Biomedical Engineering Reference
In-Depth Information
pesticides, such as those used in the Vietnam defoliants,
are produced. Other isomers, which may have been
present in the formulations along with the 2,3,7,8 con-
figurations, are also considered to have higher toxicity
than the dioxins and furans with different chlorine atom
arrangements.
Dioxin contaminants of Agent Orange have persisted
in the environment in Vietnam for over thirty years. In
addition to a better understanding of the outcomes of
exposure, an improved understanding of residue levels
and rates of migration of dioxin and other chemicals into
the environment is needed. ''Hot spots'' containing high
levels of dioxin in soil have been identified and others are
presumed to exist but have yet to be located.
Dioxin has migrated through soil and has been trans-
ported through natural processes such as windblown dust
and erosion into the aquatic environment. Contamina-
tion of soil and sediments provides a reservoir source of
dioxin for direct and indirect exposure pathways for
humans and wildlife. Movement of dioxin through the
food web results in bioconcentration and biomagnifica-
tion with potential ecological impacts and continuing
human exposure. Research is needed to develop ap-
proaches for more rapid and less expensive screening of
dioxin residue levels in soil, sediment, and biological
samples, which can be applied in Vietnam.
Actually, a number of defoliating agents were used in
Vietnam, including those listed in
Table 8.2-2
. Most of
the formulations included the two herbicides 2,4-D and
2,4,5-T. The combined product was mixed with kerosene
or diesel fuel and dispersed by aircraft, vehicle, and hand
spraying. An estimated 80 million liters of the formula-
tion was applied in South Vietnam during the war.
30
The Agent Orange problem illustrates the problem of
uncertainty in characterizing and enumerating effects.
There is little consensus on whether the symptoms and
disorders suggested to be linked to Agent Orange are
sufficiently strong and well documented; that is, provide
weight of evidence, to support cause and effect. This
complicates bioethical decision making since the factual
premises are fraught with uncertainties.
Japanese metal industries
As in military decisions, industrial decisions also have
significant long-term health considerations.
Minamata mercury case
One of the most telling cases of improper bioethical de-
cision making was that of Minamata, a small factory town
on Japan's Shiranui Sea. Minamata means ''nitrogen,''
emblematic of the town's production of commercial
fertilizer by the Chisso Corporation for decades, begin-
ning in 1907.
31
Beginning in 1932, the company produced
pharmaceutical products, perfumes, and plastics and
processed petrochemicals. Chisso became highly profit-
able, notably because it became the only Japanese source
of a high-demand primary chemical, diotyl phthalate
(DOP), a plasticizing agent. These processes needed the
reactive organic compound, acetaldehyde, which is pro-
duced using mercury. The residents of Minamata payed
a huge price for this industrial heritage. Records indicate
that from 1932 to 1968, the company released approxi-
mately 27 tons of mercury compounds into the adjacent
Minamata Bay. This directly affected the dietary intake of
toxic mercury by fisherman, farmers, and their families in
Kumamoto, a small village about 900 kilometers from
Tokyo. The consumed fish contained extremely elevated
concentrations of a number of mercury compounds,
including the highly toxic methylated forms (i.e., mono-
methyl mercury and dimethyl mercury), leading to classic
symptoms of methyl mercury poisoning. In fact, the
symptoms were so pronounced that the syndrome of these
effects came to be known as the ''Minamata disease.''
In the middle of the 1950s, residents began to report
what they called the ''strange disease,'' including the
classic form of mercury toxicity; that is, disorders of the
central nervous system (CNS) and peripheral nervous
systems (PNS). Diagnoses included numbness in lips and
limbs, slurred speech, and constricted vision. A number
of people engaged in uncontrollable shouting. Pets and
domestic animals also demonstrated mercury toxicity,
including cat suicides and birds dying in flight. These
events were met with panic by the townspeople.
Table 8.2-2 Formulations of defoliants used in the Vietnam war
Agent
Formulation
Purple
2,4-D and 2,4,5-T used between 1962 and 1964
Green
Contained 2,4,5-T and was used during 1962-1964
Pink
Contained 2,4,5-T and was used during 1962-1964
Orange
A formulation of 2,4-D and 2,4,5-T used between
1965 and 1970
White
A formulation of picloram and 2,4-D
Blue
Contained cacodylic acid
Orange II
2,4-D and 2,4,5-T used in 1968 and 1969
(also sometimes referred to as ''Super Orange'')
Dinoxol
2,4-D and 2,4,5-T. Small quantities were tested in
Vietnam between 1962 and 1964
Trinoxol
2,4,5-T. Small quantities tested in Vietnam during
1962-1964
Source: Agent Orange website:
http://www.lewispublishing.com/orange.htm
;
accessed on 22 April 2005.
