Acute toxicity of sodium dichromate to goldfish, Carassium auratus

Chromium is a common contaminant in ground water and surface water. It also enters into the environment as effluent from several industrial operations such as tanneries, ceramic, mining, dying, electroplating, metal finishing, printing and pharmaceutical industries. Chromium exists in the environment in divalent, trivalent and hexavalent forms, but the hexavalent form is more toxic than the other forms. Release of chromium containing effluents from the industries into the aquatic environment poses a major threat to the growth and survival of icthyofauna. In this study we evaluated the dose-response and time-response relationships of chromium (sodium dichromate) toxicity to goldfish. The study was conducted using 96-hour static renewal bioassay, according to the U.S. EPA protocol. Study results indicated that the mortality rate of gold fish increased with increasing concentrations of chromium and exposure time periods. LC50 values of 187.99 +/- 5.42 mg/L, 124.7 +/- 5.68 mg/L, 107.04 +/- 4.32 mg/L and 85.7 +/- 4.89 mg/L were computed for 24 h, 48 h, 72 h and 96 h of exposure respectively. In summary, these data indicate that the toxicity of sodium dichromate to Carassius auratus fish is both concentration- and time-dependent.