Allocation factors for chemical guideline derivation
Rolling revision of the WHO Guidelines for Drinking-water Quality
Background
The Guidelines for Drinking-water Quality use a variety of allocation factors (to allocate the proportion of a tolerable daily intake, or TDI, attributable to drinking-water) for deriving guideline values for chemicals. Where there is not sufficient exposure information to derive chemical-specific allocation factors, default values are used. The explanation of the process by which allocation factors are chosen (in chapter 8 of the Guidelines for Drinking-water Quality) needs greater clarity.
Expected end-product(s)
- Revised text in chapter 8 and section 2.3.2 of Guidelines for Drinking-water Quality Volume 1 for inclusion in the first addendum to the Third Edition;
- Revised text in Policies and Procedures Manual;
- Revised text in chapter 8 of Guidelines for Drinking-water Quality for inclusion in second addendum to Third Edition
Progress to date
The Guidelines for Drinking-water Quality Working Group meeting (Geneva, 2004) agreed on a plan of work, and revised text has been prepared for inclusion in the Policies and Procedures Manual and the first addendum to the Third Edition. The Guidelines for Drinking-water Quality Working Group meeting (Geneva, 2005) agreed on the need for additional text, for possible inclusion in the second addendum. The Guidelines for Drinking-water Quality Working Group meeting (Geneva, 2006) agreed to revise text for the second addendum to the Third Edition. The Policies and Procedures Manual has been updated.
The draft text is now available for review. Comments are welcome following the format on the comment sheet, below.
Comments on the draft background documents above should be sent before 15 May 2007 to gdwqintake@who.int.