dioxinlike

Dioxinlike is a terminology used to describe chemicals that are structurally or toxicologically similar to dioxins, particularly those that act through a common mechanism involving the aryl hydrocarbon receptor (AhR). The term is most often applied to polychlorinated dibenzo-p-dioxins (PCDDs), polychlorinated dibenzofurans (PCDFs), and certain polychlorinated biphenyls (PCBs) known as dioxinlike PCBs. Not all PCBs are dioxinlike; non-dioxinlike PCBs have different toxicological profiles.

Mechanism and assessment are centered on the AhR pathway. When dioxinlike compounds bind AhR, the receptor translocates to the nucleus and alters the expression of target genes such as CYP1A1. This shared mechanism underlies the use of toxic equivalency approaches to compare potencies among congeners. The toxicity of a mixture is expressed as toxic equivalency (TEQ), calculated by summing the products of each congener’s concentration and its toxic equivalency factor (TEF) relative to 2,3,7,8-TCDD, the reference dioxin. TEFs, compiled and updated by organizations such as the World Health Organization, allow risk assessors to quantify overall dioxinlike toxicity in foods, air, and environmental samples.

Environmental significance is linked to persistence, lipophilicity, and bioaccumulation. Dioxinlike compounds persist in the environment and concentrate in fatty tissues, often biomagnifying through food chains. Human exposure is mainly through animal-derived foods, though releases from industrial processes, waste incineration, and combustion contribute to environmental levels.

Regulatory and health-context discussions commonly use the dioxinlike TEQ framework to set guidelines, conduct monitoring, and assess risks to human health and ecosystems.