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Dioxins and furans are some of the most toxic chemicals known to science.

A draft report released for public comment in September 1994 by the US Environmental Protection Agency clearly describes dioxin as a serious public health threat.

The public health impact of dioxin may rival the impact that DDT had on public health in the 1960's. According to the EPA report, not only does there appear to be no "safe" level of exposure to dioxin, but levels of dioxin and dioxin-like chemicals have been found in the general US population that are "at or near levels associated with adverse health effects."

Dioxin is a general term that describes a group of hundreds of chemicals that are highly persistent in the environment. The most toxic compound is 2,3,7,8-tetrachlorodibenzo-p-dioxin or TCDD.

The toxicity of other dioxins and chemicals like PCBs that act like dioxin are measured in relation to TCDD. Dioxin is formed as an unintentional by-product of many industrial processes involving chlorine such as waste incineration, chemical and pesticide manufacturing and pulp and paper bleaching.

Dioxin was the primary toxic component of Agent Orange, was found at Love Canal in Niagara Falls, NY and was the basis for evacuations at Times Beach, MO and Seveso, Italy. REFER

Dioxin is formed by burning chlorine-based chemical compounds with hydrocarbons. The major source of dioxin in the environment comes from waste-burning incinerators of various sorts and also from backyard burn-barrels.

Dioxin pollution is also affiliated with paper mills which use chlorine bleaching in their process and with the production of Polyvinyl Chloride (PVC) plastics and with the production of certain chlorinated chemicals (like many pesticides).

The terms dioxins and dioxin-like compounds (DLC[1]) commonly refer to a class of highly toxic compounds that are environmental pollutants and persistent organic pollutants (POPs). The terms usually refers to or is associated with

Polychlorinated dibenzodioxins

• Polychlorinated dibenzodioxins (PCDDs), or simply dioxins, technically a derivative of dibenzodioxin

Polychlorinated dibenzofurans

• Polychlorinated dibenzofurans (PCDFs), or simply furans, technically a derivative of dibenzofurans. Whilst they strictly speaking are not dioxins, they have dioxin-like properties

Polychlorinated biphenyls

• Polychlorinated biphenyls (PCBs), which also strictly speaking are not dioxins, but some have "dioxin-like" properties. They can under certain conditions form the more toxic dibenzodioxins and dibenzofurans through partial oxidation

Dioxin (chemical)

• Finally, it may refer to Dioxin (chemical), the basic chemical unit of the more complex dioxins

Because dioxins refer to such a broad class of compounds, that vary widely in toxicity, the concept of toxic equivalent (TEQ) has been developed to facilitate risk assessment and regulatory control.

Toxic equivalent factors (TEFs) exist for selected congeners of dioxins, furans and PCBs. The reference congener is the most toxic dioxin 2,3,7,8-TCDD which per definition has a TEF of unity.

	(ITEF) Intentional Toxic Equivalent Factors for the dioxin congeners of concern (NATO/CCMS)[2] 2,3,7,8-TCDD 1 2,3,7,8-TCDF 0.1 1,2,3,7,8-PeCDD 0.5 2,3,4,7,8-PeCDF 0.5 1,2,3,7,8-PeCDF 0.05 1,2,3,4,7,8-HxCDD 0.1 1,2,3,6,7,8-HxCDD 0.1 1,2,3,4,7,8-HxCDF 0.1 1,2,3,7,8,9-HxCDD 0.1 1,2,3,7,8,9-HxCDF 0.1 1,2,3,6,7,8-HxCDF 0.1 1,2,3,4,6,7,8-HpCDD 0.01 2,3,4,6,7,8-HxCDF 0.1 OCDD 0.001 1,2,3,4,6,7,8-HpCDF 0.01 1,2,3,4,7,8,9-HpCDF 0.01 OCDF 0.001		For furan isomers[3] Isomer Name WHO/EPA TEF 2378 TCDF Tetrachlorodibenzofuran 0.1 0.1 12378 PeCDF Pentachlorodibenzofuran 0.03 0.05 23478 PeCDF Pentachlorodibenzofuran 0.3 0.5 123678 HxCDF Hexachlorodibenzofuran 0.1 0.1 123789 HxCDF Hexachlorodibenzofuran 0.1 0.1 123478 HxCDF Hexachlorodibenzofuran 0.1 0.1 234678 HxCDF Hexachlorodibenzofuran 0.1 0.1 1234678 HpCDF Heptachlorodibenzofuran 0.01 0.01 1234789 HpCDF Heptachlorodibenzofuran 0.01 0.01 12346789 OCDF Octachlorodibenzofuran 0.0003 0.001
	(T = tetra, P = penta, Hx = hexa, Hp = hepta, O = octa)