WHO Toxic Equivalance Factors

• Based on all available data

  • In vivo endpoints given more weight than in vitro measurements

• “Order of Magnitude” Estimates

• Fundamental to evaluation of this group of compounds

• Useful, interim process

• Growing empirical basis and theoretically sound

• Five compounds make up about 80% of total TEQ in human tissues

  • 2,3,7,8-TCDD, 1,2,3,7,8-PeCDD, 1,2,3,6,7,8-HxCDD, 2,3,4,7,8,-PeCDF, 3,3’,4,4’,5-PeCB (PCB#126)

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