dioxinsfurans

Dioxins and furans are a group of chemically related, persistent environmental pollutants that include polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs). Hundreds of individual congeners exist, defined by patterns of chlorine substitution on two benzene rings. They are highly lipophilic and resistant to environmental degradation, leading to long half-lives in air, water, soil, and sediments and the tendency to accumulate in the food chain, especially in animal fats.

Most dioxins and furans are not produced intentionally. They are byproducts of combustion and certain industrial processes, including waste incineration, biomass burning, metal smelting, and chlorine bleaching of pulp. They can be emitted during normal operations or released during accidents, and they can travel long distances, depositing in remote regions and persisting in soils and sediments for years.

Human exposure primarily occurs through diet, particularly fatty animal products, though inhalation of contaminated air and, to a lesser extent, dermal contact can contribute. Because many congeners share similar toxic effects, risk is typically assessed using toxic equivalency factors (TEFs) to express overall toxicity as a toxic equivalent (TEQ) relative to the most toxic congener, TCDD. Dioxins and furans act mainly through binding to the aryl hydrocarbon receptor (AhR) and can cause cancer, developmental and reproductive effects, immune suppression, and other health issues in animals and humans. The International Agency for Research on Cancer classifies TCDD as a human carcinogen.

Regulation focuses on emission controls and source reduction. Internationally, the Stockholm Convention aims to eliminate or reduce PCDDs and PCDFs. Monitoring uses sensitive analytical methods such as GC-MS to measure TEQ levels in air, foods, and environmental samples. Cleanup emphasizes prevention, containment, and remediation of contaminated sites, though complete degradation remains challenging due to persistence.