. The merit of this approach is that once the thermodynamic and biological contributions to food web bioaccumulation are computed for an ecosystem, the deconvoluted model provides a relatively simple approach for calculating concentrations of chemicals in organisms for a range of possible surface water and sedimentary concentrations. This approach is especially useful for calculating bioaccumulation of pollutants from freely dissolved concentrations measured using passive sampling devices or predicted by fate and transport models. The deconvoluted approach makes it possible to develop regulatory guidelines for a set of surface water and sediment (or porewater) concentration combinations for a water body that is able to achieve a risk-based target for fish concentration. Environ Toxicol Chem 2021;40:2145-2155. © 2021 SETAC.
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http://dx.doi.org/10.1002/etc.5106DOI Listing
August 2021

Normalizing the Biomagnification Factor.

Environ Toxicol Chem 2021 Apr 5;40(4):1204-1211. Epub 2021 Feb 5.

ARC Arnot Research & Consulting, Toronto, Ontario, Canada.

Following a recent proposal of normalizing the experimentally derived biomagnification factor (BMF) to a 5% lipid content in fish, we explore the normalization of the BMF of lipophilic chemicals in fish. We illustrate with theoretical models and experimental data that the BMF of lipophilic chemicals is a function of the lipid content of the diet and that poorly metabolizable, lipophilic chemicals biomagnify in organisms to a greater degree when present in higher-lipid content food. The proposed normalization of the laboratory BMF to the lipid content of the fish and subsequent standardization to a 5% fish lipid content, which is numerically identical to normalizing the BMF to a 5% dietary lipid content, has the potential to underestimate the biomagnification potential of lipophilic substances in aquatic food webs. The BMF normalized to both the lipid content of the fish and the lipid content of the diet, which is the biomagnification metric included in the Organisation for Economic Co-operation and Development's bioaccumulation testing guideline 305, better represents real-world biomagnification than the proposed BMF normalized and standardized to a 5% lipid content in fish. Environ Toxicol Chem 2021;40:1204-1211. © 2020 SETAC.
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http://dx.doi.org/10.1002/etc.4953DOI Listing
April 2021

In vitro-in vivo extrapolation of hepatic and gastrointestinal biotransformation rates of hydrophobic chemicals in rainbow trout.

Aquat Toxicol 2020 Nov 11;228:105629. Epub 2020 Sep 11.

Department of Biological Sciences, Simon Fraser University, Burnaby, British Columbia, Canada; School of Resource and Environmental Management, Simon Fraser University, Burnaby, British Columbia, Canada. Electronic address:

Hepatic in vitro biotransformation assays, in combination with in vitro-in vivo extrapolation (IVIVE) and bioaccumulation modeling, can be used to support regulatory bioaccumulation assessments. In most applications, however, these methods ignore the possibility of extrahepatic metabolism. Here we evaluated intestinal biotransformation in rainbow trout using S9 fractions prepared from the upper intestinal (GIT) epithelium. Measured levels of activity determined using standard substrates for phase I and phase II biotransformation enzymes were within 2-fold of activities measured in hepatic S9 fractions. In vitro intrinsic clearance rates for 2-ethylhexyl-4-methoxycinnamate (EHMC; an organic sunscreen agent) and two polycyclic aromatic hydrocarbons (pyrene [PYR] and benzo(a)pyrene [BAP]) were significantly higher in liver S9 fractions than in GIT S9 fractions. For octocrylene (OCT; a second sunscreen agent), however, in vitro intrinsic clearance rates were higher in GIT S9 fractions compared to liver S9 fractions. An existing 'liver only' IVIVE model was expanded to consider biotransformation in both the liver and GIT. Relevant IVIVE scaling factors were developed by morphological, histological, and biochemical evaluation of trout intestines. For chemicals biotransformed at higher rates by hepatic S9 fractions (i.e., BAP, PYR, EHMC), the 'liver & GIT' model yielded whole-body biotransformation rate constants (k) that were within 1.2 to 1.4-fold of those estimated using the 'liver only' model. In contrast to these findings, the mean k for OCT obtained using the 'liver & GIT' model was 3.3 times higher than the mean k derived using the 'liver only' model and was in good agreement with empirical k estimates determined previously for trout (<20 % difference). The results of this study suggest that current 'liver only' IVIVE approaches may underestimate in vivo biotransformation rates for chemicals that undergo substantial biotransformation in the GIT.
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http://dx.doi.org/10.1016/j.aquatox.2020.105629DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7962060PMC
November 2020

Trophic magnification of legacy persistent organic pollutants in an urban terrestrial food web.

Sci Total Environ 2020 Apr 20;714:136746. Epub 2020 Jan 20.

School of Resource and Environmental Management, Faculty of the Environment, Simon Fraser University, Burnaby, British Columbia V5A 1S6, Canada; Simon Fraser University, Dept. of Biological Sciences, 8888 University Drive, Burnaby, British Columbia V5A 1S6, Canada. Electronic address:

Legacy persistent organic pollutants (POPs), including organochlorine pesticides (OCPs), polychlorinated biphenyls (PCBs), and polybrominated diphenyl ethers (PBDEs), persist for generations in the environment and often negatively impact endocrine functions in exposed wildlife. Protocols to assess the bioaccumulation potential of these chemicals within terrestrial systems are far less developed than for aquatic systems. Consequently, regulatory agencies in Canada, the United States, and the European Union rely primarily on aquatic information for the bioaccumulation assessment of chemicals. However, studies have shown that some chemicals that are not bioaccumulative in aquatic food webs can biomagnify in terrestrial food webs. Thus, to better understand the bioaccumulative behaviour of chemicals in terrestrial systems, we examined trophic magnification of hydrophobic POPs in an urban terrestrial food web that included an avian apex predator, the Cooper's hawk (Accipiter cooperii). Over 100 samples were collected from various trophic levels of the food web including hawk eggs, songbirds, invertebrates, and berries and analysed for concentrations of 38 PCB congeners, 20 OCPs, 20 PBDE congeners, and 7 other brominated flame retardants listed on the Government of Canada's Chemicals Management Plan. We determined trophic magnification factors (TMFs) for contaminants that had a 50% or greater detection frequency in all biota samples and compared these terrestrial TMFs to those observed in aquatic systems. TMFs in this terrestrial food web ranged between 1.2 (0.21 SE) and 15 (4.0 SE), indicating that the majority of these POPs are biomagnifying. TMFs of the legacy POPs investigated in this terrestrial food web increased in a statistically significant relationship with both the logarithm of the octanol-air (log K) and octanal-water partition (log K) coefficients of the POPs. POPs with a log K >6 or a log K >5 exhibited biomagnification potential in this terrestrial food web.
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http://dx.doi.org/10.1016/j.scitotenv.2020.136746DOI Listing
April 2020

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

Environ Toxicol Chem 2020 03 24;39(3):574-586. Epub 2020 Jan 24.

Department of Biological Sciences, Simon Fraser University, Burnaby, British Columbia, Canada.

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 (k ) of 0.54 ± 0.06 and 0.09 ± 0.01 d , respectively. The k 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 and 396 L kg , respectively, whereas those of OCT averaged 0.0084 kg lipid kg lipid and 1267 L kg . These values are 1 to 2 orders of magnitude lower than the BMFs and BCFs generated for reference chemicals of similar log K . In addition, for both chemicals, derived BMFs and BCFs fell below established bioaccumulation criteria (1.0 kg lipid kg lipid and 2000 L kg , 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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http://dx.doi.org/10.1002/etc.4638DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7424631PMC
March 2020

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

Environ Toxicol Chem 2020 01 30;39(1):171-188. Epub 2019 Nov 30.

Toxicology & Environmental Science Division, ExxonMobil Biomedical Sciences, Annandale, New Jersey, USA.

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 one-compartment 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 2019;39:171-188. © 2019 SETAC.
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http://dx.doi.org/10.1002/etc.4599DOI Listing
January 2020

Growth-Correcting the Bioconcentration Factor and Biomagnification Factor in Bioaccumulation Assessments.

Environ Toxicol Chem 2019 09 1;38(9):2065-2072. Epub 2019 Aug 1.

School of Resource and Environmental Management, Simon Fraser University, Burnaby, British Columbia, Canada.

We illustrate that the Organisation for Economic Co-operation and Development guideline 305 (OECD-305) for growth-correcting bioconcentration factors (BCFs) and biomagnification factors (BMFs) violates the mass-balance assumption underlying the definition of BCFs and BMFs and provides unrealistic estimates of BCFs and BMFs of chemicals in nongrowing fish. We present and test alternative methods for growth-correcting BCFs and BMFs that maintain mass balance. We conclude that the OECD-305-recommended growth correction of BCFs and BMFs causes error, is unnecessary, and should be revisited. Environ Toxicol Chem 2019;38:2065-2072. © 2019 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals, Inc. on behalf of SETAC.
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http://dx.doi.org/10.1002/etc.4509DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6852268PMC
September 2019

Development and evaluation of a mechanistic model to assess the fate and removal efficiency of hydrophobic organic contaminants in horizontal subsurface flow treatment wetlands.

Water Res 2019 03 26;151:183-192. Epub 2018 Dec 26.

Department of Civil and Environmental Engineering, Faculty of Engineering, National University of Singapore (NUS), 21 Lower Kent Ridge Rd, 119077, Singapore.

A mechanistic model for assessing the fate and removal efficiency of hydrophobic organic contaminants in horizontal subsurface flow treatment wetlands was developed and evaluated using empirical concentration data from Singapore's Lorong Halus Treatment Wetland. This treatment wetland consists of a series of horizontal subsurface flow reed beds. The model, calibrated for the Lorong Halus Treatment Wetland, provided an adequate description of the concentrations of nine neutral organic substances in water, rhizomes and emergent vegetation in the wetland. The model was applied to investigate the sensitivity of the contaminant removal efficiency to environmental conditions and physicochemical properties of contaminants that enter the wetland. The water-budget of the wetland was found to exhibit an important influence on both the mass-removal efficiency and reduction of contaminant concentrations that can be achieved through wetland treatment. The model illustrated that removal pathways of organic contaminants in the wetland varied as a function of the properties of the contaminants. The mass-removal efficiency of the treatment wetland was greatest for chemicals with a log K between 3.0 and 5.0 and log K > -1.0. Removal of contaminants through volatilization was found to be greatest for substances with a log K between 3 and 5 and log K > 0. Transpiration flux in vegetation was found to be most important for substances with a log K between 4.5 and 5.5 and a log K between -5.0 and 0.0. Biotransformation rates of the contaminants in the wetland media play a crucial role in the removal of contaminants from wastewater. The model provides a tool for assessing the removal capacity of treatment wetlands for neutral organic contaminants and evaluating trade-offs in the design and operation of a horizontal subsurface flow treatment wetland.
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http://dx.doi.org/10.1016/j.watres.2018.12.020DOI Listing
March 2019

Concentration dependence of in vitro biotransformation rates of hydrophobic organic sunscreen agents in rainbow trout S9 fractions: Implications for bioaccumulation assessment.

Environ Toxicol Chem 2019 03 13;38(3):548-560. Epub 2019 Feb 13.

Department of Biological Sciences, Simon Fraser University, Burnaby, British Columbia, Canada.

In vitro biotransformation studies were performed to support the bioaccumulation assessment of 3 hydrophobic organic ultraviolet filters (UVFs), 4-methylbenzylidene camphor (4-MBC), 2-ethylhexyl-4-methoxycinnamate (EHMC), and octocrylene. In vitro depletion rate constants (k ) were determined for each UVF using rainbow trout liver S9 fractions. Incubations performed with and without added cofactors showed complete (4-MBC) or partial (EHMC and octocrylene) dependence of k on addition of the reduced form of nicotinamide adenine dinucleotide phosphate (NADPH), suggesting that hydrolysis of EHMC and octocrylene by NADPH-independent enzymes (e.g., carboxylesterases) is an important metabolic route. The concentration dependence of k was then evaluated to estimate Michaelis-Menten parameters (K and V ) for each UVF. Measured k values were then extrapolated to apparent whole-body biotransformation rate constants using an in vitro-in vivo extrapolation (IVIVE) model. Bioconcentration factors (BCFs) calculated from k values measured at concentrations well below K were closer to empirical BCFs than those calculated from k measured at higher test concentrations. Modeled BCFs were sensitive to in vitro binding assumptions employed in the IVIVE model, highlighting the need for further characterization of chemical binding effects on hepatic clearance. The results suggest that the tested UVFs are unlikely to accumulate to levels exceeding the European Union Registration, Evaluation, Authorisation, and Restriction regulation criterion for bioaccumulative substances (BCF > 2000 L kg ). However, consideration of appropriate in vitro test concentrations and binding correction factors are important when IVIVE methods are used to refine modeled BCFs. Environ Toxicol Chem 2019;38:548-560. © 2018 SETAC.
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http://dx.doi.org/10.1002/etc.4342DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6477924PMC
March 2019

AGRO-2014: A time dependent model for assessing the fate and food-web bioaccumulation of organic pesticides in farm ponds: Model testing and performance analysis.

Sci Total Environ 2018 Oct 26;639:1324-1333. Epub 2018 May 26.

Valent USA Corporation, 6560 Trinity Court, Dublin, CA 94568, USA.

A time-dependent environmental fate and food-web bioaccumulation model is developed to improve the evaluation of the behaviour of non-ionic hydrophobic organic pesticides in farm ponds. The performance of the model was tested by simulating the behaviour of 3 hydrophobic organic pesticides, i.e., metaflumizone (CAS Number: 139968-49-3), kresoxim-methyl (CAS Number: 144167-04-4) and pyraclostrobin (CAS Number: 175013-18-0), in microcosm studies and a Bluegill bioconcentration study for metaflumizone. In general, model-calculated concentrations of the pesticides were in reasonable agreement with the observed concentrations. Also, calculated bioaccumulation metrics were in good agreement with observed values. The model's application to simulate concentrations of organic pesticides in water, sediment and biota of farm ponds after episodic pesticide applications is illustrated. It is further shown that the time dependent model has substantially better accuracy in simulating the concentrations of pesticides in farm ponds resulting from episodic pesticide application than corresponding steady-state models. The time dependent model is particularly useful in describing the behaviour of highly hydrophobic pesticides that have a potential to biomagnify in aquatic food-webs.
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http://dx.doi.org/10.1016/j.scitotenv.2018.05.115DOI Listing
October 2018

A chemical activity approach to exposure and risk assessment of chemicals: Focus articles are part of a regular series intended to sharpen understanding of current and emerging topics of interest to the scientific community.

Environ Toxicol Chem 2018 05;37(5):1235-1251

TG Environmental Research, Sharnbrook, Bedfordshire, United Kingdom.

To support the goals articulated in the vision for exposure and risk assessment in the twenty-first century, we highlight the application of a thermodynamic chemical activity approach for the exposure and risk assessment of chemicals in the environment. The present article describes the chemical activity approach, its strengths and limitations, and provides examples of how this concept may be applied to the management of single chemicals and chemical mixtures. The examples demonstrate that the chemical activity approach provides a useful framework for 1) compiling and evaluating exposure and toxicity information obtained from many different sources, 2) expressing the toxicity of single and multiple chemicals, 3) conducting hazard and risk assessments of single and multiple chemicals, 4) identifying environmental exposure pathways, and 5) reducing error and characterizing uncertainty in risk assessment. The article further illustrates that the chemical activity approach can support an adaptive management strategy for environmental stewardship of chemicals where "safe" chemical activities are established based on toxicological studies and presented as guidelines for environmental quality in various environmental media that can be monitored by passive sampling and other techniques. Environ Toxicol Chem 2018;37:1235-1251. © 2018 The Authors. Published by Wiley Periodicals, Inc. on behalf of SETAC.
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http://dx.doi.org/10.1002/etc.4091DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5994922PMC
May 2018

Estimating the Bioconcentration Factors of Hydrophobic Organic Compounds from Biotransformation Rates Using Rainbow Trout Hepatocytes.

Arch Environ Contam Toxicol 2018 Aug 17;75(2):295-305. Epub 2018 Mar 17.

Department of Biology, Simon Fraser University, 8888 University Drive, Burnaby, BC, V5A 1S6, Canada.

Determining the biotransformation potential of commercial chemicals is critical for estimating their persistence in the aquatic environment. In vitro systems are becoming increasingly important as screening methods for assessing the potential for chemical metabolism. Depletion rate constants (k) for several organic chemicals with high octanol-water partition coefficient (K) values (9-methylanthracene, benzo(a)pyrene, chrysene, and PCB-153) in rainbow trout hepatocytes were determined to estimate biotransformation rate constants (k) that were used in fish bioconcentration factor (BCF) models. Benzo[a]pyrene was rapidly biotransformed when incubated singly; however, its depletion rate constant (k) declined 79% in a mixture of all four chemicals. Chrysene also exhibited significant biotransformation and its depletion rate constant declined by 50% in the mixture incubation. These data indicate that biotransformation rates determined using single chemicals may overestimate metabolism in environments containing chemical mixtures. Incubations with varying cell concentrations were used to determine whether cell concentration affected k estimates. No statistically significant change in depletion rate constants were seen, possibly due to an increase in nonspecific binding of hydrophobic chemicals as cell density increased, decreasing overall biotransformation. A new model was used to estimate BCFs from k values calculated from empirically derived k values. The inclusion of k in models resulted in significantly lower BCF values (compared k = 0). Modelled BCF values were consistent with empirically derived BCF values from the literature.
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http://dx.doi.org/10.1007/s00244-018-0508-zDOI Listing
August 2018

In vitro to in vivo extrapolation of biotransformation rates for assessing bioaccumulation of hydrophobic organic chemicals in mammals.

Environ Toxicol Chem 2017 07 6;36(7):1934-1946. Epub 2017 Feb 6.

School of Resource and Environmental Management, Simon Fraser University, Burnaby, British Columbia, Canada.

Incorporating biotransformation in bioaccumulation assessments of hydrophobic chemicals in both aquatic and terrestrial organisms in a simple, rapid, and cost-effective manner is urgently needed to improve bioaccumulation assessments of potentially bioaccumulative substances. One approach to estimate whole-animal biotransformation rate constants is to combine in vitro measurements of hepatic biotransformation kinetics with in vitro to in vivo extrapolation (IVIVE) and bioaccumulation modeling. An established IVIVE modeling approach exists for pharmaceuticals (referred to in the present study as IVIVE-Ph) and has recently been adapted for chemical bioaccumulation assessments in fish. The present study proposes and tests an alternative IVIVE-B technique to support bioaccumulation assessment of hydrophobic chemicals with a log octanol-water partition coefficient (K ) ≥ 4 in mammals. The IVIVE-B approach requires fewer physiological and physiochemical parameters than the IVIVE-Ph approach and does not involve interconversions between clearance and rate constants in the extrapolation. Using in vitro depletion rates, the results show that the IVIVE-B and IVIVE-Ph models yield similar estimates of rat whole-organism biotransformation rate constants for hypothetical chemicals with log K  ≥ 4. The IVIVE-B approach generated in vivo biotransformation rate constants and biomagnification factors (BMFs) for benzo[a]pyrene that are within the range of empirical observations. The proposed IVIVE-B technique may be a useful tool for assessing BMFs of hydrophobic organic chemicals in mammals. Environ Toxicol Chem 2017;36:1934-1946. © 2016 SETAC.
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http://dx.doi.org/10.1002/etc.3718DOI Listing
July 2017

In Vivo Biotransformation Rates of Organic Chemicals in Fish: Relationship with Bioconcentration and Biomagnification Factors.

Environ Sci Technol 2016 12 2;50(24):13299-13308. Epub 2016 Dec 2.

Department of Biological Sciences, Simon Fraser University , Burnaby, British Columbia V5A 1S6, Canada.

In vivo dietary bioaccumulation experiments for 85 hydrophobic organic substances were conducted to derive the in vivo gastrointestinal biotransformation rates, somatic biotransformation rates, bioconcentration factors (BCF), and biomagnification factors (BMF) for improving methods for bioaccumulation assessment and to develop an in vivo biotransformation rate database for QSAR development and in vitro to in vivo biotransformation rate extrapolation. The capacity of chemicals to be biotransformed in fish was found to be highly dependent on the route of exposure. Somatic biotransformation was the dominant pathway for most chemicals absorbed via the respiratory route. Intestinal biotransformation was the dominant metabolic pathway for most chemicals absorbed via the diet. For substances not biotransformed or transformed exclusively in the body of the fish, the BCF and BMF appeared to be closely correlated. For substances subject to intestinal biotransformation, the same correlation did not apply. We conclude that intestinal biotransformation and bioavailability in water can modulate the relationship between the BCF and BMF. This study also supports a fairly simple rule of thumb that may be useful in the interpretation of dietary bioaccumulation tests; i.e., chemicals with a BMF of <1 tend to exhibit BCFs based on either the freely dissolved (BCF) or the total concentration (BCF) of the chemical in the water that is less than 5000.
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http://dx.doi.org/10.1021/acs.est.6b03602DOI Listing
December 2016

Chemical activity-based environmental risk analysis of the plasticizer di-ethylhexyl phthalate and its main metabolite mono-ethylhexyl phthalate.

Environ Toxicol Chem 2017 06 21;36(6):1483-1492. Epub 2016 Dec 21.

Institute of Ocean Sciences, Ocean Sciences Division, Fisheries and Oceans Canada, Sidney, British Columbia, Canada.

The present study applies a chemical activity-based approach to: 1) evaluate environmental concentrations of di-ethylhexyl phthalate (DEHP; n = 23 651) and its metabolite mono-ethylhexyl phthalate (MEHP; n = 1232) in 16 environmental media from 1174 studies in the United States, Canada, Europe, and Asia, and in vivo toxicity data from 934 studies in 20 species, as well as in vitro biological activity data from the US Environmental Protection Agency's Toxicity Forecaster and other sources; and 2) conduct a comprehensive environmental risk analysis. The results show that the mean chemical activities of DEHP and MEHP in abiotic environmental samples from locations around the globe are 0.001 and 10 , respectively. This indicates that DEHP has reached on average 0.1% of saturation in the abiotic environment. The mean chemical activity of DEHP in biological samples is on average 100-fold lower than that in abiotic samples, likely because of biotransformation of DEHP in biota. Biological responses in both in vivo and in vitro tests occur at chemical activities between 0.01 to 1 for DEHP and between approximately 10 and 10 for MEHP, suggesting a greater potency of MEHP compared with DEHP. Chemical activities of both DEHP and MEHP in biota samples were less than those causing biological responses in the in vitro bioassays, without exception. A small fraction of chemical activities of DEHP in abiotic environmental samples (i.e., 4-8%) and none (0%) for MEHP were within the range of chemical activities associated with observed toxicological responses in the in vivo tests. The present study illustrates the chemical activity approach for conducting risk analyses. Environ Toxicol Chem 2017;36:1483-1492. © 2016 SETAC.
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http://dx.doi.org/10.1002/etc.3689DOI Listing
June 2017

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

Environ Toxicol Chem 2016 12 12;35(12):2968-2976. Epub 2016 Jul 12.

Department of Biological Sciences, Simon Fraser University, Burnaby, British Columbia, Canada.

The present study develops, applies, and tests a method for deriving empirical bioconcentration factors and somatic biotransformation rate constants from dietary bioaccumulation tests and simplified bioaccumulation experiments that measure depuration rates. In this approach, measurement of the chemical concentration in the water is not required. The method aims to improve bioaccumulation assessment, reduce cost and animal use, and shorten experiments. Environ Toxicol Chem 2016;35:2968-2976. © 2016 SETAC.
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http://dx.doi.org/10.1002/etc.3481DOI Listing
December 2016

Evaluating the roles of biotransformation, spatial concentration differences, organism home range, and field sampling design on trophic magnification factors.

Sci Total Environ 2016 May 15;551-552:438-51. Epub 2016 Feb 15.

Health and Environmental Sciences, Dow Corning Corporation, 2200 W. Salzburg Road, Auburn, MI 48611, USA.

Trophic magnification factors (TMFs) are field-based measurements of the bioaccumulation behavior of chemicals in food-webs. TMFs can provide valuable insights into the bioaccumulation behavior of chemicals. However, bioaccumulation metrics such as TMF may be subject to considerable uncertainty as a consequence of systematic bias and the influence of confounding variables. This study seeks to investigate the role of systematic bias resulting from spatially-variable concentrations in water and sediments and biotransformation rates on the determination of TMF. For this purpose, a multibox food-web bioaccumulation model was developed to account for spatial concentration differences and movement of organisms on chemical concentrations in aquatic biota and TMFs. Model calculated and reported field TMFs showed good agreement for persistent polychlorinated biphenyl (PCB) congeners and biotransformable phthalate esters (PEs) in a marine aquatic food-web. Model testing showed no systematic bias and good precision in the estimation of the TMF for PCB congeners but an apparent underestimation of model calculated TMFs, relative to reported field TMFs, for PEs. A model sensitivity analysis showed that sampling designs that ignore the presence of concentration gradients may cause systematically biased and misleading TMF values. The model demonstrates that field TMFs are most sensitive to concentration gradients and species migration patterns for substances that are subject to a low degree of biomagnification or trophic dilution. The model is useful in anticipating the effect of spatial concentration gradients on the determination of the TMF; guiding species collection strategies in TMF studies; and interpretation of the results of field bioaccumulation studies in study locations where spatial differences in chemical concentration exist.
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http://dx.doi.org/10.1016/j.scitotenv.2016.02.013DOI Listing
May 2016

Modeling (137)Cs bioaccumulation in the salmon-resident killer whale food web of the Northeastern Pacific following the Fukushima Nuclear Accident.

Sci Total Environ 2016 Feb 3;544:56-67. Epub 2015 Dec 3.

School of Resource & Environmental Management, Faculty of Environment, Simon Fraser University, 8888 University Drive, Burnaby, BC V5A 1S6, Canada.

To track the long term bioaccumulation of (137)Cs in marine organisms off the Pacific Northwest coast of Canada, we developed a time dependent bioaccumulation model for (137)Cs in a marine mammalian food web that included fish-eating resident killer whales. The model outcomes show that (137)Cs can be expected to gradually bioaccumulate in the food web over time as demonstrated by the increase of the apparent trophic magnification factor of (137)Cs, ranging from 0.76 after 1 month of exposure to 2.0 following 30 years of exposure. (137)Cs bioaccumulation is driven by relatively rapid dietary uptake rates, moderate depuration rates in lower trophic level organisms and slow elimination rates in high trophic level organisms. Model estimates of the (137)Cs activity in species of the food web, based on current measurements and forecasts of (137)Cs activities in oceanic waters and sediments off the Canadian Pacific Northwest, indicate that the long term (137)Cs activities in fish species including Pacific herring, wild Pacific salmon, sablefish and halibut will remain well below the current (137)Cs-Canada Action Level for consumption (1000 Bq/kg) following a nuclear emergency. Killer whales and Pacific salmon are expected to exhibit the largest long term (137)Cs activities and may be good sentinels for monitoring (137)Cs in the region. Assessment of the long term consequences of (137)Cs releases from the Fukushima aftermath should consider the extent of ecological magnification in addition to ocean dilution.
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http://dx.doi.org/10.1016/j.scitotenv.2015.11.097DOI Listing
February 2016

Bioaccumulation of decamethylpentacyclosiloxane (D5): A review.

Environ Toxicol Chem 2015 Dec 30;34(12):2703-14. Epub 2015 Oct 30.

Department of Biology, Institute of Applied Sciences, University of North Texas, Denton, Texas, USA.

Decamethylpentacyclosiloxane (D5) is a widely used, high-production volume personal care product with an octanol-water partition coefficient (log K(OW)) of 8.09. Because of D5's high K(OW) and widespread use, it is subject to bioaccumulation assessments in many countries. The present study provides a compilation and an in-depth, independent review of bioaccumulation studies involving D5. The findings indicate that D5 exhibits depuration rates in fish and mammals that exceed those of extremely hydrophobic, nonbiotransformable substances; that D5 is subject to biotransformation in mammals and fish; that observed bioconcentration factors in fish range between 1040 L/kg and 4920 L/kg wet weight in laboratory studies using non-radiolabeled D5 and between 5900 L/kg and 13 700 L/kg wet weight in an experiment using C(14) radiolabeled D5; and that D5 was not observed to biomagnify in most laboratory experiments and field studies. Review of the available studies shows a high degree of internal consistency among findings from different studies and supports a broad comprehensive approach in bioaccumulation assessments that includes information from studies with a variety of designs and incorporates multiple bioaccumulation measures in addition to the K(OW) and bioconcentration factor.
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http://dx.doi.org/10.1002/etc.3242DOI Listing
December 2015

Food Web Bioaccumulation Model for Resident Killer Whales from the Northeastern Pacific Ocean as a Tool for the Derivation of PBDE-Sediment Quality Guidelines.

Arch Environ Contam Toxicol 2016 Jan 20;70(1):155-68. Epub 2015 Aug 20.

School of Resource and Environmental Management, Faculty of Environment, Simon Fraser University, 8888 University Drive, Burnaby, BC, V5A 1S6, Canada.

Resident killer whale populations in the NE Pacific Ocean are at risk due to the accumulation of pollutants, including polybrominated diphenyl ethers (PBDEs). To assess the impact of PBDEs in water and sediments in killer whale critical habitat, we developed a food web bioaccumulation model. The model was designed to estimate PBDE concentrations in killer whales based on PBDE concentrations in sediments and the water column throughout a lifetime of exposure. Calculated and observed PBDE concentrations exceeded the only toxicity reference value available for PBDEs in marine mammals (1500 μg/kg lipid) in southern resident killer whales but not in northern resident killer whales. Temporal trends (1993-2006) for PBDEs observed in southern resident killer whales showed a doubling time of ≈5 years. If current sediment quality guidelines available in Canada for polychlorinated biphenyls are applied to PBDEs, it can be expected that PBDE concentrations in killer whales will exceed available toxicity reference values by a large margin. Model calculations suggest that a PBDE concentration in sediments of approximately 1.0 μg/kg dw produces PBDE concentrations in resident killer whales that are below the current toxicity reference value for 95 % of the population, with this value serving as a precautionary benchmark for a management-based approach to reducing PBDE health risks to killer whales. The food web bioaccumulation model may be a useful risk management tool in support of regulatory protection for killer whales.
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http://dx.doi.org/10.1007/s00244-015-0215-yDOI Listing
January 2016

Review of existing terrestrial bioaccumulation models and terrestrial bioaccumulation modeling needs for organic chemicals.

Integr Environ Assess Manag 2016 Jan 28;12(1):123-34. Epub 2015 Sep 28.

European Chemicals Agency, Helsinki, Finland.

Protocols for terrestrial bioaccumulation assessments are far less-developed than for aquatic systems. This article reviews modeling approaches that can be used to assess the terrestrial bioaccumulation potential of commercial organic chemicals. Models exist for plant, invertebrate, mammal, and avian species and for entire terrestrial food webs, including some that consider spatial factors. Limitations and gaps in terrestrial bioaccumulation modeling include the lack of QSARs for biotransformation and dietary assimilation efficiencies for terrestrial species; the lack of models and QSARs for important terrestrial species such as insects, amphibians and reptiles; the lack of standardized testing protocols for plants with limited development of plant models; and the limited chemical domain of existing bioaccumulation models and QSARs (e.g., primarily applicable to nonionic organic chemicals). There is an urgent need for high-quality field data sets for validating models and assessing their performance. There is a need to improve coordination among laboratory, field, and modeling efforts on bioaccumulative substances in order to improve the state of the science for challenging substances.
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http://dx.doi.org/10.1002/ieam.1690DOI Listing
January 2016

Characterization of ecological risks from environmental releases of decamethylcyclopentasiloxane (D5).

Environ Toxicol Chem 2015 Dec 24;34(12):2715-22. Epub 2015 Jul 24.

School of Resource and Environmental Management, Simon Fraser University, Burnaby, British Columbia, Canada.

Decamethylcyclopentasiloxane (D5) is used in personal care products and industrial applications. The authors summarize the risks to the environment from D5 based on multiple lines of evidence and conclude that it presents negligible risk. Laboratory and field studies show that D5 is not toxic to aquatic organisms or benthic invertebrates up to its solubility limit in water or porewater or its sorptive capacity in sediment. Comparison of lipid-normalized internal concentrations with measured concentrations in benthos indicates that field-collected organisms do not achieve toxic levels of D5 in their tissues, suggesting negligible risk. Exposure to D5 resulted in a slight reduction of root biomass in barley at test concentrations 2 orders of magnitude greater than measured D5 levels in biosolids-amended soils and more than twice as high as the maximum calculated sorptive capacity of the soil. No effects were observed in soil invertebrates exposed to similar concentrations, indicating that D5 poses a de minimis risk to the terrestrial environment. High rates of metabolism and elimination of D5 compared with uptake rates from food results in biodilution in the food web rather than biomagnification, culminating in de minimis risk to higher trophic level organisms via the food chain. A fugacity approach substantiates all conclusions that were made on a concentration basis.
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http://dx.doi.org/10.1002/etc.3041DOI Listing
December 2015

Fugacity and activity analysis of the bioaccumulation and environmental risks of decamethylcyclopentasiloxane (D5).

Environ Toxicol Chem 2015 Dec 24;34(12):2723-31. Epub 2015 Jul 24.

Exponent, Bellevue, Washington, USA.

As part of an initiative to evaluate commercial chemicals for their effects on human and environmental health, Canada recently evaluated decamethylcyclopentasiloxane (D5; CAS no. 541-02-06), a high-volume production chemical used in many personal care products. The evaluation illustrated the challenges encountered in environmental risk assessments and the need for the development of better tools to increase the weight of evidence in environmental risk assessments. The present study presents a new risk analysis method that applies thermodynamic principles of fugacity and activity to express the results of field monitoring and laboratory bioaccumulation and toxicity studies in a comprehensive risk analysis that can support risk assessments. Fugacity and activity ratios of D5 derived from bioaccumulation measures indicate that D5 does not biomagnify in food webs, likely because of biotransformation. The fugacity and activity analysis further demonstrates that reported no-observed-effect concentrations of D5 normally cannot occur in the environment. Observed fugacities and activities in the environment are, without exception, far below those corresponding with no observed effects, in many cases by several orders of magnitude. This analysis supports the conclusion of the Canadian Board of Review and the Minister of the Environment that D5 does not pose a danger to the environment. The present study further illustrates some of the limitations of a persistence-bioaccumulation-toxicity-type criteria-based risk assessment approach and discusses the merits of the fugacity and activity approach to increase the weight of evidence and consistency in environmental risk assessments of commercial chemicals.
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http://dx.doi.org/10.1002/etc.2942DOI Listing
December 2015

Concentration dependence of biotransformation in fish liver S9: Optimizing substrate concentrations to estimate hepatic clearance for bioaccumulation assessment.

Environ Toxicol Chem 2015 Dec 15;34(12):2782-90. Epub 2015 Oct 15.

Department of Biological Sciences, Simon Fraser University, Burnaby, British Columbia, Canada.

In vitro bioassays to estimate biotransformation rate constants of contaminants in fish are currently being investigated to improve bioaccumulation assessments of hydrophobic contaminants. The present study investigates the relationship between chemical substrate concentration and in vitro biotransformation rate of 4 environmental contaminants (9-methylanthracene, pyrene, chrysene, and benzo[a]pyrene) in rainbow trout (Oncorhynchus mykiss) liver S9 fractions and methods to determine maximum first-order biotransformation rate constants. Substrate depletion experiments using a series of initial substrate concentrations showed that in vitro biotransformation rates exhibit strong concentration dependence, consistent with a Michaelis-Menten kinetic model. The results indicate that depletion rate constants measured at initial substrate concentrations of 1 μM (a current convention) could underestimate the in vitro biotransformation potential and may cause bioconcentration factors to be overestimated if in vitro biotransformation rates are used to assess bioconcentration factors in fish. Depletion rate constants measured using thin-film sorbent dosing experiments were not statistically different from the maximum depletion rate constants derived using a series of solvent delivery-based depletion experiments for 3 of the 4 test chemicals. Multiple solvent delivery-based depletion experiments at a range of initial concentrations are recommended for determining the concentration dependence of in vitro biotransformation rates in fish liver fractions, whereas a single sorbent phase dosing experiment may be able to provide reasonable approximations of maximum depletion rates of very hydrophobic substances.
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http://dx.doi.org/10.1002/etc.3117DOI Listing
December 2015

Somatic and gastrointestinal in vivo biotransformation rates of hydrophobic chemicals in fish.

Environ Toxicol Chem 2015 Oct 17;34(10):2282-94. Epub 2015 Aug 17.

School of Resource and Environmental Management, Simon Fraser University, Burnaby, British Columbia, Canada.

To improve current bioaccumulation assessment methods, a methodology is developed, applied, and investigated for measuring in vivo biotransformation rates of hydrophobic organic substances in the body (soma) and gastrointestinal tract of the fish. The method resembles the Organisation for Economic Co-operation and Development (OECD) 305 dietary bioaccumulation test but includes reference chemicals to determine both somatic and gastrointestinal biotransformation rates of test chemicals. Somatic biotransformation rate constants for the test chemicals ranged between 0 d(-1) and 0.38 (standard error [SE] 0.03)/d(-1) . Gastrointestinal biotransformation rate constants varied from 0 d(-1) to 46 (SE 7) d(-1) . Gastrointestinal biotransformation contributed more to the overall biotransformation in fish than somatic biotransformation for all test substances but 1. Results suggest that biomagnification tests can reveal the full extent of biotransformation in fish. The common presumption that the liver is the main site of biotransformation may not apply to many substances exposed through the diet. The results suggest that the application of quantitative structure-activity relationships (QSARs) for somatic biotransformation rates and hepatic in vitro models to assess the effect of biotransformation on bioaccumulation can underestimate biotransformation rates and overestimate the biomagnification potential of chemicals that are biotransformed in the gastrointestinal tract. With some modifications, the OECD 305 test can generate somatic and gastrointestinal biotransformation data to develop biotransformation QSARs and test in vitro-in vivo biotransformation extrapolation methods.
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http://dx.doi.org/10.1002/etc.3050DOI Listing
October 2015

Toward ecosystem-based sediment quality guidelines for polychlorinated biphenyls (PCBs).

Integr Environ Assess Manag 2015 Oct 12;11(4):689-700. Epub 2015 May 12.

School of Resource and Environmental Management, Simon Fraser University, Burnaby, British Columbia, Canada.

To investigate whether Sediment Quality Guidelines (SQGs) for polychlorinated biphenyls (PCBs) in Canada and British Columbia achieve their objective of protecting ecosystems, we measured and compiled concentrations of PCB congeners in sediments, bivalves, crustaceans, fish, and marine mammals from 3 areas off the Pacific coast of British Columbia, Canada. The concentration data showed that whereas PCB concentrations in sediments were predominantly below the SQG of 20 µg/kg dry weight, large fractions of the PCB concentrations in fish and shellfish species exceeded the tissue residue guideline for the consumption of fish and shellfish by wildlife (i.e., 50 µg/kg wet weight [ww]) but were below the tissue residue guideline for the consumption of fish and shellfish by human populations (i.e., 2000 µg/kg ww). Also, PCB concentrations in marine mammals exceeded toxicity reference concentrations. The concentration data were used to develop species- and location-specific Biota-Sediment Accumulation Factors (BSAF = Cbiota /Csediment ), that were used to estimate PCB concentrations in wildlife species that may exist if the PCB concentration in sediments are equal to the SQGs. The results show that if the PCB concentration is equal to the SQGs, then PCB concentrations in most wildlife species can be expected to exceed the tissue residue guideline for the consumption of fish and shellfish by wildlife species and by humans, as well as toxicity reference concentrations for marine mammals. A methodology for developing SQGs for PCBs that are protective of the health of different wildlife species and human consumers of fish and shellfish from general Canadian and coastal First Nations populations was developed and applied. The proposed guidelines may provide useful guidance to establish SQGs for PCBs that can account for the ecological diversity in coastal environments and that better achieve the intent of the guidelines to protect ecosystems. The proposed methodology for guideline development may also be useful in the development of SQGs for other bioaccumulative substances.
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http://dx.doi.org/10.1002/ieam.1638DOI Listing
October 2015

In vitro biotransformation rates in fish liver S9: effect of dosing techniques.

Environ Toxicol Chem 2014 Aug 20;33(8):1885-93. Epub 2014 Jun 20.

School of Resource and Environmental Management, Simon Fraser University, Burnaby, British Columbia, Canada.

In vitro biotransformation assays are currently being explored to improve estimates of bioconcentration factors of potentially bioaccumulative organic chemicals in fish. The present study compares thin-film and solvent-delivery dosing techniques as well as single versus multiple chemical dosing for measuring biotransformation rates of selected polycyclic aromatic hydrocarbons in rainbow trout (Oncorhynchus mykiss) liver S9. The findings show that biotransformation rates of very hydrophobic substances can be accurately measured in thin-film sorbent-dosing assays from concentration-time profiles in the incubation medium but not from those in the sorbent phase because of low chemical film-to-incubation-medium mass-transfer rates at the incubation temperature of 13.5 °C required for trout liver assays. Biotransformation rates determined by thin-film dosing were greater than those determined by solvent-delivery dosing for chrysene (octanol-water partition coefficient [KOW ] =10(5.60) ) and benzo[a]pyrene (KOW  =10(6.04) ), whereas there were no statistical differences in pyrene (KOW  =10(5.18) ) biotransformation rates between the 2 methods. In sorbent delivery-based assays, simultaneous multiple-chemical dosing produced biotransformation rates that were not statistically different from those measured in single-chemical dosing experiments for pyrene and benzo[a]pyrene but not for chrysene. In solvent-delivery experiments, multiple-chemical dosing produced biotransformation rates that were much smaller than those in single-chemical dosing experiments for all test chemicals. While thin-film sorbent-phase and solvent delivery-based dosing methods are both suitable methods for measuring biotransformation rates of substances of intermediate hydrophobicity, thin-film sorbent-phase dosing may be more suitable for superhydrophobic chemicals.
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http://dx.doi.org/10.1002/etc.2636DOI Listing
August 2014

Mathematical relationships between metrics of chemical bioaccumulation in fish.

Environ Toxicol Chem 2013 Jul 17;32(7):1459-66. Epub 2013 May 17.

Environmental & Resource Studies, Trent University, Peterborough, Ontario, Canada.

Five widely used metrics of bioaccumulation in fish are defined and discussed, namely the octanol-water partition coefficient (KOW ), bioconcentration factor (BCF), bioaccumulation factor (BAF), biomagnification factor (BMF), and trophic magnification factor (TMF). Algebraic relationships between these metrics are developed and discussed using conventional expressions for chemical uptake from water and food and first-order losses by respiration, egestion, biotransformation, and growth dilution. Two BCFs may be defined, namely as an equilibrium partition coefficient KFW or as a nonequilibrium BCFK in which egestion losses are included. Bioaccumulation factors are shown to be the product of the BCFK and a novel equilibrium multiplier M containing 2 ratios, namely, the diet-to-water concentration ratio and the ratio of uptake rate constants for respiration and dietary uptake. Biomagnification factors are shown to be proportional to the lipid-normalized ratio of the predator/prey values of BCFK and the ratio of the equilibrium multipliers. Relationships with TMFs are also discussed. The effects of chemical hydrophobicity, biotransformation, and growth are evaluated by applying the relationships to a range of illustrative chemicals of varying KOW in a linear 4-trophic-level food web with typical values for uptake and loss rate constants. The roles of respiratory and dietary intakes are demonstrated, and even slow rates of biotransformation and growth can significantly affect bioaccumulation. The BCFK s and the values of M can be regarded as the fundamental determinants of bioaccumulation and biomagnification in aquatic food webs. Analyzing data from food webs can be enhanced by plotting logarithmic lipid-normalized concentrations or fugacities as a linear function of trophic level to deduce TMFs. Implications for determining bioaccumulation by laboratory tests for regulatory purposes are discussed.
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http://dx.doi.org/10.1002/etc.2205DOI Listing
July 2013
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