BOARD MEETING DATE: December 3, 2004
AGENDA NO. 25

Notification of OEHHA’s Finalization of Cancer Potency Factors

SYNOPSIS:

The March 2000 amendments to Rule 1402 – Control of Toxic Air Contaminants from Existing Sources, require that staff notify the Board and affected parties when risk values for toxic air contaminants are changed or added to the lists of compounds in Rule 1401 – New Source Review of Toxic Air Contaminants. On August 29, 2003, the Office of Environmental Health Hazard Assessment (OEHHA) finalized Toxicity Equivalency Factors (TEFs) for use in calculating Cancer Potency Factors and Chronic Reference Exposure Levels (REL) for speciated polychlorinated biphenyls (PCB), for 2 polychlorinated dibenzo-p-dioxins (PCDD), and 1 polychlorinated dibenzofuran (PCDF). In addition, on August 2, 2004 the OEHHA finalized the Cancer Potency factor for naphthalene. At the March 2005 Board meeting, staff will propose amendments to Rule 1401 for the above mentioned toxic air contaminants and report on potential impacts to facilities subject to Rules 1401 and 1402.

COMMITTEE:

Not Applicable

RECOMMENDED ACTION:

Receive and file.

Barry R. Wallerstein, D.Env.
Executive Officer

Background

On March 17, 2000, the Board adopted amendments to Rule 1402 – Control of Toxic Air Contaminants from Existing Sources. In conjunction with the amendments to Rule 1402, the Board directed staff to notify them and affected facilities after OEHHA finalizes changes to a toxic air contaminant (TAC) risk value, and to establish a 12-month lead time (or shorter, if the Board approves another schedule through an official Board action) for using the new TAC risk value in a risk assessment for Rule 1402. This notification fulfills that Board directive.

Revisions to Risk Values

OEHHA establishes risk values for TACs and the Scientific Review Panel (SRP) reviews and finalizes these values. Recently the Air Toxics Hot Spots Program Risk Assessment Guidelines have changed. Part of the change includes the usage of an Inhalation Potency Factor in place of the Unit Risk Factor that had been used previously. Final action is taken when the Director of OEHHA signs the document and posts the information on the internet. The SRP met and approved Toxicity Equivalency Factors (TEFs) for use in calculating Inhalation Potency Factors and Chronic Reference Exposure Levels (Chronic RELs) for speciated polychlorinated biphenyls (PCBs), and revision of TEFs for 2 polychlorinated dibenzo-p-dioxins (PCDD) and 1 polychlorinated dibenzofuran (PCDF) on June 20, 2003. The Director of OEHHA finalized and adopted the factor on August 29, 2003. The SRP met and approved the Inhalation Potency Factor for Naphthalene on May 19, 2004 and the Director of OEHHA finalized and adopted the factor on August 2, 2004.

The Inhalation Potency Factors and Chronic RELs calculated for PCBs, PCDDs and PCDF are shown in Table I below. The manufacture of PCBs was discontinued in the United States in 1976 because of their persistence, toxicity, and ecological damage via water pollution. PCDDs and PCDF are most widely emitted from chemical and combustion processes where high temperatures are maintained and a source of chlorine and hydrocarbons is present, as in polyvinyl chloride (PVC) production. Naphthalene (CAS No. 91-20-3) was assigned a risk value of 3.4 x 10^-5 (µg/m³)^-1 or an Inhalation Potency Factor of 1.2 x 10^-1 (mg/kg-day)^-1. This corresponds to a screening value of 9.51 X 10^-1 pounds/year per one-in-a million cancer risk. Naphthalene is most commonly used in moth repellent, fungicide, smokeless powder, cutting fluid, lubricant, synthetic resins, synthetic tanning, preservative, textile chemicals, emulsion breakers, scintillation counters, antiseptics, and is emitted through vehicle exhaust, wood burning and tobacco smoke.

Prior to adding or updating risk values, Rule 1402 also requires staff to report to the Board within 150 days of final action by OEHHA on potential impacts for facilities subject to Rule 1402. This requirement appears in both Rules 1401 and 1402 and therefore staff is proposing the same change for both. Rule 1401 – New Source Review of Toxic Air Contaminants, also requires an analysis of these same compounds that are used for new source review. A report containing analysis of the impacts of the new risk factor on facilities subject to Rules 1401 and 1402 and proposed amendments to Rule 1401 to update the tables relative to PCB, PCDD, PCDF and Naphthalene will be presented at the March 2005 Board meeting.

Table I – Risk Values

¹ “Congener” is a term in chemistry that refers to one of many variants or configurations of a common chemical structure. For example, PCBs occur in different forms, or congers.
 

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