Global Monitoring Program for Understanding the Fate of Persistent Man-Made Chemicals in the Tropical Environment

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In order to elucidate the comprehensive behavior of persistent organochlorines such as PCBs, DDTs and BHCs, the present investigation has been undertaken in the terrestrial and coastal environments of tropical and subtropical Asia. Beside this, the fate of organochlorines in the tropical environment and its global implications are also described in the present study, based on the survey of western North and South Pacific and Indian oceans. Consequently, the following results were obtained :1) The environmental samples from tropical Asia revealed more prominent contamination by organochlorine insecticides rather than PCBs which were mainly used for industrial purposes. However, considerable PCB contamination was observed in various samples from urban areas, suggesting the gradual widespread usage of PCBs even in tropical countries.2) It was generally observed that the residue levels of organochlorine insecticides in soil and sediments were found to be much lower in tropical regions than … More in temperate ones, whereas those levels in air were comparable in both regions. According to the application test of BHC in the tropical paddy field and flux modeling of it in watershed, it was noted that the applied insecticides were rapidly transported to atmosphere to a large extent, suggesting the tropical regions have a greater impact on the global environment.3) At the same time, considerable BHC levels were recorded in the oceanic waters off Norther Pacific and polar regions, far away from the source. The calculations of mass transfer of BHCs between air and water revealed that BHC has a strong tendency to transfer from air to water, implying that northern North Pacific and nearby polar waters may play a role as one of the sink for such contaminants.On the whole, it could be said that large quantities of persistent man-made chemicals used in the tropics are released into the atmosphere. They disperse through "long-range atmospheric transport" on global terms and ultimately deposit into the sink like northern North Pacific. Such a sink should also be considered in ecotoxicological perspective as they may play a major role in the bioaccumulation of residues and toxic manifestation to resident marine organisms. Less