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Dioxin/Furan Levels
an indicator of toxic contaminants in coastal
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Dioxins and Furans:
What Are They?
Dioxins are the group of 75 compounds consisting of two benzene rings
linked by two oxygens and with at least one chlorine atom. Furans are
the group of 135 compounds consisting of two benzene rings linked by one
oxygen and with one or more chlorine atoms.
The dioxins and furans with chlorine atoms at the 2, 3, 7, and 8 positions
are considered the most toxic. Of these, 2,3,7,8-chlorodibenzo-p-dioxin
(T4CDD) has the highest toxicity, is the most studied and best known,
and is the standard to which the toxicity of the other dioxin and furans
is compared.
Toxic Equivalence Factors for Dioxins and Furans
Toxic Equivalence Factors (TEF) (WHO 1998) standardize
the toxicity of the dioxins and furans, to derive a toxic equivalence
as 2,3,7,8-T4CDD. The TEF for the dioxins and furans without chlorine
atoms at the 2, 3, 7, and 8 positions is zero.
Dioxin
2,3,7,8-T4CDD
1,2,3,7,8-P5CDD
1,2,3,4,7,8-H6CDD
1,2,3,6,7,8-H6CDD
1,2,3,7,8,9-H6CDD
1,2,3,4,7,8,9-H7CDD
08CDD
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TEF
1.0
1.0
0.1
0.1
0.1
0.01
0.0001
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Furan
2,3,7,8-T4CDF
1,2,3,7,8-P5CDF
2,3,4,7,8-P5CDF
1,2,3,4,7,8-H6CDF
1,2,3,6,7,8-H6CDF
2,3,4,6,7,8-H6CDF
1,2,3,7,8,9-H6CDF
1,2,3,4,6,7,8-H7CDF
1,2,3,4,7,8,9-H7CDF
O8CDF
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TEF
0.1
0.05
0.5
0.1
0.1
0.1
0.1
0.01
0.01
0.0001
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Toxic Equivalence (TEQ)
The toxic equivalence, or TEQ, of a combination of dioxins and furans
is calculated by applying the TEF to each concentration of the congener
in a sample and summing. Congener concentrations that are below the detection
limit are assigned a value of 0 (zero) when calculating TEQ according
to the Environment Canada procedure.
Reference
Van den Berg, M., et al. (World Health Organization - WHO),
Toxic Equivalency Factors (TEFs) for PCBs, PCDDs, PCDFs for Humans
and Wildlife, Environmental Health Perspectives, Volume 106,
Number 12, December 1998, pp. 775 - 791.
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