The study on the source of environmental pollution by dioxins in Vietnam based on the ratio of dioxin-isomers

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The purpose of this study was to clarify the source of environmental pollution by dioxins in Vietnam based on the ratio of dioxin-isomers. Since 2005, the researches were conducted every year for 3 years at herbicide sprayed Cam Chinh commune in Quang Tri province and non-sprayed Cam Phuc commune, Ha Tinh province in Vietnam respectively. As environmental material,27 soils (20 in the sprayed area and 7 in the non-sprayed area) were collected. As human material, 156 breast milk (84 in the sprayed area and 72 in the non-sprayed area) and pooled serum collected from 284 sera (144 in the sprayed area and 140 in the non-sprayed area) were analyzed. As results, dioxin concentration in soil was significantly higher in the sprayed area and in the non-sprayed area. Among isomers, 2,3,7,8-TCDD was also significantly higher in the spared area. In human samples, our result showed that isomers were significantly superior in the sprayed area concentrated on PCDFs rather than PCDDs. Isomers such as 1,2,3,4,6,7,8-HpCDD, 1,2,3,4,7,8-HxCDF, 1,2,3,6,7,8-HxCDF, 1,2,3,4,6,7,8HpCDF and 1,2,3,4,7,8,9-HpCDF were not always similar to those in the non-sprayed area. They were prominent isomers in the sprayed area. Our studies clearly showed that these five isomers were characteristic isomers in the sprayed area which determine a quality or a feature of exposure to dioxin. In conclusion, we revealed areal differences of concentration levels of 2,3,7,8-substituted isomers in human specimen and suggested level differences of the isomers were attributed to a quality or a feature of exposure sources in the area.