Experimental studies on the toxicity of certain heavy metals and persistent organic pollutants on the Nile tilapia health

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Abstract

This study was carried out to experimentally assess the acute and chronic effects of heavy metals {HMs; Zn, Cu, and Pb} and the persistent organic pollutants {POPs; Aroclor 1254 (A) and Decabromodiphenyl ether 98% (D)} on bioaccumulation, biochemical parameters and the histology of the Nile tilapia "Oreochromis niloticus". The groups that were exposed to AD10 HMs showed alterations related to each of HMs and ADs groups, such as the reduction in Hb & RBC (related to HMs) and the increase in platelets and WBC (related to ADs). In addition, a significant increase was recorded in ALT, ALP, and glucose and a significant reduction in total protein (related to HMs) was associated with a significant reduction in total bilirubin and an elevation in GGT (related to ADs). Histopathological investigations showed muscle neoplasia indicating early warning for carcinogenic risks. Severe liver focal areas of necrosis and fibrosis were noticed, indicating the destruction of liver cells with an increase in liver enzymes’ levels. Accumulation of hemosiderin in the liver and spleen due to excessive red blood cell destruction (haemolysis) explained the reduction in Hb and RBCs observed in fish groups exposed to HMs and AD10HMs mixtures. Liver & spleen lymphocyte infiltration may be associated with a massive elevation in lymphocytes in HMLC10, ADs & AD10HMLC5 mixtures. Thus, the present work would provide a measurable simulating model for the effects of environmental pollutants by using different chemical mixtures and responsive parameters for many physiological functions and histological structures as biomarkers for toxicity.

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