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Air Toxicology and Epidemiology

Air Toxics Hot Spots Program Risk Assessment Guidelines. Part III. The Determination of Chronic Reference Exposure Levels for Airborne Toxicants
[02/23/00]

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Memorandum from Joan E. Denton Ph. D., Director, OEHHA to Winston Hickox, Cal/EPA Agency Secretary

Subject: ADOPTION OF CHRONIC REFERENCE EXPOSURE LEVELS FOR AIRBORNE TOXICANTS

In accordance to Health and Safety Code, Section 44300 et seq. (The Air Toxics Hot Spots Information and Assessment Act, AB 2588, Connelly as amended by SB 1731, Calderon), the Office of Environmental Health Hazard Assessment (OEHHA) hereby adopts Chronic Reference Exposure Levels (REL) for 22 chemicals (attachment).

OEHHA is mandated to develop risk assessment guidelines, which will be used by state and local agencies to implement the Air Toxics Hot Spots program. Development of these guidelines is proceeding in stages. There are four technical support documents describing the scientific basis for: acute RELs, chronic RELs, cancer potency factors, and exposure assessments. The fifth document is a guidance manual based on the four technical support documents. All four technical support documents have undergone the public review stages.

This document on RELs is the third document that has completed the peer review stage, and the third to be in final form.

A chronic REL is an airborne level that would pose no significant health risk to individuals exposed to that level for an indefinite period of time. RELs are based solely on health considerations and are developed from the best available data in the scientific literature. OEHHA has completed a technical support document, Air Toxics Hot Spots Program Risk Assessment Guidelines. Part III. The Determination of Chronic Reference Exposure Levels for Airborne Toxicants. It provides the methodology used to develop the chronic RELs and a summary for each REL, which describes its chemical and physical properties, its acute health effects, and the data used to calculate the REL. This document underwent internal peer review, two public workshops, and two public comment periods. The document was peer reviewed by the Scientific Review Panel on Toxic Air Contaminants and was discussed at their meetings in
September 1999, October 1999, and November 1999. At their February 1, 2000 meeting, the Panel endorsed the document and the first 22 RELs. The final document incorporates changes in response to the Panel's comments and will be available on our Web site. Additional chronic RELs will be added after the Panel reviews and approves them.

Follow this link to download a PDF copy of this memorandum.

Follow this link to view the Chronic Reference Exposure Levels adopted in February 2000.

Follow this link to download a PDF table of the Chronic Reference Exposure Levels adopted in February 2000.

Follow this link to download a PDF copy of the document Air Toxics Hot Spots Program Risk Assessment Guidelines. Part III. The Determination of Chronic Reference Exposure Levels for Airborne Toxicants ( Does NOT include individual chemical summaries)

Follow this link to download a PDF copy of the Chronic Toxicity Summaries for the 22 Chemicals