Notice of Public Comment/Workshops on Proposed Revised Reference Exposure Levels for 1,3-Butadiene

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The Office of Environmental Health Hazard Assessment (OEHHA) is soliciting public comments on a draft document describing proposed revised Reference Exposure Levels (RELs) for 1,3-butadiene.  Reference Exposure Levels are concentrations in air that are not anticipated to result in adverse non-cancer health effects for specified exposure durations in the general population, including sensitive subpopulations.  OEHHA is required to develop guidelines for conducting health risk assessments under the Air Toxics Hot Spots Program (Health and Safety Code Section 44360 (b) (2)).  In response to this statutory requirement, OEHHA in 2008 adopted a Technical Support Document (TSD) that contains updated guidelines for the development of acute, 8 hour, and chronic RELs.  These guidelines have already been used to develop updated RELs for several chemicals, and OEHHA is now presenting a draft update to the RELs for 1,3‑butadiene.  The values proposed are as follows:

  • Acute REL (for a 1-hour exposure): 0.5 mg/m3
  • 8-Hour REL (for repeated 8-hour exposures): 28 µg/m3
  • Chronic REL(for long-term exposures):  7 µg/m3

We are seeking comments on the revised RELs for 1,3-butadiene, and the application in the RELs document of the revised methodology to protect infants, children and other sensitive subpopulations.  Following this public comment period, the RELs for 1,3-butadiene 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 draft documents become available here on May 18, 2012The availability of the document on this site will commence a 60-day public review period that will end on July 17, 2012

Public workshops will be held during this period at which comments may be provided in person.  One workshop will occur at 10:00 a.m. – 3:00 p.m. on July 9, 2012 at:

Room 10,
Elihu Harris Building
1515 Clay St., 2nd Floor
Oakland, CA 94612

A second public workshop will be held at 10:00 a.m. – 1:00 p.m. on July 11, 2012 at:

Conference Room CC-2
South Coast Air Quality Management District
21865 Copley Drive
Diamond Bar, CA 91765

Please direct your comments on the documents,in writing or by e-mail, and any inquiries concerning technical matters or availability of the documents 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


Telephone: (510) 622-3145

Information about dates and agenda for meetings of the Scientific Review Panel can be obtained from the California Air Resources Board web page at