The ecotoxicity testing of chemicals for prospective environmental safety assessment is an area in which a high number of vertebrates are used across a variety of industry sectors. Refining, reducing, and replacing the use of animals such as fish, birds, and amphibians for this purpose addresses the ethical concerns and the increasing legislative requirements to consider alternative test methods. Members of the UK-based National Centre for the Replacement, Refinement and Reduction of Animals in Research (NC3Rs) Ecotoxicology Working Group, consisting of representatives from academia, government organizations, and industry, have worked together over the past 6 y to provide evidence bases to support and advance the application of the 3Rs in regulatory ecotoxicity testing. The group recently held a workshop to identify the areas of testing, demands, and drivers that will have an impact on the future of animal use in regulatory ecotoxicology. As a result of these discussions, we have developed a pragmatic approach to prioritize and realistically address key opportunity areas, to enable progress toward the vision of a reduced reliance on the use of animals in this area of testing. This paper summarizes the findings of this exercise and proposes a pragmatic strategy toward our key long-term goals-the incorporation of reliable alternatives to whole-organism testing into regulations and guidance, and a culture shift toward reduced reliance on vertebrate toxicity testing in routine environmental safety assessment. Integr Environ Assess Manag 2016;12:417-421. © 2015 SETAC

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Fish bioconcentration test guidelines generally require that bioconcentration factors (BCFs) are determined at two exposure concentrations. However, recent revisions to the OECD test guideline for bioconcentration testing (TG 305) provide the option to use only one exposure concentration, when justification is provided, although two concentrations may still be required for some regulatory purposes. Recently, this justification has been demonstrated for plant protection product active ingredients. To determine whether this justification has a broader validity for general chemicals, an analysis of 236 BCF studies on general chemicals was conducted. The results presented here again demonstrate that BCF values do not significantly differ between concentrations when more than one concentration is used. This relationship is particularly strong for BCFs ⩾1000L/kg, which is beneficial, since only chemicals with BCFs >2000L/kg may require regulatory action. This analysis therefore provides a data-driven rationale for using the one test concentration approach for general chemical substances and thus could contribute to a substantial reduction in the use of fish in bioconcentration tests.

Fish acute toxicity tests are conducted as part of regulatory hazard identification and risk-assessment packages for industrial chemicals and plant protection products. The aim of these tests is to determine the concentration which would be lethal to 50% of the animals treated. These tests are therefore associated with suffering in the test animals, and Organisation for Economic Cooperation and Development test guideline 203 (fish, acute toxicity) studies are the most widely conducted regulatory vertebrate ecotoxicology tests for prospective chemical safety assessment. There is great scope to apply the 3Rs principles-the reduction, refinement, and replacement of animals-in this area of testing. An expert ecotoxicology working group, led by the UK National Centre for the Replacement, Refinement and Reduction of Animals in Research, including members from government, academia, and industry, reviewed global fish acute test data requirements for the major chemical sectors. The present study highlights ongoing initiatives and provides an overview of the key challenges and opportunities associated with replacing, reducing, and/or refining fish acute toxicity studies-without compromising environmental protection.

Disclaimer:The views and statements expressed in this paper are a reflection of the workshop on "Investigating Endocrine Disrupting Properties in Fish and Amphibians: Opportunities to Apply the 3Rs" (held 25 February 2020 in London, UK) as summarised by the authors. The views or statements expressed in this publication do not necessarily represent the views of the organizations to which the authors are affiliated, and those organizations cannot accept any responsibility for such views or statements. Acknowledgments:We are extremely grateful to all 51 workshop delegates for their participation and valuable input. The workshop was made possible by financial and inkind support from the NC3Rs and HESI.