JOEM • Volume 46, Number 5, May 2004
Letters
to the Editor : Readers are invited to submit
letters for publication in this department. Submit them to: The Editor, Journal
of Occupational and Environmental Medicine,
Food as a Source of Dioxin Exposure in the Residents of
To
the Editor: The
article by Schecter et al. [1] uses laboratory results of 16 food samples
collected from various areas in Bien Hoa City, Vietnam, “to determine if food
is the route of current intake of TCDD into persons living in Vietnamese
'hotspots'” and concludes that “Clearly, food, including duck, chicken, some
fish, and a toad, appears responsible for elevated TCDD in residents of Bien
Hoa City, even though the original Agent Orange contamination occurred 30 - 40
years before sampling.” The methodology used and the data and information
provided in the article do not appear to support the conclusion.
The
authors referred to
The
article states “It is probable that consumption of food is responsible
for elevation of TCDD levels in persons living near the
1) to link elevated TCDD levels in food samples with the dioxin
“hot spot” and
2) to link elevated TCDD levels in food samples with elevated
blood TCDD levels in residents of
There
are strong indicators suggesting the presence of potential sources other than
Agent Orange for the current dioxin contamination in
According
to the article, “possible sources of PCBs include electrical transformers or
capacitors and hydraulic fluid used during the
The other
indicator is untreated industrial waste from industrial zones located within
All
of these industries are considered as potential sources of dioxin
contamination. The untreated industrial waste, including wastewater, has been
discharged directly into the environment and has caused serious environmental
pollution, especially the
In
summary, the authors should use a more appropriate method to determine whether
food is the route of current intake of TCDD into persons living in Vietnamese
“hot spots” such as the leak of Agent Orange at the Bien Hoa Airbase in 1970.
Regardless the method used, adequate and appropriate supporting data should be
provided 1) to link the Bien Hoa dioxin “hot spot” with the TCDD contaminated
areas where food are produced, 2) to link elevated TCDD levels in soil and
sediment samples with elevated TCDD levels in food grown within the
contaminated areas, and 3) to link elevated TCDD levels in food consumed by
persons living in the contaminated areas with elevated TCDD levels in their
blood. If other persistent organic pollutants are detected, additional
potential sources should be evaluated to determine the “true” route of the
dioxin contamination in the studied area.
Truyet
T. Mai, PhD
Vietnamese
American Science and Technology Society,
1. Schecter A, Quynh HT, Pavuk M, Papke O, Malisch R,
Constable JD. Food as a source of dioxin exposure in the
residents of
We thank Dr Truyet T. Mai for his interest in our recently
published article on dioxin from Agent Orange as a continuing source of current
contamination of food in one location in Vietnam.[1]
We appreciate his interest in the environmental and health effects of dioxin
exposure in
Although
Dr Mai voices no criticisms of our analytical methods, we feel that it is
appropriate to reemphasize what method we used to examine human blood, soil,
sediment, wildlife, and food for 2,3,7,8-TCDD (TCDD)
where Agent Orange had been sprayed or stored. After cleanup, all samples were
analyzed by high-resolution gas chromatography-high resolution mass
spectroscopy (GC-MS) with the use of appropriate chemical standards conducted
by ERGO Research Laboratory, which is certified by the World Health
Organization for the determination of congener specific dioxins, dibenzofurans,
and PCBs in human tissue and food. This method is the current “gold standard”
for determination of dioxin exposure regardless of the original source of the
dioxin. [3-8]
2,3,7,8-TCDD,
unquestionably from Agent Orange, has been identified in humans and their food
sources since 1970 when one of us (J.D.C.) collected human milk and fish from
heavily Agent Orange sprayed areas of Vietnam for dioxin analyses. These
pioneer dioxin analyses showed as much as 1850 parts per trillion of 2,3,7,8-TCDD on a lipid basis in some nursing mothers' milk,
which is the highest human milk level ever recorded and which can be compared
to the US and south of Vietnam current background level of approximately 2 ppt;
whereas in fish up to 1020 ppt wet weight (ww) was detected compared with a
usual background of less than 0.01 ppt ww. [9-12] Subsequently,
blood and fat samples were used to estimate Agent Orange exposure. As a result,
some US Vietnam veterans were shown to be carrying elevated levels of the
specific dioxin (2,3,7,8-TCDD), which contaminates
Agent Orange. [7,13-15]
Part
of Bien Hoa City is a dioxin “hot spot” not only because of the history of herbicide
spraying and of a major Agent Orange spill as documented by the US Department
of Defense but also by the determination of elevated 2,3,7,8-TCDD
(and only this of many dioxin congeners measured) in selected inhabitants
chosen for greater likelihood of herbicide exposure. Contamination of human or
environmental samples with products of incineration,16,17 pentachlorophenol,
[8,18] contaminated rice oil19-21 or, as here, Agent Orange, results in
characteristic patterns of the 7 chlorinated dioxin, 10 chlorinated
dibenzofuran, and 12 PCB congeners, which characterizes or “fingerprints” the
source of the exposure. The elevation of only this specific dioxin, and no
dibenzofurans or PCBs, [3,4,6,22-27] is persuasive
evidence that the material originated from Agent Orange either sprayed,
spilled, or inadequately stored with resulting leakage.
To elaborate, as a result of municipal waste incineration,
many other dioxins and dibenzofurans are characteristically formed, especially
octachlorodibenzodioxin. [16] If chlorine is used for bleaching, paper and pulp effluents
typically contain 2,3,7,8-TCDF and 2,3,7,8-TCDD.
Pentachlorophenol is typically contaminated with higher chlorinated dioxins and
dibenzofurans with eight, seven, and six chlorines, not tetrachlorinated
dioxins or dibenzofurans. [8,18]
The
fact that food of animal origin is the route of intake of over 95% of the
intake of dioxins in humans is now well documented. [28-32] The
purpose of our article was to document, in this location and at this time, the
link between the dioxin-contaminated population and the contamination of their
food. The food that we sampled was, in fact, representative of that eaten by
our human subjects. All our higher levels of TCDD were found in food from the
contaminated lake or nearby in this study, consistent with findings from
previous work. [24,25,33,34]
The
Bien Hoa “hot spot” is quite similar to the one in the central highlands
studied by a Canadian environmental team which shows similar elevation of 2,3,7,8-TCDD in human tissue, soil, sediment, and food. [5,6]
In
his reference to PCBs, Dr Mai seems to be mistaken in describing them as being
characteristically contaminated with dioxins and dibenzofurans. In fact, their
characteristic contaminants are dibenzofurans. [35] When heated to certain
temperatures in the presence of oxygen, even more dibenzofurans are typically
formed. [36,37] Although there is considerable
similarity between dioxins and dibenzofurans, they are different compounds. It
was the dibenzofurans in rice oil resulting from heated PCBs that were
primarily responsible for the Yusho rice oil poisoning of 1969 in
From
a public health perspective, we agree that it would be useful to determine the
history of PCB importation in
We
certainly agree with Dr Mai that Agent Orange is not the only toxic chemical
that is to be found in
The
evidence is overwhelming that, although it has been 30 years since the last direct
contamination with Agent Orange in Vietnam, there is continued exposure of the
population and that these high levels come through food because many of those
with high levels of TCDD, up to 413 ppt, which is the highest blood level ever
found in a Vietnamese, were born long after the use of Agent Orange had ceased.
Levels of TCDD above current background of approximately 2 ppt were found in
95% of the population tested. Bien Hoa remains a dioxin hot spot, currently
with high levels of TCDD in human blood, soil, food, and sediment samples.
Because most dioxin enters humans through the food chain and because we found
many food samples with elevated levels of 2,3,7,8-TCDD,
and this particular dioxin only, among the more than 20 dioxins, dibenzofurans
and PCBs we studied, we can feel very confident that their food is the
continuing route of intake in the people of Bien Hoa, regardless of the precise
origin of every food tested. Although our research focuses mainly on TCDD
exposure in
This
letter was prepared with the assistance of K.C. Tung and Ana Nguyen.
References
1.
Schecter AJ, Quynh HT, Pavuk M, Papke O, Malisch R, Constable JD. Food as a source of dioxin exposure in the residents of
2.
Mai TT. Environmental Pollution in
3.
Schecter AJ, Constable JD, Arghestani S, Tong H, Gross
ML. Elevated levels of 2,3,7,8 tetrachlorodibenzodioxin in adipose tissue of
certain
4.
Michalek JE, Wolfe WH, Miner JC, et al. Indices of TCDD exposure and TCDD body
burden in veterans of Operation Ranch Hand. J Expo Anal Environ Epidemiol.
1995;52:209-223.
5.
Hatfield Consultants and 10-80 Committee. Preliminary
Assessment of Environmental Impacts Related to Spraying of Agent Orange
Herbicide During the Vietnam War.
6.
Dwernychuk LW, Cau H, Hatfield C, et al. Dioxin reservoirs in southern Vietnam
--a legacy of Agent Orange. Chemosphere. 2002;47:117-137.
7.
Kahn PC, Gochfeld M, Nygren M, et al. Dioxin and dibenzofurans in blood and
adipose tissue of Agent Orange-exposed Vietnam veterans and matched controls. JAMA. 1988;259:1661-1667.
8.
Schecter AJ, Papke O, Pavuk M, et al. Exposure and related chemicals in human
tissues. In: Schecter A, Gasiewicz T, eds. Dioxins and Health. 2nd ed.
9.
Baughman RW, Messelson M. An analytic method for detecting TCDD (dioxin) levels
of TCDD in samples from
10.
Baughman RW. Tetrachlorodibenzo-p-Dioxins in the environment: highresolution
mass spectrometry at the picogrum level [dissertation].
11.
Schecter AJ, Dai LC, Thuy LTB, et al. Agent Orange and the Vietnamese: the
persistence of elevated dioxin levels in human tissues. Am
J Public Health. 1995; 85:516-522.
12.
Schecter AJ, Pavuk M. Are Vietnamese food exports contaminated with dioxin from
Agent Orange? J Tox Environ Health Part A. 2003;66:1391-1404.
13.
Kahn PC, Gochfeld M, Nygren M, et al. Dioxin and dibenzofurans in blood and
adipose tissue of Agent Orange-exposed Vietnam veterans and matched controls. JAMA. 1988;259:1661-1667.
14.
Schecter AJ, Ryan JJ, Constable JD, et al. Partitioning of 2,3,7,8-chlorinated
dibenzo-p-dioxins and dibenzofurans between adipose tissue and plasma lipid of
20 Massachusetts Vietnam veterans. Chemosphere.
1990;20:951-958.
15.
Schecter AJ, McGee H, Stanley J, et al. Dioxin, dibenzofuran, and PCB levels in
the blood of
16.
Olie, K,
17.
Schecter AJ, Malkin R, Pa¨pke O, Ball M, Brandt-Rauf PW. Dioxin levels in blood
of municipal incinerator workers. Med Sci Res. 1991;19:331-332.
18.
Schecter AJ, Jiang K, Papke O, Furst P, Furst C. Comparison of dibenzodioxin
levels in blood and milk in agricultural workers and others
following pentachlorophenol exposure in
19.
Masuda, Y. The Yusho rice oil poisoning incident. In:
Schecter AJ, Gasiewicz T, eds. Dioxins and Health. 2nd ed.
20.
Guo YL, Yu M, Hsu C. The Yucheng rice oil poisoning incident.
In: Schecter AJ, Gasiewicz T, eds. Dioxins and Health,.
2nd ed.
21. Schecter AJ, Startin J, Wright C, Pa¨pke O, Ball M, Lis
A. Concentrations of polychlorinated dibenzo-p-dioxins and dibenzofurans in
human placental and fetal tissues from the
22.
Westing A. Herbicides in war: past and present. In: Westing A, ed. Herbicides
in War.
23.
24.
Schecter AJ, Kooke R, Serne P, et al. Chlorinated dioxin and dibenzofuran
levels in food samples collected between 1985-87 in the North and South of
Vietnam. Chemosphere. 1989;18:627-634.
25.
Olie K, Schecter AJ, Constable JD, et al. Chlorinated dioxin and dibenzofuran
levels in food and wildlife samples in the North and South of Vietnam. Chemosphere. 1989;19:493-496.
26.
Schecter AJ, Tong HY, Monson SJ, Gross ML. Levels of 2,3,7,8-TCDD
in silt samples collected between 1985-1986 from rivers in the north and south
of
27. Schecter AJ, Eitzer BD, Hites RA. Chlorinated dioxin and dibenzofuran
levels in sediments collected from rivers in
28.
Startin JR, Rose MD. Dioxins and Dioxinlike PCBs in Food.
In: Schecter A, Gasiewicz T, eds. Dioxins and Health. 2nd ed.
29.
Travis CC, Hattemer-Frey H. Human exposure to 2,3,7,8-TCDD.
Chemosphere. 1987;16:2331-2342.
30.
31.
World Health Organization. Polychlorinated
Dibenzo-para-Dioxins. In: IARC Monographs on the Evaluation of
Carcinogenic Risks to Humans. 1997;69:33-136.
32. Gilman A, Newhook R,
33.
Schecter AJ, Dai LC, Papke O, et al. Recent dioxin
contamination from Agent Orange in residents of a southern
34.
Schecter AJ, Pavuk M, Constable JD, et al. A follow-up: high level of dioxin
contamination in Vietnamese from Agent Orange, three decades after the end of
spraying [Letter]. J Occup Environ Med. 2002;44:218-220.
35.
Erickson, Mitchell. Analytical Chemistry of PCBs. 2nd ed.
36.
Buser HR. Formation, occurrence and analysis of polychlorinated dibenzofurans,
dioxins, and related compounds. Environ Health Perspect. 1985;60:259-267.
37.
Schecter AJ, Tiernan T. Occupational exposure to polychlorinated dioxins,
polychlorinated furans, polychlorinated biphenyls and biphenylenes after an
electrical panel and transformer accident in an office building in Binghamton,
NY. Environ Health Perspect. 1985;60:305-313.
38.
Schecter AJ, Furst P, Kruger C, et al. Levels of polychlorinated dibenzofurans,
dibenzodioxins, PCBs, DDT, and DDE, hexachlorobenzene, dieldrin,
hexachlorocyclo-hexanes and oxychlordane in human breast milk from the United
States, Thailand, Vietnam, and Germany. Chemosphere.
1989;18:445,454.
39.
Schecter AJ, Tionolo P, Dai LC, et al. Blood levels of DDT and breast cancer
risk among women living in the North of Vietnam. Archiv Environ Contam
Toxicol. 1997;334:453-456.
40. Schecter AJ, Quynh HT, Pavuk M, et al. New findings of dioxins, dibenzofurans,
PCBs, DDT/DDE, HCB, and HCH in food from a Vietnam TCDD contaminated area and a
comparison area. Organohalogen Compounds. 2003;64:231-234.
41.
Nhan DD, Am NM, Carvalho FP, Villeneuve JP, Cattini C. Organochlorine
pesticides and PCBs along the coast of north Vietnam. Sci Total Environ. 1999;237/ 238:363-371.
42.
Thao VD, Kawano M, Matsuda M, et al. Chlorinated hydrocarbon insecticide and
polychlorinated biphenyl residues in soils from southern provinces of Vietnam. Int
J Environ Anal Chem. 1993;50:147-159.
43.
Kannan K, Tanabe S, Quynh HT, et al. Residue pattern and dietary intake of
persistent organochlorine compounds in foodstuffs from
44.
Pavuk M, Schecter A, Akhtar F, Michalek J. Serum TCDD levels and thyroid system
effects in the US Air Force veterans. Ann Epidemiol. 2003;13: 335-343.
45.
Longnecker MP, Michalek JE. Serum dioxin level in relation to diabetes mellitus
among Air Force veterans with background levels of exposure. Epidemiology.
2000;
46. Henriksen GL,
47.