Applying the 3Rs in fish acute toxicity testing

Fish acute toxicity studies are the most widely conducted test in ecotoxicology and cause severe suffering, with many thousands of animals used worldwide each year. They are used to determine the Lethal Concentration of a substance that causes death in 50% of the test population (LC50) during short-term exposure – over hours or days – and are the only standardised fish test where death is the intended endpoint. They are currently required to meet global regulations across many chemical sectors before products can be marketed, including agrochemicals, biocides, and industrial chemicals.

Two of our in-house data analysis projects, supported by expert working groups, have led to recommendations on ways to replace, reduce and refine fish acute toxicity studies. Utilising QSARs to predict fish acute toxicity of pesticide metabolites explored the potential to use computational methods to replace the animal tests.  Applying the threshold approach in fish acute toxicity studies developed a framework which can reduce the number of fish used by approximately 40% and decrease the suffering of test animals.

We are currently preparing a cross-sector paper with the NC3Rs Ecotoxicology Working Group, on key opportunities to apply the 3Rs in fish acute testing. This focuses on accelerating the acceptance of alternative approaches; reducing the number of tests required (e.g. by the waiving of studies based on low expected exposure levels and/or reduced number of test species); and refining practices within mandatory in vivo studies (e.g. through use of evident toxicity rather than death as an endpoint). Briony Labram presented a summary of this paper at SETAC SciCon 2020, which can be accessed below.

Strategies to avoid acute toxicity testing of pesticide metabolites in fish.
Guidance to reduce and refine fish acute toxicity testing.
Watch our presentation from SETAC SciCon 2020 on the outcomes of our expert working group.