User:FlorenceOpoku98/Agent Orange

Agent Orange

Agent Orange is a herbicide and defoliant chemical that is a mixture of two herbicides, 2,4,5-T and 2,4-D. It is well known as one of the "tactical use" Rainbow Herbicides used by the U.S. military during the Vietnam War to clear land and vegetation for military operations. The U.S. warfare program, nicknamed Operation Ranch Hand,sprayed Agent Orange and gallons of other herbicides over Vietnam, Laos, and Cambodia to eliminate forests and crops near the border that provided food sources and enemy cover for North Vietnamese and Viet Cong troops.

Dioxin or TCDD, the most toxic chemical of its family, was found in Agent Orange and caused major health problems for many individuals. Between 1961 and 1971, up to four million people in Vietnam were exposed to the defoliant and the Vietnamese government reports as many as three million have suffered illness because of it. The defoliant also impacted US military veterans and their families. The US government has documented higher cases of leukemia, Hodgkin's lymphoma, and various kinds of cancer in exposed US military veterans. An epidemiological study done by the Centers for Disease Control and Prevention showed that there was an increase in the rate of birth defects of the children of military personnel as a result of Agent Orange.Agent Orange has also caused substantial environmental damage in Vietnam by defoliating over 3,100,000 hectares (31,000 km² or 11,969 mi²) of forest. Defoliants eroded tree cover and seedling forest stock, making reforestation difficult in numerous areas. Animal species diversity sharply reduced in contrast with unsprayed areas. [copied from Agent Orange]]

Chemical Composition

The active ingredient of Agent Orange was an equal mixture of two phenoxy herbicides– 2,4-dichlorophenoxyacetic acid(2,4-D) and 2,4,5-trichlorophenoxyacetic acid(2,4,5-T) – in iso-octyl esterform, which contained traces of the dioxin 2,3,7,8-tetrachlorodibenzo-p-dioxin(TCDD). [copied from Agent Orange] It was also reported to be contaminated with 2,3,7,8-tetrachlorodibenzo-p-dioxin (dioxin) in the range of <0.05 to 50 parts per million.

Toxicology

Agent Orange primarily consists of dioxins, a very potent chemical in its family. Dioxins are pollutants that are released into the environment by burning waste, diesel exhaust, chemical manufacturing, and other processes.By itself, dioxin is extremely stable in environmental and biological breakdown. Because of its water insolubility and lipophilicity, dioxin concentrates in sediments. It also bioaccumulates in fatty tissues of fish, birds, reptiles, and mammals in the food chain.

TCDD is a synthetic substance and is one chemical compound out of the polychlorinated “dibenzo-p-dioxin” family. TCDD is the most toxic member of dioxins and is listed as a human carcinogen by the U.S. Environmental Protection Agency.  TCDD is extremely fat-soluble and bioaccumulates when it enters the environment through the food web and in the human body. TCDD enters the human body with the assistance of a cellular protein called aryl hydrocarbon receptor (AhR), otherwise known as the Ah-receptor. This protein has a high affinity to binding and is found in low numbers in the human cell. When the human body is exposed to TCDD, the TCDD first has to recognize and bind to Ah-receptor protein. After TCDD binds to the receptor, it then travels to DNA-binding sites on the nucleus, and alters gene expression. In humans, TCDD typically is stored in the liver. It can also accumulate in the epithelial and nervous tissue for longterm storage.

Health Effects

After TCDD enters the body, it can remain for many years due to its ability to store in fatty tissues. Its half life in humans lasts 7 to 11 years. High levels of TCDD may lead to small increase in diabetes risk. Short term exposure of humans to high levels of TCDD can cause skin irregularities. A well-known skin disease caused by TCDD exposure is called chloracne, a severe form of blackheads, cysts, and leisons that spreads from the face to the upper body. Long-term exposure to TCDD may damage the liver, immune system, nervous system, endocrine system, and reproductive organs.

Adverse heath effects of TCDD can include cardiovascular disease, cancer, endometriosis, early menopause, reduced testosterone and thyroid hormones, skin, tooth, and nail abnormalities, missing limbs, altered growth, and altered metabolism. The National Institutes of Occupational Health and Safety reported its cancer mortality studies of US workers exposed to TCDD and found that mortality has increased for all cancers combined (stomach, liver, nasal cancers, Hodgkin’s disease, non-Hodgkin’s lymphoma, etc.), particularly around those with the longest occupational exposure.

Vietnamese people

Main article: Effects of Agent Orange on the Vietnamese people

[copied fromAgent Orange]]

The government of Vietnam says that 4 million of its citizens were exposed to Agent Orange, and as many as 3 million have suffered illnesses because of it; these figures include their children who were exposed. The Red Cross of Vietnam estimates that up to 1 million people are disabled or have health problems due to contaminated Agent Orange. The United States government has challenged these figures as being unreliable.

According to a study by Dr. Nguyen Viet Nhan, children in the areas where Agent Orange was used have been affected and have multiple health problems, including cleft palate, mental disabilities, hernias, and extra fingers and toes. In the 1970s, high levels of dioxin were found in the breast milk of South Vietnamese women, and in the blood of U.S. military personnel who had served in Vietnam. The most affected zones are the mountainous area along Truong Son (Long Mountains) and the border between Vietnam and Cambodia. The affected residents are living in substandard conditions with many genetic diseases.

In 2006, Anh Duc Ngo and colleagues of the University of Texas Health Science Center published a meta-analysis that exposed a large amount of heterogeneity (different findings) between studies, a finding consistent with a lack of consensus on the issue. Despite this, statistical analysis of the studies they examined resulted in data that the increase in birth defects/relative risk (RR) from exposure to agent orange/dioxin "appears" to be on the order of 3 in Vietnamese-funded studies, but 1.29 in the rest of the world. There is data near the threshold of statistical significance suggesting Agent Orange contributes to still-births, cleft palate, and neural tube defects, with spina bifida being the most statistically significant defect. The large discrepancy in RR between Vietnamese studies and those in the rest of the world has been ascribed to bias in the Vietnamese studies.

Twenty-eight of the former U.S. military bases in Vietnam where the herbicides were stored and loaded onto airplanes may still have high levels of dioxins in the soil, posing a health threat to the surrounding communities. Extensive testing for dioxin contamination has been conducted at the former U.S. airbases in Da Nang, Phù Cát District and Biên Hòa. Some of the soil and sediment on the bases have extremely high levels of dioxin requiring remediation. The Da Nang Air Base has dioxin contamination up to 350 times higher than international recommendations for action. The contaminated soil and sediment continue to affect the citizens of Vietnam, poisoning their food chain and causing illnesses, serious skin diseases and a variety of cancers in the lungs, larynx, and prostate.

Ecological Impact

About 17.8%—3,100,000 hectares (31,000 km2; 12,000 sq mi) of the total forested area of Vietnam was sprayed during the war, which disrupted the ecological equilibrium. Dioxins are persistent in the environment, which caused erosion from loss of tree cover and loss of seedling forest stock, which meant meant that reforestation was difficult (or impossible) in many areas. Many defoliated forest areas were quickly invaded by aggressive pioneer species, such as bamboo and cogon grass, making forest regeneration difficult and unlikely. Animal species diversity was also impacted; in one study, a Harvard biologist found 24 species of birds and 5 species of mammals in a sprayed forest, while in two adjacent sections of unsprayed forest there were 145 and 170 species of birds and 30 and 55 species of mammals.

Dioxins from Agent Orange have persisted in the Vietnamese environment since the war, settling in the soil and sediment and entering the food chain through animals and fish which feed in the contaminated areas. The movement of dioxins through the food web has resulted in bioconcentration and biomagnification. The areas most heavily contaminated with dioxins are former U.S. air bases. [copied from Agent Orange]

In Aluoi Valley of central Vietnam, relatively high levels of TCDD were measured in the environment, specifically in the soil, and in species that foraged around the contaminated area, including fish and duck, where the contaminant accumulated in fat tissue. Samples that were collected in A So village from 1996 to 1999 revealed high levels of TCDD found in breast milk and human blood, mainly due to the fact that the village was situated on a former military base where Agent Orange was sprayed in the valley and stored at the base. TCDD was transferred throughout the food chain from contaminated soil to fish pond sediments, where fish and duck became contaminated, which then transferred to human populations, which was measured in the breast milk and blood samples. When TCDD disturbs the soil, it can be mobilized and introduced into animal and human food chains.

Residual TCDD concentrations in Vietnam are a result from spray frequency and distribution, partitioning, bioavailability, recycling in the ecosystem, decomposition, and storage for Agent Orange.

Due to the 5.5 million hectares of forest that were sprayed one or more times between 1961 to 1971, plant and animal communities have been significantly disrupted, altered and simplified due to the reduction of biomass, biodiversity, nutrient loss, and ecosystem productivity. In forested areas that were sprayed more than once, the ecological consequences were more drastic, which caused the land to convert to Imperata grasslands and bamboo brakes. The conversion to this type of landscape makes it very unlikely for the natural forest to grow back for many years.

The trees present in the Vietnam forests were mangroves, which are very susceptible to defoliants such as Agent Orange. Some areas that were only sprayed once were not able to recover, although there was regeneration of mangrove trees in some areas. The saltwater ferns that were also present in the forests, known as Achrosticum aureaum, were not able to grow after Agent Orange exposure. Mangrove forests typically have unusual soil conditions, which means that the herbicides may fail to decompose.

The destruction of the mangrove forests had severe impacts on the local animal populations. The insectivorous or frugivorous birds were no longer found in the defoliated forests, although barn swallows, Hirundo rustic, which are migrant from the north, were found. Since mangrove forests are typically rich in bird species, the lack of land birds demonstrated the impact from Agent Orange.