A, HT Quynh, M Pavuk, O Päpke, R Malisch and JD Constable.
2003. Food as a source of dioxin exposure in the residents
of Bien Hoa City, Vietnam. Journal
of Occupational and Environmental Medicine 45:781–788.
years after Agent Orange spraying ended in Vietnam, a team of research
scientists reports that some food being eaten by Vietnamese today
remains heavily contaminated by dioxin and related chemicals. Their
results help understand why high levels of dioxin continue to be
found in Vietnamese, decades after the initial exposures. They also
warn that Vietnamese children today, even though never directly
exposed to spraying, are at risk to the health effects of dioxin
because of the food they eat.
all types of food are problematic. While duck was exceptionally
high, and chicken and some fish far above thresholds for health
concerns, beef and pork were relatively clean. In contaminated animal
meat, the highest levels were observed within the fat, as is expected
because of dioxin's chemical characteristics. This adds to health
concerns, however, because some fats are considered a delicacy in
did they do? Schecter and his co-workers obtained samples
of various food types from Vietnamese markets in Bien Hoa City,
an area known for high dioxin contamination, and shipped them on
dry ice to Germany for state-of-the-art chemical analysis. The 16
samples they analyzed spanned free-ranging and cooped chickens,
free-ranging ducks, pork, beef, fish and a toad. Compounds measured
included a series of dioxin congeners, including TCDD, dibenzofurans,
some PCBs as well as a series of organochlorine pesticides like
DDT and HCB. Because of the high levels of dioxin observed by the
German lab, three samples were also analyzed by a second, independent
laboratory, also in Germany.
did they find?
and related contaminants were detected in all 16 samples analyzed.
This is summarized in the graph to the right, adapted from
Schecter et al. TEQ
is an index based on toxicity that reflects the combined effect
of dioxin-like contaminants. Different colors within the bars
reflect how much different classes of contaminants contribute
to total TEQ.
few sampled items stood out as "markedly elevated,"
notably two sampled free-ranging ducks. High levels were also
observed in two free-ranging chickens, a toad and a fish.
Caged chicken were lower. Beef and pork were relatively low,
meeting European standards (below) , as were four of the fish
et al. note that TCDD, the most toxic form of dioxin,
made the largest contribution to total TEQ toxicity. This
is shown in the graph above (white vs. purple vs. red portions
of the bars).
comparison, TEQ levels in US food typically are well below
1 TEQ ppt, as indicated in the table to the left (from the
US National Academy of Sciences, Dioxins
and dioxin-like compounds in the food supply, 2003, p97).
the levels observed in Vietnamese food are literally "off-the-charts"
compared to what occurs in US food. Amounts encountered in
duck, toad, some chicken and some fish are also extremely
high compared to UK
and European standards:1-3 ppt for meat, 4 ppt for fish,
0.75-3 ppt for fat and oils, etc.fish (4 ng WHO-TEQ/kg fresh
does it mean? These results provide a clear explanation
for why residents of Bien Hoa City still carry high dioxin levels,
30 years after spraying of Agent Orange ended. Sufficient dioxin
and dioxin-like contaminants remain distributed in the environment
to reach extremely high levels in some food items important to the
et al. comment on the wide variability of TEQ levels in
food items taken from one local area, ranging from 0.11 ppt TEQ
in a sample of beef to 343 ppt TEQ in a free-ranging duck. These
data suggest it may be possible to develop guidelines for food consumption
that could be used to reduce human exposures. More data, including
replicate samples from different food types, will be necessary to
be confident in the utility of such guidelines, but already the
data indicate that free-ranging chickens and ducks should be avoided.
Four of five species of fish sampled were relatively uncontaminated;
the one fish with high levels burrows in the bottom mud of a heavily
contaminated lake. Further research might therefore clarify which
species can be consumed with comparative safety.
wide variability in TEQ levels in local foods also complicates efforts
to use relatively crude estimates of dioxin exposure, such as geographic
patterns of spraying, as a basis for epidemiological assessments
of dioxin risk. The food variability will bias such studies toward
negatives, particularly if dietary differences among people
within and among areas lead to large differences in dioxin consumption.