Реферат по предмету "На английском языке"


Agent Orange And Dioxin Essay Research Paper

Agent Orange And Dioxin Essay, Research Paper
In 1961, the United States began spraying herbicides in its military campaign to defoliate
the jungles of southern Vietnam. Mimicking Smokey Bear, American pilots chuckled
Remember, only you can prevent forests, as they dropped weed killers over target sites.
But as research progressed, the true nature of the chemicals which they were spraying
came to light. It is certainly no longer a laughing matter when it is realized that Agent
Orange, a fifty-fifty mixture of 2,4,D and 2,4,5,T usually mixed with kerosene or diesel
fuel, could be as deadly to humans as it is to plants.
The military research of herbicides dates back to World War II. A grant was provided
by the National Research Council to develop a chemical to destroy rice crops in Japan.
2,4,D and 2,4,5,T was the result. A discussion between President Roosevelt and White
House Chief of Staff, Admiral William D. Leahy determined that this heinous chemical
should not be used. But in 1961 President Kennedy signed two orders allowing Agent
Orange to be used in Vietnam (one to destroy crops and the other to defoliate the
jungle). Defoliation stripped the jungle of vegetation. Left barren, it no longer provided
camouflage for the Viet Cong, their supply routes and base camps would be more prone
to aerial attacks. Crop destruction denied the communists of local food sources. This
forced them to divert more resources to provide and transport foods from other regions.
But just as important, crop destruction also weakened enemy morale and forced villagers
to move to cities where they could be more easily controlled.
The program for spraying herbicides over Vietnam was either called Operation Trail
Dust or Operation Ranch Hand. It began in 1961 and peaked from 1967 to 1969.
Various methods were employed to systematically spray these chemicals, which were
dispersed by aircraft, vehicle, boat, and hand-spraying. On ground, they were used by
soldiers to clear the perimeters of their base camps. Riverboats were used to spray the
riverbanks. Most damage to the jungle was done by air. The Air Force Operation Ranch
Hand, as it was called, used C-123 cargo aircrafts (providers) and helicopters to drop the
majority of the herbicides. There were an estimated 19.4 million gallons dropped during
the Vietnam War, sixty percent of which were Agent Orange. The average C-123 aircraft
could dump eleven thousand pounds of agent orange over three hundred acres in four
minutes.
There were many types of herbicides used by the United States in Vietnam. Each was
named after the color of the four inch band painted around the fifty-five gallon drums in
which it was contained: Agent White, Purple, Blue, Green, Pink and Orange.
The effects of the sprayings on the jungle were immediately recognizable. Estimates
show that six million acres or twenty percent of the entire land area of the republic of
South Vietnam was covered with chemical poisons. The President of South Vietnam,
Nguyen Van Thieu, announced that herbicides had destroyed twenty-three percent of
forests in his country. Scientists from the American Association for the Advancement of
Science who visited Vietnam in 1970 reported that bamboo had spread to reclaim forest
floors that hardwoods once claimed. Nearly all trees of coastal mangroves were destroyed
after one spraying and were not expected to return to their normal states for at least one
hundred years. More than six thousand two hundred and fifty square miles of south
Vietnam still can not be farmed because of defoliation.
The effects of the herbicides on humans were less obvious. Agent Orange is a
mixture of two major compounds- 2,4,Dichlorophenoxy acetic acid and
2,4,5,Trichlorophenoxy acetic acid. By mimicking a natural plant growth hormone, auxin,
these herbicides are able to induce plants to grow themselves past their natural levels of
tolerance. They were first used in the 1940 s in the United States to destroy weeds in
grain fields, pastures and turf. By the 1960 s, these herbicides had become an important
method of controlling weeds. Unfortunately, it was unknown at that time that Agent
Orange also contained one of the most lethal compounds known to man, dioxin. It s
ironic that the dioxin that makes agent orange so deadly isn t even an intended part of
the plant killer.
Dioxin generally refers to a group of about seventy-five chemicals made of two
benzene rings with substituted chlorines. They are by-products in the manufacture of
chlorine products like Polychlorinated Biphenyl oils or the burning of chlorine containing
wastes such as PVC pipes. In the production of chlorophenoxy herbicides, they were
unwanted chemicals that couldn t be removed. Dioxin is also produced by automobiles
(chlorinated chemicals are deliberately added to fuels), steel mills ( chlorinated solvents,
cutting oils and plastics are put into the furnaces), recycling smelters for copper, lead,
and steel ( the products recycled in them contain significant quantities of PVC, such as
cable coatings, battery casings, automobile components, and so on), sawmills ( use of
pentachlorophenol as a wood preservative), hazardous waste incinerators ( burn
chlorinated solvents or, like those that Dow operates, burn copious wastes from the
manufacture of chlorinated plastics, pesticides, and other chemicals), cement kilns,
industrial untreated wood burning, forest fires, and sewage sludge incineration. Dioxin is
usually taken in by the ingestion of beef, dairy products, milk, chicken, pork, fish, eggs,
soil and water.
The toxicity of the 75 different chlorinated dioxins and 135 different chlorinated
furans (related family of compounds) is highly variable. The 2,3,7,8-TCDD
(Tetrachlorodibenzo-p-dioxin) found in Agent Orange has been described as one of the
most toxic chemicals known to man, based on animal studies. However epidemiological
studies of humans exposed to this compound have failed to conclusively attribute
significant health effects except chloracne at high doses. Other dioxins, such as
octachlorodibenzo-p-dioxin (OCDD), have very low toxicity.
A study conducted by the National Institute of Occupational Safety and Health
(NIOSH) on roughly three thousand five hundred workers from U.S. plants that used to
produced chemicals contaminated with TCDD confirmed previous findings that high
exposure to TCDD resulted in significant increase in cancer deaths. NIOSH found an
average increase in cancer mortality of thirteen percent in the group and an increase of
sixty percent among workers with the highest level of TCDD exposure.
The mechanism by which dioxin causes damage at the cellular level is not exactly
known. It has been assumed that dioxin may be stored in fat cells and is activated by
internal stress to induce chromosomal and cellular damage. Whatever the case, the
toxicity of dioxin is unquestioned. Even at extremely small levels, it has been proven to
be a deadly poison. Animal studies have shown that guinea pigs could die by a single
dose that weighs less than a billionth of their body weight. In mice and rats, low levels
of dioxin have been reported to cause decreased weight, lowered reproductive rate and
internal hemorrhaging. Studies have found that, when given an oral dose of 210 ng/kg
for 78 weeks, rats developed increase incidences in liver, hard palate, and tongue tumors.
In 1969, the extensive use of herbicides was halted after a National Institute of Health
report concluded that dioxin caused stillbirth in mice. The last herbicide operation was
flown two years later.
The cessation for the use of herbicides had come too late. By then, thousands of
American soldiers and countless Vietnamese villagers had already been exposed to dioxin.
Americans who came in contact with this poison included those who fought in the
jungles, patrolled the rivers by boat, or participated in the spraying of herbicides. Many
came home and were reported to have high increases in illnesses that were extremely
uncommon in the general population. In contrast to animal studies, the cause and effect
of dioxin on the veterans were not well determined because the amount of exposure is
difficult to quantify among those who claimed to have been illed by dioxin.
But the correlation between dioxin and the reported illnesses are well documented.
The Institute of Medicine had found that there is sufficient evidence of a statistical
association between dioxin or herbicides and soft tissue sarcoma ( tumors in muscles, fat,
fibrous tissues, and vessels serving these tissues as well as the peripheral nervous
system), non-Hodgkin s lymphoma ( tumors or enlargement of the lymphnodes or lymph
glands), Hodgkin s Disease ( enlargement of the lymphnodes and spleen which often
begins in a cervical node on the side of the neck and spreads through the body),
chloracne ( an acne form eruption caused by chlorine compounds), dioxin related liver
disorders, diabetes ( a variety of disorders linked to high or low glucose levels),
malformations and other reproductive and developmental effects and endocrine disruption
( malfunction of the hormonal system). In scientific terms, statistical association means
that there is an extremely low probability, less than five percent, that the events occurred
randomly. A study by the Center for Disease Control found that there is a fifty percent
higher rate of non-Hodgkin s Lymphoma among Vietnam vets than vets who didn t serve
in Vietnam.
The Department of Veterans Affairs had provided special compensation for those who
have become ill due to dioxin. Veterans who have chloracne, Hodgkin s disease, multiple
myeloma ( tumor normally found in bone marrow), non-Hodgkin s Lymphoma, porphyria
cutanea tarda ( a disturbance in hemoglobin which is essential to normal functioning of
the cells and tissues of the body), respiratory cancers, soft tissue sarcoma, acute and
subacute peripheral neuropathy ( abnormal changes in the peripheral nervous system), and
prostate cancer could qualify for monthly payments. The VA does not require that
veterans prove that they were harmed by dioxin. It is assumed that all personnel who
served in Vietnam have been exposed to it. The believed amount of time for dioxin to
leave the body naturally (by either being metabolized or eliminated by normal biological
processes) is 8.7 human years (determined by the Ranch Hand follow-up studies).
Unlike their American counterparts, Vietnamese victims were exposed to dioxin on a
long term basis. It is believed that the chemicals remained on the ground for twelve
years. Each year, monsoon rains would spread the chemicals to uncontaminated areas by
flushing it into streams and rivers. Many health experts believe that dioxin is in the food
chain of southern Vietnam. It is carried in drinking water or by the fish caught in
contaminated streams. but relatively little is known about the effects of dioxin on the
villagers that were sprayed on. In part, this is due to their isolation from local
authorities and hospitals.
The Vietnamese veterans and their families, however, did file a class action suit
against seven chemical companies: Dow Chemical, Monsanto, Uniroyal, Hercules,
Diamond Shamrock, Thompson Chemical, and T.H. Agriculture. It was settled out of
court in May 1984 for victims and families of those exposed to herbicides for one-
hundred and eighty million dollars ( of which the lawyers got a staggering one hundred
million dollars… go figure). The amount given to the qualifying was pathetic. For
example, A woman whose husband suffered, and eventually died, leaving her and three
children was given just over three thousand dollars. And another man who suffered from
a brain tumor and other herbicide related diseases for over three years was given only
one thousand eight hundred and sixty dollars. And in another case a platoon that
operated in a part of Vietnam that had been heavily sprayed has had five of it s twenty
members diagnosed as suffering from dioxin poisoning. That s twenty-five percent. That s
five hundred percent above that national average for these types of disorders. This in
itself is scary but the researcher was only able to locate six of the twenty members of
his platoon. How many of those that weren t contacted had similar symptoms? Veterans
tell story after story of veterans who suddenly age. Their hair falls out in clumps, what
remains turns white. They suffer from strange nerve disorders, irritableness, weight loss,
palsies and finally, death. None of the five men found from that platoon were given any
kind of compensation from the Agent Orange Veteran Payment Program.
Perhaps the most extensive long-term damage of dioxin was done to the second
generation victims. It has been found that Vietnam veterans generally have lower sperm
counts that those who didn t serve in the war. In addition, their children have been more
prone to birth defects pertaining to the skin, nervous system, heart, kidneys and oral
clefts. Sudden Infant Death Syndrome is four times more likely in those born to
Vietnamese veterans.
Difficult and premature births are a commonality at the Tu Du Obstetrical and
Gynecological Hospital in Vietnam, which receives the bulk of the patients who received
the largest amounts of defoliants in Vietnam. A hospital study in 1987 found that thirty
percent of the seventeen thousand babies delivered at the hospital were either difficult of
premature. The comparative rates of all south Vietnam is ten percent and for the whole
country, it is eight percent.
Instances of birth defects are also extremely high at the hospital. Here, infants born
without arms, legs, shoulders, and ears have all been found. Others have been born with
gross cleft palates or were hydrocephalic ( water on the brain). In 1987 alone, forty
infants suffered from neural tube defects ( abnormality of the fallopian tubes), forty from
cleft palates, and thirty-two from malformation or absence of arms and legs. Every year
since 1975, the hospital has been the site of five or more siamese twins. Physicians at
the hospital report that a deformed fetus is delivered every two to three days. A room at
the hospital contains jars which store aborted and full fetuses with atrocious genetic
defects. For us, they are reminders of what happens when one tinkers with mother
nature.


Не сдавайте скачаную работу преподавателю!
Данный реферат Вы можете использовать для подготовки курсовых проектов.

Поделись с друзьями, за репост + 100 мильонов к студенческой карме :

Пишем реферат самостоятельно:
! Как писать рефераты
Практические рекомендации по написанию студенческих рефератов.
! План реферата Краткий список разделов, отражающий структура и порядок работы над будующим рефератом.
! Введение реферата Вводная часть работы, в которой отражается цель и обозначается список задач.
! Заключение реферата В заключении подводятся итоги, описывается была ли достигнута поставленная цель, каковы результаты.
! Оформление рефератов Методические рекомендации по грамотному оформлению работы по ГОСТ.

Читайте также:
Виды рефератов Какими бывают рефераты по своему назначению и структуре.