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Testing chemicals for endocrine disruption using fewer fish

Head shot of Dr Ioanna Katsiadaki

A 50 per cent reduction in fish using the three-spined stickleback to test for harmful effects of chemicals. An endocrine disruptor is a term given to chemicals that, when absorbed into the body, either mimic or block hormones. 

Some chemicals that are released into the environment can have this harmful effect, particularly on the sexual development of humans and other wildlife.

A test that studies changes in the sexual development of fish is currently used to indicate whether a chemical has the potential to cause harm. International guidelines state that typically 800 fish should used per chemical when using zebrafish, the Japanese medaka and the three-spined stickleback.

NC3Rs-funded researcher, Dr Ioanna Katsiadaki, Cefas, has identified that this number can be reduced by 25% in any of these fish, which has lead to a change in the guideline. However, by using the stickleback exclusively for this test, her research shows this number could be reduced by 50% to just 400 fish per test chemical.


OCED (2011). Test No. 234: Fish Sexual Development Test. OCED Guidelines for the testing of Chemicals, Section 2. OCED Publishing.