Dioxins, or polychlorinated dibenzo-p-dioxins and polychlorinated dibenzo furans (PCDD/Fs) are a group of persistent and extremely toxic chlorinated organic compounds. Dioxins are of a very stable nature and accumulate as they move up the food chain to humans.
Dioxin concentrations are commonly reported as toxic equivalents (TEQ), which is the sum of the congener concentrations multiplied by their specific TEQ-factors. The extreme toxicity of 2,3,7,8-Tetra-CDD (also known as Seveso-dioxin) is the reference and has a TEQ-factor of 1. Dioxins and furans containing higher numbers of chlorine atoms (including the 2-, 3-, 7- and 8 positions) have lower TEQ-factors. Since 1997, the World Health Organisation has recognised 2,3,7,8-TCDD as carcinogenic for humans.
Dioxin emission sources
Major sources of dioxin emission and contamination are known to be processes like waste incineration, metal production, bio-fuel incineration and uncontrolled combustion, for example fires at landfill sites. The European regulations stipulate that air emissions should be less than 0.1 ng TEQ/Nm3. Dioxin emission has previously been used as argument towards waste incineration. In fact, waste incineration only contributes to a small extent to the total air emissions. The existing EU prohibition of depositing combustible material has resulted in increased waste incineration, thereby reducing the risk of uncontrolled landfill fires, which may cause large and diffuse dioxin emission sources. Under stable combustion conditions, dioxins are almost completely destroyed during incineration, but are reformed to some extent by de-novo synthesis during the cooling of the flue gas and during dust separation at temperatures between 200-450°C. The waste incinerators act as dioxin sinks since more dioxins are destroyed than formed.
A number of technologies are today used to destroy or separate dioxins from gases in dry or wet applications. Götaverken Miljö offers a method, the ADIOX® technology, to capture the dioxin molecules and to prevent the dioxin emission caused by the so called "memory effect".
Read more in WHO's fact sheet.