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The occurrence of some carcinogenic metals; Cu, Ni, Pb and Cd was investigated in sediment samples collected from 12 stations at Great Bitter and Timsah lakes. In the same time, two of the most famous edible bivalve species (Ruditapes decussatus and Paratapes undulatus) live buried in these sediments were chosen for measuring the same metals within their edible tissues in order to investigate the permissibility limits for human consumption. The bio-available forms of these metals were measured in the bulk sediments and the finest fractions (Ø3, Ø4 and Ø5) and in the edible tissues (flesh) of the selected bivalve individuals using a flame atomic absorption spectrophotometer (AAS). The finest fraction (Ø5) recorded the highest averages of most carcinogenic metals at Great Bitter and Timsah lakes with significant occurrences of Cd at both lakes. Carcinogenic Cd in the edible tissues of P. undulates and R. decussatus showed neglected low contents at the Great Bitter and Timsah lakes in spite of its very high contents in the surrounding sediment layer. Ni, Cu, and Pb averages in the edible tissues of P. undulates at the Great Bitter lake were 1.32, 0.23 and 0.37 μg/g wet wt. respectively. The averages of Ni, Cu and Pb in R. decussatus at Timsah Lake, were; 1.30, 0.24 and 0.95 μg/g wet wt. and in P. undulates were; 0.79, 0.14, and 1.15 μg/g wet wt. respectively. Bio-sediment accumulation factor (BSAF) in the different bivalve species at the Great Bitter and Timsah lakes were much lower than unity (<<<1.0) indicating that the bivalves tend to accumulate their needs only from the surrounding environment. Finally, the investigated metals in the edible tissues of the different bivalve species are within the permissible safe limits for human consumption except for Pb that exceeds these limits and showed a slight hazard to health risk. [ABSTRACT FROM AUTHOR]