October 2004 - Announcement of project for the re-evaluation of human and mammalian toxic equivalency factors (TEFs) of dioxins and dioxin-like compounds and request for information
During the last 15 years, WHO through the International Programme on Chemical Safety (IPCS) has established and regularly re-evaluated toxic equivalency factors (TEFs) for dioxins and related compounds through expert consultations. WHO-TEF values have been established for humans and mammals, birds and fish (Ahlborg et al 1990; Van den Berg et al 1998). These international consensus TEFs have been developed for application in risk management in various Member States and have been adopted formally by a number of countries and supranational bodies, including, among others, Canada, Japan, the United States and the European Union.
During the last assessment 1997 at the WHO-IPCS expert consultation in Stockholm, it was agreed to re-evaluate TEF values on a regular basis, preferably at five-year intervals. Such a re-evaluation should be based on new scientific information published in the peer reviewed literature subsequent to the last expert consultation.
WHO, working through IPCS, has now initiated a project to review the current human and mammalian TEFs. The project will, as a first step, aim to update the database summarizing all published studies on the relative potency of dioxins, furans, and dioxin-like PCBs. In a second step, an expert consultation will be held in the summer of 2005 to evaluate the need for update the human and mammalian TEF values as published in 1998 (Van den Berg et al 1998). Background papers will be prepared in advance of the expert consultation. These papers will address issues identified during the review of the updated database as well as methodological approaches for the derivation of TEFs based on the information compiled in this database.
WHO considers this re-evaluation of TEF values an important effort that requires an open and transparent process. Individual scientists and organizations are requested to provide information of relevance to this project.
Incoming proposals will be reviewed by an international steering group (experts appointed by WHO based on their scientific knowledge in the field) for scientific merit, feasibility and applicability. Authors of all selected proposals will be invited to write short background papers for considerations at the expert consultation. A public hearing preceding the expert consultation where proposals can be presented is currently under consideration.
The outcome of the expert consultation will be presented at the 25th Symposium on Organohalogen Compounds and related compounds (Dioxin 2005) in Toronto (Canada). The final report of the expert consultation will be published in a peer-reviewed journal.