Animal Use Replacement, Reduction, and Refinement: Development of an Integrated Testing Strategy for Bioconcentration of Chemicals in Fish

Abstract

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.

Toward improved models for predicting bioconcentration of well‐metabolized compounds by rainbow trout using measured rates of in vitro intrinsic clearance

“…This information has substantial value for prioritizing limited testing resources and may provide important support for bioaccumulation assessments within the context of a weightof-evidence approach [54]. Eventually, we expect these or similar methods to be endorsed by governmental regulatory authorities as part of a tiered approach to bioaccumulation assessment [54,55]. To achieve this goal it will be necessary to evaluate the models using well-matched (same species, life stage, temperature, etc.)…”

Transport, Accumulation and Transformation Processes

“…However, it does suggest that once the MW is in the region of 700-1100, depending on other factors, a reduced BCF may be expected. Hence, while recognizing the uncertainties in the interpretation of experimental results, de Wolf et al [43] recommended that to demonstrate a reduced BCF a substance should have either:…”

“…In conclusion, there would appear to be no clear cut-off value for molecular size beyond which no absorption will take place. While recognizing the uncertainties in the interpretation of experimental results, de Wolf et al [43] Lipinksi's rule of 5 Lipinski et al [54] identified five physical chemical characteristics that influence solubility and absorption across the mammalian intestinal lumen using more than 2,200 drug development tests. These characteristics have been rigorously reviewed [55,56] and are used to develop commercial models to estimate absorption in mammals.…”

“…A low TEER value indicates the tissue has greater absorption potential. Although the studies by Lipinski et al [54], Wenlock et al [55], Vieth et al [57] and Proudfoot [56] focused on absorption across the intestinal lumen, the more restrictive TEER for fish gills [43] implies that the equations and concepts can be reapplied to conservatively estimated absorption in fish.…”

Time to recognize zebrafish ‘affective’ behavior

“…At the same time, the simplicity of zebrafish behavioral paradigms helps reduce possible stress to the animal and time it is subjected to testing. The aquatic paradigms adhere to the 3Rs principle (de Wolf et al, 2007), as fish are less sentient than rodents, and typically use less invasive administration of drugs (i.e., immersion/inhalation vs. injections). Furthermore, unlike rodent developmental models of stress, zebrafish embryos can be exposed to neonatal stressors without having to consider the environmental effects on the mother (Teraoka et al, 1993).…”