Organochlorine pesticides and heavy metals in fish reared in treated sewage effluents and fish grown in farms using polluted surface waters in Egypt

In a full scale experimental study, raw sewage from the City of Suez, Egypt was treated using a stabilization pond system. Fish grown in the treated sewage was compared with fish from one of the farms which receives contaminated surface water in Lake Manzala. Organochlorine pesticides were detected at higher levels in fish from Lake Manzala farms, than in fish reared in the treated sewage of the City of Suez. The highest levels were due to p,p'DDT and its metabolites, followed by Lindane and HCB. Furthermore, the concentrations of Pb and Cd were significantly higher in the fish from the Lake Manzala farm, than in the fish from Suez. In addition, the concentration levels of Pb and Cd in the fish from Lake Manzala exceeded the international contaminant limits for human consumption. In general, fish grown in this region have high levels of pesticides and metal contaminants. It is interesting to note that in spite of possible cultural bias against fish grown in treated sewage effluents, have lower levels of toxic chemicals than some of the marketed fish, harvested from polluted surface waters.