Environmental occurrence of organochlorines in the east coast of Thailand

The measurements of organochlorine pesticides in mussels and oysters collected along the east coast of Thailand indicate that DDTs, chlordanes (CHLs), hexachlorocyclohexanes (HCHs) and hexachlorobenzene (HCB) are the main organochlorine residues. The results of the study revealed that DDT residues were present in the highest concentration in green mussels and oysters, followed by CHLs, HCHs, and HCB. However, the residue levels in the present study were much lower than those found elsewhere in the tropical coastal water of Asia. Pollychlorinated biphenyls (PCBs) were present also in high concentrations in urban and industrial areas. It is interesting that tetra-, penta-, hexa- and hepta-chlorinated isomers were the predominant homologues in both the mussel and oyster samples. The PCB profile in the sediment column from the study area, reflects the active use of PCBs along the east coast of Thailand during the period of 1972-1992. Considering the low levels of organochlorine pesticides (OCs) and PCBs in green mussels and oysters found in this study, the contamination from these organic pollutants in the study area is not particularly serious in the view of human health and ecosystem perspectives.