Conventional Test Method:

Fish Acute Toxicity (OECD TG 203)

Alternative Test Method:

Name & Description:
Upper Threshold Concentration (UTC) Step-Down Approach
(a tiered testing strategy to be implemented with OECD TG 203)

Algae and daphnia (crustaceans) are exposed to the test compound to determine EC50 values (growth inhibiting concentration for algae; immobilizing concentration for daphnia). The lowest EC50 is labeled the "Upper Threshold Concentration" (UTC). Fish are then exposed to the UTC; if no fish die then hazard classification of the compound is based on the EC50. If there is mortality then the compound is tested further using the fish acute toxicity test to determine the lethal concentration (LC50) in fish.

Validation Status:
EU: Endorsed as a valid testing strategy by ESAC
Regulatory Status:
EU: Accepted for the assessment of acute aquatic toxicity for hazard classification (2006)
Effect or Potential Effect on Animal Use:
(Reduces the number of fish used by 65%)
  • ECVAM (2006) ESAC Statement on the scientific validity of the upper threshold concentration (UTC) step-down approach - A new testing strategy to reduce the use of fish in acute aquatic toxicity testing.
  • Hutchinson T.H., Barrett S., Buzby M., Constable D., Hartmann A., Hayes E., Huggett D., Länge R., Lillicrap A.D., Straub J.O. and Thompson R.S. (2003) A strategy to reduce the numbers of fish used in acute ecotoxicity testing of pharmaceuticals. Environmental Toxicology & Chemistry 22(12):3031-3036.
  • Jeram S., Riego Sintes J.M., Halder M.K., Baraibar Fentanes J., Sokull-Klüttgen B. and Hutchinson T.H. (2005) A strategy to reduce the use of fish in acute ecotoxicity testing of new chemical substances notified in the European Union. Regulatory Toxicology and Pharmacology 42(2):218-224.
  • OECD (2010) Short Guidance on the Threshold Approach for Acute Fish Toxicity, Series on Testing and Assessment No. 126.
Information Last Reviewed:
May 2012