2,3,7,8-Tetrachlorodibenzodioxin

2,3,7,8-Tetrachlorodibenzodioxin (TCDD) is a highly toxic polychlorinated dibenzo-p-dioxin formed as an industrial contaminant and combustion byproduct. It persists in the environment and disrupts biological processes through the aryl hydrocarbon receptor.

Aryl hydrocarbon receptor: A ligand-activated transcription factor that regulates genes involved in responses to chemicals and other signals. TCDD binds this receptor, initiating many of its toxic effects.
Agent Orange: A herbicide mixture used by the United States military during the Vietnam War, contaminated with TCDD during manufacture. TCDD contaminated some Agent Orange, connecting the compound to a major wartime exposure.
Gas chromatography–mass spectrometry: An analytical technique that separates compounds by gas chromatography and identifies them by mass spectrometry. It is used to measure trace TCDD in environmental and biological samples.
Chloracne: A severe acne-like skin eruption caused by exposure to certain halogenated aromatic compounds. Chloracne is a characteristic effect of substantial TCDD exposure.
Polychlorinated dibenzo-p-dioxins: A family of chlorinated dibenzo-p-dioxin compounds with varying numbers and positions of chlorine atoms. TCDD is one particularly toxic member of this larger chemical family.
CYP1A1: An enzyme that metabolizes foreign compounds and is induced by activation of the aryl hydrocarbon receptor. Its induction is a common molecular marker of TCDD exposure and receptor activation.
Pentachlorophenol: A chlorinated aromatic compound formerly used widely as a wood preservative and pesticide. Manufacture and use of chlorinated chemicals such as this can generate dioxin contaminants.
High-resolution mass spectrometry: Mass spectrometry that distinguishes ions with very similar mass-to-charge ratios using precise mass measurements. Its selectivity supports reliable analysis of TCDD at very low concentrations.
Carcinogen: An agent capable of causing cancer by increasing its incidence or altering its development. TCDD is classified as carcinogenic to humans by the International Agency for Research on Cancer.
Polychlorinated dibenzofurans: A family of chlorinated compounds structurally related to dibenzo-p-dioxins, with a different arrangement of oxygen atoms. These related pollutants can share toxic mechanisms with TCDD but have a distinct ring structure.

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DefoliantBroader topic: This contaminant drove much of Agent Orange's enduring health and environmental legacy.