In vitro biotransformation of surfactants in fish. Part II – Alcohol ethoxylate (C16EO8) and alcohol ethoxylate sulfate (C14EO2S) to estimate bioconcentration potential

139

151

A key challenge in ecotoxicology is to assess the potential risks of chemicals to the wide range of species in the environment on the basis of laboratory toxicity data derived from a limited number of species. These species are then assumed to be suitable surrogates for a wider class of related taxa. For example, Daphnia spp. are used as the indicator species for freshwater aquatic invertebrates. Extrapolation from these datasets to natural communities poses a challenge because the extent to which test species are representative of their various taxonomic groups is often largely unknown, and different taxonomic groups and chemicals are variously represented in the available datasets. Moreover, it has been recognized that physiological and ecological factors can each be powerful determinants of vulnerability to chemical stress, thus differentially influencing toxicant effects at the population and community level. Recently it was proposed that detailed study of species traits might eventually permit better understanding, and thus prediction, of the potential for adverse effects of chemicals to a wider range of organisms than those amenable for study in the laboratory. This line of inquiry stems in part from the ecology literature, in which species traits are being used for improved understanding of how communities are constructed, as well as how communities might respond to, and recover from, disturbance (see other articles in this issue). In the present work, we develop a framework for the application of traits-based assessment. The framework is based on the population vulnerability conceptual model of Van Straalen in which vulnerability is determined by traits that can be grouped into 3 major categories, i.e., external exposure, intrinsic sensitivity, and population sustainability. Within each of these major categories, we evaluate specific traits as well as how they could contribute to the assessment of the potential effects of a toxicant on an organism. We then develop an example considering bioavailability to explore how traits could be used mechanistically to estimate vulnerability. A preliminary inventory of traits for use in ecotoxicology is included; this also identifies the availability of data to quantify those traits, in addition to an indication of the strength of linkage between the trait and the affected process. Finally, we propose a way forward for the further development of traits-based approaches in ecotoxicology.

Section: Toxicokineticsmentioning

confidence: 99%

Framework for traits‐based assessment in ecotoxicology

Rubach

Ashauer

Buchwalter

et al. 2011

139

151

“…Standardized methods to measure in vivo biotransformation rates of high K OW chemicals in biota do not currently exist. Recently, in vitro biotransformation methods have been developed and tested to measure biotransformation rates (Han et al 2007; Dyer et al 2009). These methods are promising and have the potential to include biotransformation in bioaccumulation screening when methods for extrapolation of in vitro to in vivo biotransformation rates become available in the future.…”

Section: Tmf Alternativesmentioning

confidence: 99%

Use of trophic magnification factors and related measures to characterize bioaccumulation potential of chemicals

Conder

Gobas

Borgå

et al. 2011

Recent technical workgroups have concluded that trophic magnification factors (TMFs) are useful in characterizing the bioaccumulation potential of a chemical, because TMFs provide a holistic measure of biomagnification in food webs. The objectives of this article are to provide a critical analysis of the application of TMFs for regulatory screening for bioaccumulation potential, and to discuss alternative methods for supplementing TMFs and assessing biomagnification in cases where insufficient data are available to determine TMFs. The general scientific consensus is that chemicals are considered bioaccumulative if they exhibit a TMF > 1. However, comparison of study-derived TMF estimates to this threshold value should be based on statistical analyses such that variability is quantified and false positive and false negative errors in classification of bioaccumulation potential are minimized. An example regulatory decision-making framework is presented to illustrate the use of statistical power analyses to minimize assessment errors. Suggestions for considering TMF study designs and TMFs obtained from multiple studies are also provided. Alternative bioaccumulation metrics are reviewed for augmenting TMFs and for substituting in situations in which field data for deriving TMFs are unavailable. Field-derived, trophic level-normalized biomagnification factors (BMF(TL) s), biota-sediment accumulation factors (BSAF(TL) s), and bioaccumulation factors (BAF(TL) s) are recommended if data are available, because these measures are most closely related to the biomagnification processes characterized by TMFs. Field- and laboratory-derived BAFs and bioconcentration factors are generally less accurate in predicting biomagnification. However, bioconcentration factors and BAFs remain useful for characterizing bioaccumulation as a result of the transfer of chemicals from abiotic environmental compartments to lower trophic levels. Modeling that incorporates available laboratory and field data should also be considered for augmenting assessments of bioaccumulation potential. Modeling can provide a TMF-focused assessment for new or unreleased chemicals in the absence of field data by estimating TMF values and theoretical relationships between physical-chemical properties and TMF values (quantitative structure-activity relationships). An illustration of the use of physicochemical properties for estimating TMFs is provided. Overall, TMFs provide valuable information regarding bioaccumulation potential and should be incorporated into regulatory decision making following the suggestions outlined in this article.

“…In vitro estimation of biotransformation potential —Biotransformation potential of fish has been investigated in liver slices (Schmieder et al 2000), whole liver homogenates (de Wolf et al 1993b), liver subfractions (Kolanczyk et al 1999; Dyer et al 2003; Perdu‐Durand et al 2004), isolated hepatocytes, and cell lines (Segner 1998; Cravedi et al 2001; Segner and Cravedi 2001; Dyer and Bernhard 2004). The xenobiotic metabolite pattern produced by fish hepatocytes in vitro is generally similar to that observed in vivo (Segner and Cravedi 2001).…”

Section: Review Of Alternative Approachesmentioning

confidence: 99%

“…Dyer et al (2003) applied an approach to derive a BCF cell for various surfactants using carp primary hepatocytes and cultured hepatocytes (PLHC‐1 cells). The rates of uptake and loss of the test chemical from the cellular systems were estimated assuming 1st‐order kinetics and the BCF in the cells determined by a ratio of uptake rate to the rate of loss.…”

Section: Review Of Alternative Approachesmentioning

confidence: 99%

Animal use replacement, reduction, and refinement: Development of an integrated testing strategy for bioconcentration of chemicals in fish

Wolf¹,

Comber²,

Douben

et al. 2007

When addressing the use of fish for the environmental safety of chemicals and effluents, there are many opportunities for applying the principles of the 3Rs: Reduce, Refine, and Replace. The current environmental regulatory testing strategy for bioconcentration and secondary poisoning has been reviewed, and alternative approaches that provide useful information are described. Several approaches can be used to reduce the number of fish used in the Organization for Economic Cooperation and Development (OECD) Test Guideline 305, including alternative in vivo test methods such as the dietary accumulation test and the static exposure approach. The best replacement approach would seem to use read‐across, chemical grouping, and quantitative structure‐activity relationships with an assessment of the key processes in bioconcentration: Adsorption, distribution, metabolism, and excretion. Biomimetic extraction has particular usefulness in addressing bioavailable chemicals and is in some circumstances capable of predicting uptake. Use of alternative organisms such as invertebrates should also be considered. A single cut‐off value for molecular weight and size beyond which no absorption will take place cannot be identified. Recommendations for their use in bioaccumulative (B) categorization schemes are provided. Assessment of biotransformation with in vitro assays and in silico approaches holds significant promise. Further research is needed to identify their variability and confidence limits and the ways to use this as a basis to estimate bioconcentration factors. A tiered bioconcentration testing strategy has been developed taking account of the alternatives discussed.