Agent Name


Alternative Name


CAS Number




Major Category

Other Classes


2,3,7,8-Czterochlorodwubenzo-p-dwuoksyny [Polish]; 2,3,7,8-TCDD; 2,3,7,8-Tetra polychlorinated dibenzo-p-dioxin; 2,3,7,8-Tetrachlorodibenzo(b,e)(1,4)dioxin; 2,3,7,8-Tetrachlorodibenzo-1,4-dioxin; 2,3,7,8-Tetrachlorodibenzo-p-dioxin; 2,3,7,8-Tetrachlorodibenzo-p-dioxin [Dioxin and dioxin-like; compounds]; 2,3,7,8-Tetrachlorodibenzodioxin; Dibenzo(b,e)(1,4)dioxin, 2,3,7,8-tetrachloro-; Dibenzo-p-dioxin, 2,3,7,8-tetrachloro-; Dioksyny [Polish]; Dioxin; Dioxin (herbicide contaminant); Dioxine; TCDBD; TCDD; Tetrachlorodibenzo-p-dioxin; Tetrachlorodibenzodioxin; Tetradioxin; [ChemIDplus] UN2811


Halogenated Polyaromatics


Colorless to white, crystalline solid; [NIOSH]


No commercial uses; By-product of waste incineration, pulp and paper mill bleaching, and chemical production of 2,4,5-T, hexachlorophene, vinyl chloride, trichlorophenol, and pentachlorophenol; [Reference #2, p. 377] Levels in 2,4,5-T manufactured in the 1960s was as high as 100 mg/kg; High-exposure populations in the past included workers producing the herbicide 2,4,5-T and residents in Seveso, Italy contaminated by a factory explosion in 1976; [Reference #1]


Dioxins accumulate in adipose tissue; they are animal carcinogens. Chloracne is the only overt clinical sign of dioxin exposure in humans. Of the 22 isomers of tetra-chlorinated dioxin, 2,3,7,8-TCDD is the one that contaminated the production of 2,4,5-trichlorophenol, Silvex, and 2,4,5-T. In acute animal studies, TCDD is toxic to the liver. Recent studies failed to find an association between TCDD and porphyrin levels; [LaDou, p. 517-20] Causes adverse reproductive effects in animals; No documented evidence of congenital abnormalities in humans; [REPROTOX] "There are no firmly established relationships between concentrations (mainly considering TCDD) and health effects in people. Observations following industrial and accidental exposures have suggested that acute exposures resulting in serum concentrations of about 800 pg/g of lipid might be necessary to induce clinical effects such as chloracne, although levels in the thousands of pg/g of lipid do not always produce this effect." [Reference #2, p. 384] IARC classification for 2,3,7,8-Tetrachlorodibenzo-p-dioxin is "known" and for other isomers is " not classifiable"; An increased risk for all cancers combined was found in the high-exposure populations studied; [Reference #1] The German MAK Commission classifies TCDD as class 4, defined as: "Substances with carcinogenic potential for which genotoxicity plays no or at most a minor role. No significant contribution to human cancer risk is expected, provided the MAK value is observed. " [Guide to Occupational Exposure Values, p. xi] Mean levels in exposed workers were 2000 ppt in the US cohort, 1434 ppt in accident workers in the Dutch cohort, and 1008 ppt in the BASF workers (Germany) with chloracne. Levels were up to 2252 ppt in the Boehringer cohort (Germany). These levels are comparable to levels in rats that developed hepatocellular nodules when fed 10 ng/kg bw daily (1500-2000 ppt) and that developed hepatocellular carcinoma when fed 100 ng/kg/bw daily (5,000-10,000 ppt). [Reference #1] Among 773 pentachlorophenol workers exposed to chlorinated dioxins from 1937 to 1980 with up to 64 years of follow-up, no increased mortality was found except for possibly an increased risk of non-Hodgkin lymphoma based on 4 deaths. [PMID 19786897]


NIOSH recommends lowest feasible level of exposure. TCDD product contamination is limited to 0.01 to 0.05 ppm. For drinking water, MCL is 0.05 ppt. FDA limit for dioxins in fish is 25 ppt. [ATSDR Case Studies]

Reference Link

IARC Summary of Monograph on TCDD

Exposure Assessment



1.0E-8 mg/m3, inhalable fraction

Vapor Pressure

1.5E-9 mm Hg

Half Life

Whole body: 7.1 years (2.9 to 26.9 years); [TDR, p. 1111] Estimated at around 7 years; [Reference #2, p. 379]

Reference Link

CDC: 4th National Report on Human Exposure to Environmental Chemicals - 2009 (6.5 MB pdf)

Adverse Effects

Hepatotoxin, Secondary

Reproductive Toxin




IARC Carcinogen

Known Carcinogen

NTP Carcinogen

Human Carcinogen

Links to Other NLM Databases
Health Studies

Human Health Effects from Hazardous Substances Data Bank:

Toxicity Information


Chemical Information

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Biomedical References

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Related Information in HazMap

Occupational diseases associated with exposure to this agent: