Notice of Extension of Public Comment/Workshops on Chronic Toxicity Summary for Silica (Crystalline, Respirable)

May 16, 2003

The Office of Environmental Health Hazard Assessment (OEHHA) has released a draft document, Chronic Toxicity Summary for Silica (Crystalline, Respirable) to solicit public comment. This draft document has been developed by OEHHA for use in implementing the Air Toxics Hot Spots Program (Health and Safety Code Section 44300 et seq.). OEHHA developed four Technical Support Documents (TSDs) and a Guidance Manual pursuant to Health and Safety Code Section 44360, which provided the scientific basis for values used in assessing risk from exposure to facility emissions. The TSD for the Determination of Chronic Reference Exposure Levels (Part III of the TSD series), which has already undergone public and peer review and been adopted by OEHHA, describes the methodology for risk assessment for materials having adverse health impacts following chronic exposures. The present document presents a toxicity summary and chronic REL for crystalline silica, particularly when this material is composed of particles of respirable size (≤10 µm). If approved by the Scientific Review Panel on Toxic Air Contaminants, and adopted by the Director of OEHHA, this document will form a further addendum to the Part III TSD. OEHHA is seeking comments on the Chronic Toxicity Summary for Silica (Crystalline, Respirable), including its clarity, and the appropriateness of the methodology and data on which the REL derivation is based. 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.

The Chronic Toxicity Summary for Silica became available on the OEHHA Home Page at http://www.oehha.ca.gov on April 25, 2003. The availability of the document on this site commenced a public review period that was originally scheduled to end on May 23, 2003. OEHHA has received requests from interested parties seeking an extension of the comment period to allow for the submittal of complete and relevant scientific material. OEHHA hereby extends the public comment period by 30 days. It will now end on June 22, 2003.

Public workshops for the public to comment on the summary will be held in Fresno on May 9, 2003 and in Oakland on May 20, 2003, as previously scheduled. Information on the public workshops is as follows:

DATE and TIME: May 9, 2003 from 10a.m. - 2p.m.
PLACE: San Joaquin Valley Unified APCD
1990 E. Gettysburg Avenue
Fresno, CA 93726
Governing Board Room

DATE and TIME: May 20, 2003 from 10a.m. - 2p.m.
PLACE: Elihu Harris State Office Building
1515 Clay St.
Oakland, CA 94612
Room 234, 2nd Floor

Please direct any inquiries concerning technical matters, or availability of the Chronic Toxicity Summary for Silica (Crystalline, Respirable), to:

Dr. John Budroe
Chief, Air Toxicology and Risk Assessment Section
Air, Community, and Environmental Research Branch
Office of Environmental Health Hazard Assessment
1515 Clay Street, 16th Floor
Oakland, CA, 94612

E–mail: John.Budroe@oehha.ca.gov (link sends e-mail)

Telephone: (510) 622-3145

Information about dates and agenda for meetings of the Scientific Review Panel can be obtained from the ARB web page at http://www.arb.ca.gov/srp/srp.htm.