Dying for change: A roadmap to refine the fish acute toxicity test after 40 years of applying a lethal endpoint.

The fish acute toxicity test (TG203; OECD, 2019) is frequently used and highly embedded in hazard and risk assessment globally. The test estimates the concentration of a chemical that kills 50% of the fish (LC) over a 96 h exposure and is considered one of the most severe scientific procedures undertaken. Over the years, discussions at the Organisation for Economic Co-operation and Development (OECD) have resulted in changes to the test which reduce the number of fish used, as well as the development of a (potential) replacement test (TG236, OECD, 2013).

Aquatic toxicity tests with substances that are poorly soluble in water and consequences for environmental risk assessment.

Aquatic toxicity tests with substances that are poorly soluble in water have been conducted using different methods, and estimates of toxicity have varied accordingly. The present study illustrates differences in toxicity values resulting from variation in test designs and solution preparation methods, and offers guidance on the best way to conduct these tests. Consequences for environmental risk assessment and classification are also discussed.

Introduction of moribund category to OECD fish acute test and its effect on suffering and LC50 values.

It has become common practice in many laboratories in Europe to introduce the criterion "moribund" to reduce the suffering in fish acute lethality tests. Fish with severe sublethal symptoms might be declared moribund and are removed from the test as soon as this occurs (premature discontinuation of experiment). Moribund fish affect main study outcomes as the median lethal concentration (LC50) derived on fish declared as moribund may be lower than the conventional LC50.

Can we reduce the number of fish in the OECD acute toxicity test?

OECD (Organisation for Economic Co-operation and Development) Guideline 203, Fish Acute Toxicity Test, states that the test should be performed using at least five concentrations in a geometric series with a separation factor not exceeding 2.2, with at least seven fish per concentration. However, the efficiency of this design can be questioned, because it often results in only one concentration that causes partial mortality (mortality >0% and <100%).

Environmental effect assessment for sexual endocrine-disrupting chemicals: Fish testing strategy.

Current standard testing and assessment tools are not designed to identify specific and biologically highly sensitive modes of action of chemicals, such as endocrine disruption. This information, however, can be important to define the relevant endpoints for an assessment and to characterize thresholds of their sublethal, population-relevant effects. Starting a decade ago, compound-specific risk assessment procedures were amended by specifically addressing endocrine-disrupting properties of substances.

Multi-criteria decision analysis of test endpoints for detecting the effects of endocrine active substances in fish full life cycle tests.

Fish full life cycle (FFLC) tests are increasingly required in the ecotoxicological assessment of endocrine active substances. However, FFLC tests have not been internationally standardized or validated, and it is currently unclear how such tests should best be designed to provide statistically sound and ecologically relevant results. This study describes how the technique of multi-criteria decision analysis (MCDA) was used to elicit the views of fish ecologists, aquatic ecotoxicologists and statisticians on optimal experimental designs for assessing the effects of endocrine active chemicals on fish.

The chironomid acute toxicity test: development of a new test system.

This paper describes the basis for a water-only acute chironomid toxicity test guideline using first-instar larvae. The method is based on the OECD test guidelines for the acute Daphnia sp. immobilization test and the long-term tests with Chironomus sp.

Determination of vitellogenin kinetics in male fathead minnows (Pimephales promelas).

A lack of knowledge persists concerning the combination of kinetics on protein and mRNA levels of the most commonly used biomarker for estrogenic influences-vitellogenin (VTG). Consequently, male fathead minnows were exposed to 17alpha-ethinylestradiol (EE(2)) for 35 days, followed by an equally long depuration period in a flow-through system. VTG mRNA levels reached a plateau after 3 days of exposure, which remained stable until 3 days after EE(2) removal.

Aquatic toxicity testing of sparingly soluble, volatile, and unstable substances and interpretation and use of data. Task Force of the European Centre for Ecotoxicology and Toxicology of Chemicals.

Aquatic toxicity tests were originally designed for individual compounds that are soluble and stable in water. For sparingly soluble substances that are not toxic at the solubility limit, the issue is whether tests should be performed with insoluble test substance present. Based on a literature evaluation of the physiology of uptake, it was concluded that only the dissolved fraction is available for uptake and that the insoluble test substance may introduce artifacts that aggravate data interpretation.