WHO re-evaluates dioxin TEF values

["Darryl Luscombe" <luscombe@mail.bigpond.com>]

The World Health Organisation Experts Group have re-evaluated the TEF 
values for dioxins and dioxin-like compounds. They have also issued 
TEF values for fish and birds, which differ from mammal values in 
some cases. This is to be released in the December Environmental 
Health Perspectives (Abstract below).

Of particular interest is the re-evaluation of a number of the I-TEF 
values for humans /mammals for the following CDD/Fs (old TEF/new 
TEF):

1,2,3,7,8 PeCDD (0.5 / 1.0)
Octa CDD (0.001 / 0.0001)
Octa CDF (0.001 / 0.0001)

.. and changes to some of the PCBs
---------------------------------------------------------------------
Environmental Health Perspectives Volume 106, Number 12, December 
1998

Toxic Equivalency Factors (TEFs) for PCBs, PCDDs, PCDFs for Humans and
Wildlife 

Martin Van den Berg1 Linda Birnbaum, Albertus T.C. Bosveld, Björn
Brunström, Philip Cook, Mark Feeley, John P. Giesy, Annika Hanberg, 
Ryuichi Hasegawa, Sean W. Kennedy, Timothy Kubiak,John Christian 
Larsen, F.X. Rolaf van Leeuwen, A.K. Djien Liem, Cynthia Nolt, 
Richard E. Peterson, Lorenz Poellinger, Stephen Safe, Dieter 
Schrenk, Donald Tillitt, Mats Tysklind, Maged Younes, Fredrik Wærn, 
and Tim Zacharewski

Abstract
An expert meeting was organized by the World Health Organization (WHO)
and held in Stockholm on 15-18 June 1997. The objective of this
meeting was to derive consensus toxic equivalency factors (TEFs) for
polychlorinated dibenzo-p-dioxins (PCDDs) and dibenzofurans (PCDFs)
and dioxinlike polychlorinated biphenyls (PCBs) for both human, fish,
and wildlife risk assessment. Based on existing literature data, TEFs
were (re)evaluated and either revised (mammals) or established (fish
and birds). A few mammalian WHO-TEFs were revised, including
1,2,3,7,8-pentachlorinated DD, octachlorinated DD, octachlorinated DF,
and PCB 77. These mammalian TEFs are also considered applicable for
humans and wild mammalian species. Furthermore, it was concluded that
there was insufficient in vivo evidence to continue the use of TEFs
for some di-ortho PCBs, as suggested earlier by Ahlborg et al.
[Chemosphere 28:1049-1067 (1994)]. In addition, TEFs for fish and
birds were determined. The WHO working group attempted to harmonize
TEFs across different taxa to the extent possible. However, total
synchronization of TEFs was not feasible, as there were orders of a
magnitude difference in TEFs between taxa for some compounds. In this
respect, the absent or very low response of fish to mono-ortho PCBs is
most noticeable compared to mammals and birds. Uncertainties that
could compromise the TEF concept were also reviewed, including
nonadditive interactions, differences in shape of the dose-response
curve, and species responsiveness. In spite of these uncertainties, it
was concluded that the TEF concept is still the most plausible and
feasible approach for risk assessment of halogenated aromatic
hydrocarbons with dioxinlike properties. Key words: dioxins, humans,
PCBs, polychlorinated biphenyls, TEFs, toxic equivalency,
uncertainties, wildlife. Environ Health Perspect 106:775-792 (1998).
[Online 10 November 1998]

http://ehpnet1.niehs.nih.gov/docs/1998/106p775-792vandenberg/abstract.
html 


cheers
darryl

-------------------------------------------------
Dr Darryl Luscombe
Toxics Campaigner
Greenpeace Australia Ltd
PO Box 3307, Sydney, 2000, Australia
Ph 61-2-9263 0346   Fax 61-2-9261 4588
--------------------------------------------------
To most people solutions mean finding the answers.  
But to chemists solutions are things that are still all mixed up.
--------------------------------
Dr Darryl Luscombe
Toxics Campaigner
Greenpeace Australia
PO BOX 3307, Sydney, NSW 2001
ph 61-2-9263 0346   Fax 61-2-9261 4588