Free-range chicken eggs as a bioindicator of dioxin contamination in Vietnam, including long-term Agent Orange impact

PCDD/Fs contamination of free-range chicken eggs and soils from private Vietnam households was studied. The possibility of using free-range eggs as bio-indicators of dioxin contamination was considered as the soil-chicken-egg exposure pathway is considered to be the most sensitive exposure pathway of dioxins in soils to humans. A large territory from Dong Nai province in the south to Lao Cai province in the north was covered by the research. All analyses were performed by HRGC-HRMS method. PCDD/Fs levels in eggs from the majority of southern households exceeded the EC limit for eggs and egg products (2.5 pg WHO-TEQ2005 g−1 lipid). Total TEQs ranged from 0.4 to 361 pg WHO-TEQ2005 g−1 lipid in eggs and from 0.1 to 1272 pg WHO-TEQ2005/g in soil. 2,3,7,8-TCDD contribution was statistically significantly higher in both eggs and soils in sprayed with Agent Orange areas, indicating its long-term impact. In order to assess within site variation, a total of 62 individual eggs from 14 private households were analyzed. Mean relative standard deviation of total TEQ values in individual eggs within the separate households was 27%. Rather good correlation of PCDD/Fs concentration in eggs and respective soils was observed for all dioxin congeners and for hexa- and hepta-furans (except for 1,2,3,7,8,9-HxCDF). Higher bioaccumulation for lower chlorinated congeners was confirmed. The current study of using eggs as bio-indicators for large POPs contaminated sites may be suggested as a policy approach to evaluate human exposure to dioxin/POPs contaminated sites for known or suspected contaminated areas.