Notice of Public Comment/Workshops for Draft Technical Support Document for Cancer Potency Factors 2008

This document was finalized on June 1, 2009.

The Office of Environmental Health Hazard Assessment (OEHHA) is releasing a draft document, Technical Support Document for Cancer Potency Factors: Methodologies for derivation, listing of available values, and adjustments to allow for early life stage exposures, to solicit public comment.  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)).  OEHHA in 1999 developed a “Technical Support Document (TSD) Describing Available Cancer Potency Factors” in response to this statutory requirement.  This new draft document is designed to replace that original TSD, and presents methodology revised to reflect scientific knowledge and techniques developed since the previous guidelines were prepared.  In particular the new draft document explicitly includes consideration of possible differential effects of air toxics on the health of infants, children and other sensitive subpopulations, in accordance with the mandate of 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.).  The new methods described include the use of Benchmark Dose methodology for the estimation of low-dose cancer potencies, and the application of age-specific adjustment factors in estimating the risks faced by infants and children from exposure to carcinogens.

We are seeking comments on this document, in particular on the revisions to the existing approved methodology, and the appropriateness of the revised methodology to protect infants and children and other sensitive subpopulations.  Following this public comment period, 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 (SRP).

The revised draft does not include any new cancer potencies developed explicitly using the new guidelines, although updated methods including the benchmark dose approach have been applied in OEHHA’s more recent cancer potency estimates.  The only change to the listing of potency values and the collection of compound summaries is the addition of a value and summary for ethylbenzene which were recently approved by the SRP and adopted by OEHHA on 11/14/07.

The draft document becomes available on the OEHHA web site on June 23, 2008.  The availability of the document on this site will commence a 60-day public review period that will end on August 22, 2008.

Public workshops will be held at 10.00 am – 1.00 p.m. on Thursday August 14, 2008 in Diamond Bar and at 10.00 am – 1.00 p.m. on Friday August 15, 2008 in Oakland.  Location information is as follows:

Diamond Bar Oakland

Room  (tba)  Room 12,
South Coast Air Quality Management District  Elihu Harris Building
21865 Copley Dr,  1515 Clay St., 2nd Floor
Diamond Bar, CA 91765  Oakland, CA 94612

Please direct any inquiries concerning technical matters or availability of this document to Dr. Andrew G. Salmon at (510) 622-3191 or

Please direct your comments, in writing, regarding the document to:
Dr. Andrew G. Salmon
Chief, Air Toxicology and Risk Assessment Unit
Office of Environmental Health Hazard Assessment
1515 Clay St., 16th Floor
Oakland, CA  94612.

We are happy to receive comments on all aspects of the technical support document and the new supporting materials (including Appendix J).  We particularly invite comments on the proposed use of sensitivity factors to allow for the increased impacts of exposures to carcinogens early in life: whether the age windows identified are correctly delineated; whether additional windows should be specified; and whether the values of the adjustment factors proposed are appropriate in the light of the data presented in Appendix J.  Please note that the individual chemical summaries and potency values are not being revisited at this stage of the revision program, and we will not be addressing any comments on these as part of this public comment process.  The existing process for requesting revisions or delisting of existing values (Appendix G) continues to be available to any interested party having concerns about specific values.

APPENDIX A -Lookup Table.

APPENDIX B: No changes proposed

APPENDIX C: Toxicity Equivalence Factors for Dioxins, PCDFs and PCBs.

APPENDIX D: TAC Documents cited.

APPENDIX E: Carcinogen classifications.

APPENDIX F: Asbestos fiber concentration conversions.

APPENDIX G: Procedure for requesting reconsideration or delisting of cancer potency values.

APPENDIX H: Exposure Routes and study types used.

APPENDIX I: Barton et al. (2005).

APPENDIX J: Early Life Cancer Susceptibility.

APPENDIX K: Additions and corrections to the document and list of potencies.