General structure of PCDDs where n and m can range from 0 to 4

Polychlorinated dibenzodioxins (PCDDs), or simply dioxins, are a group of long-lived polyhalogenated organic compounds that are primarily anthropogenic, and contribute toxic, persistent organic pollution in the environment.[1]

They are commonly but inaccurately referred to as dioxins for simplicity, because every PCDD molecule contains a dibenzo-1,4-dioxin skeletal structure, with 1,4-dioxin as the central ring. Members of the PCDD family bioaccumulate in humans and wildlife because of their lipophilic properties, and may cause developmental disturbances and cancer.

Because dioxins can persist in the environment for more than 100 years, the majority of PCDD pollution today is not the result of recent emissions, but the cumulative result of synthetic processes undertaken since the beginning of the 20th century, including organochloride-related manufacturing, incineration of chlorine-containing substances such as polyvinyl chloride (PVC), and chlorine bleaching of paper.[2][3] Forest fires and volcanic eruptions have also been cited as an airborne source, although their contribution to the current levels of PCDD accumulation are minor in comparison.[4][5] Incidents of dioxin poisoning resulting from industrial emissions and accidents were first recorded as early as the mid 19th century during the Industrial Revolution.[6]

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

Chemical structure of dibenzo-1,4-dioxins

The skeletal formula and substituent numbering scheme of the parent compound dibenzo-1,4-dioxin

The structure of dibenzo-1,4-dioxin consists of two benzene rings joined by two oxygen bridges. This makes the compound an aromatic diether. 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).[7]

number formula name CAS Number InChIKey
PCDD-1 1-chlorodibenzo-p-dioxin 39227-53-7 VGGGRWRBGXENKI-UHFFFAOYSA-N
PCDD-2 2-chlorodibenzo-p-dioxin 39227-54-8 GIUGGRUEPHPVNR-UHFFFAOYSA-N
PCDD-12 1,2-dichlorodibenzo-p-dioxin 54536-18-4 DFGDMWHUCCHXIF-UHFFFAOYSA-N
PCDD-13 1,3-dichlorodibenzo-p-dioxin 50585-39-2 AZYJYMAKTBXNSX-UHFFFAOYSA-N
PCDD-14 1,4-dichlorodibenzo-p-dioxin 54536-19-5 MBMUPQZSDWVPQU-UHFFFAOYSA-N
PCDD-16 1,6-dichlorodibenzo-p-dioxin 38178-38-0 MAWMBEVNJGEDAD-UHFFFAOYSA-N
PCDD-17 1,7-dichlorodibenzo-p-dioxin 82291-26-7 IJUWLAFPPVRYGY-UHFFFAOYSA-N
PCDD-18 1,8-dichlorodibenzo-p-dioxin 82291-27-8 PLZYIHQBHROTFD-UHFFFAOYSA-N
PCDD-19 1,9-dichlorodibenzo-p-dioxin 82291-28-9 JZDVJXBKJDADAY-UHFFFAOYSA-N
PCDD-23 2,3-dichlorodibenzo-p-dioxin 29446-15-9 YCIYTXRUZSDMRZ-UHFFFAOYSA-N
PCDD-27 2,7-dichlorodibenzo-p-dioxin 33857-26-0 NBFMTHWVRBOVPE-UHFFFAOYSA-N
PCDD-28 2,8-dichlorodibenzo-p-dioxin 38964-22-6 WMWJCKBJUQDYLM-UHFFFAOYSA-N
PCDD-123 1,2,3-trichlorodibenzo-p-dioxin 54536-17-3 SKMFBGZVVNDVFR-UHFFFAOYSA-N
PCDD-124 1,2,4-trichlorodibenzo-p-dioxin 39227-58-2 HRVUKLBFRPWXPJ-UHFFFAOYSA-N
PCDD-126 1,2,6-trichlorodibenzo-p-dioxin 69760-96-9 XQBPVWBIUBCJJO-UHFFFAOYSA-N
PCDD-127 1,2,7-trichlorodibenzo-p-dioxin 82291-30-3 TXJMXDWFPQSYEQ-UHFFFAOYSA-N
PCDD-128 1,2,8-trichlorodibenzo-p-dioxin 82291-31-4 QBEOCKSANJLBAE-UHFFFAOYSA-N
PCDD-129 1,2,9-trichlorodibenzo-p-dioxin 82291-32-5 DQLRDBDQLSIOIX-UHFFFAOYSA-N
PCDD-136 1,3,6-trichlorodibenzo-p-dioxin 82291-33-6 LNPVMVSAUXUGHH-UHFFFAOYSA-N
PCDD-137 1,3,7-trichlorodibenzo-p-dioxin 67028-17-5 RPKWIXFZKMDPMH-UHFFFAOYSA-N
PCDD-138 1,3,8-trichlorodibenzo-p-dioxin 82306-61-4 FJAKCOBYQSEWMT-UHFFFAOYSA-N
PCDD-139 1,3,9-trichlorodibenzo-p-dioxin 82306-62-5 DGDADRUTFAIIQQ-UHFFFAOYSA-N
PCDD-146 1,4,6-trichlorodibenzo-p-dioxin 82306-63-6 UTTYFTWIJLRXKB-UHFFFAOYSA-N
PCDD-147 1,4,7-trichlorodibenzo-p-dioxin 82306-64-7 NBWAQBGJBSYXHV-UHFFFAOYSA-N
PCDD-178 1,7,8-trichlorodibenzo-p-dioxin 82306-65-8 CAPCTZJHYADFNX-UHFFFAOYSA-N
PCDD-237 2,3,7-trichlorodibenzo-p-dioxin 33857-28-2 ZSIZNEVHVVRPFF-UHFFFAOYSA-N
PCDD-1234 1,2,3,4-tetrachlorodibenzo-p-dioxin 30746-58-8 DJHHDLMTUOLVHY-UHFFFAOYSA-N
PCDD-1236 1,2,3,6-tetrachlorodibenzo-p-dioxin 71669-25-5 XEZBZSVTUSXISZ-UHFFFAOYSA-N
PCDD-1237 1,2,3,7-tetrachlorodibenzo-p-dioxin 67028-18-6 SKGXYFVQZVPEFP-UHFFFAOYSA-N
PCDD-1238 1,2,3,8-tetrachlorodibenzo-p-dioxin 53555-02-5 BXKLTNKYLCZOHF-UHFFFAOYSA-N
PCDD-1239 1,2,3,9-tetrachlorodibenzo-p-dioxin 71669-26-6 CMVHZKSHSHQJHS-UHFFFAOYSA-N
PCDD-1246 1,2,4,6-tetrachlorodibenzo-p-dioxin 71669-27-7 KQNBZUDHTCXCNA-UHFFFAOYSA-N
PCDD-1247 1,2,4,7-tetrachlorodibenzo-p-dioxin 71669-28-8 SMPHQCMJQUBTFZ-UHFFFAOYSA-N
PCDD-1248 1,2,4,8-tetrachlorodibenzo-p-dioxin 71669-29-9 XGIKODBWQSAEFQ-UHFFFAOYSA-N
PCDD-1249 1,2,4,9-tetrachlorodibenzo-p-dioxin 71665-99-1 WDAHVJCSSYOALR-UHFFFAOYSA-N
PCDD-1267 1,2,6,7-tetrachlorodibenzo-p-dioxin 40581-90-6 SAMLAWFHXZIRMP-UHFFFAOYSA-N
PCDD-1268 1,2,6,8-tetrachlorodibenzo-p-dioxin 67323-56-2 YYUFYZDSYHKVDP-UHFFFAOYSA-N
PCDD-1269 1,2,6,9-tetrachlorodibenzo-p-dioxin 40581-91-7 ZKMXKYXNLFLUCD-UHFFFAOYSA-N
PCDD-1278 1,2,7,8-tetrachlorodibenzo-p-dioxin 34816-53-0 YDZCLBKUTXYYKS-UHFFFAOYSA-N
PCDD-1279 1,2,7,9-tetrachlorodibenzo-p-dioxin 71669-23-3 QIKHBBZEUNSCAF-UHFFFAOYSA-N
PCDD-1289 1,2,8,9-tetrachlorodibenzo-p-dioxin 62470-54-6 WELWFAGPAZKSBG-UHFFFAOYSA-N
PCDD-1368 1,3,6,8-tetrachlorodibenzo-p-dioxin 33423-92-6 OTQFXRBLGNEOGH-UHFFFAOYSA-N
PCDD-1369 1,3,6,9-tetrachlorodibenzo-p-dioxin 71669-24-4 QAUIRDIJIUMMEP-UHFFFAOYSA-N
PCDD-1378 1,3,7,8-tetrachlorodibenzo-p-dioxin 50585-46-1 VPTDIAYLYJBYQG-UHFFFAOYSA-N
PCDD-1379 1,3,7,9-tetrachlorodibenzo-p-dioxin 62470-53-5 JMGYHLJVDHUACM-UHFFFAOYSA-N
PCDD-1469 1,4,6,9-tetrachlorodibenzo-p-dioxin 40581-93-9 QTIIAIRUSSSOHT-UHFFFAOYSA-N
PCDD-1478 1,4,7,8-tetrachlorodibenzo-p-dioxin 40581-94-0 FCRXUTCUWCJZJI-UHFFFAOYSA-N
PCDD-2378 (TCDD) 2,3,7,8-tetrachlorodibenzo-p-dioxin 1746-01-6 HGUFODBRKLSHSI-UHFFFAOYSA-N
PCDD-12346 1,2,3,4,6-pentachlorodibenzo-p-dioxin 67028-19-7 LNWDBNKKBLRAMH-UHFFFAOYSA-N
PCDD-12347 1,2,3,4,7-pentachlorodibenzo-p-dioxin 39227-61-7 WRNGAZFESPEMCN-UHFFFAOYSA-N
PCDD-12367 1,2,3,6,7-pentachlorodibenzo-p-dioxin 71925-15-0 RLGWDUHOIIWPGN-UHFFFAOYSA-N
PCDD-12368 1,2,3,6,8-pentachlorodibenzo-p-dioxin 71925-16-1 VKDGHBBUEIIEHL-UHFFFAOYSA-N
PCDD-12369 (PCDD-14678) 1,2,3,6,9-pentachlorodibenzo-p-dioxin 82291-34-7 NWKWRHSKKNELND-UHFFFAOYSA-N
PCDD-12378 1,2,3,7,8-pentachlorodibenzo-p-dioxin 40321-76-4 FSPZPQQWDODWAU-UHFFFAOYSA-N
PCDD-12379 (PCDD-23468) 1,2,3,7,9-pentachlorodibenzo-p-dioxin 71925-17-2 UAOYHTXYVWEPIB-UHFFFAOYSA-N
PCDD-12389 (PCDD-23467) 1,2,3,8,9-pentachlorodibenzo-p-dioxin 71925-18-3 VUMZAVNIADYKFC-UHFFFAOYSA-N
PCDD-12467 1,2,4,6,7-pentachlorodibenzo-p-dioxin 82291-35-8 SEKDDGLKEYEVQK-UHFFFAOYSA-N
PCDD-12468 1,2,4,6,8-pentachlorodibenzo-p-dioxin 71998-76-0 SJJWALZHAWITMS-UHFFFAOYSA-N
PCDD-12469 1,2,4,6,9-pentachlorodibenzo-p-dioxin 82291-36-9 GNQVSAMSAKZLKE-UHFFFAOYSA-N
PCDD-12478 1,2,4,7,8-pentachlorodibenzo-p-dioxin 58802-08-7 QUPLGUUISJOUPJ-UHFFFAOYSA-N
PCDD-12479 (PCDD-13468) 1,2,4,7,9-pentachlorodibenzo-p-dioxin 82291-37-0 QLBBXWPVEFJZEC-UHFFFAOYSA-N
PCDD-12489 (PCDD-13467) 1,2,4,8,9-pentachlorodibenzo-p-dioxin 82291-38-1 KLLFLRKEOJCTGC-UHFFFAOYSA-N
PCDD-123467 1,2,3,4,6,7-hexachlorodibenzo-p-dioxin 58200-66-1 NLBQVWJHLWAFGJ-UHFFFAOYSA-N
PCDD-123468 1,2,3,4,6,8-hexachlorodibenzo-p-dioxin 58200-67-2 IMALTUQZEIFHJW-UHFFFAOYSA-N
PCDD-123469 1,2,3,4,6,9-hexachlorodibenzo-p-dioxin 58200-68-3 UDYXCMRDCOVQLG-UHFFFAOYSA-N
PCDD-123478 1,2,3,4,7,8-hexachlorodibenzo-p-dioxin 39227-28-6 WCYYQNSQJHPVMG-UHFFFAOYSA-N
PCDD-123678 1,2,3,6,7,8-hexachlorodibenzo-p-dioxin 57653-85-7 YCLUIPQDHHPDJJ-UHFFFAOYSA-N
PCDD-123679 (PCDD-124678) 1,2,3,6,7,9-hexachlorodibenzo-p-dioxin 64461-98-9 BQOHWGKNRKCEFT-UHFFFAOYSA-N
PCDD-123689 (PCDD-134678) 1,2,3,6,8,9-hexachlorodibenzo-p-dioxin 58200-69-4 GZRQZUFXVFRKBI-UHFFFAOYSA-N
PCDD-123789 (PCDD-234678) 1,2,3,7,8,9-hexachlorodibenzo-p-dioxin 19408-74-3 LGIRBUBHIWTVCK-UHFFFAOYSA-N
PCDD-124679 1,2,4,6,7,9-hexachlorodibenzo-p-dioxin 39227-62-8 BSJDQMWAWFTDGD-UHFFFAOYSA-N
PCDD-124689 (PCDD-134679) 1,2,4,6,8,9-hexachlorodibenzo-p-dioxin 58802-09-8 URELDHWUZUWPIU-UHFFFAOYSA-N
PCDD-1234678 1,2,3,4,6,7,8-heptachlorodibenzo-p-dioxin 35822-46-9 WCLNVRQZUKYVAI-UHFFFAOYSA-N
PCDD-1234679 1,2,3,4,6,7,9-heptachlorodibenzo-p-dioxin 58200-70-7 KTJJIBIRZGQFQZ-UHFFFAOYSA-N
PCDD-12346789 octachlorodibenzo-p-dioxin 3268-87-9 FOIBFBMSLDGNHL-UHFFFAOYSA-N

The toxicity of PCDDs depends on the number and positions of the chlorine atoms. Congeners that have chlorine 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.[8]

Historical perspective

Structure of 2,3,7,8-tetrachlorodibenzodioxin (TCDD)

Low concentrations of dioxins existed in nature prior to industrialization as a result of natural combustion and geological processes.[9][10] Dioxins were first unintentionally produced as by-products from 1848 onwards as Leblanc process plants started operating in Germany.[6] 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-tetrachlorodibenzodioxin (TCDD), became well known as a contaminant of Agent Orange, a herbicide used in the Malayan Emergency and the Vietnam War.[11] Later, dioxins were found in Times Beach, Missouri[12] and Love Canal, New York[13] and Seveso, Italy.[14] More recently, dioxins have been in the news with the poisoning of President Viktor Yushchenko of Ukraine in 2004,[15] the Naples Mozzarella Crisis,[16] the 2008 Irish pork crisis, and the German feed incident of 2010.[17]

Sources of dioxins

The United States Environmental Protection Agency inventory of sources of dioxin-like compounds is possibly the most comprehensive review of the sources and releases of dioxins,[18] but other countries now have substantial research as well.

Concentration profile of PCDD in a dated sediment core from Esthwaite Water, Cumbria, UK

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 herbicides. In many developed nations there are now emissions regulations which have dramatically decreased the emissions[18] and thus alleviated some concerns, although the lack of continuous sampling of dioxin emissions causes concern about the understatement of emissions. In Belgium, 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, whether the chlorine is present as chloride ions 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:[18]

When first carried out in 1987, the original US EPA inventory of dioxin sources revealed that incineration represented more than 80% of known dioxin sources. As a result, US EPA implemented new emissions requirements. These regulations succeeded 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. Since 1987, however, backyard barrel burning has showed almost no decrease, and is now the largest source of dioxin emissions, producing about one third of the total output.[18]

In incineration, dioxins can also reform or form de novo in the atmosphere 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.[19] 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[citation needed] 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.[20] Compounds involved include the wood preservative pentachlorophenol, and also herbicides such as 2,4-dichlorophenoxyacetic acid (or 2,4-D) and 2,4,5-trichlorophenoxyacetic acid (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.[21]

Sources of human intake

A chart illustrating how much dioxin the average American consumes per day. (Note: pg = picogram, or one trillionth of a gram, or 10−12 g).[22]

Tolerable daily, monthly or annual intakes have been set by the World Health Organization 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.[22][23]

Children are passed substantial body burdens by their mothers, and breastfeeding increases the child's body burden.[24] Dioxin exposure can also occur from contact with Pentachlorophenol (Penta) treated lumber as Pentachlorophenol often contains dioxins as a contaminant. 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.[25] Breast fed children usually still have higher dioxin body burdens than non breast fed children. The WHO still recommends breast feeding for its other benefits.[26] In many countries dioxins in breast milk have decreased by even 90% during the two last decades.[27]

Dioxins are present in cigarette smoke.[28] 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").


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 for highly chlorinated dioxins (4–8 chlorine atoms) in humans ranges from 4.9 to 13.1 years.[29]

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.[30] The oxidized dioxins can then be more readily excreted rather than stored for a long time.[citation needed]


Space-filling model of 2,3,7,8-tetrachlorodibenzodioxin

2,3,7,8-Tetrachlorodibenzodioxin (TCDD) is considered the most toxic of the congeners (for the mechanism of action, see 2,3,7,8-Tetrachlorodibenzodioxin and Aryl hydrocarbon receptor). 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). This toxicity rating is called the Toxic Equivalence Factor concept, or TEF. 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.[8] 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.[31]

Dioxins and other persistent organic pollutants (POPs) are subject to the Stockholm Convention. The treaty obliges signatories to take measures to eliminate where possible, and minimize where not possible to eliminate, all sources of dioxin.

Health effects in humans

Chloracne on the ear and neck of a herbicide production worker

Dioxins build up primarily in fatty tissues over time (bioaccumulation), so even small exposures may eventually reach dangerous levels. In 1994, the US EPA reported that dioxins are a probable carcinogen, but noted that non-cancer effects (reproduction and sexual development, immune system) may pose a greater threat to human health. TCDD, the most toxic of the dibenzodioxins, is classified as a Group 1 carcinogen by the International Agency for Research on Cancer (IARC). TCDD has a half-life of approximately 8 years in humans, although at high concentrations, the elimination rate is enhanced by metabolism.[32] The health effects of dioxins are mediated by their action on a cellular receptor, the aryl hydrocarbon receptor (AhR).[33]

Exposure to high levels of dioxins in humans causes a severe form of persistent acne, known as chloracne.[34] 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.[35] Other effects in humans (at high dose levels) may include:

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.[43]

Dioxins accumulate in food chains in a fashion similar to other chlorinated compounds (bioaccumulation). This means that even small concentrations in contaminated water can be concentrated up a food chain to dangerous levels because of 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.[44] In particular, TCDD has been shown to be teratogenic, mutagenic, carcinogenic, immunotoxic, and hepatotoxic. Furthermore, alterations in multiple endocrine and growth factor systems have been reported. The most sensitive effects, observed in multiple species, appear to be developmental, including effects on the developing immune, nervous, and reproductive systems.[45] 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:

In rodents, including rats,[46] mice,[47] hamsters and guinea pigs,[48] birds,[49] and fish.[50]
In rodents[46][51] and fish.[52]
In rodents,[51] chickens,[53] and fish.[54]
In rodents[45] and fish.[55]
In rodents[56] and fish.[57]

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 thousandfold or more, and even among rat strains there may be thousandfold differences.[44]

Agent Orange

U.S. Army Huey helicopter spraying Agent Orange over Vietnamese agricultural land

Main article: Agent Orange

Agent Orange was the code name for one of the herbicides and defoliants the U.S. military used as part of its herbicidal warfare program, Operation Ranch Hand, during the Vietnam War from 1961 to 1971. It was a mixture of 2,4,5-T and 2,4-D. The 2,4,5-T used was contaminated with 2,3,7,8-tetrachlorodibenzodioxin (TCDD), an extremely toxic dioxin compound.

During the Vietnam war, between 1962 and 1971, the United States military sprayed 20,000,000 U.S. gallons (76,000,000 L) of chemical herbicides and defoliants in Vietnam, eastern Laos and parts of Cambodia, as part of Operation Ranch Hand.[58]

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.[59] In South Vietnam alone, an estimated 10 million hectares of agricultural land were ultimately destroyed.[60] 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.[61][62]

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.[63] The Red Cross of Vietnam estimates that up to 1 million people are disabled or have health problems due to Agent Orange contamination.[64] The United States government has challenged these figures as being unreliable and unrealistically high.[65][66]

Dioxin exposure incidents

See also: Dioxin controversy

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.[91]

Also novel bio-assays like DR CALUX are nowadays used in identification of dioxins and dioxin-like compounds. The advantage in respect to HRGC/HRMS is that it is able to scan many samples at lower costs. Also it is able to detect all compounds that interact with the Ah-receptor which is responsible for carcinogenic effects.[92]

See also


  1. ^ Weber, Roland; Tysklind, Mats; Gaus, Caroline (1 March 2008). "Dioxin - contemporary and future challenges of historical legacies". Environmental Science and Pollution Research. 15 (2): 96–100. doi:10.1065/espr2008.01.473. ISSN 1614-7499. PMID 18380226. S2CID 36662487.
  2. ^ Beychok, Milton R. (January 1987). "A data base for dioxin and furan emissions from refuse incinerators". Atmospheric Environment. 21 (1): 29–36. Bibcode:1987AtmEn..21...29B. doi:10.1016/0004-6981(87)90267-8.
  3. ^ Kjeller, Lars-Owe.; Rappe, Christoffer. (1 February 1995). "Time Trends in Levels, Patterns, and Profiles for Polychlorinated Dibenzo-p-dioxins, Dibenzofurans, and Biphenyls in a Sediment Core from the Baltic Proper". Environmental Science & Technology. 29 (2): 346–355. Bibcode:1995EnST...29..346K. doi:10.1021/es00002a010. ISSN 0013-936X. PMID 22201380.
  4. ^ "Dioxins and their effects on human health". Retrieved 28 February 2022.
  5. ^ Jaspers, Veerle; Megson, David; O’Sullivan, Gwen (1 January 2014), O’Sullivan, Gwen; Sandau, Court (eds.), "Chapter 7 - POPs in the Terrestrial Environment", Environmental Forensics for Persistent Organic Pollutants, Amsterdam: Elsevier, pp. 291–356, doi:10.1016/b978-0-444-59424-2.00007-4, ISBN 978-0-444-59424-2, retrieved 28 February 2022
  6. ^ a b c Weber R, Tysklind M, Gaus C (2008). "Dioxin - contemporary and future challenges of historical legacies". Environmental Science and Pollution Research. 15 (2): 96–100 (p.97). doi:10.1065/espr2008.01.473. PMID 18380226.
  7. ^ Nomenclature and physico-chemical properties of PCDDs and PCDFs. In: Dioxins in the Environment: What are the health risks? INSERM Collective Expert Evaluation Reports (2000). (2011-03-18). Retrieved on 2011-06-09.
  8. ^ a b Van den Berg M, Birnbaum LS, Denison M, et al. (2006). "The 2005 World Health Organization reevaluation of human and Mammalian toxic equivalency factors for dioxins and dioxin-like compounds". Toxicol. Sci. 93 (2): 223–41. doi:10.1093/toxsci/kfl055. PMC 2290740. PMID 16829543.
  9. ^ "Compilation of EU Dioxin Exposure and Health Data" (PDF). Archived from the original (PDF) on 16 June 2007. Retrieved 4 June 2007.
  10. ^ "FDA/CFSAN — Questions and Answers about Dioxins". Archived from the original on 1 June 2007. Retrieved 4 June 2007.
  11. ^ Schecter A, Birnbaum L, Ryan JJ, Constable JD (July 2006). "Dioxins: an overview". Environ Res. 101 (3): 419–28. Bibcode:2006ER....101..419S. doi:10.1016/j.envres.2005.12.003. PMID 16445906.
  12. ^ "Times Beach Record of Decision Signed". United States Environmental Protection Agency. Retrieved 4 June 2007.
  13. ^ "Love Canal Record of Decision Signed". United States Environmental Protection Agency. Retrieved 4 June 2007.
  14. ^ "4 Seveso: A paradoxical classic disaster". Archived from the original on 27 May 2010. Retrieved 4 June 2007.
  15. ^ a b Castellani, Federica (2004). "Yushchenko's acne points to dioxin poisoning". Nature: news041122–8. doi:10.1038/news041122-8. Retrieved 14 January 2009.
  16. ^ McCarthy, Michael; Phillips, John (22 March 2008). "Italy's toxic waste crisis, the Mafia – and the scandal of Europe's mozzarella". The Independent. London. Archived from the original on 19 April 2013. Retrieved 28 March 2008.
  17. ^ a b c "Dioxin in Feed Fats from Schleswig-Holstein" (PDF). Archived from the original (PDF) on 9 May 2013. Retrieved 27 November 2011.
  18. ^ a b c d "An Inventory of Sources and Environmental Releases of Dioxin-Like Compounds in the U.S. for the Years 1987, 1995, and 2000" (PDF). 1 November 2006. EPA/600/P-03/002f, Final Report
  19. ^ Cheung WH, Lee VK, McKay G (March 2007). "Minimizing dioxin emissions from integrated MSW thermal treatment". Environ Sci Technol. 41 (6): 2001–7. Bibcode:2007EnST...41.2001C. doi:10.1021/es061989d. PMID 17410797.
  20. ^ Kulkami P.S.; Crespo J.G.; Afonso C.A.M. (2008). "Dioxins sources and current remediation technologies - a review". Environment International. 34 (1): 139–153. doi:10.1016/j.envint.2007.07.009. PMID 17826831.
  21. ^ Latch DE, Packer JL, Stender BL, VanOverbeke J, Arnold WA, McNeill K (March 2005). "Aqueous photochemistry of triclosan: formation of 2,4-dichlorophenol, 2,8-dichlorodibenzo-p-dioxin, and oligomerization products". Environ Toxicol Chem. 24 (3): 517–25. doi:10.1897/04-243r.1. PMID 15779749. S2CID 19322739.
  22. ^ a b Schecter A, Cramer P, Boggess K, et al. (2001). "Intake of dioxins and related compounds from food in the U.S. population" (PDF). J. Toxicol. Environ. Health A. 63 (1): 1–18. doi:10.1080/152873901750128326. PMID 11346131. S2CID 15153932.
  23. ^ Liem A.K.; Furst P.; Rappe C. (2000). "Exposure of populations to dioxins and related compounds". Food Additives and Contaminants. 17 (4): 241–259. doi:10.1080/026520300283324. PMID 10912239. S2CID 24861588.
  24. ^ Przyrembel H, Heinrich-Hirsch B, Vieth B (2000). "Exposition to and Heal Theffects of Residues in Human Milk". Short and Long Term Effects of Breast Feeding on Child Health. Advances in Experimental Medicine and Biology. Vol. 478. pp. 307–25. doi:10.1007/0-306-46830-1_27. ISBN 0-306-46405-5. PMID 11065082.
  25. ^ "Consultation on assessment of the health risks of dioxins; re-evaluation of the tolerable daily intake (TDI): Executive summary". Food Additives and Contaminants. 17 (4): 223–240. 2000. doi:10.1080/713810655. PMID 10912238. S2CID 216644694.
  26. ^ Healthy Milk, Healthy Baby – Chemical Pollution and Mother's Milk – Chemicals: Dioxins and Furans. Retrieved on 2011-06-09.
  27. ^ "WHO Fact Sheet – "Persistent organic pollutants in human milk" (PDF). December 2009. Archived from the original (PDF) on 4 March 2016. Retrieved 29 April 2017.
  28. ^ Ball M, Paepke O, Lis A (1990). "Polychlordibenzodioxine und Polychlordibenzofurane in Cigarettenrauch" (PDF). Beitr. Tabakforsch. Int. 14 (6): 393–402. Archived from the original (PDF) on 18 December 2008.
  29. ^ Milbrath MO, Wenger Y, Chang CW, Emond C, Garabrant D, Gillespie BW, Jolliet O (March 2009). "Apparent half-lives of dioxins, furans, and polychlorinated biphenyls as a function of age, body fat, smoking status, and breast-feeding". Environmental Health Perspectives. 117 (3): 417–25. doi:10.1289/ehp.11781. PMC 2661912. PMID 19337517.
  30. ^
  31. ^ Tuomisto, J. The toxic equivalency principle and its application in dioxin risk assessment. In: R. Pohjanvirta (editor): The AH Receptor in Biology and Toxicology. Wiley, 2011. ISBN 978-0-470-60182-2.
  32. ^ Geusau A, Schmaldienst S, Derfler K, Päpke O, Abraham K (June 2002). "Severe 2,3,7,8-tetrachlorodibenzo- p-dioxin (TCDD) intoxication: kinetics and trials to enhance elimination in two patients". Arch Toxicol. 76 (5–6): 316–25. doi:10.1007/s00204-002-0345-7. PMID 12107649. S2CID 5684780.
  33. ^ Bock KW, Köhle C (August 2006). "Ah receptor: dioxin-mediated toxic responses as hints to deregulated physiologic functions". Biochem Pharmacol. 72 (4): 393–404. doi:10.1016/j.bcp.2006.01.017. PMID 16545780.
  34. ^ a b Geusau A, Abraham K, Geissler K, Sator MO, Stingl G, Tschachler E (August 2001). "Severe 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) intoxication: clinical and laboratory effects". Environmental Health Perspectives. 109 (8): 865–9. doi:10.1289/ehp.01109865. JSTOR 3454832. PMC 1240417. PMID 11564625.
  35. ^ IARC monograph: "Polychlorinated Dibenzo-para-dioxins"
  36. ^ Alaluusua S, Calderara P, Gerthoux PM, et al. (2004). "Developmental dental aberrations after the dioxin accident in Seveso". Environ. Health Perspect. 112 (13): 1313–8. doi:10.1289/ehp.6920. PMC 1247522. PMID 15345345.
  37. ^ Peterson RE, Theobald HM, Kimmel GL (1993). "Developmental and reproductive toxicity of dioxins and related compounds: cross-species comparisons". Crit Rev Toxicol. 23 (3): 283–335. doi:10.3109/10408449309105013. PMID 8260069.
  38. ^ Pelclová D, Urban P, Preiss J, et al. (2006). "Adverse health effects in humans exposed to 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD)". Reviews on Environmental Health. 21 (2): 119–38. doi:10.1515/reveh.2006.21.2.119. PMID 16898675. S2CID 44739227.
  39. ^ Pavuk M, Schecter AJ, Akhtar FZ, Michalek JE (May 2003). "Serum 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) levels and thyroid function in Air Force veterans of the Vietnam War". Ann Epidemiol. 13 (5): 335–43. doi:10.1016/s1047-2797(02)00422-2. PMID 12821272.
  40. ^ Baccarelli A, Mocarelli P, Patterson DG, et al. (2002). "Immunologic effects of dioxin: new results from Seveso and comparison with other studies". Environ. Health Perspect. 110 (12): 1169–73. doi:10.1289/ehp.021101169. PMC 1241102. PMID 12460794.
  41. ^ Eskenazi B, Mocarelli P, Warner M, et al. (2002). "Serum dioxin concentrations and endometriosis: a cohort study in Seveso, Italy". Environ. Health Perspect. 110 (7): 629–34. doi:10.1289/ehp.02110629. PMC 1240907. PMID 12117638.
  42. ^ Arisawa K, Takeda H, Mikasa H (February 2005). "Background exposure to PCDDs/PCDFs/PCBs and its potential health effects: a review of epidemiologic studies". J Med Invest. 52 (1–2): 10–21. doi:10.2152/jmi.52.10. PMID 15751269.
  43. ^ "Dioxin pollution leads to more baby girls -study". Reuters. 18 October 2007. Retrieved 22 October 2007.
  44. ^ a b R. Pohjanvirta, J. Tuomisto, Short-term toxicity of 2,3,7,8-tetrachlorodibenzop- dioxin in laboratory animals: effects, mechanisms, and animal models, Pharmacological Reviews 1994: 46: 483–549.
  45. ^ a b Birnbaum LS, Tuomisto J; Tuomisto (2000). "Non-carcinogenic effects of TCDD in animals". Food Additives and Contaminants. 17 (4): 275–88. doi:10.1080/026520300283351. PMID 10912242. S2CID 45117354.
  46. ^ a b National Toxicology, Program (2006). "NTP technical report on the toxicology and carcinogenesis studies of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) (CAS No. 1746-01-6) in female Harlan Sprague-Dawley rats (Gavage Studies)". National Toxicology Program Technical Report Series (521): 4–232. PMID 16835633.
  47. ^ Peters JM, Narotsky MG, Elizondo G, Fernandez-Salguero PM, Gonzalez FJ, Abbott BD (January 1999). "Amelioration of TCDD-induced teratogenesis in aryl hydrocarbon receptor (AhR)-null mice". Toxicol Sci. 47 (1): 86–92. doi:10.1093/toxsci/47.1.86. PMID 10048156.
  48. ^ Kransler KM, McGarrigle BP, Olson JR (January 2007). "Comparative developmental toxicity of 2,3,7,8-tetrachlorodibenzo-p-dioxin in the hamster, rat and guinea pig". Toxicology. 229 (3): 214–25. doi:10.1016/j.tox.2006.10.019. PMID 17126467.
  49. ^ Bruggeman V, Swennen Q, De Ketelaere B, Onagbesan O, Tona K, Decuypere E (September 2003). "Embryonic exposure to 2,3,7,8-tetrachlorodibenzo-p-dioxin in chickens: effects of dose and embryonic stage on hatchability and growth". Comp Biochem Physiol C. 136 (1): 17–28. doi:10.1016/s1532-0456(03)00168-6. PMID 14522596.
  50. ^ Carney SA, Prasch AL, Heideman W, Peterson RE (January 2006). "Understanding dioxin developmental toxicity using the zebrafish model". Birth Defects Res A. 76 (1): 7–18. doi:10.1002/bdra.20216. PMID 16333842.
  51. ^ a b Mann PC (1997). "Selected lesions of dioxin in laboratory rodents". Toxicologic Pathology. 25 (1): 72–9. doi:10.1177/019262339702500114. PMID 9061855. S2CID 9819569.
  52. ^ Grinwis GC, Vethaak AD, Wester PW, Vos JG (March 2000). "Toxicology of environmental chemicals in the flounder (Platichthys flesus) with emphasis on the immune system: field, semi-field (mesocosm) and laboratory studies". Toxicol Lett. 112–113: 289–301. doi:10.1016/s0378-4274(99)00239-8. PMID 10720744.
  53. ^ El-Sabeawy F, Enan E, Lasley B (August 2001). "Biochemical and toxic effects of 2,3,7,8-tetrachlorodibenzo-p-dioxin in immature male and female chickens". Comp Biochem Physiol C. 129 (4): 317–27. doi:10.1016/s1532-0456(01)00199-5. PMID 11489429.
  54. ^ Zodrow JM, Stegeman JJ, Tanguay RL (January 2004). "Histological analysis of acute toxicity of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) in zebrafish". Aquat Toxicol. 66 (1): 25–38. doi:10.1016/j.aquatox.2003.07.002. PMID 14687977.
  55. ^ Heiden TK, Carvan MJ, Hutz RJ (April 2006). "Inhibition of follicular development, vitellogenesis, and serum 17beta-estradiol concentrations in zebrafish following chronic, sublethal dietary exposure to 2,3,7,8-tetrachlorodibenzo-p-dioxin". Toxicol Sci. 90 (2): 490–9. doi:10.1093/toxsci/kfj085. PMID 16387744.
  56. ^ Holladay SD (October 1999). "Prenatal immunotoxicant exposure and postnatal autoimmune disease". Environ Health Perspect. 107 (Suppl 5): 687–91. doi:10.1289/ehp.99107s5687. JSTOR 3434328. PMC 1566248. PMID 10502532.
  57. ^ Spitsbergen JM, Schat KA, Kleeman JM, Peterson RE (June 1986). "Interactions of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) with immune responses of rainbow trout". Vet Immunol Immunopathol. 12 (1–4): 263–80. doi:10.1016/0165-2427(86)90130-3. PMID 3765346.
  58. ^ Pellow, David N. Resisting Global Toxics: Transnational Movements for Environmental Justice, MIT Press, 2007, p. 159, (ISBN 0-262-16244-X).
  59. ^ SBSG, 1971: p. 36
  60. ^ Luong, 2003: p. 3
  61. ^ Fawthrop, Tom; "Vietnam's war against Agent Orange", BBC News, 14 June 2004
  62. ^ Fawthrop, Tom; "Agent of Suffering", Guardian, 10 February 2008
  63. ^ York, Geoffrey; Mick, Hayley; "Last Ghost of the Vietnam War" Archived 2009-03-31 at the Wayback Machine, The Globe and Mail, 12 July 2008
  64. ^ Jessica King (10 August 2012). "U.S. in first effort to clean up Agent Orange in Vietnam". CNN. Retrieved 11 August 2012.
  65. ^ "Defoliation" entry in Spencer C. Tucker, ed. (2011). The Encyclopedia of the Vietnam War (2nd ed.). ABC-CLIO. ISBN 978-1-85109-961-0.
  66. ^ BEN STOCKING (22 May 2010) Vietnam, US still in conflict over Agent Orange Associated Press Writer
  67. ^ Collins JJ, Strauss ME, Levinskas GJ, Conner PR (January 1993). "The mortality experience of workers exposed to 2,3,7,8-tetrachlorodibenzo-p-dioxin in a trichlorophenol process accident". Epidemiology. 4 (1): 7–13. doi:10.1097/00001648-199301000-00003. PMID 8420584. S2CID 20291372.
  68. ^ Hay, Alastair (1982). The chemical scythe: lessons of 2, 4, 5-T, and dioxin. Springer. pp. 106–109. ISBN 978-0-306-40973-8.
  69. ^ Hoppe, Robert (2010). The Governance of Problems: Puzzling, Powering and Participation. The Policy Press. p. 151. ISBN 978-1-84742-629-1.
  70. ^ Eijndhoven, J. van; C. Worrell (1991). "Active and passive provision of risk information". In Roger E. Kasperson, Pieter Jan M. Stallen (ed.). Communicating risks to the public: international perspectives. Springer. p. 48. ISBN 978-0-7923-0601-6. Retrieved 19 October 2010.
  71. ^ Miroslav Šuta: Spolana — časovaná bomba na břehu Labe, Sedmá generace, 10/2002
  72. ^ Christoph EH, Umlauf GC, Bidoglio G (September 2004). "PCDD/Fs and Dioxin-like PCBs in Soils after the Flooding of River Elbe and Mulde in 2002". DIOXIN 2004 – 24th Intern. Symposium on Halogenated Environmental Organic Pollutants and POPs, 6–10 September 2004. Berlin.
  73. ^ Miroslav Šuta: Dioxinové kachny "made in Spolana", Sedmá generace, 3/2003
  74. ^ Greenpeace: Carcinogens in human blood near Spolana can cause serious health problems Archived 2009-04-30 at the Wayback Machine
  75. ^ Contamination of chicken eggs near the Spolchemie Ústí nad Labem chemical plant in the Czech Republic by dioxins, PCBs and hexachlorobenzene Archived 2011-07-26 at the Wayback Machine International POP Elimination Network (IPEN)
  76. ^ Hornblum, Allen M. (1998). Acres of skin: human experiments at Holmesburg Prison: a story of abuse and exploitation in the name of medical science. Routledge. p. 38. ISBN 978-0-415-91990-6. Retrieved 27 February 2010.
  77. ^ "Seveso – 30 Years After" (PDF). Archived from the original (PDF) on 31 December 2006. Retrieved 4 June 2007.
  78. ^ "Icmesa chemical company, Seveso, Italy. 9th July 1976". Retrieved 4 June 2007.
  79. ^ "Seveso". Retrieved 4 June 2007.
  80. ^ "AROUND THE NATION; Times Beach, Mo., Board Moves to Seal Off Town — New York Times". The New York Times. 27 April 1983. Retrieved 4 June 2007.
  81. ^ "AROUND THE NATION; Times Beach, Mo., Votes Itself Out of Existence — New York Times". The New York Times. 3 April 1985. Retrieved 4 June 2007.
  82. ^ Artur Asafiev (29 June 2019). "Ufa Losing Battle Against Dioxins". BlueLink – the Civic Action Network.
  83. ^ Belgian PCB and Dioxin Incident of January–June 1999: Exposure Data and Potential Impact on Health, Environ Health Perspect 109:265–273 (2001). Retrieved on 2011-06-09.
  84. ^ Geusau A, Tschachler E, Meixner M, et al. (1999). "Olestra increases faecal excretion of 2,3,7,8-tetrachlorodibenzo-p-dioxin". Lancet. 354 (9186): 1266–7. doi:10.1016/S0140-6736(99)04271-3. PMID 10520643. S2CID 30933045.
  85. ^ "Miss. jury rules for DuPont in $14m dioxin case". CNN. Retrieved 22 August 2008.[permanent dead link]
  86. ^ "Jury Finds DuPont Dioxins Not Responsible for Child's Death". 11 June 2007. Retrieved 22 August 2008.
  87. ^ McCarthy, Michael; Phillips, John (22 March 2008). "Italy's toxic waste crisis, the Mafia – and the scandal of Europe's mozzarella". The Independent. London. Archived from the original on 19 April 2013. Retrieved 28 March 2008.
  88. ^ Report Inter-Agency Review Group Dioxin (Dec 2008) Archived 2010-12-09 at the Wayback Machine. (PDF). Retrieved on 2011-06-09.
  89. ^ "Peacelink" (PDF). Archived from the original (PDF) on 25 February 2009. Retrieved 31 January 2009.
  90. ^ "Dioxin contamination in Germany Closing information note" (PDF). Archived from the original (PDF) on 14 December 2011. Retrieved 27 November 2011.
  91. ^ Method Collections | Measurement Science | Office of the Science Advisor | US EPA. (2006-06-28). Retrieved on 2011-06-09.
  92. ^ Behnisch, Peter. "" (PDF). Archived from the original (PDF) on 18 April 2014. Retrieved 18 April 2014.