Levels of polychlorinated dioxins/furans (PCDD/PCDF) in selected environmental samples (soils, sediments, fish, and farm animals) were analyzed from the area of Phong My commune (Thua Thien-Hue province, Vietnam). This area was affected by Agent Orange spraying during the Vietnam war (1968–1971). Whereas PCDD/PCDF content in soil and sediment samples is relatively low and ranges between 0.05 and 5.1 pg WHO-TEQ/g for soils and between 0.7 and 6.4 pg WHO-TEQ/g for sediments, the PCDD/PCDF content in poultry muscle and liver in most cases exceeded the maximum permissible limit of dioxin content per unit fat mass. In some cases of soil and sediments samples, 2,3,7,8-TCDD represented more than 90% of the total PCDD/PCDF, which indicates Agent Orange as the main source.
The potential for TCDD contamination in Vietnam is a consequence of the war (1962–1971), during which the US Army forces used about 72 million litres of phenoxy and other herbicidal agents [
The concentrations of TCDD as high as 1000 mg/kg were found in soil and sediment samples more than 30 years after Agent Orange sprays in most affected areas of Vietnam. Elevated concentrations were also identified in foods and wildlife [
Atmospheric deposition leads to contamination of surface water and sediments, soil, and surface of plants and thus represents a significant point of entry into the food chain. Owing to their lipophilic character, dioxins are capable of bio-accumulation in adipose tissues of animals within both terrestrial and aquatic food chains, and subsequently also of people. Moreover, several studies have demonstrated association between concentrations of dioxins in fish and molluscs and concentrations in the environment where they live [
Various adverse effects of dioxins on human health have been reported including: cancer risk, immune deficiency, reproductive and developmental abnormalities, central and peripheral nervous system pathology, endocrine disruption, decreased pulmonary functions and bronchitis, altered serum testosterone level, eyelid pathology, nausea, vomiting, loss of appetite, skin rashes, hypertrichosis, liver damage, elevated serum cholesterol and triglycerides, and enamel hypomineralization of permanent first molars in children [
In the case of Vietnam, unambiguous sources of contamination (so-called hot spots), such as former depots of chemicals and air bases, were identified and their contamination levels were precisely determined and assessed [
Sampling was conducted in the postconflict area of Phong My commune (Figure
Map of Thua Thien-Hue province showing the target area of Phong My commune.
The sampling area is shown in Figure
Map of sampling area in Phong My commune.
The samples were analyzed in the Czech Republic division of ALS laboratory. An ALS standard analytical procedure, according to the United States Standard EPA 1613 [
After preconcentration and spiking with the standard solution, a fraction of the final extract was analyzed by HRGC-HRMS (Double Gas chromatograph 6890N, HRMS Finnigan MAT 95 XP, and Gas chromatograph Trace GC Ultra, HRMS DFS Thermo Electron Corporation). The gas chromatograph was equipped with a TriPlus autosampler. The separation of each PCDD/PCDF was ensured by a column with polar stationary phase and the detection was carried out by a mass spectrometer working in the MID operating conditions with high resolution
The ALS laboratory is accredited by the Czech Accreditation Institute for a comprehensive range of analyses (testing laboratory number 1163), according to the international norm EN ISO/IEC 17025:2005. The quality of dioxin analysis at ALS laboratory was also verified by the participation in international interlaboratory studies during 2006–2009 when collected samples were analysed there (see Table
Overview of international interlaboratory studies—determination of PCDD/F-TEQ in environmental matrices.
Name of study | Implementer | Lab code | Matrix | TEQ | ALS value (ng/g) or (pg/uL) | Refer. value (ng/g) or (pg/uL) |
|
---|---|---|---|---|---|---|---|
International Interlaboratory Study IIS-01 on sludge samples, 2006 | Luc Levert, M.Sc. Chimiste Chef de division Matériaux de Reference, Centre d'expertise en analyse environnementale du Québec, Canada | 425 | Sludge 1 | Lower bound | 0.0197 | 0.0179 | NA |
Upper bound | 0.0197 | 0.0179 | |||||
Sludge 2 | Lower bound | 0.0103 | 0.0101 | ||||
Upper bound | 0.0103 | 0.0101 | |||||
Solution | Lower bound | 86.5 | 85.8 | ||||
Upper bound | 86.5 | 85.8 | |||||
|
|||||||
International sediment exchange for tests on organic contaminants, Exchange Programme (SETOC), 2006, I.Q | SETOC-Wepal |
ECCM (841) | Sediment 1 | Lower bound | 0.0233 | 0.0216 | NA |
Upper bound | 0.0233 | 0.0216 | |||||
Sediment 2 | Lower bound | 0.0430 | 0.0312 | ||||
Upper bound | 0.0430 | 0.0312 | |||||
Sludge 3 | Lower bound | 0.0450 | 0.0424 | ||||
Upper bound | 0.0450 | 0.0424 | |||||
Soil 4 | Lower bound | 0.0864 | 0.142 | ||||
Upper bound | 0.105 | 0.142 | |||||
|
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11th round of the International Intercalibration Study, 2006 (in cooperation with Wepal-SETOC) | Profesor Bert van Bavel, Chairman and Coordinator of International Intercalibration Studies, Dyltabruk, Sweden | 153 | Ash A | Lower bound | 0.179 | 0.151 | 0.74 |
Upper bound | 0.179 | 0.151 | |||||
Ash B | Lower bound | 0.343 | 0.333 | 0.32 | |||
Upper bound | 0.343 | 0.333 | |||||
Ash C | Lower bound | 0.196 | 0.192 | 0.21 | |||
Upper bound | 0.196 | 0.192 | |||||
Sediment A | Lower bound | 0.0233 | 0.0233 | −0.03 | |||
Upper bound | 0.0233 | 0.0233 | |||||
Sediment B | Lower bound | 0.0356 | 0.0340 | 0.45 | |||
Upper bound | 0.0356 | 0.0340 | |||||
Sludge C | Lower bound | 0.0450 | 0.0445 | −0.04 | |||
Upper bound | 0.0450 | 0.0445 | |||||
Soil D | Lower bound | 0.162 | 0.151 | 0.69 | |||
Upper bound | 0.162 | 0.151 | |||||
Solution R | Lower bound | 83.7 | 82.2 | 0.17 | |||
Upper bound | 83.7 | 82.2 | |||||
|
|||||||
12th round of the International Intercalibration Study, 2007 (in cooperation with Wepal-SETOC) | Profesor Bert van Bavel, Chairman and Coordinator of International Intercalibration Studies, Dyltabruk, Sweden | 153 | Ash A | Lower bound | 2.97 | 2.90 | 0.24 |
Upper bound | 2.97 | 2.90 | |||||
Ash B | Lower bound | 1.06 | 1.07 | 0.04 | |||
Upper bound | 1.06 | 1.08 | |||||
Ash C | Lower bound | 0.257 | 0.268 | −0.18 | |||
Upper bound | 0.257 | 0.269 | |||||
Sediment A | Lower bound | 0.0526 | 0.0600 | −0.94 | |||
Upper bound | 0.0526 | 0.0600 | |||||
Sediment B | Lower bound | 0.0229 | 0.0270 | −0.78 | |||
Upper bound | 0.0239 | 0.0270 | |||||
Sediment C | Lower bound | 8.67 | 9.05 | −0.09 | |||
Upper bound | 8.67 | 9.05 | |||||
Sludge D | Lower bound | 0.00192 | 0.0029 | −0.72 | |||
Upper bound | 0.00279 | 0.0032 | |||||
Solution | Lower bound | 25.1 | 22.1 | 1.78 | |||
Upper bound | 25.1 | 22.1 | |||||
|
|||||||
Cambridge Isotope Laboratories, 2007 International Interlaboratory Study on Fly Ash Reference Material | Jay Grazio, Study Coordinator, |
ALS Czech Rep. | Fly ash | Lower bound |
0.112 |
0.133 |
NA |
|
|||||||
13th round of the International Intercalibration Study, 2008 (in cooperation with Wepal-SETOC) | Profesor Bert van Bavel, Chairman and Coordinator of International Intercalibration Studies, Dyltabruk, Sweden | 153 | Ash A | Lower bound | 0.162 | 0.165 | 0.08 |
Upper bound | 0.162 | 0.165 | |||||
Ash B | Lower bound | 1.01 | 1.00 | 0.25 | |||
Upper bound | 1.01 | 1.00 | |||||
Ash C | Lower bound | 0.186 | 0.167 | 0.50 | |||
Upper bound | 0.186 | 0.167 | |||||
Sediment A | Lower bound | 0.0283 | 0.0373 | −1.27 | |||
Upper bound | 0.0285 | 0.0380 | |||||
Sediment B | Lower bound | 0.0360 | 0.0345 | 0.22 | |||
Upper bound | 0.0360 | 0.0350 | |||||
Sediment C | Lower bound | 0.726 | 0.723 | 0.17 | |||
Upper bound | 0.726 | 0.721 | |||||
Sediment D | Lower bound | 0.00183 | 0.00328 | −1.03 | |||
Upper bound | 0.00312 | 0.00363 | |||||
Solution | Lower bound | 319 | 312 | 0.39 | |||
Upper bound | 319 | 312 | |||||
|
|||||||
14th round of the International Intercalibration Study, 2009 (in cooperation with Wepal-SETOC) | Profesor Bert van Bavel, Chairman and Coordinator of International Intercalibration Studies, Dyltabruk, Sweden | 153 | Ash A | Lower bound | 0.167 | 0.179 | NA |
Upper bound | 0.167 | 0.180 | |||||
Ash B | Lower bound | 0.995 | 0.995 | ||||
Upper bound | 0.995 | 0.995 | |||||
Ash C | Lower bound | 0.941 | 0.915 | ||||
Upper bound | 0.941 | 0.915 | |||||
Sediment A | Lower bound | 0.00331 | 0.00940 | ||||
Upper bound | 0.00385 | 0.00961 | |||||
Sediment B | Lower bound | 0.0664 | 0.0781 | ||||
Upper bound | 0.0664 | 0.0782 | |||||
Sediment C | Lower bound | 0.203 | 0.213 | ||||
Upper bound | 0.203 | 0.214 | |||||
Sediment D | Lower bound | 0.148 | 0.150 | ||||
Upper bound | 0.148 | 0.150 | |||||
Solution | Lower bound | 152 | 158 | ||||
Upper bound | 152 | 158 |
The content of individual PCDD/PCDF congeners in soils and sediments is summarized in Table
The contents of individual PCDD/F levels in soils and sediments (pg WHO-TEQ/g);
Congeners | Min | Max | Average | Standard deviation | Median | MAD |
---|---|---|---|---|---|---|
2,3,7,8-TCDD | <DL | 5.50 | 0.449 | 1.06 | <DL | <DL |
1,2,3,7,8-PeCDD | <DL | 2.80 | 0.069 | 0.407 | <DL | <DL |
1,2,3,4,7,8-HxCDD | <DL | 0.920 | 0.021 | 0.132 | <DL | <DL |
1,2,3,6,7,8-HxCDD | <DL | 1.40 | 0.042 | 0.204 | <DL | <DL |
1,2,3,7,8,9-HxCDD | <DL | 2.30 | 0.139 | 0.369 | <DL | <DL |
1,2,3,4,6,7,8-HpCDD | <DL | 3.30 | 0.171 | 0.474 | 0.051 | 0.026 |
OCDD | <DL | 5.70 | 0.408 | 0.851 | 0.180 | 0.113 |
2,3,7,8-TCDF | <DL | 0.036 | 0.001 | 0.005 | <DL | <DL |
1,2,3,7,8-PeCDF | <DL | <DL | <DL | <DL | <DL | <DL |
2,3,4,7,8-PeCDF | <DL | 0.083 | 0.002 | 0.012 | <DL | <DL |
1,2,3,4,7,8-HxCDF | <DL | 0.084 | 0.003 | 0.017 | <DL | <DL |
1,2,3,6,7,8-HxCDF | <DL | 0.084 | 0.002 | 0.012 | <DL | <DL |
1,2,3,7,8,9-HxCDF | <DL | <DL | <DL | <DL | <DL | <DL |
2,3,4,6,7,8-HxCDF | <DL | 0.055 | 0.002 | 0.009 | <DL | <DL |
1,2,3,4,6,7,8-HpCDF | <DL | 0.280 | 0.016 | 0.041 | <DL | <DL |
1,2,3,4,7,8,9-HpCDF | <DL | 0.005 | <DL | 0.001 | <DL | <DL |
OCDF | <DL | 2.20 | 0.094 | 0.377 | <DL | <DL |
|
||||||
WHO-PCDD/F TEQ (pg/g) | <DL | 24.7 | 1.42 | 0.231 |
MAD: median absolute deviation; <DL: value under detection limit of the analytical method.
The sediment samples originated from beds of ponds and reservoirs, where dioxins adsorbed on the mineral (argillaceous) part can theoretically be washed away during the monsoon season. In the case of sediment samples, the content of toxic congeners PCDD/PCDF is quite similar to the congeners’ content found in the soil samples. Total PCDD/PCDF content in the sediments ranges between 0.7 and 6.4 pg WHO-TEQ/g. Similarly, the PCDD/PCDF levels in sediments from mangrove forests in Can Gio, South Vietnam, rural sites in Hue, central Vietnam, and from urban sites in Hanoi, the capital of Vietnam, varied between 2.7 and 9.6 pg WHO-TEQ/g [
The PCDD/PCDF content in fish muscle is summarized in Table
The contents of individual PCDD/F levels in fish muscle (pg WHO-TEQ/g);
Congener | Min | Max | Average | Standard deviation | Median | MAD |
---|---|---|---|---|---|---|
2,3,7,8-TCDD | <DL | 1.20 | 0.326 | 0.480 | 0.124 | 0.124 |
1,2,3,7,8-PeCDD | <DL | 0.810 | 0.122 | 0.253 | <DL | 0.036 |
1,2,3,4,7,8-HxCDD | <DL | 0.084 | 0.014 | 0.027 | <DL | 0.007 |
1,2,3,6,7,8-HxCDD | <DL | 0.740 | 0.084 | 0.211 | <DL | 0.014 |
1,2,3,7,8,9-HxCDD | <DL | 0.081 | 0.009 | 0.023 | <DL | <DL |
1,2,3,4,6,7,8-HpCDD | <DL | 0.100 | 0.017 | 0.033 | <DL | 0.002 |
OCDD | <DL | 0.012 | 0.002 | 0.004 | <DL | <DL |
2,3,7,8-TCDF | <DL | 0.120 | 0.028 | 0.044 | 0.008 | 0.007 |
1,2,3,7,8-PeCDF | <DL | 0.020 | 0.003 | 0.006 | <DL | 0.003 |
2,3,4,7,8-PeCDF | <DL | 0.620 | 0.158 | 0.223 | 0.040 | 0.046 |
1,2,3,4,7,8-HxCDF | <DL | 0.054 | 0.008 | 0.016 | <DL | 0.002 |
1,2,3,6,7,8-HxCDF | <DL | 0.098 | 0.011 | 0.026 | <DL | 0.006 |
1,2,3,7,8,9-HxCDF | <DL | <DL | <DL | <DL | <DL | <DL |
2,3,4,6,7,8-HxCDF | <DL | 0.050 | 0.007 | 0.016 | <DL | <DL |
1,2,3,4,6,7,8-HpCDF | <DL | 0.004 | 0.001 | 0.001 | <DL | <DL |
1,2,3,4,7,8,9-HpCDF | <DL | <DL | <DL | <DL | <DL | <DL |
OCDF | <DL | <DL | <DL | <DL | <DL | <DL |
|
||||||
WHO-PCDD/F TEQ (pg/g fat) | <DL | 3.99 | 0.789 | 0.172 |
MAD: median absolute deviations, <DL: value under detection limit of the analytical method.
The PCDD/PCDF levels in poultry (ducks and chickens) liver and muscle (converted to pg per unit mass of fat tissue) are summarized in Table
The contents of individual PCDD/F levels in poultry liver and muscle (pg WHO-TEQ/g fat);
Congener | Min | Max | Average | Standard deviation | Median | MAD |
---|---|---|---|---|---|---|
2,3,7,8-TCDD | <DL | 5.60 | 1.75 | 1.79 | 1.10 | 1.10 |
1,2,3,7,8-PeCDD | <DL | 1.800 | 0.596 | 0.720 | <DL | <DL |
1,2,3,4,7,8-HxCDD | <DL | 0.320 | 0.091 | 0.103 | 0.086 | 0.086 |
1,2,3,6,7,8-HxCDD | <DL | 0.730 | 0.248 | 0.220 | 0.190 | 0.099 |
1,2,3,7,8,9-HxCDD | <DL | 0.590 | 0.115 | 0.164 | 0.077 | 0.077 |
1,2,3,4,6,7,8-HpCDD | <DL | 0.140 | 0.051 | 0.046 | 0.039 | 0.031 |
OCDD | <DL | 0.013 | 0.006 | 0.004 | 0.005 | 0.003 |
2,3,7,8-TCDF | 0.120 | 2.30 | 0.567 | 0.624 | 0.280 | 0.130 |
1,2,3,7,8-PeCDF | <DL | 0.210 | 0.057 | 0.055 | 0.041 | 0.025 |
2,3,4,7,8-PeCDF | 0.290 | 1.90 | 0.805 | 0.477 | 0.720 | 0.330 |
1,2,3,4,7,8-HxCDF | <DL | 0.650 | 0.203 | 0.171 | 0.160 | 0.050 |
1,2,3,6,7,8-HxCDF | <DL | 0.700 | 0.185 | 0.180 | 0.140 | 0.079 |
1,2,3,7,8,9-HxCDF | <DL | 0.048 | 0.007 | 0.015 | <DL | <DL |
2,3,4,6,7,8-HxCDF | <DL | 0.330 | 0.087 | 0.094 | 0.072 | 0.072 |
1,2,3,4,6,7,8-HpCDF | <DL | 0.050 | 0.010 | 0.015 | <DL | <DL |
1,2,3,4,7,8,9-HpCDF | <DL | 0.009 | 0.001 | 0.002 | <DL | <DL |
OCDF | <DL | 0.001 | <DL | <DL | <DL | <DL |
|
||||||
WHO-PCDD/F TEQ (pg/g fat) | 0.41 | 15.4 | 4.80 | 2.91 |
MAD: median absolute deviations, <DL: value under detection limit of the analytical method.
In the case of hens, this phenomenon can be explained by reduced concentration of dioxins in the body as a consequence of egg production. In some cases, various contamination sources other than Agent Orange spraying, such as local combustion processes, cannot be unambiguously excluded. This fact is due to the presence of highly-chlorinated congener OCDD and also because of elevated concentrations of furans (Table
The Agent Orange defoliant was contaminated mainly by the 2,3,7,8-TCDD congener, formed by condensation of two molecules of 2,4,5-trichlorophenol used for production of the herbicide—2,4,5-trichlorophenoxyacetic acid (2,4,5 T). This information was used in exposure assessment of American troops in chemical units who, during the war, came into direct contact with Agent Orange. Of 13 examined congeners of dioxins and furans, only TCDD was present in increased concentrations in blood serum samples TCDD [
The PCDD/PCDF content in most of the investigated pork and beef meat samples does not exceed the limit of European Directive EC number 199/2006. In pork samples, the average PCDD/PCDF content was 0.36 pg WHO-TEQ/g, corresponding to 0.55 pg WHO-TEQ per gram of fat. In beef samples, the average content was 0.51 pg WHO-TEQ/g, which corresponds to 1.3 pg WHO-TEQ per gram of fat. According to European Directive EC number 199/2006, the limit content of dioxins in pork meat is 1 pg WHO-TEQ (PCDD/PCDF/PCB) per gram of fat. As expected, the PCDD/PCDF content in samples of vegetables and fruits is quite low. Total WHO-TEQ concentration in cassava, papaya, bananas, and batatas is 0.014 pg/g, 0.03 pg/g, 0.02 pg/g and 0.018 pg/g, respectively. No detectable content of the congener 2,3,7,8-TCDD was found in tested samples.
Even though the concentrations of dioxins in soil, sediment, and animal tissues were not significantly high (for soil and sediment the concentrations were in all cases below Vietnamese threshold values 1000 ppt TEQ or 150 ppt TEQ-TCVN 8183:2009: National Standard for Dioxins Threshold in Soil and Sediment), the cancer and noncancer risks for local inhabitants, arising from a dietary exposure (especially from fish and poultry consumption), are possible. The values of the hazard index HI for the noncarcinogenic risk of the monitored age categories ranged between 13.3 and 17.7 for maximum PCDD/PCDF concentrations in foodstuffs, while the ILCR values (lifetime increase in probability of tumour disease development) for the investigated population groups ranged between
The assessment of spreading of the PCDD/PCDF contamination in the environment of the examined area is limited by several facts. (i) From the geological point of view, the examined area is located in a very active environment with high temperature and high rainfall, plus extensive deforestation and poor forest management. The top layer of soil is repeatedly transferred and flushed down to the valley, where it accumulates in local depressions (dams, lakes, and streams). A part of the material is transported directly to the sea. (ii) In spite of the considerable persistence of the examined substances, their decomposition is accelerated by long-lasting high temperatures and repeated transport. During the transport, intensive turbulence helps dissolution of large amounts of various substances and thus accelerates chemical decomposition of PCDD/PCDF. (iii) The area where the investigation of the contamination was performed is quite large and did not allow detailed examination through a regular network of sampling spots. Thus, we cannot exclude existence of sites with a higher degree of contamination than was revealed during the investigation. (iv) Even though rice constitutes a substantial part of the local inhabitants’ diet, the PCDD/F content in rice was not analyzed within our investigation of the food chain components. Similarly, some relatively often consumed species of aquatic plants (e.g.,
Clearly, there are no immediate remedies to eliminate the possibility of PCDD/PCDF exposure to inhabitants of the region. Nor is the contamination encountered at Phong My commune likely to be unique in defoliated areas of Vietnam. Such measures, which usually depend on removing PCDD/PCDF from the environment, are expensive, and contamination hotspots are therefore dealt with first. The levels of contamination in areas only hit by herbicide sprays (such as Phong My commune) are orders of magnitude lower than those in hot spots and hence it is suitable to focus on measures that prevent these compounds from entering the food chain rather than on their total elimination from the environment. Since a majority of local inhabitants consume above-average amounts of fish [
Similarly, for breeding of poultry, cattle, pigs, and other domestic animals, it is recommended to build a clean environment: fixed and strictly delimited areas for poultry or stables and pens for pigs. The animals should be fed only demonstrably clean feed; the rest of potentially contaminated foodstuffs (bones, entrails, skin, fat, etc.) should be excluded from the feed. Farmers should minimise the stay of cattle and domestic pigs in muddy terrain, thus preventing them from drinking strongly mudded water and minimizing contact with the sediments in natural pools, where increased contamination by PCDD/PCDF was found. Animals foraging on soil contaminated with PCDD/PCDF at low levels may bioaccumulate these compounds to unacceptable levels [
Results of the assessment of health risks caused by exposure to dioxins in the environment (soils and sediments) and foodstuffs of the local inhabitants (liver and muscle of farm animals, fruits, and vegetables) in Phong My commune area show a potential risk from the increased PCDD/PCDF levels in the environment. Since these highly dangerous bioaccumulative and persistent substances are known carcinogens and teratogens, reducing exposure to as low as reasonably achievable is desirable. Therefore, technically and financially attainable remedial measures should be taken to reduce the exposure to these contaminants as much as possible. In addition to measures that inhabitants can take themselves, action is needed from health-care organisations, public institutions, and political authorities responsible for the health of the environment, safety of foodstuffs, quality of farm animal feed, and so forth. Raising public awareness of both the health threats arising from exposure to PCDD/PCDF and ways to minimise those threats is a key tool in dealing with the described risks. Even with fairly conservative assumptions, the ascertained health risks suggest that greater attention should be paid to the behavior and toxicity of the PCDD and PCDF group, and to exploration of exposure reduction possibilities.
The authors declares that there is no conflict of interests regarding the publication of this paper.
This research was financially supported by the Czech Ministry of Environment in the framework of the Official Development Assistance by the Project “Rehabilitation of Thua Thien-Hue Province affected by AO/dioxin Contamination” (Project no. RP 6/2006) and by the Internal Grant Agency of the Institute of Tropics and Subtropics, CULS Prague (Project no. 51130/1312/3122).