An expert workshop was held on 28 to 30 June 2005 at WHO Headquarters in Geneva. Preceding the workshop on 27 June, was a Public Session, to give interested parties an opportunity to express their views on the subjects to be addressed in the workshop and for follow-up activities.

During the workshop, the expert group developed and applied a systematic decision scheme to review existing TEFs, using the WHO 98 TEF values (Van den Berg et al., EHP 106, 1998) and the recently published updated database of relative potencies (Haws et al., ToxSci 89, 4-30, 2006) as a starting point. Previous decisions of the 1997 expert consultation were reviewed in light of new data and of the distribution of REP values. For each congener, the decision scheme was applied and the 2005 TEF value derived and expressed as half-log increments. The decision taken for each congener is described in detail which significantly increases the transparency of the TEF derivation and allows for easier refinement should new data become available.

As a result, a number of TEF values have been changed, notably for PCBs, octachlorinated congeners and pentachlorinated furans.

In addition the expert group commented in detail on the application of the TEF concept and the possible inclusion of new compounds into this concept. Recommendations are also given for future developments in this area.

The outcome of this expert consultation has now been accepted as peer-reviewed article in the journal Toxicological Sciences.
 

(click here for fulltext of website WHO).
(click here for list of 2005 TEF's).

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