The concentration of some heavy metals (Fe, Zn, Cu, Pb, and Cd) in gills and muscle of Oreochromis niloticus obtained from four khores (El-Madiq, Amada, Tushka, and Dahmit) of Lake Nasser, Egypt during winter (january) and spring (May) 2016  was investigated using atomic absorption spectrophotometry and the histological alterations in these organs were also studied.
The present results indicated that the accumulations of Fe, Zn, Pb, and Cd  exceeded the recommended limit in fish gills. However, the levels of Fe and Zn exceeded the recommended limit in muscles. Cu level was the lowest one in gills and muscles.
Bioaccumulation factor (BAF) listed high score for Fe, Pb, and Cd in gills during the spring season at Dahmit khore. While Fe and Zn listed high score in the muscles of fish at Dahmit khore.
Histopathological alterations recorded in gills of O.niloticus in this study including hyperplasia of the epithelium which led to a fusion of lamellae, epithelial lifting, aleukocytes infiltration and severe necrotic change. On the other hand, muscles of the investigated fish showed severe edema and splitting muscle fibers as a result of the accumulated metals.