Dioxins

Dioxins refer to a family of chemically related compounds known as polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs). They are persistent organic pollutants that are highly lipophilic and resistant to environmental degradation. Most dioxins are not produced on purpose; they are byproducts of combustion processes (such as waste incineration and industrial operations) and chlorine bleaching in the paper industry.

The dioxin family is large, with many individual congers identified. In risk assessment, dioxin-like toxicity is described using toxic equivalency factors (TEFs) relative to the most toxic congener, 2,3,7,8-tCDD, and results are expressed as a single TEQ (toxic equivalent) value. Dioxins tend to accumulate in adipose tissue and biomagnify through food chains, so dietary exposure—especially through animal fats, dairy products, and fish—is a primary concern for humans worldwide.

Toxicity is largely mediated by binding to the aryl hydrocarbon receptor (AhR), which alters gene expression and can disrupt development, immune function, and hormone signaling. TCDD is the prototypical and most toxic congener. Dioxins are persistent in the body and environment, with long biological half-lives; effects may include carcinogenicity, immunotoxicity, and reproductive or developmental effects at certain exposure levels.

Regulatory frameworks focus on limiting releases and reducing human exposure. The Stockholm Convention aims to eliminate or restrict dioxin production and release. Monitoring uses TEQ frameworks to assess risk in foods and the environment, and mitigation includes emission controls in industry and methods such as activated carbon adsorption to remove dioxins from emissions. Notable historical incidents, such as the Seveso disaster, highlighted the health and environmental risks associated with dioxins.