Polychlorinated biphenyls (PCBs, not to be confused with printed circuit boards) are not subject to the European Waste Incineration Directive, but emissions can be controlled in the same way as dioxins and furans; incineration is controlled to minimise their production, and the flue gas is treated post-combustion.
The structure comprises two joined phenyl rings (six carbon atoms). Chlorine atoms may be attached to this structure at any of positions 2-6 and 2′-6′ in the above picture, which gives 209 flavours. Hydrogen atoms are attached to the remaining positions.
Of the 209 PCB flavours, the twelve below exhibit dioxin-like properties and are given toxicity ratings by the World Health Organization (WHO). PCBs are commonly regarded as highly toxic compounds that are environmental pollutants and persistent organic pollutants.The reference molecule for rating toxicity is 2,3,7,8-Tetrachlorodibenzo-p-dioxin.
|
Flavour |
Formula |
WHO Toxicity |
|
3,3′,4,4′-Tetrachlorobiphenyl |
C12H6Cl4 |
0.0001 |
|
3,4,4′,5-Tetrachlorobiphenyl |
C12H6Cl4 |
0.0003 |
|
2,3,3′,4,4′-Pentachlorobiphenyl |
C12H5Cl5 |
0.00003 |
|
2,3,4,4′,5-Pentachlorobiphenyl |
C12H5Cl5 |
0.00003 |
|
2,3′,4,4′,5-Pentachlorobiphenyl |
C12H5Cl5 |
0.00003 |
|
2′,3,4,4′,5-Pentachlorobiphenyl |
C12H5Cl5 |
0.00003 |
|
3,3′,4,4′,5-Pentachlorobiphenyl |
C12H5Cl5 |
0.1 |
|
2,3,3′,4,4′,5-Hexachlorobiphenyl |
C12H4Cl6 |
0.00003 |
|
2,3,3′,4,4′,5′-Hexachlorobiphenyl |
C12H4Cl6 |
0.00003 |
|
2,3′,4,4′,5,5′-Hexachlorobiphenyl |
C12H4Cl6 |
0.00003 |
|
3,3′,4,4′,5,5′-Hexachlorobiphenyl |
C12H4Cl6 |
0.03 |
|
2,3,3′,4,4′,5,5′-Heptachlorobiphenyl |
C12H3Cl7 |
0.00003 |
For more information, see the Wikipedia articles about polychlorinated biphenyls and dioxins and dioxin-like compounds.