Organic Contaminants in the Marine Environment of Manila Bay, Philippines

Organochlorine pesticides (OCs) and polychlorobiphenyls (PCBs) were determined in sediments and oysters' soft tissues (Cassostrea gigas) collected in selected sites of Manila Bay. Overall, the concentration levels were very low. In sediments, PCBs were the compounds present in higher concentrations, with I 13PCB pound congeners averaging 0.69 +/- A 0.46 ng/g (dry weight), followed by I DDT pound averaging 0.53 +/- A 0.28 ng/g and I chlordane pound with 0.26 +/- A 0.28 ng/g. Concentrations measured in oysters averaged 20 +/- A 17 ng/g (dry weight) for I 13PCB pound and were higher than I DDT pound, with 9.5 +/- A 2.4 ng/g, and I chlordane pound, with 3.8 +/- A 3.1 ng/g. No dissolved residues of polar compounds, such as herbicides, and organophosphorous and organochlorine pesticides were found in the bay water. In general, results showed that concentrations of organochlorine pesticide residues, such as DDT, hexachlorocyclohexane, chlordane, lindane, endosulfan, and heptachlor in sediments and oysters were low in comparison with other coastal areas in Asia, although PCB concentrations in oysters were relatively high in some zones of Manila Bay and indicative of loose control of industrial chemical waste discharges into the bay. Nevertheless, current concentrations of persistent organochlorine contaminants in sediments were under threshold effect levels (TELs) and chronic toxic effects are, thus, unlikely to generate impairment of marine biota in Manila Bay.