Adoption of Air Toxics Hot Spots Risk Assessment Guidelines Part I: Technical Support Document for The Determination of Acute RELs for Airborne Toxicants

The Office of Environmental Health Hazard Assessment (OEHHA) is releasing to the public the Technical Support Document for The Determination of Acute Reference Exposure Levels for Airborne Toxicants as part of the Air Toxics "Hot Spots" Program Risk Assessment Guidelines. In 1992, Senate Bill (SB) 1731 amended the Air Toxics "Hot Spots" Information and Assessment Act of 1987 (Assembly Bill 2588 as codified in Health and Safety Code Section 44300 et seq.) to require OEHHA to prepare risk assessment guidelines for facilities subject to the Act. SB 1731 also requires OEHHA to conduct public workshops and seek review and comment by the public, regulated community, and the Scientific Review Panel on Toxic Air Contaminants prior to formal adoption of the guidelines. The original FINAL (January 1995) of this document went through a 90-day public comment period. The Scientific Review Panel draft (October 1998) went through a 30 day public comment period and was reviewed by the Panel at its meetings on December 2, 1998, January 15, 1999 and February 10, 1999. The Panel approved the document at their February 10, 1999 meeting.

The document contains reviews of the acute health effects for 51 chemical contaminants and recommends acute Reference Exposure Levels (RELs) for each chemical based on the most appropriate and sensitive adverse health effect. The 51 chemicals are a portion of the 450 chemicals for which emissions must be quantified under the Hot Spots Statute. The reader will find a heavy emphasis on the utilization of available human data, with two-thirds of the acute RELs based on observed human health outcomes. In addition, traditional 10-fold default values for uncertainty factors for the RELs have been reduced in specific cases due to scientific improvements in considering the extrapolation of the LOAEL to a NOAEL, while also considering the severity of the health effects involved.

OEHHA responses to comments submitted during the public comment period are also attached.

The REL document is available for download below in sections as Adobe Acrobat PDF files. The main document includes Appendices A & B.  Appendix A, Acute Reference Exposure Levels Summary Table and Table of Hazard Index Target Organs, is also available as a separate file.  Due to size, Appendix C, Acute Toxicity Summaries, is in 4 sections.  Appendices D, E, and F are packaged together.

You will need the FREE program Acrobat Reader to view or print these files.

Link to Public Comments

The OEHHA response to each comment follows in separate paragraphs. Comments were either directly transcribed from the original comments received, or were excerpted and summarized, as indicated.