Toxicity study of diethyl phthalate on Clarias gariepinus fingerlings
Diethyl Phthalate (DEP) is used as a plasticizer, a detergent base, in aerosol sprays, as a perfume binder and after shave lotion. It is known to be a contaminant of fresh water and marine ecosystem. Therefore, a study was designed to determine the acute toxicity effects of DEP on a fresh water fish, Clarias gariepinus fingerlings. The fish was treated with 50, 75, 100 and 150 μg/l. DEP was dissolved in distilled water to determine the LC50. There was 100% mortality observed in 150 μg/l. The LC50 of DEP was estimated at log toxicant concentration as 2.217, 2.734, 3.435 and 3.931 μg/l at 24, 48, 72, 96 h and 1.871μg/l for the total death. This shows that the impacts are dose and time dependent with respect to marked reduction in mortality rate. At sub-lethal concentrations of the test substance at 30, 40, 60 and 80 μg/l in a renewal bioassay system, the water and the test compound were changed intermittently. One group was maintained as a control in dechlorinated water. There was significant difference (P < 0.05) in brain and muscle AchE activity compared to the control. The liver ACP activity was statistically significant (P < 0.05) at day 15 while the muscle ACP in other treatment groups showed no significant difference (P > 0.05). Liver AST showed no significance in all treated groups (P > 0.05) and liver ALT activity was statistically significant (P < 0.05) at day 30 only. The haematological parameters (HB, PCV, RBC and WBC) carried out showed that haemoglobin and erythrocyte levels estimated in all treatment groups to the duration of exposure showed no significant difference (P > 0.05) compared to the control. The park cell volume showed a significant difference (P < 0.05) at day 30 only. The leucocyte count throughout the exposure period showed that the mean values are statistically significant (P < 0.05) at day 15 only compared to the control. The mean cell volume (MCV) showed a significant difference at day 15 (P < 0.05) whereas mean cell haemoglobin (MCH) and mean cell haemoglobin concentration (MCHC) showed no significant difference (P > 0.05) throughout the exposure period. No significant difference was seen between the lymphocytes and the neutrophils. In day 0 and 15 only, the monocytes and the lymphocytes showed a significant difference (P < 0.05). The gill damages indicated toxicity of DEP with raised lamella, oedema of the lamella epithelia, loss of lamellar epithelium, mild oedema and raising of the filament. The liver damage showed focal necrosis and vacuolization, hepatocyte degeneration in the liver. These alterations may have long term effects on that that are continuously exposed to DEP in the aquatic environment.
Keywords: Diethyl phthalate, Clarias gariepinus, acute toxicity, sublethal toxicity, heamatology, biochemical, histopathology, environment.