A Re-Examination of the Toxicity Test for Water Pollutants

In toxicity tests carried out in Japan, adult or young adult fish having relatively stable tolerance and relatively low sensitivity to various toxicants are usually used. However, in order to preserve the ecosystem, fish in the early stage of life, which are more sensitive to toxicants than adult or young adult fish, should be used as test organisms in the toxicity test. Medaka in the early stage of life were therefore exposed to 0.1 ppm Cd solution and their resistance to Cd toxicity was examined. As a result it was shown that resistance to Cd toxicity in medaka of early stage of life was steady from seven to twenty days after hatching. It is therefore suggested that medaka fry could be used as a test organism in toxicity tests.