TEq: Difference between revisions
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'''TEq, TCDD equivalent quantity, toxicity equivalent''' (see also [[TEF]]). Different congeners of dibenzo-p-dioxins and dibenzofurans have many of the same biological effects but they are differently potent, meaning that different doses are needed to cause the same effect (Figure 8). E.g. 1,2,3,4,7,8-hexachlorodibenzo-p-dioxin (HxCDD) is one tenth as toxic as TCDD. To be able to assess the effects of a mixture, all congeners are "normalised" to the effects of TCDD, e.g. the amount or concentration of HxCDD is multiplied by the equivalency factor 0.1 (its TEF is 0.1). When all congeners are given as "equivalents of TCDD" they can be simply added and the sum gives the total toxicity of the mixture. Various TEq values have been developed, e.g. WHO-TEq, Nordic TEq and international TEq or I-TEq. WHO-TEq values are based on the most recent scientific consensus. The differences between the respective TEFs are not great. Also the most important dioxin-like PCBs have been given TEF values, but it should be appreciated that PCBs may have other effects that cannot be expressed by a TCDD-equivalency. (For more information on TEq concept and its use, see Ahlborg et al., Eur. J. Pharmacol. 1992:228:179-199; Van den Berg et al., Environ. Health Persp., 1998:106:775-792). | |||
[[Image:Dioxin figure8a.jpg|Image:Dioxin_figure8a.jpg]] | |||
[[Image:Dioxin figure8b.jpg|Image:Dioxin_figure8b.jpg]] | |||
==See also== | |||
* [[TEF concept]] | |||
* [[Ah receptor ligands]] | |||
* [[TEF concept in environmental health assessment]] | |||
* [[TEF concept and uncertainty analysis]] | |||
* [[Additivity of TEFs]] | |||
* [[TEF concept and ecology]] | |||
* [[TEF concept and Ah receptor]] | |||
* [[Estimating TEF values]] | |||
* [[History of TEF concept]] | |||
Revision as of 07:28, 31 May 2010
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TEq, TCDD equivalent quantity, toxicity equivalent (see also TEF). Different congeners of dibenzo-p-dioxins and dibenzofurans have many of the same biological effects but they are differently potent, meaning that different doses are needed to cause the same effect (Figure 8). E.g. 1,2,3,4,7,8-hexachlorodibenzo-p-dioxin (HxCDD) is one tenth as toxic as TCDD. To be able to assess the effects of a mixture, all congeners are "normalised" to the effects of TCDD, e.g. the amount or concentration of HxCDD is multiplied by the equivalency factor 0.1 (its TEF is 0.1). When all congeners are given as "equivalents of TCDD" they can be simply added and the sum gives the total toxicity of the mixture. Various TEq values have been developed, e.g. WHO-TEq, Nordic TEq and international TEq or I-TEq. WHO-TEq values are based on the most recent scientific consensus. The differences between the respective TEFs are not great. Also the most important dioxin-like PCBs have been given TEF values, but it should be appreciated that PCBs may have other effects that cannot be expressed by a TCDD-equivalency. (For more information on TEq concept and its use, see Ahlborg et al., Eur. J. Pharmacol. 1992:228:179-199; Van den Berg et al., Environ. Health Persp., 1998:106:775-792).
