BOARD MEETING DATE: November 7, 2008
AGENDA NO. 24

REPORT:

Notification of State-Approved Cancer Risk Value for Ethylbenzene

SYNOPSIS:

Rules 1401 – New Source Review of Toxic Air Contaminants and 1402 – Control of Toxic Air Contaminants from Existing Sources, require that staff notify the Governing Board and affected parties before risk values for toxic air contaminants are added to or changed in Rule 1401. The Office of Environmental Health Hazard Assessment approved a cancer risk value for ethylbenzene in November 2007. At a later Board meeting, staff will propose amendments to Rule 1401 to add ethylbenzene and will analyze potential impacts of new, modified, and existing sources.

COMMITTEE:

Stationary Source, October 17, 2008, Reviewed

RECOMMENDED ACTIONS:

Receive and file.
 

Barry R. Wallerstein, D.Env.
Executive Officer

Background

Rules 1401 – New Source Review of Toxic Air Contaminants and 1402 – Control of Toxic Air Contaminants from Existing Sources, require staff to notify the Board and affected parties when risk values for toxic air contaminants are added to or changed in Rule 1401. This Board letter serves as the notification.

Rule 1401 will be amended to list ethylbenzene as a carcinogen. Ethylbenzene is currently listed in Rule 1401 as a TAC with a chronic risk value established in August 2000. In November 2007, the Office of Environmental Health Hazard Assessment (OEHHA) adopted a cancer potency value for ethylbenzene. OEHHA establishes risk values for toxic air contaminants (TACs) and the Scientific Review Panel (SRP) reviews and finalizes these values. Once OEHHA has adopted a risk value, Rule 1401 is amended to add the TAC or revise the risk value of an existing TAC.
 

Cancer Risk Value

On November 14, 2007 OEHHA adopted a cancer potency value for ethylbenzene (CAS Registry Number 100-41-4) of 0.0087 (mg/kg-d)^-1. This corresponds to a screening value of 13.1 pounds per year per one in one million cancer risk at a receptor distance of 25 meters. These values are shown in Table I below.
 

Table I – Risk Value

Ethylbenzene

Ethylbenzene was identified under section 112(b)(1) of the U.S. Clean Air Act as a Hazardous Air Pollutant in the 1990 amendment and was recognized by the California Air Resources Board as a toxic air contaminant on April 8, 1993. OEHHA approved a chronic reference exposure limit (REL) in 2000 and ethylbenzene was added to the Rule 1401 list of TACs with a chronic REL that same year. The chronic REL was based on effects to the liver, kidney, and endocrine system. A study by the National Toxicology Program in 1999 was found to show clear evidence of the compound’s carcinogenicity. The Scientific Review Panel reviewed this and several other studies and, because of the scientific evidence and potential for significant human exposure, a cancer potency value was developed and adopted by OEHHA in November 2007. The studies are discussed in OEHHA’s “Long-term Health Effects of Exposure to Ethylbenzene” (OEHHA, November 2007) and can be found at http://www.oehha.ca.gov/air/hot_spots/pdf/Ethylbenzene_FINAL110607.pdf.

Ethylbenzene is a colorless, flammable liquid. It is a natural constituent of crude petroleum and is found in gasoline and diesel fuels and their exhaust. It is also a component of exhaust from other fuels such as natural gas, propane, butane, and digester gas. Heating of petroleum residuum during the production of blown asphalt produces ethylbenzene emissions. Sources of ethylbenzene emissions include petroleum storage facilities, especially gasoline storage because of the high vapor pressure of gasoline. Crude oil and diesel storage have much lower ethylbenzene emissions because of their low vapor pressure. Sources of ethylbenzene from fuel combustion include power producers, refineries, and landfills. Other sources of ethylbenzene emissions from raw materials include chemical manufacturers, coatings manufacturers, large furniture manufacturing operations, and large vehicle manufacturers.
 

Affected Industries

Rule 1402 regulates toxic air contaminants at existing facilities and implements the state AB 2588 Air Toxics “Hot Spots Program. Requirements of Rule 1402 include air toxics inventories, public notification, health risk assessments, and/or risk reductions depending upon facility-wide risk levels. The cancer risk threshold in Rule 1402 is 10 in one million for public notification and 25 in one million, as demonstrated by a health risk assessment, for risk reduction.

The AQMD currently requires AB 2588 facilities to report ethylbenzene emissions since the compound is currently listed as a chronic TAC in Rule 1401. Data from the Annual Emissions Reporting database and permitting data for service stations were used to identify facilities potentially impacted by the addition of a cancer risk value for ethylbenzene.

There are approximately 4,600 gasoline stations in the Basin and, because their cancer risk levels will be higher with ethylbenzene risk included, some may be affected by the addition of the cancer risk value. Other industries potentially affected by the addition of the cancer risk value include: electric, gas, and sanitary service providers with ethylbenzene emissions primarily from fuel combustion; petroleum refining and related industries with emissions from fuel storage and combustion; furniture and wood products manufacturing with emissions primarily from coatings; bulk fuel storage and transportation operations and pipelines; transportation equipment manufacturing (coatings); fabricated metal products manufacturing (coatings); and chemicals and allied products manufacturing (raw materials). The remaining facilities are manufacturing facilities with ethylbenzene emissions from combustion of fuel. An analysis of impacts on affected facilities will be provided in the staff report when Rule 1401 is amended.