dioxine

Dioxine, in several languages a term for dioxins, refers to a family of chemically related compounds that includes polychlorinated dibenzo-p-dioxins (PCDDs) and, in some classifications, polychlorinated dibenzofurans (PCDFs). The core structure consists of two benzene rings connected by two oxygen atoms, with chlorine substituents occupying multiple positions, yielding hundreds of congeners. The toxicity among congeners varies, and the mixtures found in the environment are usually a complex combination of many compounds.

PCDDs and PCDFs differ in their exact arrangements, but both groups are persistent pollutants. The degree of chlorination ranges from one to seven chlorine atoms for each class, producing a wide spectrum of chemical properties and toxic potential. The most studied congener is 2,3,7,8-TCDD, used as a reference compound in toxicology due to its high potency.

Formation and occurrence: Dioxins are predominantly unintentional byproducts of combustion and certain industrial processes, including waste incineration, chlorine bleaching, metal smelting, and some chemical syntheses. They are highly persistent in soil and sediment, resist environmental degradation, and bioaccumulate in the food chain, especially in fatty animal tissues. They can be transported long distances via air and water.

Toxicology and health effects: Exposure to dioxins can cause skin conditions such as chloracne, liver and immune system effects, endocrine disruption, and may be associated with an increased cancer risk at higher exposures. Risk assessments commonly use toxic equivalency factors (TEFs) to express the combined toxicity of mixtures as a single toxic equivalent (TEQ).

Regulation and measurement: International efforts aim to reduce releases and exposure, notably under the Stockholm Convention on Persistent Organic Pollutants. Monitoring programs and regulatory controls address production, emissions, and food safety. Detection relies on sensitive analytical methods, such as high-resolution gas chromatography–mass spectrometry, with TEQ calculations to summarize overall toxicity.