TEF

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TEF (TCDD equivalency factor, toxic equivalency factor), a relative toxicity factor of a PCDD/F or PCB congener as related to TCDD. TEF values vary from 1 to 0.00001 or 0 (Table 4; see also TEq). The latest re-evaluation of TEF values was that by WHO in 1998, and these TEF values have been used in this booklet as WHO-TEF for PCDD/Fs and PCB-TEF for PCBs. TEq = ΣTEFi*Ci, where Ci is the amount (or concentration) of congener i.

Table 4. Toxic equivalency factors for all PCDD/Fs and PCBs that have a TEF>0. Other congeners are not supposed to have dioxin-like effects. IUPAC numbers for PCBs are given in parenthesis.

Congener	WHO-TEF
PCDDs
2,3,7,8-TCDD	1
1,2,3,7,8-PeCDD	1
1,2,3,4,7,8-HxCDD	0.1
1,2,3,6,7,8-HxCDD	0.1
1,2,3,7,8,9-HxCDD	0.1
1,2,3,4,6,7,8-HpCDD	0.01
OCDD	0.0001
PCDFs
2,3,7,8-TCDF	0.1
1,2,3,7,8-PeCDF	0.05
2,3,4,7,8-PeCDF	0.5
1,2,3,4,7,8-HxCDF	0.1
1,2,3,6,7,8-HxCDF	0.1
1,2,3,7,8,9-HxCDF	0.1
2,3,4,6,7,8-HxCDF	0.1
1,2,3,4,6,7,8-HpCDF	0.01
1,2,3,4,7,8,9-HpCDF	0.01
OCDF	0.0001
Non-ortho-PCBs
3,3’,4,4’-TCB (77)	0.0001
3,4,4’,5-TCB (81)	0.0001
3,3’,4,4’,5-PeCB (126)	0.1
3,3’,4,4’,5,5’-HxCB (169)	0.01
Mono-ortho-PCBs
2,3,3’,4,4’-PeCB (105)	0.0001
2,3,4,4’,5-PeCB (114)	0.0005
2,3’,4,4’,5-PeCB (118)	0.0001
2’,3,4,4’,5-PeCB (123)	0.0001
2,3,3’,4,4’,5-HxCB (156)	0.0005
2,3,3’,4,4’,5’-HxCB (157)	0.0005
2,3’,4,4’,5,5’-HxCB (167)	0.00001
2,3,3’,4,4’,5,5’-HpCB (189)	0.0001