Organochlorine residues in soils and ediments from manila and nearby Rovinces, Philippines

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Abstract
Concentrations of DDT and its metabolites (DDTs), HCH isomers (HCHs: hexachlorocyclohex‐anes), chlordane compounds (CHLs), HCB (hexachlorobenzene) were determined in agricultural soils, dumpsite soils, and riverine sediments collected from Manila and its nearby provinces in the Philippines. Relatively low DDT and HCH residue levels were detected in agricultural soil samples examined. These findings reflect the decline in the usage of organochlorine chemicals for agricultural purposes in the Philippines. In the case of the dumpsite soils collected from Smokey Mountain, significant DDT, HCB, and HCH residue levels were detected, which may be attributed to the extensive use of organochlorine chemicals for public health purposes. While marked levels of PCB residues could be due to the PCB‐contaminated industrial wastes dumped in the area. Significant levels of CHLs and DDTs were also observed in Pasig river sediments coming from industrial sources, as the river is used as an internal artery for the transport of raw materials used in the processing and manufacturing of various industrial plants and factories that abound along the river. Although organochlorine residue levels found in agricultural soils and riverine sediments were comparable with other developing tropical countries in Asia, concentrations of some organochlorine residues in non‐agricultural (dumpsite) soils examined in this study were higher than those reported from other countries. This finding underscores the significant contamination of the soils in a major open dumpsite (Smokey Mountain).