Bioconcentration studies with the freshwater amphipod Hyalella azteca: are the results predictive of bioconcentration in fish?

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Bioaccumulation assessment predominantly relies on the bioconcentration factor (BCF) as the sole decisive metric. The test guideline 305 by the Organisation for Economic Co‐operation and Development (OECD) provides the standard procedure for deriving this in vivo fish BCF, which is not only expensive and labor‐intensive, but also requires many animals. Accordingly, there is a great need for and interest in alternative methods that can help to reduce, replace, and refine vertebrate tests, as described in the 3R principles. Two alternative approaches have been developed: the bioconcentration test with the freshwater amphipod Hyalella azteca and the OECD test guideline 319 which provides a method to determine experimentally derived in vitro metabolism rates that can then be incorporated into in silico prediction models for rainbow trout BCF calculation. In the present study both alternative methods were applied to 5 substances of different physicochemical characteristics. The results were compared with literature values of fish in vivo BCFs and additional BCFs obtained with the alternative methods, if available. Potential differences between the results of the test methods are discussed utilizing information such as in vivo metabolism rates. The currently available data set suggests that these 2 alternative methods pose promising alternatives to predict bioaccumulation in fish, although defined applicability domains have yet to be determined. Environ Toxicol Chem 2020;39:1813–1825. © 2020 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC

Section: Hybitmentioning

confidence: 99%

Section: Hybitmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Comparison of Alternative Methods for Bioaccumulation Assessment: Scope and Limitations of In Vitro Depletion Assays with Rainbow Trout and Bioconcentration Tests in the Freshwater Amphipod Hyalella azteca

Kosfeld

Ebersbach

et al. 2020

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Bioconcentration, Metabolism, and Spatial Distribution of ¹⁴C‐Labeled Laurate in the Freshwater Amphipod Hyalella azteca

Raths

Kuehr

Schlechtriem

2020

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Regulatory assessment of the bioaccumulation from water is commonly based on bioconcentration factors (BCFs) derived from fish flow-through tests. Such experiments require many laboratory animals and are time-consuming and costly. An alternative test setup for organic, neutral compounds using the amphipod Hyalella azteca was recently suggested, resulting in BCF values which show a strong correlation with fish BCF data. In the present study, the bioconcentration potential of the ionic compound laurate was elucidated in H. azteca. The sodium salt of 1-14 C laurate was applied to H. azteca in a flow-through and a semistatic approach. Because of rapid biodegradation, a semistatic approach with frequent medium replacements was required to ensure a stable medium concentration. Laurate was also rapidly metabolized by H. azteca. A large proportion of the total radioactivity measured in the amphipod tissue was not extractable, suggesting that mineralized laurate was accumulated in the calcified exoskeleton of H. azteca. This was confirmed in a further study using carbonate [ 14 C]. A lipid-normalized (5.0%) Hyalella BCF of 8.9 was calculated for laurate, measured as free fatty acids. The results of the bioconcentration studies with H. azteca confirm the low bioaccumulation potential of the test item previously observed in fish. However, more organic ionic compounds with various properties need to be tested to assess whether a general correlation between fish and Hyalella BCF data exists. Environ Toxicol Chem 2020;39:310-322. Chemicals 14 C-lauric acid (carbonyl carbon-labeled), dissolved in ethanol, was obtained from Hartmann Analytics (98.4% wileyonlinelibrary.com/ETC FIGURE 1: Experimental setup of the flow-through system (left) and the (semi-)static system (right). a = mixing chamber; b = aeration; c = steel grid; d = DECOTAB; e = stirrer (not during study III); f = spiked medium. Bioconcentration of laurate in the amphipod Hyalella azteca-Environmental Toxicology and Chemistry, 2020;39:310-322 311

Spatiotemporal Distribution of Hydrophobic Organic Contaminants in Spiked‐Sediment Toxicity Tests: Measuring Total and Freely Dissolved Concentrations in Porewater and Overlying Water

Hiki

Fischer

Nishimori

et al. 2021

The sediment-water interface of spiked-sediment toxicity tests is a complex exposure system, where multiple uptake pathways exist for benthic organisms. The freely dissolved concentration (C free ) in sediment pore water has been proposed as a relevant exposure metric to hydrophobic organic contaminants (HOCs) in this system. C free , however, has rarely been measured in spiked-sediment toxicity tests. In this study, we first developed a direct immersion SPME method for measuring C free in overlying and pore water in a sediment test using polydimethylsiloxane (PDMS)-coated glass fibers, resulting in sensitive and repeatable in situ measurements of HOCs. Then, we measured This article is protected by copyright. All rights reserved. Accepted ArticleC free and total dissolved concentrations (C diss ) in the sediment test systems with the freshwater amphipod Hyalella azteca, thoroughly evaluated the temporal and spatial profiles of four HOCs (phenanthrene, pyrene, benzo[a]pyrene, and chlorpyrifos). Furthermore, we examined the relationship between the measured concentrations and the lethality of H. azteca. We found that the test system was far from an equilibrium state for all four chemicals tested, where C diss in overlying water changed over the test duration and a vertical C free gradient existed at the sediment-water interface. C diss was larger than C free by a factor of 170-220 in pore water for benzo[a]pyrene due to the strong binding to dissolved organic carbon. The comparison of the median lethal concentrations (LC50) of chlorpyrifos in the sediment test and those in water-only tests indicates that C free in pore water was the most representative indicator for toxicity of this chemical. The method and findings presented in this work warrant further research on the chemical transport mechanisms and the actual exposure in sediment tests using different chemicals, sediments, and test species.