Agent Orange

Agent Orange is a herbicide recognized for its use during the Vietnam War. It is composed of equal parts of two chemicals : 2,4-D and 2,4,5-T . A less potent form of the herbicide has also been used for clearing heavy growth on a commercial basis for a number of years. However, it does not contain 2,4-D. On a commercial level, the herbicide was used in forestry control as early as the 1930s. In the 1950s through the 1960s, Agent Orange was also exported. For example, New Brunswick, Canada, was the scene of major Agent Orange spraying to control forests for industrial development. In Malaysia in the 1950s, the British used compounds with the chemical mixture 2,4,5-T to clear communication routes.

In the United States, herbicides were considered for military use towards the end of World War II, during the action in the Pacific. However, the first American military field tests were actually conducted in Puerto Rico, Texas, and Fort Drum, New York, in 1959.

That same year—1959—the Crops Division at Fort Detrick, Maryland initiated the first large-scale military defoliation effort. The project involved the aerial application of Agent Orange to about 4 mi² (10.4 km²) of vegetation. The experiment proved highly successful; the military had found an effective tool. By 1960, the South Vietnamese government, aware of these early experiments, had requested that the United States conduct trials of these herbicides for use against guerrilla forces. Spraying of Agent Orange in Southeast Asia began in 1961. South Vietnam President Diem stated that he wanted this "powder" in order to destroy the rice and the food crops that would be used by the Viet Cong. Thus began the use of herbicides as a weapon of war.

The United States military became involved, recognizing the limitations of fighting in foreign territory with troops that were not accustomed to jungle conditions. The military wanted to clear communication lines and open up areas of visibility in order to enhance their opportunities for success. Eventually, the United States military took complete control of the spray missions. Initially, there were to be restrictions: the spraying was to be limited to clearing power lines and roadsides, railroads and other lines of communications and areas adjacent to depots. Eventually, the spraying was used to defoliate the thick jungle brush, thereby obliterating enemy hiding places.

Once under the authority of the military, and with no checks or restraints, the spraying continued to increase in intensity and abandon, escalating in scope because of military pressure. It was eventually used to destroy crops, mainly rice, in an effort to deprive the enemy of food. Unfortunately, the civilian population—Vietnamese men, women, and children—was also affected. The United States military sprayed 3.6 million acres (1.5 million ha) with 19 million gal (720 million l) of Agent Orange over nine years.

The spraying also became useful in clearing military base perimeters, cache sites, and waterways. Base perimeters were often sprayed more than once. In the case of dense jungle growth, one application of spray was made for the upper and another for the lower layers of vegetation. Inland forests, mangrove forests, and cultivated lands were all targets. Through Project Ranch Hand—the Air Force team assigned to the spray missions—Agent Orange became the most widely produced and dispensed defoliant in Vietnam.

Military requirements for herbicide use were developed by the Army's Chemical Operations Division, J-3, Military Assistance Command, Vietnam, (MACV). With Project Ranch Hand underway, the spray missions increased monthly after 1962. This increase was made possible by the continued military promises to stay away from the civilians or to re-settle those civilians and re-supply the food in any areas where herbicides destroyed the food of the innocent. These promises were never kept. The use of herbicides for crop destruction peaked in 1965 when 45% of the total spraying was designed to destroy crops.

Initially, the aerial spraying took place near Saigon. Eventually the geographical base was widened. During the 1967 expansion period of herbicide procurement, when requirements had become greater than the industries' ability to produce, the Air Force and Joint Chiefs of Staff become actively involved in the herbicide program. All production for commercial use was diverted to the military, and the Department of Defense (DOD) was appointed to deal with problems of procurement and production. Commercial producers were encouraged to expand their facilities and build new plants, and the DOD made attractive offers to companies that might be induced to manufacture herbicides. A number of companies were awarded contracts. Working closely with the military, certain chemical companies sent technical advisors to Vietnam to instruct personnel on the methods and techniques necessary for effective use of the herbicides.

During the peak of the spraying, approximately 129 sorties were flown per aircraft. Twenty-four UC-123B aircraft were used, averaging 39 sorties per day. In addition, there were trucks and helicopters that went on spraying missions, backed up by such countries as Australia . C-123 cargo planes and helicopters were also used. Helicopters flew without cargo doors so that frequent ground fire could be returned. But the rotary blades would kick up gusts of spray, thereby delivering a powerful dose onto the faces and bodies of the men inside the plane.

The dense Vietnamese jungle growth required two applications to defoliate both upper and lower layers of vegetation. On the ground, both enemy troops and Vietnamese civilians came in contact with the defoliant. American troops were also exposed. They could inhale the fine misty spray or be splashed in the sudden and unexpected deluge of an emergency dumping. Readily absorbing the chemicals through their skin and lungs, hundreds of thousands of United States military troops were exposed as they lived on the sprayed bases, slept near empty drums, and drank and washed in water in areas where defoliation had occurred. They ate food that had been brushed with spray. Empty herbicide drums were indiscriminately used and improperly stored. Volatile fumes from these drums caused damage to shade trees and to anyone near the fumes. Those handling the herbicides in support of a particular project goal had the unfortunate opportunity of becoming directly exposed on a consistent basis. Nearly three million veterans served in Southeast Asia. There is growing speculation that nearly everyone who was in Vietnam was eventually exposed to some degree—far less a possibility for those stationed in urban centers or on the waters.

According to official sources, in addition to the Ranch Hand group at least three groups were exposed:

• A group considered secondary support personnel. This included Army pilots who may have been involved in helicopter spraying, along with the Navy and Marine pilots.
• Those who transported the herbicide to Saigon, and from there to Bien Hoa and Da Nang. Such personnel transported the herbicide in the omnipresent 55-gallon (208-l) containers.
• Specialized mechanics, electricians, and technical personnel assigned to work on various aircraft. Many of this group were not specifically assigned to Ranch Hand but had to work in aircraft that were repeatedly contaminated.

Agent Orange was used in Vietnam in undiluted form at the rate of 3–4 gal (11.4-15.2 l) per acre. 13.8 lb (6.27 kg) of the chemical 2,4,5-T were added to 12 lb (5.5 kg) of 2,4-D per acre, a nearly 50-50 ratio. This intensity is 13.3 lb (6.06 kg) per acre more than was recommended by the military's own manual. Computer tapes (HERBS TAPES) now available show that some areas were sprayed as much as 25 times in just a few short months, thereby dramatically increasing the exposure to anyone within those sprayed areas. Between 1962 and 1971 an estimated 11.2 million gal (42.4 million l) of Agent Orange were dumped over South Vietnam.

Evaluations show that the chemical had killed and defoliated 90–95% of the treated vegetation. Thirty-six percent of all mangrove forest areas in South Vietnam were destroyed. Viet Cong tunnel openings, caves, and above ground shelters were revealed to the aircraft after the herbicides were shipped in drums identified by an orange stripe and a contract identification number that enabled the government to identify the specific manufacturer. The drums were sent to a number of central transportation points for shipment to Vietnam.

Agent Orange is contaminated by the chemical dioxin , specifically TCDD. In Vietnam, the dioxin concentration in Agent Orange varied from parts per billion (ppb) to parts per million (ppm), depending on each manufacturer's production methods. The highest reported concentration in Agent Orange was 45 ppm. The Environmental Protection Agency (EPA) evacuated Times Beach , Missouri, when tests revealed soil samples there with two parts per billion of dioxin. The EPA has stated that one ppb is dangerous to humans.

Ten years after the spraying ended, the agricultural areas remained barren. Damaging amounts of dioxin stayed in the soil thus infecting the food chain and exposing the Vietnamese people. As a result there is some concern that the high levels of TCDD are responsible for infant mortality , birth defects , and spontaneous abortions that occur in higher numbers in the once sprayed areas of Vietnam. Another report indicates that thirty years after Agent Orange contaminated the area, there is 100 times as much dioxin found in the bloodstream of people living in the area than those living in non-contaminated areas of Vietnam. This is a result of the dioxin found in the soil of the once heavily sprayed land. The chemical is then passed on to humans through the food they eat. Consequently, dioxin is also spread to infants through the mother's breast milk, which will undoubtedly affect the child's development.

In 1991 Congress passed the Agent Orange Act(-Public Law 102-4), which funded the extensive scientific study of the long-term health effects of Agent Orange and other herbicides used in Vietnam. As of early 2002, Agent Orange had been linked to the development of peripheral neuropathy, type II diabetes, prostate cancer , multiple myeloma, lymphomas, soft tissue sarcomas, and respiratory cancers. Researchers have also found a possible correlation between dioxin and the development of spinal bifida, a birth defect, and childhood leukemia in offspring of exposed vets. It is important to acknowledge the statistics do not necessarily show a strong link between exposure to Agent Orange or TCDD and some of the conditions listed above. However, Vietnam veterans who were honorably discharged and have any of these "presumptive" conditions (i.e., conditions presumed caused by wartime exposure) are entitled to Veterans Administration (VA) health care benefits and disability compensation under federal law. Unfortunately many Vietnamese civilians will not receive any benefits despite the evidence that they continue to suffer from the affects of Agent Orange.

[Liane Clorfene Casten and Paula Anne Ford-Martin ]

RESOURCES

BOOKS

Committee to Review the Health Effects in Vietnam Veterans of Exposure to Herbicides, Division of Health Promotion and Disease Prevention, Institute of Medicine. Veterans and Agent Orange: Update 2000. Washington, DC: National Academy Press, 2001.

PERIODICALS

"Agent Orange Exposure Linked to Type 2 Diabetes." Nation's Health 30, no. 11 (December 2000/January 2001): 11.
"Agent Orange Victims." Earth Island Journal 17, no. 1 (Spring 2002): 15. Dreyfus, Robert. "Apocolypse Still." Mother Jones (January/February 2000). Korn, Peter."The Persisting Poison; Agent Orange in Vietnam." The Nation 252, no.13 (April 8, 1991): 440.

Young, Emma"Foul Fare." New Scientist 170, no. 2292 (May 26, 2001): 13.

OTHER

U.S. Veterans Affairs (VA). Agent Orange [June 2002]. <http://www.va.gov/agentorange>.

Agent Orange

Agent Orange defoliation damage

Reduction of animal habitat

Possible human health threat

Resources

Agent Orange is a defoliant that kills plants and causes the leaves to fall off the dying plants. The name was a code devised by the U.S. military during the development of the chemical mixture. The name arose from the orange band that marked the containers storing the defoliant.

Agent Orange was an equal mixture of two chemicals; 2, 4–D (2, 4, dichlorophenoxyl acetic acid) and 2, 4, 5–T (2, 4, 5-trichlorophenoxy acetic acid). Another compound designated TCDD (2, 3, 7, 8-tetrachlorodibenzo-para-dioxin) is a by-product of the manufacturing process and remains as a contaminant of the Agent Orange mixture. It is this dioxin contaminant that has proven to be damaging to human health.

Agent Orange was devised in the 1940s, but became infamous during the 1960s in the Vietnam War. The dispersal of a massive amount of Agent Orange throughout the tropical jungles of Vietnam (an estimated 19 million gallons were dispersed) was intended to deprive the Viet Cong of jungle cover in which they hid.

Agent Orange defoliation damage

By 1971, the use of Agent Orange in Vietnam had ended. However, the damage caused to the vegetation of the region by the spraying of Agent Orange is still visible in 2006. Agent Orange applications affected foliage of a diversity of tropical ecosystems of Vietnam, but the most severe damage occurred in the mangrove forest of coastal areas. About 306,280 acres (1,240 km²) of the coastal mangrove forest of South Vietnam was sprayed at least once. This area comprised about 40% of the South Vietnamese coastal mangrove ecosystem.

The spraying killed extensive stands of the dominant mangrove species, Rhizophora apiculata. Barren, badly eroded coastal habitat remained, which had devastating effects on the local economy. The harvesting of dead mangroves for fuel would sustain fewer people than the living forest once did, according to a 1970 report commissioned by the United States National Academy of Sciences, because the supply of mangrove wood was not being renewed. Unless a vigorous replanting program was undertaken, the report warned of a future economic loss when the dead mangroves were harvested.

The destruction of mature seed-bearing trees has made regeneration of mangroves slow and sporadic. Weed species have become dominant. Indeed, the Academy of Sciences has estimated that full recovery of the mangrove forest might take 100 years or more.

Agent Orange was sprayed over 14 million acres of inland tropical forest. A single spray treatment killed about 10% of the tall trees comprising the forest canopy. Defoliation of the trees was much more extensive, but many of the defoliated trees continued to live. Smaller shrubs, protected from the herbicide by the high canopy, comprised the majority of vegetation in sprayed areas. The total loss of commercially useful timber caused by the military application of herbicide in South Vietnam is estimated to be 26–61 million cubic yards (20–47 million m³). In areas that were sprayed repeatedly, the valuable tree species were replaced by a few resistant, commercially unimportant trees (such as Irvingia malayana and Parinari anna-mense ), along with tussock grass and bamboo. In the dry season, the stands of grass easily catch fire, and if burned repeatedly, the land is less likely to return quickly to forest. It will take many decades before the tropical forest recovers and attains its former productivity.

Because Agent Orange herbicide remains in the soil for some time, there is concern that these residues might inhibit the growth of crops and other plants. Soil bacteria break down the herbicides into smaller molecules, but complete decomposition takes years to occur. Studies performed 15 years after the spraying in South Vietnam still found degradation products of Agent Orange in the soil. These byproducts, which can be toxic, can be passed through the food web. How much Agent Orange actually reached the soil is subject to question. A large proportion of the herbicide falling onto the forest was trapped by the canopy. Few drops reached the soil directly, but much of the herbicide was eventually delivered to the forest floor by a rain of dead foliage and woody tissue. In open areas, much more of the application reached the soil directly. The contaminant TCDD is quite persistent in soil, with a half-life of three years. (In that period of time, one half of the dioxin originally applied would still be present in the soil.) In studies conducted in the United States, samples of inland soil and sediment from mangrove areas treated with herbicide still had substantial levels of TCDD after ten years. An indirect effect of the Agent Orange spraying is the poor fertility of soil in many areas, due to erosion following the destruction of soil-binding vegetation.

Reduction of animal habitat

As the rich, biodiverse, tropical forests disappeared, so did habitat for indigenous animals. Uniform grassland has poor habitat diversity compared to the complex, multi-layered tropical forest. As a result, the number of bird and mammal species living in sprayed areas declined dramatically. Most of the forest animals are adapted to living in a specific habitat and are unable to survive in the post-herbicide grassland. Wild boar, wild goat, water buffalo, tiger,

KEY TERMS

Exposure dose— The quantity of a chemical that an organism receives from the environment through inhalation, ingestion, and/or contact with the skin.

Toxicity— The extent to which a substance is poisonous.

and various species of deer became less common once the cover and food resources of the forest were removed. Domestic animals such as water buffalo, zebu, pigs, chickens, and ducks were also reported to become ill after the spraying of Agent Orange.

The defoliation and destruction of the mangrove forests had other consequences to wildlife. The number of coastal birds declined dramatically, since their habitat had vanished. Fish and crustacean populations also suffered, since their former breeding and nursery habitats in the web of channels winding beneath the mangrove trees were destroyed. Additionally, the wartime spraying of mangrove forest is thought to have contributed to the post-war decline in South Vietnam’s offshore fishery.

Possible human health threat

Agent Orange has unquestionably been a disaster for the ecology of Vietnam. But evidence also suggests that the defoliant, and in particular the TCCD dioxin component, is a health threat to soldiers who were exposed to Agent Orange during their tour of duty in Vietnam. Tests using animals have identified TCCD as the cause of a wide variety of maladies. In the mid-1990s, the “Pointman” project was begun in New Jersey, which scientifically assessed select veterans in order to ascertain if their exposure to Agent Orange had damaged them. The project is ongoing. In the meantime, veterans’ organizations continue to lobby for financial compensation for the suffering they feel has been inflicted on some soldiers by Agent Orange.

Since the late 1970s, hundreds of lawsuits have been filed against the manufacturers of Agent Orange (Dow Chemical, Monsanto, Hercules Inc., Diamond Shamrock Chemicals, Uniroyal, Thompson Chemical) by individual veterans and groups of veterans, seeking compensation for illnesses allegedly caused by the defoliant. Eventually the claims were consolidated into one lawsuit. While the link between Agent Orange and the veterans’ illness failed to be established, an award of $180 million was made.

In 2003, the Supreme Court ruled that the blanket settlement did not bar furture claims against the manfacturers of the chemical. A lawsuit brought by one veteran is ongoing as of 2006.

See also Immune system; Poisons and toxins.

Resources

BOOKS

Griffiths, Philip J. Agent Orange: Collateral Damage in Vietnam. New York: Trolley, 2003.

Institute of Medicine. Veterans and Agent Orange 2004: Update 2004. Washington: National Academies Press, 2005.

Parker, James N., and Philip M. Parker. Agent Orange: A Medical Dictionary, Bibliography, and Annotated Research Guide to Internet References. San Diego: Icon Health Publications, 2003.

Brian Hoyle

Agent Orange

Agent Orange is one of several herbicidal (plant-killing) preparations that was used by the U.S. military to destroy forests and enemy crops in Vietnam in the 1960s. Agent Orange was created by mixing equal quantities of two agricultural herbicides commonly used to kill weeds: 2,4-D and 2,4,5-T. Present in the 2,4,5-T as an impurity was 2,3,7,8-tetrachlorodibenzo-p-dioxin (usually abbreviated to TCDD), a dioxin contaminant that is highly toxic to some animals. (Dioxin is a term used collectively for a group of chemical by-products of papermaking and other manufacturing processes.)

History

During the Vietnam War (1961–75; a civil war between the communist North and the democracy-seeking South), North Vietnamese guerrillas found cover in the lush jungles of South Vietnam. To deprive their opponents of hiding places and food crops, the U.S. military instituted a program called Operation Ranch Hand, which involved the aerial spraying of herbicides. Ground spraying from boats, trucks, and backpacks occurred as well. In all, U.S. troops sprayed approximately 19 million gallons (72 million liters) of Agent Orange and other herbicides over 4 million acres (1.6 million hectares). This military strategy is thought to have saved the lives of many U.S. combat soldiers who had been sent to fight on behalf of the South Vietnamese.

Words to Know

Chloracne: A rash of skin lesions on the face, neck, and back caused by exposure to TCDD.

Herbicide: A chemical substance used to destroy or inhibit plant growth.

Hodgkin's disease: A type of cancer characterized by enlargement of the lymph nodes, spleen, and liver and with accompanied weight loss, heavy sweating, and itching of the skin.

Mangrove: Tropical coastal trees or shrubs that produce many supporting roots and that provide dense vegetation.

Non-Hodgkin's lymphoma: Tumors that develop from cells in lymph nodes, bone marrow, spleen, liver, or other sites in the body.

Soft-tissue sarcoma: A rare but varied group of tumors that arise in the muscles, connective tissue, inner layer of skin, bone, and other tissues.

Toxicity: The degree to which a chemical, in sufficient quantities, can poison humans and other organisms.

Concerns arise over health effects

Concerns about the health effects of exposure to Agent Orange were initially voiced in 1970, following a study that reported the incidence of birth defects in laboratory mice given high doses of the herbicide 2,4,5-T. TCDD, a dioxin contaminant of 2,4,5-T, was isolated as the actual cause of the birth defects. A commission established in 1970 to study the effects of herbicides on the ecology and population of South Vietnam reported that herbicides had not only destroyed vegetation and food, but 2,4,5-T and its associated dioxin contaminant might possibly have caused birth defects among South Vietnamese people who were exposed to it.

On April 15, 1970, all use of 2,4,5-T in the United States was suspended, except for the killing of weeds and brush on non-crop land. On May 9, 1970, Operation Ranch Hand flew its last mission in Vietnam, and U.S. forces stopped ground spraying in 1971. The herbicide was banned completely in 1985 by the Environmental Protection Agency.

Toxicity of TCDD. TCDD is a by-product of the manufacture of trichlorophenol, a chemical used to produce 2,4,5-T. Workers involved in accidents or spills at factories where the herbicide 2,4,5-T is manufactured have developed a condition called chloracne, a rash of skin lesions on the face, neck, and back. After researchers developed a method to produce trichlorophenol with a reduced level of TCDD as a by-product, the number of chloracne cases among factory workers in the herbicide industry decreased substantially.

The toxicity of the dioxin contaminant TCDD is the subject of continuing controversy and study. While some animals are very sensitive to TCDD, others are more tolerant to it. A very small amount can kill 50 percent of guinea pigs exposed to it, but a dose thousands of times larger is needed to cause the same number of deaths in hamsters.

Investigation of health effects

Serious health symptoms reported in 1977 by veterans of the Vietnam War spurred both the White House and the Veterans Administration (VA) to institute studies to evaluate the possible long-term health effects of herbicides and contaminants.

Exposure to TCDD in humans is measured by the amount of the contaminant found in blood and fatty tissue, where it tends to accumulate. Studies determined that levels of TCDD in the blood of chemical plant workers were strongly related to length of time of exposure.

Inadequate records of herbicide spraying and troop movements have made it difficult to determine to what degree individuals were exposed to herbicides and TCDD in Vietnam. Ranch Hand personnel who were heavily exposed to Agent Orange had significantly higher TCDD levels than other veterans. The average TCDD concentrations of Vietnam veterans who might have been exposed to Agent Orange on the ground did not differ significantly from that of other veterans and civilians.

The Agent Orange Act of 1991, passed by the U.S. Congress, ordered the National Academy of Sciences (NAS) to review and evaluate information regarding the health effects of exposure to Agent Orange and its components. Lacking enough information about the levels of herbicide exposure among Vietnam veterans to make any conclusions

regarding health effects, the NAS instead reviewed existing studies of people known to have been exposed to herbicides. In 1993, the 16-member panel of experts classified possible health effects in four categories, depending on the degree to which they could be associated with TCDD exposure.

In a 1996 update, the Institute of Medicine (IOM) reported new evidence upholding the 1993 finding of sufficient evidence of an association between TCDD exposure and various disorders with symptoms including tumors and skin lesions, including soft-tissue sarcoma, non-Hodgkin's lymphoma, Hodgkin's disease, and chloracne. Porphyria cutanea tarda (a rare skin disease) was downgraded from sufficient to "limited/suggestive evidence of an association," a category that also includes prostate cancer, multiple myeloma (cancer of bone marrow cells), and respiratory cancers (cancers of the lung, larynx, or trachea).

The IOM also reported there was new "limited/suggestive evidence" to show an association between TCDD exposure and the congenital birth defect spina bifida (incomplete closure of the spinal column at birth) in Vietnam veterans' children. A neurological disorder suffered by veterans was also placed in this category. The remaining two categories include cancers or disorders that have insufficient or no evidence of an association with TCDD exposure.

Ecological effects

The damage to the plant life of South Vietnam caused by the spraying of Agent Orange is still visible today. The most severe damage occurred in the mangrove forests (tropical trees and shrubs) of coastal areas where spraying left barren, badly eroded coastlines. The number of coastal birds declined dramatically, and with the disappearance of the web of water channels beneath the mangrove trees, fish were deprived of important breeding grounds. It is estimated that full recovery of the man-grove forests to their former state will take at least 100 years.

The loss of commercially useful timber due to aerial spraying of Agent Orange over dense inland forests was significant. About 10 percent of the tall trees making up the forest canopy were killed. Smaller shrubs now comprise the majority of vegetation in affected areas. Tussock grasses and bamboo replaced woody plants destroyed by the spraying. The beginnings of natural recovery can be seen, but it will be many years before the forests will approach their former productivity.

As the rich, diverse tropical forests disappeared, so did animal habitats. As a result, the number of bird and mammal species living in the areas that were sprayed declined dramatically. Wild boar, wild goat, water buffalo, tiger, and various species of deer became less common once the cover and food resources of the forest were removed. Domestic animals such as water buffalo, zebus (an Asian ox), pigs, chickens, and ducks were also reported to become ill after the spraying of Agent Orange.

The contaminant TCDD is not easily or quickly broken down in soil, and there is concern that herbicide residues might inhibit the growth of crops and other plants. These by-products, which can be toxic, could then be passed to humans through the food chain.

[See also Agrochemical ]

Agent Orange

Agent Orange is a defoliant that kills plants and causes the leaves to fall off the dying plants. The name was a code devised by the United States military during the development of the chemical mixture. The name arose from the orange band that marked the containers storing the defoliant.

Agent Orange was an equal mixture of two chemicals; 2, 4–D (2,4, dichlorophenoxyl acetic acid ) and 2, 4, 5–T (2, 4, 5-trichlorophenoxy acetic acid). Another compound designated TCDD (2, 3, 7, 8-tetra-chlorodibenzo-para-dioxin) is a by-product of the manufacturing process and remains as a contaminant of the Agent Orange mixture. It is this dioxin contaminant that has proven to be damaging to human health.

Agent Orange was devised in the 1940s, but became infamous during the 1960s in the Vietnam War. The dispersal of a massive amount of Agent Orange throughout the tropical jungles of Vietnam (an estimated 19 million gallons were dispersed) was intended to deprive the Viet Cong of jungle cover in which they hid.

Agent Orange defoliation damage

By 1971, the use of Agent Orange in Vietnam had ended. However, the damage caused to the vegetation of the region by the spraying of Agent Orange is still visible today. Agent Orange applications affected foliage of a diversity of tropical ecosystems of Vietnam, but the most severe damage occurred in the mangrove forest of coastal areas. About 306,280 acres (1,240 km2) of the coastal mangrove forest of South Vietnam was sprayed at least once. This area comprised about 40% of the South Vietnamese coastal mangrove ecosystem .

The spraying killed extensive stands of the dominant mangrove species , Rhizophora apiculata. Barren, badly eroded coastal habitat remained, which had devastating effects on the local economy. The harvesting of dead mangroves for fuel would sustain fewer people than the living forest once did, according to a 1970 report commissioned by the United States National Academy of Sciences, because the supply of mangrove wood was not being renewed. Unless a vigorous replanting program was undertaken, the report warned of a future economic loss when the dead mangroves were harvested.

The destruction of mature seed-bearing trees has made regeneration of mangroves slow and sporadic. Weed species have become dominant. Indeed, the Academy of Sciences has estimated that full recovery of the mangrove forest might take 100 years or more.

Agent Orange was sprayed over 14 million acres of inland tropical forest. A single spray treatment killed about 10% of the tall trees comprising the forest canopy. Defoliation of the trees was much more extensive, but many of the defoliated trees continued to live. Smaller shrubs, protected from the herbicide by the high canopy, comprised the majority of vegetation in sprayed areas. The total loss of commercially useful timber caused by the military application of herbicide in South Vietnam is estimated to be 26–61 million yd3 (20–47 million m3). In areas that were sprayed repeatedly, the valuable tree species were replaced by a few resistant, commercially unimportant trees (such as Irvingia malayana and Parinari annamense), along with tussock grass and bamboo. In the dry season, the stands of grass easily catch fire, and if burned repeatedly, the land is less likely to return quickly to forest. It will take many decades before the tropical forest recovers and attains its former productivity.

Because Agent Orange herbicide remains in the soil for some time, there is concern that these residues might inhibit the growth of crops and other plants. Soil bacteria break down the herbicides into smaller molecules, but complete decomposition takes years to occur. Studies performed 15 years after the spraying in South Vietnam still found degradation products of Agent Orange in the soil. These byproducts, which can be toxic, can be passed through the food web. How much Agent Orange actually reached the soil is subject to question. A large proportion of the herbicide falling onto the forest was trapped by the canopy. Few drops reached the soil directly, but much of the herbicide was eventually delivered to the forest floor by a rain of dead foliage and woody tissue . In open areas, much more of the application reached the soil directly. The contaminant TCDD is quite persistent in soil, with a half-life of three years. (In that period of time, one half of the dioxin originally applied would still be present in the soil.) In studies conducted in the United States, samples of inland soil and sediment from mangrove areas treated with herbicide still had substantial levels of TCDD after ten years. An indirect effect of the Agent Orange spraying is the poor fertility of soil in many areas, due to erosion following the destruction of soil-binding vegetation.

Reduction of animal habitat

As the rich, biodiverse, tropical forests disappeared, so did habitat for indigenous animals. Uniform grassland has poor habitat diversity compared to the complex, multi-layered tropical forest. As a result, the number of bird and mammal species living in sprayed areas declined dramatically. Most of the forest animals are adapted to living in a specific habitat and are unable to survive in the post-herbicide grassland. Wild boar, wild goat, water buffalo, tiger, and various species of deer became less common once the cover and food resources of the forest were removed. Domestic animals such as water buffalo, zebu, pigs , chickens, and ducks were also reported to become ill after the spraying of Agent Orange.

The defoliation and destruction of the mangrove forests had other consequences to wildlife . The number of coastal birds declined dramatically, since their habitat had vanished. Fish and crustacean populations also suffered, since their former breeding and nursery habitats in the web of channels winding beneath the mangrove trees were destroyed. Additionally, the wartime spraying of mangrove forest is thought to have contributed to the post-war decline in South Vietnam's offshore fishery.

Possible human health threat

Agent Orange has unquestionably been a disaster for the ecology of Vietnam. But evidence also suggests that the defoliant, and in particular the TCCD dioxin component, is a health threat to soldiers who were exposed to Agent Orange during their tour of duty in Vietnam. Tests using animals have identified TCCD as the cause of a wide variety of maladies. In the mid-1990s, the "Pointman" project was begun in New Jersey, which scientifically assessed select veterans in order to ascertain if their exposure to Agent Orange had damaged them. The project is ongoing. In the meantime, veterans organizations continue to lobby for financial compensation for the suffering they feel has been inflicted on some soldiers by Agent Orange.

See also Immune system; Poisons and toxins.

Resources

books

Gough, M. Agent Orange: The Facts. New York: Perseus Books, 1986.

National Academy of Sciences. Veterans and Agent Orange:Health Effects of Herbicides Used in Vietnam. Washington, DC: National Academy Press, 1994.

Schuck, P.H.H. Agent Orange on Trial: Mass Toxic Disasters in the Courts. Boston: Harvard University Press, 1990.

Other

Department of Vetrans Affairs. "Where Can I Get Information on Agent Orange?" (June 23, 2000) [cited October 25, 2002]. <www.VA.gov>.

Brian Hoyle

KEY TERMS

Exposure dose

—The quantity of a chemical that an organism receives from the environment through inhalation, ingestion, and/or contact with the skin.

Toxicity

—The extent to which a substance is poisonous.

Agent Orange

Agent Orange is a defoliant, that is, a chemical that kills plants and causes the leaves to fall off the dying plants. The name was a code devised by the United States military during the development of the chemical mixture. The name arose from the orange band that marked the containers storing the defoliant.

Agent Orange was an equal mixture of two chemicals; 2, 4–D (2,4, dichlorophenoxyl acetic acid) and 2, 4, 5–T (2, 4, 5-trichlorophenoxy acetic acid). Another compound designated TCDD (which stands for 2, 3, 7, 8-tetrachlorodibenzo-para-dioxin) is a by-product of the manufacturing process, and remains as a contaminant of the Agent Orange mixture. It is this dioxin contaminant that has proven to be damaging to human health.

Agent Orange was devised in the 1940s. It was widely used during the 1960s during the Vietnam War. The dispersal of a massive amount of Agent Orange throughout the tropical jungles of Vietnam (an estimated 19 million gallons were dispersed) was intended to deprive the Viet Cong of jungle cover in which to hide.

By 1971, the use of Agent Orange in Vietnam had ended. Even today, however, the damage caused to the vegetation of the region by the spraying of Agent Orange is still visible. Agent Orange applications affected foliage of a diversity of tropical ecosystems of Vietnam, but the most severe damage occurred in the forested coastal areas.

Agent Orange was sprayed over 14 million acres of inland tropical forest. A single spray treatment killed about 10% of the tall trees comprising the forest canopy.

Because Agent Orange herbicide remains in the soil for some time, the contaminant TCDD is quite persistent in soil, with a half-life of three years. (In that period of time, one half of the dioxin originally applied would still be present in the soil.)

Evidence also suggests that the defoliant, and in particular the TCCD dioxin component, is a health threat to soldiers who were exposed to Agent Orange during their tour of duty in Vietnam. Tests using animals have identified TCCD as the cause of a wide variety of maladies. In the mid 1990s, the "Pointman" project was begun in New Jersey, which scientifically assessed select veterans in order to ascertain if their exposure to Agent Orange had damaged them. The project is ongoing. In the meantime, veterans organizations continue to lobby for financial compensation for the suffering they assert has been inflicted on some soldiers by Agent Orange.

█ FURTHER READING:

BOOKS:

Gough, M. Agent Orange: The Facts. New York: Perseus Books, 1986.

National Academy of Sciences. Veterans and Agent Orange: Health Effects of Herbicides Used in Vietnam. Washington, DC: National Academy Press, 1994.

Schuck, P. H. H. Agent Orange on Trial: Mass Toxic Disasters in the Courts. Boston: Harvard University press, 1990.