The soils, tropical climate, and network of canals and rivers of southern Vietnam have created one of the most diverse tropical jungles and intensely cultivated landscapes of Southeast Asia. This paradise has a long h...The soils, tropical climate, and network of canals and rivers of southern Vietnam have created one of the most diverse tropical jungles and intensely cultivated landscapes of Southeast Asia. This paradise has a long history of numerous wars, foreign occupations, and most recently the Second Indochina War (aka the Vietnam War 1965-1972) which defoliated rain forests and ancient wetland mangroves and left behind contaminated soil and sediment hotspots. During this war, the United States (US) military sprayed 80 million liters of Agent Orange contaminated with the dioxin TCDD in a guerrilla war against communist insurgents. Agent Orange was a synthetic plant growth regulator comprised of equal amounts of two herbicides 2,4-dichloro phenoxyacetic acid C8H6Cl2O3 (2,4-D) and 2,4,5-trichlorophenoxyacetic acid C8H5Cl3O3 (2,4,5-T). TCDD, the dioxin, 2,3,7,8-tetrachlorodibenzodioxin (C12H4Cl4O2) was an unintended byproduct of the accelerated combustion process used in the manufacture of herbicides containing 2,4,5-T. Agent Orange has frequently been blamed for soil and sediment contamination and long-term human health problems;however, the true source of harm is the dioxin TCDD. Agent Orange has a short half-life of days and weeks after application to vegetation, and has not been found to persist, after 50 years, in the water or soils of southern Vietnam. However, the half-life of dioxin TCDD depends on where it is deposited and varies from 1 to 3 years on soil surfaces that have been fully exposed to sunlight, to as long as 20 to 50 years or more when buried in tropical subsoils, and more than 100 years in river and sea sediments. Dioxin TCDD was heavily concentrated in the US Air Force bases in Vietnam where the herbicides were stored, loaded on planes and helicopters for aerial spraying, and used extensively around military base perimeter fences as a security measure to prevent surprise attacks. Bien Hoa Air Force base, 40 km northeast of Ho Chi Minh City, continues to be one of the mega-hotspots where after 48 years the dioxin TCDD levels in fish and shrimp are still high and fishing is banned in ponds and lakes adjacent to the airbase. Although expensive, one of the most effective remediation to dioxin TCDD contaminated soils is incineration which is the recommended method of dioxin TCDD disposal.展开更多
Pringle Creek, identified as the source of dioxin/furan (PCDD/F) contamination to a Lake Ontario harbour was remediated in 2008. Surface sediment collected in 2013 near the floodplain remediation was no longer contami...Pringle Creek, identified as the source of dioxin/furan (PCDD/F) contamination to a Lake Ontario harbour was remediated in 2008. Surface sediment collected in 2013 near the floodplain remediation was no longer contaminated (∑<sub>17</sub>PCDD\Fs < 60 pg/g dw), but residual contamination extended downstream to the creek mouth (surface sediment maximum: ∑<sub>17</sub>PCDD\Fs 2900 pg/g dw). Nevertheless, sediment ∑<sub>17</sub>PCDD/F concentrations were lower in 2013 than pre-remediation suggesting that cleaner sediment was being deposited in the creek. Core data confirmed the decrease in sediment contamination through time since the most contaminated sediment was buried. Prior to the development of a remediation strategy for the harbour, the transport of bed-load and suspended sediment contaminated with PCDD/F was assessed. The challenge was the shallow water depth (0.6 m) throughout the creek thereby requiring non-standard sediment traps designed for this study. Suspended sediment collected in traps in 2014 showed residual contamination at the remediated site (∑<sub>17</sub>PCDD\Fs: 380 pg/g dw;TEQ (TEF fish) < 0.6 pg/g), with concentrations increasing with distance downstream mirroring surface sediment: mean ∑17PCDD\Fs concentration for suspended sediment at the creek mouth was 2200 pg/g (SD 260 pg/g dw) indicating PCDD/F contributions to the harbour. However, congener patterns in bottom sediment and suspended sediment near the remediated site and extending about 100 m downstream were similar to background upstream patterns consistent with atmospheric deposition as the source rather than the historical source which indicated that floodplain remedial actions were successful.展开更多
During 2016, following the implementation of a dioxin contamination monitoring in poultry meat (ducks) in a slaughterhouse, a positive sample was found. The investigation identified the wood shavings used as bedding m...During 2016, following the implementation of a dioxin contamination monitoring in poultry meat (ducks) in a slaughterhouse, a positive sample was found. The investigation identified the wood shavings used as bedding material in the duck farm as the possible source of contamination of these animals. In this episode, contamination profiles of higher and lower concentrations, seem to be very similar, being OCDD, OCDF and 1,2,3,4,6,7,8-HpCDD responsible for 74.4% of the total contamination of those animals. The study revealed a reduction of poultry contamination after the removal of the source of contamination, with an average daily depletion percentage level ranging between 1.43% and 4.35%.展开更多
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-chic...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 bioindicators 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.展开更多
文摘The soils, tropical climate, and network of canals and rivers of southern Vietnam have created one of the most diverse tropical jungles and intensely cultivated landscapes of Southeast Asia. This paradise has a long history of numerous wars, foreign occupations, and most recently the Second Indochina War (aka the Vietnam War 1965-1972) which defoliated rain forests and ancient wetland mangroves and left behind contaminated soil and sediment hotspots. During this war, the United States (US) military sprayed 80 million liters of Agent Orange contaminated with the dioxin TCDD in a guerrilla war against communist insurgents. Agent Orange was a synthetic plant growth regulator comprised of equal amounts of two herbicides 2,4-dichloro phenoxyacetic acid C8H6Cl2O3 (2,4-D) and 2,4,5-trichlorophenoxyacetic acid C8H5Cl3O3 (2,4,5-T). TCDD, the dioxin, 2,3,7,8-tetrachlorodibenzodioxin (C12H4Cl4O2) was an unintended byproduct of the accelerated combustion process used in the manufacture of herbicides containing 2,4,5-T. Agent Orange has frequently been blamed for soil and sediment contamination and long-term human health problems;however, the true source of harm is the dioxin TCDD. Agent Orange has a short half-life of days and weeks after application to vegetation, and has not been found to persist, after 50 years, in the water or soils of southern Vietnam. However, the half-life of dioxin TCDD depends on where it is deposited and varies from 1 to 3 years on soil surfaces that have been fully exposed to sunlight, to as long as 20 to 50 years or more when buried in tropical subsoils, and more than 100 years in river and sea sediments. Dioxin TCDD was heavily concentrated in the US Air Force bases in Vietnam where the herbicides were stored, loaded on planes and helicopters for aerial spraying, and used extensively around military base perimeter fences as a security measure to prevent surprise attacks. Bien Hoa Air Force base, 40 km northeast of Ho Chi Minh City, continues to be one of the mega-hotspots where after 48 years the dioxin TCDD levels in fish and shrimp are still high and fishing is banned in ponds and lakes adjacent to the airbase. Although expensive, one of the most effective remediation to dioxin TCDD contaminated soils is incineration which is the recommended method of dioxin TCDD disposal.
文摘Pringle Creek, identified as the source of dioxin/furan (PCDD/F) contamination to a Lake Ontario harbour was remediated in 2008. Surface sediment collected in 2013 near the floodplain remediation was no longer contaminated (∑<sub>17</sub>PCDD\Fs < 60 pg/g dw), but residual contamination extended downstream to the creek mouth (surface sediment maximum: ∑<sub>17</sub>PCDD\Fs 2900 pg/g dw). Nevertheless, sediment ∑<sub>17</sub>PCDD/F concentrations were lower in 2013 than pre-remediation suggesting that cleaner sediment was being deposited in the creek. Core data confirmed the decrease in sediment contamination through time since the most contaminated sediment was buried. Prior to the development of a remediation strategy for the harbour, the transport of bed-load and suspended sediment contaminated with PCDD/F was assessed. The challenge was the shallow water depth (0.6 m) throughout the creek thereby requiring non-standard sediment traps designed for this study. Suspended sediment collected in traps in 2014 showed residual contamination at the remediated site (∑<sub>17</sub>PCDD\Fs: 380 pg/g dw;TEQ (TEF fish) < 0.6 pg/g), with concentrations increasing with distance downstream mirroring surface sediment: mean ∑17PCDD\Fs concentration for suspended sediment at the creek mouth was 2200 pg/g (SD 260 pg/g dw) indicating PCDD/F contributions to the harbour. However, congener patterns in bottom sediment and suspended sediment near the remediated site and extending about 100 m downstream were similar to background upstream patterns consistent with atmospheric deposition as the source rather than the historical source which indicated that floodplain remedial actions were successful.
文摘During 2016, following the implementation of a dioxin contamination monitoring in poultry meat (ducks) in a slaughterhouse, a positive sample was found. The investigation identified the wood shavings used as bedding material in the duck farm as the possible source of contamination of these animals. In this episode, contamination profiles of higher and lower concentrations, seem to be very similar, being OCDD, OCDF and 1,2,3,4,6,7,8-HpCDD responsible for 74.4% of the total contamination of those animals. The study revealed a reduction of poultry contamination after the removal of the source of contamination, with an average daily depletion percentage level ranging between 1.43% and 4.35%.
文摘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 bioindicators 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.
