Transport and bioaccumulation of polychlorinated dibenzo-p-dioxins and dibenzofurans at the Bien Hoa Agent Orange hotspot in Vietnam

Abstract

The Bien Hoa airbase (south of Vietnam) is known as one of the Agent Orange hotspots which have been seriously contaminated by Agent Orange/dioxin during the Vietnam War. Hundreds of samples including soil, sediment and fish were collected at the Bien Hoa Agent Orange hotspot for assessment of the environmental contamination caused by dibenzo-p-dioxins and polychlorinated dibenzofurans (PCDD/Fs). The toxicity equivalency quotient (TEQ) concentration of PCDD/Fs in soil and sediment varied from 7.6 to 962,000 and 17 to 4860 pg/g dry wt, respectively, implying very high contamination of PCDD/Fs in several areas. PCDD/F levels in fish ranged between 1.8 and 288 pg/g TEQ wet wt and was generally higher than advisory guidelines for food consumption. 2,3,7,8-Tetrachlorinated dibenzo-p-dioxins (2,3,7,8-TCDD) contributed 66-99 % of TEQ for most of the samples, suggesting 2,4,5-trichlorophenoxyacetic acid (2,4,5-T) from Agent Orange as the major source of the contamination. The vertical transport of PCDD/Fs was observed in soil column with high TEQ levels above 1000 pg/g dry wt (Vietnamese limit for necessary remediation activities- TCVN 8183:2009 (2009)) even at a depth of 1.8 m. The vertical transport of PCDD/Fs has probably mainly taken place during the "Ranch Hand" defoliant spray activities due to the leaks and spills of phenoxy herbicides and solvents. The congener patterns suggest that transports of PCDD/Fs by weathering processes have led to their redistribution in the low-land areas. Also, an estimate for the total volume of contaminated soil requiring remediation to meet Vietnamese regulatory limits is provided.

Correlating Biodegradation Kinetics of 2,4-Dichlorophenoxyacetic Acid (2,4-D) and 2,4,5-Trichlorophenoxyacetic Acid (2,4,5-T) to the Dynamics of Microbial Communities Originating From Soil in Vietnam Contaminated With Herbicides

“…Soils and sediments in the vicinity of Bien Hoa airbase were polluted with high concentrations of herbicides and dioxins due to large spills (Dwernychuk et al, 2002;Mai et al, 2007). The toxicity equivalent (TEQ) concentration of polychlorinated dibenzo-pdioxins and polychlorinated dibenzofurans (PCDD/Fs) in soil and sediment varied from 7.6 to 962,000 and 17 to 4,860 ng/kg dry weight, respectively (Thuong et al, 2015). Since the end of Operation Ranch Hand in 1971, there has been an increasing concern about the human and environmental health effects associated with these spills.…”

A Review of Public Health in Vietnam: 50 Years after Agent Orange was Sprayed

“…A recent publication by Thuong et al 2015 provided in-depth analyses of the contamination of Bien Hoa Airbase to include both the loading and storage sites for RANCH HAND missions, and the PACER IVY site, where 11,000 drums of Agent Orange were re-drummed and shipped to Johnston Island in April 1972 [12,24]. The TEQ concentrations of PCDD/Fs in soils and sediments varied from 7.6 to 962,000 pg/g and 17 to 4,860 pg/g (ppt), respectively [24].…”

A Comprehensive Evaluation of Dioxins and Furans Occurrence in River Sediments from a Secondary Steel Recycling Craft Village in Northern Vietnam

“…Additionally, sediment samples collected from e-waste recycling sites in Bui Dau village, My Hao district, and Hung Yen province have revealed the presence of dioxin compounds [21]. Furthermore, sediment near the Bien Hoa airbase, a known hotspot for Agent Orange contamination, has also been found to be contaminated with dioxins [22]. The study of sediment in the Saigon River, the Mekong River, and coastal sediment near Vung Tau in southern Vietnam also revealed the presence of dioxins [23].…”