Exploring Fish Bioassay of Textile Dye Wastewaters and Their Selected Constituents in Terms of Mortality and Erythrocyte Disorders

Acute (4 day) and short-term (7 day) toxicity studies (at 1/5th and 1/10th of LC(50)) of textile dye wastewaters and their selected ingredients (azo dye methyl red and heavy metals Cd, Cu, Ni and Zn) were made on a freshwater fish Gambusia affinis under laboratory conditions. LC(50) value was found to be the lowest in four cases, and the EC(50) value for reduction in erythrocyte counts in the remaining four tests. Thus, the reduction in erythrocyte counts to the 50% level was similar in sensitivity to fish mortality. The short-term toxicity studies revealed significant disorders in erythrocyte morphology (poikilocytosis) and its counts to be the better indices for toxicity monitoring in the absence of fish mortality.