الفهرس 
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Abstract
The pollution of the aquatic environment with heavy metals has become a serious health problem during recent years. Untreated municipal and industrial wastes together with inputs from the atmosphere are the major sources of heavy metal pollution, especially in areas near to industrial and agricultural discharges that are considered the major source of heavy metal poisoning of fish. Lead (Pb) and cadmium (Cd) are among the most dangerous of these heavy metals. Heavy metals are treated with special care and great importance due to their highly toxic effects on fish as it inhibits growth, survivability and reproduction.
A total number of 150 Oreochromis niloticus were collected from fish farms at Porg El-Arab (Alexandria),El- Abbassa and Sahl El-Hesania (Sharkia), three times per season, analysis for presence of lead and cadmium in the liver, kidney and muscle of fish. The water samples were collected from the same places and times, analysis for presence of lead and cadmium.
Screening of the levels of lead and cadmium in water samples in the four seasons at the previously mentioned fish farms revealed that the mean values of lead and cadmium were the lowest significant in winter season compared to other seasons. These metals concentration were highly significant increase in fish farm at Sahl El-Hesania compared to other fish farms. The mean values of lead and cadmium were the highest significant in summer season in fish farm at Sahl El-Hesania compared to other season and other fish farms. The levels of lead and cadmium in water samples in the four seasons from fish farms at Porg El-Arab (Alexandria), El- Abbassa and Sahl El-Hesania (Sharkia) are higher than the permissible limits& so constitute potential health hazard.