Dioxins
Dioxins refers mainly to three chlorinated groups of substances: polychlorinated dibenzo-p-dioxins, (PCDDs), polychlorinated dibenzofurans (PCDFs), and dioxin-like polychlorinated biphenyls (dl-PCBs), which are regulated by EU concerning chemical analysis limits.
Dioxins are schematically presented as two rings of carbon atoms, connected by two oxygen bridges, with chlorine atoms attached to the carbon atoms, (these can be substituted by other halogenated elements, like bromine, fluorine and iodine to form dioxins).
Furans has the same molecule structure, with the difference that instead of two (2) oxygen bridges, the carbon rings are connected by one (1) oxygen bridge.
Dioxin-like PCBs (dl-PCBs) lack an oxygen bridge. The possible known combinations with chlorine atoms (congeners) are 75 for dioxins (PCDDs), 135 for furans (PCDFs), and 217 PCBs congeners. Of these chlorinated congeners, 29 are found to be toxic and therefore regulated in EU; 7 PCDDs, 10 PCDFs, and 12 dl-PCBs.
Regulated EU limits for chlorinated dioxins are 2.5 pg TEQ/g for dioxins and furans (PCDD/F) concerning chemical analysis. For dl-PCBs with chemical analysis an action limited of 1.75 pg TEQ/g is regulated, while for the sum of dioxins this limit is 5.0 pg TEQ/g.
Still not regulated in the EU are the other halogenated dioxins, furans and dioxin-like PCBs, such as biphenyls, brominated and mixed halogenated dioxins, and substances with dioxin-like properties.
Dioxin chemical (GC-MS) analysis
Chemical gas chromatography-mass spectrometry (GC-MS) analysis is congener-specific, measuring only those compounds regulated by the EU: 7 chlorinated dioxins (PCDD), 10 chlorinated furans (PCDF), and 12 dioxin-like polychlorinated biphenyls (dl-PCBs).
Dioxin bioassay DR CALUX analysis
The bioassay DR CALUX® (Dioxin Responsive Chemical Activated LUciferase gene eXpression) is used for quantification of dioxins, furans and dioxin-like PCBs (dl-PCBs). Results obtained with DR CALUX are expressed in pg TEQ or BEQ/g product, (TEQ, toxic equivalent or BEQ, bioanalytical equivalent). Analyses are performed by BioDetection Systems (BDS) in Amsterdam, the Netherlands (NL), an accredited laboratory under RvA L401.
The DR CALUX method measures effects on the aryl hydrocarbon receptor (ArH). This receptor also responds to other dioxin-like substances, including brominated and/or mixed chlorine/bromine dioxins (PBDD/F-PXDD/F).
Brominated flame retardants (BFRs) are widely used in the manufacture of plastics and electronics and form a substantial part of modern waste streams. Brominated dioxins have been shown to have equivalent toxicity to chlorinated dioxins. However, they are not regulated under EU legislation on emissions and food safety. The chemical analysis by Gas Chromatography-Mass Spectrometry (GC-MS) is congener specific, whereas, the dioxin-related bioassay (DR CALUX) quantifies the overall toxicity of a mixture, including chlorinated and mixed halogenated dioxins.
