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Notice of Public Comment for Revisions to TSD for Cancer Potency Factors Appendix C - Use of Toxicity Equivalence Factors Scheme for Estimating Toxicity of Mixtures of Dioxin-like Chemicals

The Office of Environmental Health Hazard Assessment (OEHHA) is releasing a draft document, Use of the Toxicity Equivalency Factor (TEFWHO 97 and TEFWHO 05) Scheme for Estimating Toxicity of Mixtures of Dioxin-Like Chemicals to solicit public comment. This is a revision to the previous version which appears as Appendix C of the Technical Support Document for Cancer Potency Factors. OEHHA is required to develop guidelines for conducting health risk assessments under the Air Toxics Hot Spots Program (Health and Safety Code Section 44360(b)(2)) and also to explicitly include consideration of possible differential effects on the health of infants, children and other sensitive subpopulations, according to the Children’s Environmental Health Protection Act (Senate Bill 25, Escutia, Chapter 731, Statutes of 1999, Health and Safety Code Sections 39669.5 et seq.). OEHHA in 2009 adopted the revised Technical Support Document for Cancer Potency Factors (“the TSD”) in response to these statutory requirements.

This draft document is designed to update Appendix C to the TSD, which describes how to estimate risks from exposure to dioxin-like chemicals. The existing appendix recommends use of a table of Toxicity Equivalence Factors (TEFs) which was published in 1997 by an expert committee convened by the World Health Organization (WHO). In 2005 the WHO committee published a revised table of TEFs, and this version of Appendix C to the TSD is designed to reflect this update and also to review recent scientific literature on this methodology.

We are seeking public comments on this document, following which the document and any comments received, along with OEHHA’s response to these comments, will undergo review by the state’s Scientific Review Panel on Toxic Air Contaminants.

The draft document becomes available on the OEHHA Home Page at http://www.oehha.ca.gov on August 7, 2009. The availability of the document on this site will commence a 30-day public review period that will end on September 7, 2009. In response to a request from an interested party, the comment period has been extended by two weeks, to September 21, 2009. In response to a request from an interested party and the postponement of the Scientific Review Panel meeting, the comment period has been further extended to October 5, 2009.Please direct any inquiries concerning technical matters or availability of this document to Dr. Andrew G. Salmon at (510) 622-3191 or Andy.Salmon@oehha.ca.gov.

Please send comments regarding the document, preferably by email as above, or in writing to:

Dr. Andrew G. Salmon
Office of Environmental Health Hazard Assessment
1515 Clay St., 16th Floor
Oakland, CA 94612.

Information about dates and agenda for meetings of the Scientific Review Panel can be obtained from the California Air Resources Board’s web page at http://www.arb.ca.gov/srp/srp.htm.