Fish Embryo Acute Toxicity (FET) Test (OECD TG 236)
The Fish Embryo Acute Toxicity (FET) Test according to OECD TG 236 is an alternative acute toxicity assay designed to evaluate the effects of chemicals on early developmental stages of fish, typically zebrafish (Danio rerio) embryos. This test provides rapid, ethically refined information on acute toxicity without the use of fully developed fish.
In the study, fertilized fish embryos are exposed to a range of test substance concentrations under controlled laboratory conditions for up to 96 hours post-fertilization. Key endpoints assessed include coagulation, lack of somite formation, non-detachment of the tail, and absence of heartbeat, which are indicative of lethal effects during early development.
The primary outcome is the determination of concentration–response relationships and the median lethal concentration (LC₅₀), representing the concentration causing mortality in 50% of the embryos. Sublethal developmental abnormalities can also be recorded as supportive information.
This test is widely used for acute hazard identification and environmental risk assessment of chemicals, providing a rapid and reliable alternative to traditional fish acute toxicity tests.
