California OEHHA Revises RELs for 1,3-Butadiene

March 1, 2013

The Office of Environmental Health Hazard Assessment (OEHHA) have revised the "" document for by the Scientific Review Panel on Toxic Air Contaminants. The revisions of the draft were made due to comments from the Scientific Review Panel's meeting on the subject on October 16, 2012.

Under the Air Toxics Hot Spot Program [Health and Safety Code section 44360(b)], the OEHHA are required to provide guidelines for conducting health risk assessments. As a result, the OEHHA have developed Technical Support Documents (TSDs), which include the Technical Support Document for the Derivation of Non-cancer Reference Exposure levels (adopted in December 2008), and the Technical Support Document for Cancer Potency Factors (adopted in June 2009).

The OEHHA's proposed values for acute, 8-hour, and chronic RELs are 0.66mg/m3 9297 ppb), 28 ug/m3 (13 ppb), and 7 ug/m3 (3 ppb) respectively. The values were developed under the latest versions of the non-cancer REL guidelines, which includes a revised methodology to portect sensitive subpopulations such as children and infants. Once finished, the RELs for 1,3-butadiene will be added to the appendix of the Technical Support Document for the Derivation of Non-cancer Reference Exposure Levels.

A preliminary draft of the 1,3-butadiene REL document was presented on May 18, 2012 for the purpose of gathering public comment. After reviewing the comments and making relevant edits, the document was then reviewed by the State's Scientific review Panel on Toxic Air Contaminants (Health and Safety Code section 39670 et seq.) on October 16, 2012.

For information on the document, including technical matters and the availablity of documents, contact Dr. Andrew G. Salmon at (510) 622-3191 or by email at

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