Marked elevation of dioxin associated with the herbicide Agent Orange was recently found in 19 of 20 blood samples from persons living in Bien Hoa, a large city in southern Vietnam. This city is located near an air base that was used for Agent Orange spray missions between 1962 and 1970. A spill of Agent Orange occurred at this air base more than 30 years before blood samples were collected in 1999. Samples were collected, frozen, and sent to a World Health Organization--certified dioxin laboratory for congener-specific analysis as part of a Vietnam Red Cross project. Previous analyses of more than 2200 pooled blood samples collected in the 1990s identified Bien Hoa as one of several southern Vietnam areas with persons having elevated blood dioxin levels from exposure to Agent Orange. In sharp contrast to this study, our previous research showed decreasing tissue dioxin levels over time since 1970. Only the dioxin that contaminated Agent Orange, 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), was elevated in the blood of 19 of 20 persons sampled from Bien Hoa. A comparison, pooled sample from 100 residents of Hanoi, where Agent Orange was not used, measured blood TCDD levels of 2 parts per trillion (ppt). TCDD levels of up to 271 ppt, a 135-fold increase, were found in Bien Hoa residents. TCDD contamination was also found in some nearby soil and sediment samples. Persons new to this region and children born after Agent Orange spraying ended also had elevated TCDD levels. This TCDD uptake was recent and occurred decades after spraying ended. We hypothesize that a major route of current and past exposures is from the movement of dioxin from soil into river sediment, then into fish, and from fish consumption into people.

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Soil samples were collected from Changwon and Masan Cities, Korea, and analyzed for polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDDs/DFs). Nearly all tetra- through octachlorinated PCDDs/DFs including the 17 2,3,7,8-substituted PCDDs/DFs were detected in all samples. Total concentrations of PCDDs/DFs and of 2,3,7,8-tetrachlorinated dibenzo-p-dioxin (TeCDD) equivalents (TEGs) in soils ranged from 35 to 121,400 pg/g, dry weight, and from 0.2 to 3720 pg of I-TEQ/g, respectively. On the basis of guidelines for TEQ concentrations established in Germany and the United States, 9 of 23 soil samples (39% of the total samples analyzed) could not be expected to pose human health hazards. The rest of 61% of soils need measures such as investigations of source identification, soil decontamination, and/or soil removal. Total concentrations of PCDDs/DFs were greater at or near four industrial sites, which are concerned with the steel industry, petrochemical-related industry, and industrial waste incineration, than other areas. This indicates the presence of potential source areas. Soil collected from a site 50 m from an open-burning industrial waste incinerator in an industrial complex was heavily contaminated, containing a total concentration of PCDDs/DFs of 121,400 pg/g, dry weight. PCDDs/DFs were also detected in soils from the top of a 200 m mountain indicating a wide dispersal of PCDDs/DFs by atmospheric transport from point source areas. The congener pattern and relative proportions of PCDFs in soils suggest that commercial PCB preparations such as Kanechlors may be one of the sources. The wide range of PCDD/DF isomers detected in soils from many locations also suggests a multitude of sources, in addition to commercial PCBs, such as incineration of industrial wastes such as car tires, scrap wires, plastics, papers, and emission of automobile exhaust.

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Polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDDs/DFs) were measured in sediments collected from Masan Bay, Korea. Almost all tetra- through octachlorinated PCDDs/DFs were identified, including the 17 2,3,7,8-substituted PCDDs/DFs. Total concentrations of PCDDs/DFs in sediments ranged from 102 to 6,493 pg/g dry weight. Concentrations of 2,3,7,8-tetrachlorinated dibenzo-p-dioxin (TeCDD) equivalents (TEQs) in sediments estimated based on I-TEFs were in the range of 1 to 76 pg/g dry weight. Total concentrations of PCDDs/DFs in Masan Bay sediments were comparable to those reported for the Rhine and Humber Rivers on the North Sea, the Housatonic River in the United States, and some rivers and lakes in Japan and the United Kingdom. A spatial gradient of total concentrations of PCDDs/DFs decreased toward the open sea. Two of the 11 sampling sites near the coastal zone contained relatively great concentrations, suggesting the presence of point sources. The homologue composition of PCDFs in sediments from two highly contaminated locations in Masan Bay was correlated with that of commercial polychlorinated biphenyl (PCB) preparations, such as Kanechlors 300, 400, or 500. The wide range of PCDD isomers and greater concentrations of PCDDs than of PCDFs at certain locations suggest that, in addition to technical PCB preparations such as Kanechlors, other sources, like solid waste incineration, uncontrolled trash burning, and pentachlorophenol, have contributed to the contamination.