Toxicity studies of nonylphenol and octylphenol: hormonal, hematological and biochemical effects inClarias gariepinus

Abstract

Among the numerous chemicals discharged into aquatic ecosystems, nonylphenol (NP) and octylphenol (OP) have been shown to have a potent effect on the endocrine system of fish; this issue has been clearly dealt with in several studies. The objective of this study was to assess and compare the general toxicity of these estrogenic chemicals individually on Clarias gariepinus. Fish were exposed to different concentrations of both NP and OP (250, 500, 750 and 1000 μg l(-1) ) under semi-static conditions for a period of 7 days. The adverse effect was evaluated with use of blood cell counting, hemoglobin (Hb), hematocrit (HCT), hematimetric indices, bilirubin, protein, glucose, serum transaminases, serum phosphatases, lactate dehydrogenase and cortisol. The results showed a clear indication of anemia, increases in leukocyte count and bilirubin content and a reduction in plasma protein levels with higher concentrations of both the toxicants compared with controls. Furthermore, with all the concentrations the inevitable increase in serum cortisol and plasma glucose showed primary and secondary stress responses. Moreover, probable tissue damage gave rise to a series of fluctuations of enzyme levels at lower concentrations, but a decrease with higher concentrations showed the severity of the effect. Depending on the parameters examined, OP had a relatively greater effect than NP. Overall, these two chemicals seemingly affected hematology and the activity of some enzymes, leading to serious impairment of the metabolism and physiology of C. gariepinus.