1. High levels of TCDD contamination in fish and effects in human consumption in South Vietnam
Thao Nguyen
UNIVERSITY OF TEXAS HEALTH SCIENCE CENTER AT HOUSTON SCHOOL OF PUBLIC HEALTH
Introduction
This study aims to summarize some pathways that
2,3,7,8-tetrachlorodibenzo-p-dioxin (referred as
dioxin or TCDD) can be transported from
consumption of fish into the human body, investigate
the bio-accumulating processes of the toxin in the
environmental and recommend standards for safe
fish consumption. In addition, the study provides
information regarding current efforts to minimize long-
term effects of TCDD.
Key points about TCDD:
vTCDD is known as the most toxic man-made
compound and is the dominant component of
herbicide Agent Orange (AO).
vMore than 75 million litters of herbicides were
sprayed in South VN from 1962 to 1971 during
Operation Ranch Hand.
vTCDD has been linked to severe health conditions,
such as cancers, birth defects and premature deaths.
Transportation pathways
A clinical analysis of theorized pathways of exposure of
TCDD in areas of South VN and their specific
environmental characteristics was conducted. Four
different scenarios represented potential human
exposure pathways and potential toxin concentration in
human were calculated. CoZMo-POP-2 model (Fig. 1.)
was utilized to simulate the environmental settings that
facilitated fate and transportation of TCDD.
Biota-sediment accumulation factor (BSAF) was used to
calculate TCDD concentration in fish. Human absorbed
dose (DA) calculation accounted for estimated factors
related to body shaping (FS), clothing (FC), and dermal
absorption efficiency (EA).
DA=D×SA×FS×FC×EA
Hypothesis: TCDD was aborted into the environment
(i.e. forest soil and nearby aquatic systems) and was
linked to the food chain.
Topographical surveys of the most highly contaminated
areas in Bien Hoa and Da Nang as well as laboratory
analysis of TCDD concentration in 106 soil sediment
samples and tilapia and duck tissue samples were
conducted. Fig. 2. illustrated the areas of study (4,
p14433). Toxicity equivalency quotient/gram (TEQ/g) was
the unit of dioxin concentration.
Hypothesis: Weathering processes and human activities
caused erosions of the hotspots bringing toxins to
downstream ponds and lakes.
Findings:
• TCDD had high potential for bioaccumulation
• Geographical characteristics of the hotspots and
human activities contributed to the distribution and
bioaccumulation of dioxin
• Surrounding ponds and lakes had 3 to 30 folds the
amount of toxins compared to farther areas (1500
pg TEQ/g and 6540 pg/g)
• Aquatic animal tissue had TCDD concentration of
36-182 pg TEQ/g.
Current Public Health
interventions
There have been efforts from US organizations to
develop and maintain public health support to residents
living at or near the hotspots (3). Sustainability of
intervention programs and impacts of public health in
improving knowledge, attitude and practices (KAP).
• Quantitative data: 3 essential categories divided
into 12 indicators, scale 1-5
• Qualitative data: in-depth interviews
• Intervention group: 6 wards near Bien Hoa and Da
Nang
• Control group: 1 ward near Bien Hoa airbase
Findings:
• On average, interventions remained in moderate
to high levels of effectiveness thanks to
investment in training of staff, providing onsite
health screening and informing local residents.
• Long-term maintenance on knowledge and
attitude categories remained high
• Long-term maintenance on practice categories
was at moderate rate.
• Policy reinforcement and funding from the local
government ceased and could contribute to
inconsistency in practices.
The current study raised concerns regarding the
lack of regulation on TCDD levels in fish for safe
human consumption (3). Not only did local
residents consume potentially contaminated
products, but also migrants, non-locals and
tourists were unaware of dioxin’s impacts and
fishing bans.
Conclusions
The VN war ended 40 years ago, yet its consequences are
still prominent. Although great efforts from foreign research
organizations have provided significant insights about the
science behind TCDD contamination, efforts from the
Vietnamese government to manage public health concerns
are limited.
Overall strengths:
v Combined approaches were utilized to study TCDD
contaminations.
v Both qualitative and quantitative data were collected and
analyzed because of the large-scale effects of the
contamination.
v Involvement of local authorities and public health agencies
enhanced the applicability of the results.
Overall weaknesses:
v Some studies used small sample population and
nonrandomized techniques.
v Lack of longitudinal data lead to utilization of assumptions
in analysis processes.
Next steps for research:
v Continue to monitor TCDD levels in soil and aquatic
environment and to investigate future trends of
contamination.
v Narrow the gap in education the people about the levels of
toxin in the environment and potential health effects.
v Collaborate with local authorities to facilitate
improvements in public health programs and research.
v Maintain the benefits of established interventions
v Seek additional funding from both governmental and non-
governmental organizations is needed.
References
1.Armitage JM, Ginevan ME, Hewitt A, Ross JH, Watkins DK,
Solomon KR. Environmental fate and dietary exposures of humans
to TCDD as a result of the spraying of Agent Orange in upland
forests of Vietnam. The Science of the total environment. 2015;;506-
507:621-30.
2.Pham DT, Nguyen HM, Boivin TG, Zajacova A, Huzurbazar SV,
Bergman HL. Predictors for dioxin accumulation in residents living in
Da Nang and Bien Hoa, Vietnam, many years after Agent Orange
use. Chemosphere. 2015;;118:277-83.
3.Tuyet-Hanh TT, Vu-Anh L, Dunne M, Toms L, Tenkate T, Harden F.
Sustainability of Public Health Interventions to Reduce the Risk of
Dioxin Exposure at Severe Dioxin Hot Spots in Vietnam. Journal of
Community Health. 2015;;40(4):652-9.
4.Van Thuong N, Hung NX, Mo NT, Thang NM, Huy PQ, Van Binh H,
et al. Transport and bioaccumulation of polychlorinated dibenzo-p-
dioxins and dibenzofurans at the Bien Hoa Agent Orange hotspot in
Vietnam. Environmental Science and Pollution Research.
2015;;22(19):14431-41.
Abstract
This paper reviews current research projects
studying the long-term effects of 2,3,7,8-
tetrachlorodibenzo-p-dioxin (TCDD) contamination
in South Vietnam (VN), particularly former US
military airbases in Bien Hoa and Da Nang. Three
main themes were discussed in details: fate and
transportation pathways of TCDD, bioaccumulation
of TCDD and contamination in fish, and evaluation
of current Public Health interventions.
Concentration of TCDD was found to be alarmingly
high in ponds and lakes near the hotspots.
Bioaccumulation of TCDD can be transported to the
human food chain via consumption of aquaculture
plants and animals. Concentration of TCDD in fish
in local water systems in these areas of VN was
much higher than that in other location of the world.
However, Vietnamese authorities set no standard
level of TCDD in fish. In conclusion, TCDD can be
transported to the water systems via natural
weathering process or man-made activities. High
concentration of TCDD in fish and aquatic creatures
imposed concerning health effects on both local
and non-locals residents. Ongoing public health
interventions received moderate to high ratings
from local residents. However, Vietnamese
government and health agencies provided limited
support. The recommended level of TCDD
concentration in fish was 3.5 pg/g TEQ wet weight
or less based on European Commission regulation.
This study supported evidences from previous Hatfield
Consultants’ reports. Because TCDD half-life in soil was
10-15 years while most data collection studies in VN
only began 15-20 years after the war ended, estimation
of the residual and its long-term effects using similar
models is recommended for future research.
Fig. 1. Diagrammatic illustration of the scenarios and models (AGDISP v8.27,
CoZMo-POP 2, HEM) used to estimate exposures of humans in South Vietnam
to TCDD from the aerial spraying of herbicides (UC-123 aircraft) over upland
forest environments.
Bioaccumulation of TCDD and
contamination in fish
The following research, published in the Chemosphere,
investigated of serum concentration and environmental
contamination of dioxin (2) as a component of a
collaborative investigation between the Vietnamese
Government and Hatfield Consultants.
• Quantitative data: serum concentration of TCDD
• Qualitative data: demographic, SES, smoking
status, education and length of residency
• Study population: 42 participants from 5 wards
and 2 families of airport worker living close to
former US military airbases in Bien Hoa and Da
Nang
Findings:
Higher level of dioxin concentration was positively
associated with:
• Water-related activities in the hotspot areas
• Consumption of aquatic vegetation and animals
• Living in areas with frequent flooding
• Length of residency
• Proximity to the airbases and highly contaminated
dumping ponds (Fig. 3.)
Potential confounding effect of proximity of residency due
to: Insufficient data on practices, frequency and quantity
of fish consumption, and proximity to of residency was
related to fish farming and water-related activities.
Fig. 3. Comparisons of serum concentrations of TCDD and TEQ values of
residents living in different wards of Da Nang study (n = 116)
Fig. 2. Map showing Bien Hoa airbase and relevant sampling sites
(2011–2013)
Limitations Assumptions
CoZMo-POP-2 did not
account for
transportation of
sediments from forest
soil to aquatic
environmental due to
soil erosion
Estimatedpotential amount of toxins
released intothe waterways and aquatic
environment by analyzing bioaccumulation
of TCDD in livestock and aquaculture
animals
Assumed TCDD level in ponds and lake to
be equal to that in forest soils
Limiteddata and not
representative of
longitudinal average
Assumed concentration of TCDD in Agent
Orange (AO) sprayed by US aircrafts at
28.1 L/ha based on 1965 values
Scenarios were not
realistic
CoZMo-POP-2 only projected simultaneous
spraying. Periods of spraying during
Operation Ranch Hand were prolonged and
repetitive.
Findings:
• TCDD exposure from direct deposit (aerosol
spray) ranged from 280-7030 pg.
• Average 50-year simulated intake ranged from 8-
85 pg/d.
• Rates of bioaccumulation of TCDD in duck meat
were lower than those in fish, seafood, pigs and
other poultry.
Dioxin concentration in fish found in this study was much
higher compared to that found in China, Germany, Spain
and the Mediterranean Sea where contamination was
caused by industrial activities. These findings imposed
“significant health risk to people who might have
consumed […] local food items”, such as tilapia, duck,
fish, lotus roots and plants and echoed existing literature
stating that TCDD was the most toxic congener in fish,
and the contamination was still ongoing (4, p. 14437).
Vietnamese government had not issued a standardized
level of dioxin concentration in food. European
Commission’s maximum allowable level was 3.5 pg/g
TEQ wet weight (Van Thuong et al, 2015). Therefore, the
recommended TCDD level in fish caught from local ponds
and lakes in Bien Hoa and Da Nang should be at 3.5 pg/g
TEQ wet weight or less to minimize potential health
effects of dioxin on local and surrounding residents.
![High levels of TCDD contamination in fish and effects in human consumption in South Vietnam
Thao Nguyen
UNIVERSITY OF TEXAS HEALTH SCIENCE CENTER AT HOUSTON SCHOOL OF PUBLIC HEALTH
Introduction
This study aims to summarize some pathways that
2,3,7,8-tetrachlorodibenzo-p-dioxin (referred as
dioxin or TCDD) can be transported from
consumption of fish into the human body, investigate
the bio-accumulating processes of the toxin in the
environmental and recommend standards for safe
fish consumption. In addition, the study provides
information regarding current efforts to minimize long-
term effects of TCDD.
Key points about TCDD:
vTCDD is known as the most toxic man-made
compound and is the dominant component of
herbicide Agent Orange (AO).
vMore than 75 million litters of herbicides were
sprayed in South VN from 1962 to 1971 during
Operation Ranch Hand.
vTCDD has been linked to severe health conditions,
such as cancers, birth defects and premature deaths.
Transportation pathways
A clinical analysis of theorized pathways of exposure of
TCDD in areas of South VN and their specific
environmental characteristics was conducted. Four
different scenarios represented potential human
exposure pathways and potential toxin concentration in
human were calculated. CoZMo-POP-2 model (Fig. 1.)
was utilized to simulate the environmental settings that
facilitated fate and transportation of TCDD.
Biota-sediment accumulation factor (BSAF) was used to
calculate TCDD concentration in fish. Human absorbed
dose (DA) calculation accounted for estimated factors
related to body shaping (FS), clothing (FC), and dermal
absorption efficiency (EA).
DA=D×SA×FS×FC×EA
Hypothesis: TCDD was aborted into the environment
(i.e. forest soil and nearby aquatic systems) and was
linked to the food chain.
Topographical surveys of the most highly contaminated
areas in Bien Hoa and Da Nang as well as laboratory
analysis of TCDD concentration in 106 soil sediment
samples and tilapia and duck tissue samples were
conducted. Fig. 2. illustrated the areas of study (4,
p14433). Toxicity equivalency quotient/gram (TEQ/g) was
the unit of dioxin concentration.
Hypothesis: Weathering processes and human activities
caused erosions of the hotspots bringing toxins to
downstream ponds and lakes.
Findings:
• TCDD had high potential for bioaccumulation
• Geographical characteristics of the hotspots and
human activities contributed to the distribution and
bioaccumulation of dioxin
• Surrounding ponds and lakes had 3 to 30 folds the
amount of toxins compared to farther areas (1500
pg TEQ/g and 6540 pg/g)
• Aquatic animal tissue had TCDD concentration of
36-182 pg TEQ/g.
Current Public Health
interventions
There have been efforts from US organizations to
develop and maintain public health support to residents
living at or near the hotspots (3). Sustainability of
intervention programs and impacts of public health in
improving knowledge, attitude and practices (KAP).
• Quantitative data: 3 essential categories divided
into 12 indicators, scale 1-5
• Qualitative data: in-depth interviews
• Intervention group: 6 wards near Bien Hoa and Da
Nang
• Control group: 1 ward near Bien Hoa airbase
Findings:
• On average, interventions remained in moderate
to high levels of effectiveness thanks to
investment in training of staff, providing onsite
health screening and informing local residents.
• Long-term maintenance on knowledge and
attitude categories remained high
• Long-term maintenance on practice categories
was at moderate rate.
• Policy reinforcement and funding from the local
government ceased and could contribute to
inconsistency in practices.
The current study raised concerns regarding the
lack of regulation on TCDD levels in fish for safe
human consumption (3). Not only did local
residents consume potentially contaminated
products, but also migrants, non-locals and
tourists were unaware of dioxin’s impacts and
fishing bans.
Conclusions
The VN war ended 40 years ago, yet its consequences are
still prominent. Although great efforts from foreign research
organizations have provided significant insights about the
science behind TCDD contamination, efforts from the
Vietnamese government to manage public health concerns
are limited.
Overall strengths:
v Combined approaches were utilized to study TCDD
contaminations.
v Both qualitative and quantitative data were collected and
analyzed because of the large-scale effects of the
contamination.
v Involvement of local authorities and public health agencies
enhanced the applicability of the results.
Overall weaknesses:
v Some studies used small sample population and
nonrandomized techniques.
v Lack of longitudinal data lead to utilization of assumptions
in analysis processes.
Next steps for research:
v Continue to monitor TCDD levels in soil and aquatic
environment and to investigate future trends of
contamination.
v Narrow the gap in education the people about the levels of
toxin in the environment and potential health effects.
v Collaborate with local authorities to facilitate
improvements in public health programs and research.
v Maintain the benefits of established interventions
v Seek additional funding from both governmental and non-
governmental organizations is needed.
References
1.Armitage JM, Ginevan ME, Hewitt A, Ross JH, Watkins DK,
Solomon KR. Environmental fate and dietary exposures of humans
to TCDD as a result of the spraying of Agent Orange in upland
forests of Vietnam. The Science of the total environment. 2015;;506-
507:621-30.
2.Pham DT, Nguyen HM, Boivin TG, Zajacova A, Huzurbazar SV,
Bergman HL. Predictors for dioxin accumulation in residents living in
Da Nang and Bien Hoa, Vietnam, many years after Agent Orange
use. Chemosphere. 2015;;118:277-83.
3.Tuyet-Hanh TT, Vu-Anh L, Dunne M, Toms L, Tenkate T, Harden F.
Sustainability of Public Health Interventions to Reduce the Risk of
Dioxin Exposure at Severe Dioxin Hot Spots in Vietnam. Journal of
Community Health. 2015;;40(4):652-9.
4.Van Thuong N, Hung NX, Mo NT, Thang NM, Huy PQ, Van Binh H,
et al. Transport and bioaccumulation of polychlorinated dibenzo-p-
dioxins and dibenzofurans at the Bien Hoa Agent Orange hotspot in
Vietnam. Environmental Science and Pollution Research.
2015;;22(19):14431-41.
Abstract
This paper reviews current research projects
studying the long-term effects of 2,3,7,8-
tetrachlorodibenzo-p-dioxin (TCDD) contamination
in South Vietnam (VN), particularly former US
military airbases in Bien Hoa and Da Nang. Three
main themes were discussed in details: fate and
transportation pathways of TCDD, bioaccumulation
of TCDD and contamination in fish, and evaluation
of current Public Health interventions.
Concentration of TCDD was found to be alarmingly
high in ponds and lakes near the hotspots.
Bioaccumulation of TCDD can be transported to the
human food chain via consumption of aquaculture
plants and animals. Concentration of TCDD in fish
in local water systems in these areas of VN was
much higher than that in other location of the world.
However, Vietnamese authorities set no standard
level of TCDD in fish. In conclusion, TCDD can be
transported to the water systems via natural
weathering process or man-made activities. High
concentration of TCDD in fish and aquatic creatures
imposed concerning health effects on both local
and non-locals residents. Ongoing public health
interventions received moderate to high ratings
from local residents. However, Vietnamese
government and health agencies provided limited
support. The recommended level of TCDD
concentration in fish was 3.5 pg/g TEQ wet weight
or less based on European Commission regulation.
This study supported evidences from previous Hatfield
Consultants’ reports. Because TCDD half-life in soil was
10-15 years while most data collection studies in VN
only began 15-20 years after the war ended, estimation
of the residual and its long-term effects using similar
models is recommended for future research.
Fig. 1. Diagrammatic illustration of the scenarios and models (AGDISP v8.27,
CoZMo-POP 2, HEM) used to estimate exposures of humans in South Vietnam
to TCDD from the aerial spraying of herbicides (UC-123 aircraft) over upland
forest environments.
Bioaccumulation of TCDD and
contamination in fish
The following research, published in the Chemosphere,
investigated of serum concentration and environmental
contamination of dioxin (2) as a component of a
collaborative investigation between the Vietnamese
Government and Hatfield Consultants.
• Quantitative data: serum concentration of TCDD
• Qualitative data: demographic, SES, smoking
status, education and length of residency
• Study population: 42 participants from 5 wards
and 2 families of airport worker living close to
former US military airbases in Bien Hoa and Da
Nang
Findings:
Higher level of dioxin concentration was positively
associated with:
• Water-related activities in the hotspot areas
• Consumption of aquatic vegetation and animals
• Living in areas with frequent flooding
• Length of residency
• Proximity to the airbases and highly contaminated
dumping ponds (Fig. 3.)
Potential confounding effect of proximity of residency due
to: Insufficient data on practices, frequency and quantity
of fish consumption, and proximity to of residency was
related to fish farming and water-related activities.
Fig. 3. Comparisons of serum concentrations of TCDD and TEQ values of
residents living in different wards of Da Nang study (n = 116)
Fig. 2. Map showing Bien Hoa airbase and relevant sampling sites
(2011–2013)
Limitations Assumptions
CoZMo-POP-2 did not
account for
transportation of
sediments from forest
soil to aquatic
environmental due to
soil erosion
Estimatedpotential amount of toxins
released intothe waterways and aquatic
environment by analyzing bioaccumulation
of TCDD in livestock and aquaculture
animals
Assumed TCDD level in ponds and lake to
be equal to that in forest soils
Limiteddata and not
representative of
longitudinal average
Assumed concentration of TCDD in Agent
Orange (AO) sprayed by US aircrafts at
28.1 L/ha based on 1965 values
Scenarios were not
realistic
CoZMo-POP-2 only projected simultaneous
spraying. Periods of spraying during
Operation Ranch Hand were prolonged and
repetitive.
Findings:
• TCDD exposure from direct deposit (aerosol
spray) ranged from 280-7030 pg.
• Average 50-year simulated intake ranged from 8-
85 pg/d.
• Rates of bioaccumulation of TCDD in duck meat
were lower than those in fish, seafood, pigs and
other poultry.
Dioxin concentration in fish found in this study was much
higher compared to that found in China, Germany, Spain
and the Mediterranean Sea where contamination was
caused by industrial activities. These findings imposed
“significant health risk to people who might have
consumed […] local food items”, such as tilapia, duck,
fish, lotus roots and plants and echoed existing literature
stating that TCDD was the most toxic congener in fish,
and the contamination was still ongoing (4, p. 14437).
Vietnamese government had not issued a standardized
level of dioxin concentration in food. European
Commission’s maximum allowable level was 3.5 pg/g
TEQ wet weight (Van Thuong et al, 2015). Therefore, the
recommended TCDD level in fish caught from local ponds
and lakes in Bien Hoa and Da Nang should be at 3.5 pg/g
TEQ wet weight or less to minimize potential health
effects of dioxin on local and surrounding residents.](https://image.slidesharecdn.com/946510e4-c433-41fd-8d16-bf005cf2c198-160217185437/85/tcddcontaminationsouthvietnamnguyen2015-1-320.jpg)
