Dioxin - AbsoluteAstronomy.com

Polychlorinated dibenzodioxins (PCDDs), or simply dioxins, are a group of organic polyhalogenated compound

Polyhalogenated compound

Polyhalogenated compounds are any compounds with multiple substitutions of halogens. They are of particular interest and importance because halogens generally are highly reactive and also bioaccumulate in humans, and comprise a superset of which has many toxic and carcinogenic industrial...

s that are significant environmental pollutant

Pollutant

A pollutant is a waste material that pollutes air, water or soil, and is the cause of pollution.Three factors determine the severity of a pollutant: its chemical nature, its concentration and its persistence. Some pollutants are biodegradable and therefore will not persist in the environment in the...

s. They are commonly but inaccurately referred to as dioxins for simplicity, because every PCDD molecule

Molecule

A molecule is an electrically neutral group of at least two atoms held together by covalent chemical bonds. Molecules are distinguished from ions by their electrical charge...

contains a dioxin skeletal structure as the central ring. This gives the molecule a dibenzo-p-dioxin

Dibenzodioxin

Dibenzo-p-dioxin or dibenzo-1,4-dioxin is an organic heterocyclic compound in which two benzene rings are connected by a 1,4-dioxin ring. Its molecular formula is C12H8O2...

ring system. Members of the PCDD family bioaccumulate in humans and wildlife

Wildlife

Wildlife includes all non-domesticated plants, animals and other organisms. Domesticating wild plant and animal species for human benefit has occurred many times all over the planet, and has a major impact on the environment, both positive and negative....

due to their lipophilic

Lipophilic

Lipophilicity, , refers to the ability of a chemical compound to dissolve in fats, oils, lipids, and non-polar solvents such as hexane or toluene. These non-polar solvents are themselves lipophilic — the axiom that like dissolves like generally holds true...

properties, and may cause developmental disturbances and cancer

Cancer

Cancer , known medically as a malignant neoplasm, is a large group of different diseases, all involving unregulated cell growth. In cancer, cells divide and grow uncontrollably, forming malignant tumors, and invade nearby parts of the body. The cancer may also spread to more distant parts of the...

.

Dioxins occur as by-products in the manufacture of some organochlorines, in the incineration of chlorine-containing substances such as PVC

PVC

Polyvinyl chloride is a plastic.PVC may also refer to:*Param Vir Chakra, India's highest military honor*Peripheral venous catheter, a small, flexible tube placed into a peripheral vein in order to administer medication or fluids...

(polyvinyl chloride), in the chlorine bleaching of paper, and from natural sources such as volcanoes and forest fires. There have been many incidents of dioxin pollution resulting from industrial emissions and accidents; the earliest such incidents were in the mid 19th century during the Industrial Revolution

Industrial Revolution

The Industrial Revolution was a period from the 18th to the 19th century where major changes in agriculture, manufacturing, mining, transportation, and technology had a profound effect on the social, economic and cultural conditions of the times...

.

The word "dioxins" may also refer to other similarly acting chlorinated compounds (see Dioxins and dioxin-like compounds

Dioxins and dioxin-like compounds

Dioxins and dioxin-like compounds are by-products of various industrial processes, and are commonly regarded as highly toxic compounds that are environmental pollutants and persistent organic pollutants . They include:...

Chemical structure of dibenzo-p-dioxins

The structure of dibenzo-p-dioxin comprises two benzene rings joined by two oxygen bridges. This makes the compound an aromatic diether

Ether

Ethers are a class of organic compounds that contain an ether group — an oxygen atom connected to two alkyl or aryl groups — of general formula R–O–R'. A typical example is the solvent and anesthetic diethyl ether, commonly referred to simply as "ether"...

. The name dioxin formally refers to the central dioxygenated ring, which is stabilized by the two flanking benzene rings.

In PCDDs, chlorine atoms are attached to this structure at any of 8 different places on the molecule, at positions 1–4 and 6–9. There are 75 different PCDD congeners (that is: related dioxin compounds).

The toxicity of PCDDs depends on the number and positions of the chlorine atoms. Congeners that have chlorines in the 2, 3, 7, and 8 positions have been found to be significantly toxic. In fact, 7 congeners have chlorine atoms in the relevant positions which were considered toxic by the World Health Organization toxic equivalent (WHO-TEQ) scheme.

Historical perspective

Low concentrations of dioxins existed in nature prior to industrialization due to natural combustion and geological processes. Dioxins were first unintentionally produced as by-products from 1848 onwards as Leblanc process

Leblanc process

The Leblanc process was the industrial process for the production of soda ash used throughout the 19th century, named after its inventor, Nicolas Leblanc. It involved two stages: Production of sodium sulfate from sodium chloride, followed by reaction of the sodium sulfate with coal and calcium...

plants started operating in Germany. The first intentional synthesis of chlorinated dibenzodioxin was in 1872. Today, concentrations of dioxins are found in all humans, with higher levels commonly found in persons living in more industrialized countries. The most toxic dioxin, 2,3,7,8-tetrachlorodibenzo-p-dioxin

2,3,7,8-Tetrachlorodibenzodioxin

2,3,7,8-Tetrachlorodibenzo-p-dioxin is a polychlorinated dibenzo-p-dioxin . It is the most potent compound of the series and became known as a contaminant in Agent Orange, a herbicide used in the Vietnam War, as well as the Seveso disaster...

(TCDD), became well known as a contaminant of Agent Orange

Agent Orange

Agent Orange is the code name for one of the herbicides and defoliants used by the U.S. military as part of its herbicidal warfare program, Operation Ranch Hand, during the Vietnam War from 1961 to 1971. Vietnam estimates 400,000 people were killed or maimed, and 500,000 children born with birth...

, a herbicide used in the Vietnam War. To speed up chemical reactions, the U.S. manufacturers had increased the temperature in the process of preparation. This increased the concentration of TCDD many times more than other types of pesticides that were being used by U.S. farmers. Later, dioxins were found in Times Beach, Missouri

Missouri

Missouri is a US state located in the Midwestern United States, bordered by Iowa, Illinois, Kentucky, Tennessee, Arkansas, Oklahoma, Kansas and Nebraska. With a 2010 population of 5,988,927, Missouri is the 18th most populous state in the nation and the fifth most populous in the Midwest. It...

and Love Canal

Love Canal

Love Canal was a neighborhood in Niagara Falls, New York, located in the white collar LaSalle section of the city. It officially covers 36 square blocks in the far southeastern corner of the city, along 99th Street and Read Avenue...

, New York

New York

New York is a state in the Northeastern region of the United States. It is the nation's third most populous state. New York is bordered by New Jersey and Pennsylvania to the south, and by Connecticut, Massachusetts and Vermont to the east...

and Seveso

Seveso

Seveso is a town and comune in the Province of Monza and Brianza, in the Region of Lombardy. The economy of the town has traditionally been based around the furniture industry....

, Italy

Italy

Italy , officially the Italian Republic languages]] under the European Charter for Regional or Minority Languages. In each of these, Italy's official name is as follows:;;;;;;;;), is a unitary parliamentary republic in South-Central Europe. To the north it borders France, Switzerland, Austria and...

. More recently, dioxins have been in the news with the poisoning of President Viktor Yushchenko

Viktor Yushchenko

Viktor Andriyovych Yushchenko is a former President of Ukraine. He took office on January 23, 2005, following a period of popular unrest known as the Orange Revolution...

of Ukraine

Ukraine

Ukraine is a country in Eastern Europe. It has an area of 603,628 km², making it the second largest contiguous country on the European continent, after Russia...

in 2004, the Naples Mozzarella Crisis the Irish pork crisis of 2008, and the German feed incident of 2010.

Sources of dioxins

The United States Environmental Protection Agency

United States Environmental Protection Agency

The U.S. Environmental Protection Agency is an agency of the federal government of the United States charged with protecting human health and the environment, by writing and enforcing regulations based on laws passed by Congress...

inventory of sources of dioxin-like compounds is possibly the most comprehensive review of the sources and releases of dioxins, but other countries now have substantial research as well.

Occupational exposure is an issue for some in the chemical industries, historically for those making chlorophenols or chlorophenoxy acid herbicides or in the application of chemicals, notably herbicide

Herbicide

Herbicides, also commonly known as weedkillers, are pesticides used to kill unwanted plants. Selective herbicides kill specific targets while leaving the desired crop relatively unharmed. Some of these act by interfering with the growth of the weed and are often synthetic "imitations" of plant...

s. In many developed nations there are now emissions regulations which have dramatically decreased the emissions and thus alleviated some concerns, although the lack of continuous sampling of dioxin emissions causes concern about the understatement of emissions. In Belgium

Belgium

Belgium , officially the Kingdom of Belgium, is a federal state in Western Europe. It is a founding member of the European Union and hosts the EU's headquarters, and those of several other major international organisations such as NATO.Belgium is also a member of, or affiliated to, many...

, through the introduction of a process called AMESA, continuous sampling showed that periodic sampling understated emissions by a factor of 30 to 50 times. Few facilities have continuous sampling.

Dioxins are produced in small concentrations when organic material is burned in the presence of chlorine

Chlorine

Chlorine is the chemical element with atomic number 17 and symbol Cl. It is the second lightest halogen, found in the periodic table in group 17. The element forms diatomic molecules under standard conditions, called dichlorine...

, whether the chlorine is present as chloride

Chloride

The chloride ion is formed when the element chlorine, a halogen, picks up one electron to form an anion Cl−. The salts of hydrochloric acid HCl contain chloride ions and can also be called chlorides. The chloride ion, and its salts such as sodium chloride, are very soluble in water...

ion

Ion

An ion is an atom or molecule in which the total number of electrons is not equal to the total number of protons, giving it a net positive or negative electrical charge. The name was given by physicist Michael Faraday for the substances that allow a current to pass between electrodes in a...

s or as organochlorine compounds, so they are widely produced in many contexts. According to the most recent US EPA data, the major sources of dioxins are broadly in the following types:

Combustion sources, e.g. municipal waste or medical waste incinerators and private backyard barrel burning
Metal smelting
Refining and process sources
Chemical manufacturing sources
Natural sources
Environmental reservoirs

When the original US EPA inventory of dioxin sources was done in 1987, incineration represented over 80% of known dioxin sources. As a result, US EPA implemented new emissions requirements. These regulations have been very successful in reducing dioxin stack emissions from incinerators. Incineration of municipal solid waste, medical waste, sewage sludge, and hazardous waste together now produce less than 3% of all dioxin emissions. Unfortunately backyard barrel burning decreased barely at all, and is now the biggest source producing about one third of dioxin emissions.

In incineration, dioxins can also reform or form de novo in the atmosphere

Earth's atmosphere

The atmosphere of Earth is a layer of gases surrounding the planet Earth that is retained by Earth's gravity. The atmosphere protects life on Earth by absorbing ultraviolet solar radiation, warming the surface through heat retention , and reducing temperature extremes between day and night...

above the stack as the exhaust gases cool through a temperature window of 600 to 200 °C. The most common method of reducing the quantity of dioxins reforming or forming de novo is through rapid (30 millisecond) quenching of the exhaust gases through that 400 °C window. Incinerator emissions of dioxins have been reduced by over 90% as a result of new emissions control requirements. Incineration in developed countries is now a very minor contributor to dioxin emissions.

Dioxins are also generated in reactions that do not involve burning — such as chlorine bleaching fibers for paper or textiles, and in the manufacture of chlorinated phenols, particularly when reaction temperature is not well controlled. Compounds´involed include the wood preservative pentachlorophenol

Pentachlorophenol

Pentachlorophenol is an organochlorine compound used as a pesticide and a disinfectant. First produced in the 1930s, it is marketed under many trade names...

, and also herbicide

Herbicide

s such as 2,4-dichlorophenoxyacetic acid (or 2,4-D) and 2,4,5-trichlorophenoxyacetic acid

2,4,5-Trichlorophenoxyacetic acid

2,4,5-Trichlorophenoxyacetic acid , a synthetic auxin, is a chlorophenoxy acetic acid herbicide used to defoliate broad-leafed plants. It was developed in the late 1940s and was widely used in the agricultural industry until being phased out, starting in the late 1970s due to toxicity concerns....

(2,4,5-T). Higher levels of chlorination require higher reaction temperatures and greater dioxin production. Dioxins may also be formed during the photochemical breakdown of the common antimicrobial compound triclosan

Triclosan

Triclosan is an antibacterial and antifungal agent. It is a polychloro phenoxy phenol. Despite being used in many consumer products, beyond its use in toothpaste to prevent gingivitis, there is no evidence according to the American Food and Drug Administration that triclosan provides an extra...

Sources of human intake

Tolerable daily, monthly or annual intakes have been set by the World Health Organization

World Health Organization

The World Health Organization is a specialized agency of the United Nations that acts as a coordinating authority on international public health. Established on 7 April 1948, with headquarters in Geneva, Switzerland, the agency inherited the mandate and resources of its predecessor, the Health...

and a number of governments. Dioxins enter the general population almost exclusively from ingestion of food, specifically through the consumption of fish, meat, and dairy products since dioxins are fat-soluble and readily climb the food chain

Food chain

A food web depicts feeding connections in an ecological community. Ecologists can broadly lump all life forms into one of two categories called trophic levels: 1) the autotrophs, and 2) the heterotrophs...

.

Most controversial is the United States Environmental Protection Agency

United States Environmental Protection Agency

(US EPA) assessment's (draft) finding that any reference dose

Reference dose

A reference dose is the United States Environmental Protection Agency's maximum acceptable oral dose of a toxic substance. Reference doses are most commonly determined for pesticides...

that were to be set would be far below current average intakes. This is based on linear extrapolation model of cancer risk, which is not generally accepted for chemicals promoting cancer caused by other factors rather than initiating the cancer by itself.

Children are passed substantial body burdens by their mothers, and breastfeeding

Breastfeeding

Breastfeeding is the feeding of an infant or young child with breast milk directly from female human breasts rather than from a baby bottle or other container. Babies have a sucking reflex that enables them to suck and swallow milk. It is recommended that mothers breastfeed for six months or...

increases the child's body burden. Children's daily intakes during breast feeding are often many times above the intakes of adults based on body weight. This is why the WHO consultation group assessed the tolerable intake so as to prevent a woman from accumulating harmful body burdens before her first pregnancy. Breast fed children usually still have higher dioxin body burdens than non breast fed children. The WHO

World Health Organization

still recommends breast feeding for its other benefits. In many countries dioxins in breast milk have decreased by even 90% during the two last decades.

Dioxins are also in typical cigarette smoke. Dioxin in cigarette smoke was noted as "understudied" by the US EPA in its "Re-Evaluating Dioxin" (1995). In that same document, the US EPA acknowledged that dioxin in cigarettes is "anthropogenic" (man-made, "not likely in nature").

Metabolism

Dioxins are absorbed primarily through dietary intake of fat, as this is where they accumulate in animals and humans. In humans, the highly chlorinated dioxins are stored in fatty tissues and are neither readily metabolized nor excreted. The estimated elimination half-life

Half-life

Half-life, abbreviated t½, is the period of time it takes for the amount of a substance undergoing decay to decrease by half. The name was originally used to describe a characteristic of unstable atoms , but it may apply to any quantity which follows a set-rate decay.The original term, dating to...

for highly chlorinated dioxins (4–8 chlorine atoms) in humans ranges from 4.9 to 13.1 years.

The persistence of a particular dioxin congener in an animal is thought to be a consequence of its structure. Dioxins with no lateral (2, 3, 7, and 8) chlorines, which thus contain hydrogen atoms on adjacent pairs of carbons, can more readily be oxidized by cytochromes P450. The oxidized dioxins can then be more readily excreted rather than stored for a long time.

Toxicity

2,3,7,8-Tetrachlorodibenzo-p-dioxin

2,3,7,8-Tetrachlorodibenzodioxin

(TCDD) is considered the most toxic of the congener

Congener

Congener has several different meanings depending on the field in which it is used. Colloquially, it is used to mean a person or thing like another, in character or action.-Biology:In biology, congeners are organisms within the same genus...

s (for the mechanism of action, see 2,3,7,8-Tetrachlorodibenzo-p-dioxin

2,3,7,8-Tetrachlorodibenzodioxin

and Aryl hydrocarbon receptor

Aryl hydrocarbon receptor

The Aryl hydrocarbon receptor is a member of the family of basic-helix-loop-helix transcription factors. AhR is a cytosolic transcription factor that is normally inactive, bound to several co-chaperones...

). Other dioxin congeners including PCDFs and PCBs with dioxin-like toxicity, are given a toxicity rating from 0 to 1, where TCDD = 1 (see Dioxins and dioxin-like compounds

Dioxins and dioxin-like compounds

). This toxicity rating is called the Toxic Equivalence Factor concept, or TEF

TEF

The Test d'évaluation du français is a test of fluency in French for non-native speakers. It is awarded by the CCIP. It is often required to be admitted into universities and is recognized by the Federal government of Canada as a proof of fluency in immigration procedures.The test is made up of...

. TEFs are consensus values and, because of the strong species dependence for toxicity, are listed separately for mammals, fish, and birds. TEFs for mammalian species are generally applicable to human risk calculations. The TEFs have been developed from detailed assessment of literature data to facilitate both risk assessment and regulatory control. Many other compounds may also have dioxin-like properties, particularly non-ortho PCBs, one of which has a TEF as high as 0.1.

The total dioxin toxic equivalence (TEQ) value expresses the toxicity as if the mixture were pure TCDD. The TEQ approach and current TEFs have been adopted internationally as the most appropriate way to estimate the potential health risks of mixture of dioxins. Recent data suggest that this type of simple scaling factor may not be the most appropriate treatment for complex mixtures of dioxins; both transfer from the source and absorption and elimination vary among different congeners, and the TEF value is not able to accurately reflect this.

Dioxins and other persistent organic pollutant

Persistent organic pollutant

thumb|right|275px|State parties to the Stockholm Convention on Persistent Organic PollutantsPersistent organic pollutants are organic compounds that are resistant to environmental degradation through chemical, biological, and photolytic processes...

s (POPs) are subject to the Stockholm Convention

Stockholm Convention

Stockholm Convention on Persistent Organic Pollutants is an international environmental treaty, signed in 2001 and effective from May 2004, that aims to eliminate or restrict the production and use of persistent organic pollutants .- History :...

. The treaty

Treaty

A treaty is an express agreement under international law entered into by actors in international law, namely sovereign states and international organizations. A treaty may also be known as an agreement, protocol, covenant, convention or exchange of letters, among other terms...

obliges signatories to take measures to eliminate where possible, and minimize where not possible to eliminate, all sources of dioxin.

Health effects in humans

Dioxins build up primarily in fatty tissues over time (bioaccumulate), so even small exposures may eventually reach dangerous levels. In 1994, the US EPA reported that dioxins are a probable carcinogen

Carcinogen

A carcinogen is any substance, radionuclide, or radiation that is an agent directly involved in causing cancer. This may be due to the ability to damage the genome or to the disruption of cellular metabolic processes...

, but noted that non-cancer effects (reproduction and sexual development, immune system) may pose a greater threat to human health. TCDD

2,3,7,8-Tetrachlorodibenzodioxin

, the most toxic of the dibenzodioxins, is classified as a Group 1 carcinogen by the International Agency for Research on Cancer

International Agency for Research on Cancer

The International Agency for Research on Cancer is an intergovernmental agency forming part of the World Health Organisation of the United Nations....

(IARC). TCDD has a half-life of approximately 8 years in humans, although at high concentrations, the elimination rate is enhanced by metabolism. The health effects of dioxins are mediated by their action on a cellular receptor, the aryl hydrocarbon receptor

Aryl hydrocarbon receptor

(AhR).

Exposure to high levels of dioxins in humans causes a severe form of persistent acne

Acne vulgaris

Acne vulgaris is a common human skin disease, characterized by areas of skin with seborrhea , comedones , papules , pustules , Nodules and possibly scarring...

, known as chloracne

Chloracne

Chloracne is an acne-like eruption of blackheads, cysts, and pustules associated with over-exposure to certain halogenated aromatic compounds, such as chlorinated dioxins and dibenzofurans...

. High occupational or accidental levels of exposures to dioxins have been shown by epidemiological studies to lead to an increased risk of tumors at all sites. Other effects in humans (at high dose levels) may include:

Developmental abnormalities in the enamel
Tooth enamel
Tooth enamel, along with dentin, cementum, and dental pulp is one of the four major tissues that make up the tooth in vertebrates. It is the hardest and most highly mineralized substance in the human body. Tooth enamel is also found in the dermal denticles of sharks...

of children's teeth.

Central
Central nervous system
The central nervous system is the part of the nervous system that integrates the information that it receives from, and coordinates the activity of, all parts of the bodies of bilaterian animals—that is, all multicellular animals except sponges and radially symmetric animals such as jellyfish...

and peripheral nervous system
Peripheral nervous system
The peripheral nervous system consists of the nerves and ganglia outside of the brain and spinal cord. The main function of the PNS is to connect the central nervous system to the limbs and organs. Unlike the CNS, the PNS is not protected by the bone of spine and skull, or by the blood–brain...

pathology

Thyroid
Thyroid
The thyroid gland or simply, the thyroid , in vertebrate anatomy, is one of the largest endocrine glands. The thyroid gland is found in the neck, below the thyroid cartilage...

disorders

Damage to the immune system
Immune system
An immune system is a system of biological structures and processes within an organism that protects against disease by identifying and killing pathogens and tumor cells. It detects a wide variety of agents, from viruses to parasitic worms, and needs to distinguish them from the organism's own...

s

Endometriosis
Endometriosis
Endometriosis is a gynecological medical condition in which cells from the lining of the uterus appear and flourish outside the uterine cavity, most commonly on the ovaries. The uterine cavity is lined by endometrial cells, which are under the influence of female hormones...

Diabetes

Recent studies have shown that high exposure to dioxins changes the ratio of male to female births among a population such that more females are born than males.

Dioxins accumulate in food chains in a fashion similar to other chlorinated compounds (bioaccumulation

Bioaccumulation

Bioaccumulation refers to the accumulation of substances, such as pesticides, or other organic chemicals in an organism. Bioaccumulation occurs when an organism absorbs a toxic substance at a rate greater than that at which the substance is lost...

). This means that even small concentrations in contaminated water can be concentrated up a food chain to dangerous levels due to the long biological half life and low water solubility of dioxins.

Toxic effects in animals

While it has been difficult to establish specific health effects in humans due to the lack of controlled dose experiments, studies in animals have shown that dioxin causes a wide variety of toxic effects. In particular, TCDD (see this) has been shown to be teratogenic, mutagenic, carcinogenic, immunotoxic, and hepatotoxic. Furthermore, alterations in multiple endocrine and growth factor

Growth factor

A growth factor is a naturally occurring substance capable of stimulating cellular growth, proliferation and cellular differentiation. Usually it is a protein or a steroid hormone. Growth factors are important for regulating a variety of cellular processes....

systems have been reported. The most sensitive effects, observed in multiple species, appear to be developmental, including effects on the developing immune, nervous

Nervous

Nervous may refer to:* The nervous system* "Nervous" , a rockabilly/doo-wop song first recorded by Gene Summers and His Rebels in 1958* Nervous Records, a UK record label* Nervous Records , a US record label-See also:...

, and reproductive systems. The most sensitive effects are caused at body burdens relatively close to those reported in humans.

Among the animals for which TCDD toxicity has been studied, there is strong evidence for the following effects:

Birth defects (teratogenicity)

In rodents, including rats, mice, hamsters and guinea pigs, birds, and fish.

Cancer (including neoplasms in the mammalian lung, oral/nasal cavities, thyroid
Thyroid
The thyroid gland or simply, the thyroid , in vertebrate anatomy, is one of the largest endocrine glands. The thyroid gland is found in the neck, below the thyroid cartilage...

and adrenal glands, and liver, squamous cell carcinoma, and various animal hepatocarcinomas
Hepatocellular carcinoma
Hepatocellular carcinoma is the most common type of liver cancer. Most cases of HCC are secondary to either a viral hepatitide infection or cirrhosis .Compared to other cancers, HCC is quite a rare tumor in the United States...

)

In rodents and fish

Hepatotoxicity (liver toxicity)

In rodents, chickens, and fish

Endocrine disruption

In rodents and fish

Immunosuppression

In rodents and fish.

The LD50 of dioxin also varies wildly between species with the most notable disparity being between the ostensibly similar species of hamster and guinea pig. The oral LD50 for guinea pigs is as low as 0.5 to 2 μg/Kg body weight, whereas the oral LD50 for hamsters can be as high as 1 to 5 mg/Kg body weight, a difference of as much as thousand fold or more, and even among rat strains there may be thousand fold differences.

Agent Orange

Agent Orange was the code name for one of the herbicide

Herbicide

s and defoliant

Defoliant

A defoliant is any chemical sprayed or dusted on plants to cause its leaves to fall off. A classic example of a highly toxic defoliant is Agent Orange, which the United States armed forces used abundantly to defoliate regions of Vietnam during the Vietnam War from 1961 to 1970.Defoliants differ...

s used by the U.S. military

United States armed forces

The United States Armed Forces are the military forces of the United States. They consist of the Army, Navy, Marine Corps, Air Force, and Coast Guard.The United States has a strong tradition of civilian control of the military...

as part of its herbicidal warfare

Herbicidal warfare

Herbicidal warfare is a form of Chemical warfare in which the objective is to destroy the plant-based ecosystem of an area. In contrast to other forms, its use is not prohibited by international agreement...

program, Operation Ranch Hand

Operation Ranch Hand

Operation Ranch Hand was a U.S. Military operation during the Vietnam War, lasting from 1962 until 1971. It was part of the overall herbicidal warfare program during the war called "Operation Trail Dust"...

, during the Vietnam War

Vietnam War

The Vietnam War was a Cold War-era military conflict that occurred in Vietnam, Laos, and Cambodia from 1 November 1955 to the fall of Saigon on 30 April 1975. This war followed the First Indochina War and was fought between North Vietnam, supported by its communist allies, and the government of...

from 1961 to 1971.

A 50:50 mixture of 2,4,5-T and 2,4-D, it was manufactured for the U.S. Department of Defense primarily by Monsanto Corporation and Dow Chemical. The 2,4,5-T used to produce Agent Orange was later discovered to be contaminated with 2,3,7,8-Tetrachlorodibenzodioxin

2,3,7,8-Tetrachlorodibenzodioxin

, an extremely toxic dioxin compound. It was given its name from the color of the orange-striped 55 US gallon (200 L) barrels

Drum (container)

A drum is a cylindrical container used for shipping bulk cargo. Drums can be made of steel, dense paperboard , or plastics, and are generally used for the transportation and storage of liquids and powders. Drums are often certified for shipment of dangerous goods...

in which it was shipped, and was by far the most widely used of the so-called "Rainbow Herbicides

Rainbow Herbicides

The Rainbow Herbicides are a group of chemicals used by the United States military in Southeast Asia during the Vietnam War. Success with Project AGILE field tests with herbicides in South Vietnam in 1961 led to the formal herbicidal program Trail Dust...

".

During the Vietnam war, between 1962 and 1971, the United States military sprayed 20000000 gallons (75,708,240 l) of chemical herbicides and defoliants in Vietnam, eastern Laos and parts of Cambodia, as part of Operation Ranch Hand

Operation Ranch Hand

. The program's goal was to defoliate forested and rural land, depriving guerrillas of cover; another goal was to induce forced draft urbanization

Forced draft urbanization

Forced draft urbanization was a policy elaborated by Samuel P. Huntington in a 1968 article "The Bases of Accommodation" published in the journal Foreign Affairs, which described a strategy of carpet-bombing and defoliating the rural villages and jungles of Vietnam, so that peasants there would be...

, destroying the ability of peasants to support themselves in the countryside, and forcing them to flee to the U.S. dominated cities, thus depriving the guerrillas of their rural support base and food supply.

Air Force records show that at least 6,542 spraying missions took place over the course of Operation Ranch Hand. By 1971, 12% of the total area of South Vietnam had been sprayed with defoliating chemicals, which were often applied at rates that were 13 times as high as the legal USDA limit. In South Vietnam alone, an estimated 10 million hectares of agricultural land were ultimately destroyed. In some areas TCDD concentrations in soil and water were hundreds of times greater than the levels considered "safe" by the U.S. Environmental Protection Agency. Overall, more than 20% of South Vietnam's forests were sprayed at least once over a nine-year period.

The US began to target food crops in October 1962, primarily using Agent Blue

Agent Blue

Agent Blue is one of the "rainbow herbicides" that is known for its use by the United States during the Vietnam War. It was sprayed on rice paddies and other crops in an attempt to deprive the Viet Cong of valuable crops. Agent Blue is a mixture of two arsenic-containing compounds, sodium...

. In 1965, 42% of all herbicide spraying was dedicated to food crops. Rural-to-urban migration rates dramatically increased in South Vietnam, as peasants escaped the destruction and famine

Famine

A famine is a widespread scarcity of food, caused by several factors including crop failure, overpopulation, or government policies. This phenomenon is usually accompanied or followed by regional malnutrition, starvation, epidemic, and increased mortality. Every continent in the world has...

in the countryside by fleeing to the U.S.-dominated cities. The urban population in South Vietnam more than tripled: from 2.8 million people in 1958, to 8 million by 1971. The rapid flow of people led to a fast-paced and uncontrolled urbanization

Urbanization

Urbanization, urbanisation or urban drift is the physical growth of urban areas as a result of global change. The United Nations projected that half of the world's population would live in urban areas at the end of 2008....

; an estimated 1.5 million people were living in Saigon slums, while many South Vietnamese elites and U.S. personnel lived in luxury.

According to Vietnamese Ministry of Foreign Affairs, 4.8 million Vietnamese people were exposed to Agent Orange, resulting in 400,000 people being killed or maimed, and 500,000 children born with birth defects.

Dioxin exposure incidents

In 1949, in a Monsanto
Monsanto
The Monsanto Company is a US-based multinational agricultural biotechnology corporation. It is the world's leading producer of the herbicide glyphosate, marketed in the "Roundup" brand of herbicides, and in other brands...

herbicide production plant for 2,4,5-T
2,4,5-Trichlorophenoxyacetic acid
2,4,5-Trichlorophenoxyacetic acid , a synthetic auxin, is a chlorophenoxy acetic acid herbicide used to defoliate broad-leafed plants. It was developed in the late 1940s and was widely used in the agricultural industry until being phased out, starting in the late 1970s due to toxicity concerns....

in Nitro, West Virginia
Nitro, West Virginia
Nitro is a city in West Virginia, along the Kanawha River. Most of the city lies in Kanawha County, with the remainder in Putnam County. The population was 7,178 at the 2010 census.Nitro was incorporated in 1932 by Circuit Court.- City name origin :...

, 240 people were affected when a relief valve opened.

In 1963, a dioxin cloud escapes after an explosion in a Philips
Philips
Koninklijke Philips Electronics N.V. , more commonly known as Philips, is a multinational Dutch electronics company....

-Duphar plant (now Solvay
Solvay
Solvay may refer to* Solvay , an international chemicals and plastics company* the Solvay process* Ernest Solvay, its inventor* Solvay Conference* the Solvay Business School* Solvay, New York* Solvay Hut, on the Matterhorn...

Group) near Amsterdam
Amsterdam
Amsterdam is the largest city and the capital of the Netherlands. The current position of Amsterdam as capital city of the Kingdom of the Netherlands is governed by the constitution of August 24, 1815 and its successors. Amsterdam has a population of 783,364 within city limits, an urban population...

. The plant was so polluted with dioxin after the accident that it had to be dismantled, embedded in concrete, and dumped into the ocean.

Between 1965 and 1968 production of 2,4,5-trichlorophenol in Spolana
Spolana
Spolana is a Czech chemical plant in Neratovice established in 1898.The chemical factory is situated approximately 25 kilometres north of Prague at the confluence of the Košátecký Brook and the River Elbe...

Neratovice
Neratovice
Neratovice is a town in the Central Bohemian Region of the Czech Republic. It has cca 16,400 inhabitants. The Spolana chemical plant resides there. The town is part of the Prague metropolitan area....

plant in Czechoslovakia
Czechoslovakia
Czechoslovakia or Czecho-Slovakia was a sovereign state in Central Europe which existed from October 1918, when it declared its independence from the Austro-Hungarian Empire, until 1992...

seriously poisoned about 60 workers with dioxins; after 3 years of investigations of the health problems of workers, Spolana stopped manufacture of 2,4,5-T (most of which was supplied to the US military in Vietnam). Several buildings of the Spolana chemical plant were heavily contaminated by dioxins. Unknown amounts of dioxins were flushed into the Elbe
Elbe
The Elbe is one of the major rivers of Central Europe. It rises in the Krkonoše Mountains of the northwestern Czech Republic before traversing much of Bohemia , then Germany and flowing into the North Sea at Cuxhaven, 110 km northwest of Hamburg...

and Mulde
Mulde
The Mulde is a river in Saxony and Saxony-Anhalt, Germany. It is a left tributary of the Elbe and 124 km in length.The river is formed by the confluence, near Colditz, of the Zwickauer Mulde and the Freiberger Mulde , both rising from the Ore Mountains...

rivers during the 2002 European flood, contaminating the soils. Analysis of eggs and ducks found levels of dioxins 15-time higher than EU limit and high concentrations of dioxin-like PCBs in the village of Libiš. In 2004, the state health authority published a study which analysed the level of toxic substances in human blood near Spolana. According to the study, blood dioxin levels in Neratovice
Neratovice
Neratovice is a town in the Central Bohemian Region of the Czech Republic. It has cca 16,400 inhabitants. The Spolana chemical plant resides there. The town is part of the Prague metropolitan area....

, Libiš
Libiš
Libiš is a village and municipality in Mělník District in the Central Bohemian Region of the Czech Republic. -References:*This article was initially translated from the Czech Wikipedia....

and Tišice
Tišice
Tišice is a village and municipality in Mělník District in the Central Bohemian Region of the Czech Republic. -References:*This article was initially translated from the Czech Wikipedia....

were about twice the level of the control group in Benešov
Benešov
Benešov is a town in the Central Bohemian Region, Czech Republic, about southeast of Prague. The Konopiště castle and the Czech national mountain Blaník are near the town.-History:...

. The quantity of dioxin chemicals near Spolana is significantly higher than the background level in other countries, e.g., USA, Japan
Japan
Japan is an island nation in East Asia. Located in the Pacific Ocean, it lies to the east of the Sea of Japan, China, North Korea, South Korea and Russia, stretching from the Sea of Okhotsk in the north to the East China Sea and Taiwan in the south...

or Spain
Spain
Spain , officially the Kingdom of Spain languages]] under the European Charter for Regional or Minority Languages. In each of these, Spain's official name is as follows:;;;;;;), is a country and member state of the European Union located in southwestern Europe on the Iberian Peninsula...

. According to the US EPA, even the background level can pose a risk of cancer from 1:10000 up to 1: 1000, about 100 times higher than normal. The consumption of local fish, eggs, poultry and some produce was prohibited because of the post-flood contamination.

Also during 1965 through 1968, Dr. Albert M Kligman
Albert Kligman
Albert Montgomery Kligman was a dermatologist who invented Retin-A, the popular acne medication.-Biography:Kligman was born in Philadelphia to poor Jewish immigrants, his father from Ukraine and mother from England...

was contracted by the Dow Chemical Company to perform threshold tests for TCDD on inmates at Holmesburg Prison after Dow studies revealed adverse effects on workers at Dow's Midland Michigan plant were likely due to TCDD. A subsequent test by Dow in rabbit ear models when exposed to 4–8 ug usually caused a severe response. The human studies carried out in Holmesburg failed to follow Dow's original protocol and lacked proper informed consent by the participants. As a result of poor study design and subsequent destruction of records, the tests were virtually worthless even though ten inmates were exposed to 7,500 ug of TCDD.

In 1976, large amounts of dioxins were released in an industrial accident at Seveso
Seveso disaster
The Seveso disaster was an industrial accident that occurred around 12:37 pm July 10, 1976, in a small chemical manufacturing plant approximately north of Milan in the Lombardy region in Italy...

, although no immediate human fatalities or birth defects occurred.

In 1978, dioxins were some of the contaminants that forced the evacuation of the Love Canal
Love Canal
Love Canal was a neighborhood in Niagara Falls, New York, located in the white collar LaSalle section of the city. It officially covers 36 square blocks in the far southeastern corner of the city, along 99th Street and Read Avenue...

neighborhood of Niagara Falls, New York
Niagara Falls, New York
Niagara Falls is a city in Niagara County, New York, United States. As of the 2010 census, the city had a total population of 50,193, down from the 55,593 recorded in the 2000 census. It is across the Niagara River from Niagara Falls, Ontario , both named after the famed Niagara Falls which they...

.

From 1982 through to 1985, Times Beach, Missouri
Times Beach, Missouri
Times Beach, Missouri was a small town of 2,240 residents in St. Louis County, Missouri, 17 miles southwest of St. Louis and 2 mi east of Eureka, Missouri. The town was completely evacuated early in 1983 due to a dioxin scare that made national headlines...

, was bought out and evacuated under order of the United States Environmental Protection Agency
United States Environmental Protection Agency
The U.S. Environmental Protection Agency is an agency of the federal government of the United States charged with protecting human health and the environment, by writing and enforcing regulations based on laws passed by Congress...

due to high levels of dioxins in the soil caused by applications of contaminated oil meant to control dust on the town's dirt roads. The town eventually disincorporated.

In December 1991, an electrical explosion caused dioxins (created from the oxidation of polychlorinated biphenyl
Polychlorinated biphenyl
Polychlorinated biphenyls are a class of organic compounds with 2 to 10 chlorine atoms attached to biphenyl, which is a molecule composed of two benzene rings. The chemical formula for PCBs is C12H10-xClx...

) to spread through four residence halls and two other buildings on the college campus of SUNY New Paltz.

In May 1999, there was a dioxin crisis in Belgium
Dioxine affair
The Dioxin Affair was a political crisis that struck in Belgium during the spring of 1999.Contamination of feedstock with polychlorinated biphenyls was detected in animal food products, mainly eggs and chickens....

: quantities of polychlorinated biphenyls with dioxin like toxicity had entered the food chain
Food chain
A food web depicts feeding connections in an ecological community. Ecologists can broadly lump all life forms into one of two categories called trophic levels: 1) the autotrophs, and 2) the heterotrophs...

through contaminated animal feed
Compound feed
Compound feeds are feedstuffs that are blended from various raw materials and additives. These blends are formulated according to the specific requirements of the target animal...

. 7,000,000 chickens and 60,000 pigs had to be slaughtered. This scandal was followed by a landslide change in government in the elections one month later.

Explosions resulting from the terrorist attacks on the US on September 11, 2001 released massive amounts of dust into the air. The air was measured for dioxins from September 23, 2001, to November 21, 2001, and reported to be "likely the highest ambient concentration that have ever been reported." [in history]. The United States Environmental Protection Agency
United States Environmental Protection Agency
The U.S. Environmental Protection Agency is an agency of the federal government of the United States charged with protecting human health and the environment, by writing and enforcing regulations based on laws passed by Congress...

report dated October 2002 and released in December 2002 titled "Exposure and Human Health Evaluation of Airborne Pollution from the World Trade Center Disaster" authored by the EPA Office of Research and Development in Washington states that dioxin levels recorded at a monitoring station on Park Row near City Hall Park in New York
New York
New York is a state in the Northeastern region of the United States. It is the nation's third most populous state. New York is bordered by New Jersey and Pennsylvania to the south, and by Connecticut, Massachusetts and Vermont to the east...

between October 12 and 29, 2001, averaged 5.6 parts per trillion, or nearly six times the highest dioxin level ever recorded in the U.S. Dioxin levels in the rubble of the World Trade Centers were much higher with concentrations ranging from 10 to 170 parts per trillion. The report did no measuring of the toxicity of indoor air.

In a 2001 case study, physicians reported clinical changes in a 30-year-old woman who had been exposed to a massive dosage (144,000 pg/g blood fat) of dioxin equal to 16,000 times the normal body level; the highest dose of dioxin ever recorded in a human. She suffered from chloracne
Chloracne
Chloracne is an acne-like eruption of blackheads, cysts, and pustules associated with over-exposure to certain halogenated aromatic compounds, such as chlorinated dioxins and dibenzofurans...

, nausea
Nausea
Nausea , is a sensation of unease and discomfort in the upper stomach with an involuntary urge to vomit. It often, but not always, precedes vomiting...

, vomiting
Vomiting
Vomiting is the forceful expulsion of the contents of one's stomach through the mouth and sometimes the nose...

, epigastric pain, loss of appetite
Anorexia (symptom)
Anorexia is the decreased sensation of appetite...

, leukocytosis
Leukocytosis
Leukocytosis is a raised white blood cell count above the normal range in the blood. It is frequently a sign of an inflammatory response, most commonly the result of infection, and is observed in certain parasitic infections...

, anemia
Anemia
Anemia is a decrease in number of red blood cells or less than the normal quantity of hemoglobin in the blood. However, it can include decreased oxygen-binding ability of each hemoglobin molecule due to deformity or lack in numerical development as in some other types of hemoglobin...

, amenorrhoea
Amenorrhoea
Amenorrhoea , amenorrhea , or amenorrhœa, is the absence of a menstrual period in a woman of reproductive age. Physiological states of amenorrhoea are seen during pregnancy and lactation , the latter also forming the basis of a form of contraception known as the lactational amenorrhoea method...

and thrombocytopenia
Thrombocytopenia
Thrombocytopenia is a relative decrease of platelets in blood.A normal human platelet count ranges from 150,000 to 450,000 platelets per microliter of blood. These limits are determined by the 2.5th lower and upper percentile, so values outside this range do not necessarily indicate disease...

. However, other notable laboratory tests, such as immune function tests, were relatively normal. The same study also covered a second subject who had received a dosage equivalent to 2,900 times the normal level, who apparently suffered no notable negative effects other than chloracne. These patients were provided with olestra
Olestra
Olestra is a fat substitute that adds no fat, calories, or cholesterol to products. It has been used in the preparation of traditionally high-fat foods such as potato chips, thereby lowering or eliminating their fat content...

to accelerate dioxin elimination.

In 2004, a notable individual case of dioxin poisoning, Ukrainian
Ukraine
Ukraine is a country in Eastern Europe. It has an area of 603,628 km², making it the second largest contiguous country on the European continent, after Russia...

politician Viktor Yushchenko
Viktor Yushchenko
Viktor Andriyovych Yushchenko is a former President of Ukraine. He took office on January 23, 2005, following a period of popular unrest known as the Orange Revolution...

was exposed to the second-largest measured dose of dioxins, according to the reports of the physicians responsible for diagnosing him. This is the first known case of a single high dose of TCDD dioxin poisoning, and was diagnosed only after a toxicologist recognized the symptoms of chloracne
Chloracne
Chloracne is an acne-like eruption of blackheads, cysts, and pustules associated with over-exposure to certain halogenated aromatic compounds, such as chlorinated dioxins and dibenzofurans...

while viewing television news coverage of his condition.

In the early 2000s, residents of the city of New Plymouth, New Zealand, report many illnesses of people living around and working at the Dow Chemical plant. This plant ceased production of 2,4,5-T in 1987.

DuPont has been sued by 1,995 people who claim dioxin emissions from DuPont's plant in DeLisle, Mississippi, caused their cancers, illnesses or loved one's death, of these only 850 are pending as of June 2008. In August 2005, Glen Strong, an oyster fisherman with the rare blood cancer multiple myeloma, was awarded $14 million from DuPont – this ruling was overturned June 5, 2008 by a Mississippi jury who found DuPont's plant had no connection to Mr. Strong's disease. In another case, parents claim dioxin from pollution caused the death of their 8-year-old daughter; the trial took place in the summer of 2007, and a jury wholly rejected the family's claims as no scientific connection could be proven between DuPont and the family's tragic loss. DuPont's DeLisle plant is one of three titanium dioxide
Titanium dioxide
Titanium dioxide, also known as titanium oxide or titania, is the naturally occurring oxide of titanium, chemical formula . When used as a pigment, it is called titanium white, Pigment White 6, or CI 77891. Generally it comes in two different forms, rutile and anatase. It has a wide range of...

facilities (including Edgemoor, DE, and New Johnsonville, TN) that are the largest producers of dioxin in the country, according to the US EPA's Toxic Release Inventory. DuPont maintains its operations are safe and environmentally responsible.

In 2007 in Italy thousands of tonnes of foul-smelling refuse are piled up in Naples and its surrounding villages, defacing entire neighbourhoods. Polychlorinated dibenzodioxins are found in animals and humans over lethal dose. Sources of Polychlorinated dibenzodioxins was identified in refuse and pvc combustion and industrial refuse disposal in uncontrolled industrial waste disposal. In numbers animals and humans was found lethal dose.

In December 2008 in Ireland
Ireland
Ireland is an island to the northwest of continental Europe. It is the third-largest island in Europe and the twentieth-largest island on Earth...

dioxin levels in pork
Pork
Pork is the culinary name for meat from the domestic pig , which is eaten in many countries. It is one of the most commonly consumed meats worldwide, with evidence of pig husbandry dating back to 5000 BC....

were disclosed to have been between 80 and 200 times the legal limit. All Irish pork products were withdrawn from sale both nationally and internationally. In this case the dioxin toxicity was found to be mostly due to dioxin-like polychlorinated dibenzofurans and polychlorinated biphenyls and the contribution from actual polychlorinated dibenzodioxins was relatively low. It is thought that the incident resulted from the contamination of fuel oil used in a drying burner at a single feed processor, with PCBs. The resulting combustion produced a highly toxic mixture of PCBs, dioxins and furans, which was included in the feed produced and subsequently fed to a large number of pigs.
According to the last available data, in 2005 the production of dioxin by the steel industry ILVA in Taranto
Taranto
Taranto is a coastal city in Apulia, Southern Italy. It is the capital of the Province of Taranto and is an important commercial port as well as the main Italian naval base....

(Italy
Italy
Italy , officially the Italian Republic languages]] under the European Charter for Regional or Minority Languages. In each of these, Italy's official name is as follows:;;;;;;;;), is a unitary parliamentary republic in South-Central Europe. To the north it borders France, Switzerland, Austria and...

) accounted for 90.3 per cent of the overall Italian emissions, and 8.8 per cent of the European emissions.

German dioxin incidence: In January 2011 about 4700 German farms were banned from making deliveries after self-checking of an animal feed producer had showed levels of dioxin above maximum levels. This incident appeared to involve PCDDs and not PCBs. Dioxins were found in animal feed and eggs in many farms. The maximum values were exceeded twofold in feed and maximally fourfold in some individual eggs. Thus the incident was minor as compared with the Belgian crisis in 1999, and delivery bans were rapidly cleared.

Dioxin Testing

The analyses used to determine these compounds’ relative toxicity share common elements that differ from methods used for more traditional analytical determinations. The preferred methods for dioxins and related analyses use high resolution gas chromatography/mass spectrometry (HRGC/HRMS). Concentrations are determined by measuring the ratio of the analyte to the appropriate isotopically labeled internal standard.

External links

NIEHS dioxin fact sheet
What is Dioxin?
"Dioxin Homepage at Environmental Justice Advocates"
"EPA: Exposure and Human Health Reassessment of 2,3,7,8-Tetrachlorodibenzo-p-Dioxin (TCDD) and Related Compounds National Academy Sciences (NAS) Review Draft"
"Dioxins and Dioxin-like Compounds in the Food Supply: Strategies to Decrease Exposure", a 2003 report by the National Academy of Sciences
United States National Academy of Sciences
The National Academy of Sciences is a corporation in the United States whose members serve pro bono as "advisers to the nation on science, engineering, and medicine." As a national academy, new members of the organization are elected annually by current members, based on their distinguished and...
National Pollutant Inventory – Dioxin and Furan Fact Sheet
"Rhodes Remediation" Website about remediation of dioxin contaminated Homebush Bay and land in Rhodes, a suburb of Sydney, NSW, Australia. Union Carbide was the polluter.
"Researcher Dispels Myth of Dioxins and Plastic Water Bottles" Johns Hopkins Researcher explains the facts about Dioxins
"Health Risks from Dioxin and Related Compounds: Evaluation of the EPA Reassessment" Includes discussion of methods of evaluating risk of low concentrations, and Toxic Equivalency
"Dioxins in Cigarette Smoke".
Pesticide residues that are legal contaminants of tobacco
Health effects of dioxins
"Assessment of the Health Risks of Dioxins", a 1998 report by the World Health Organisation.
New Zealand Ministry of Health page on dioxins
IARC monograph: "Polychlorinated Dibenzo-para-dioxins"

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