Notice of Adoption of Cancer Inhalation Unit Risk and Slope Factors and Cancer Oral Slope Factor for Tert-Butyl Acetate

Download Cancer Inhalation Unit Risk Factor for Tert-Butyl Acetate (TBAc)

The Office of Environmental Health Hazard Assessment (OEHHA) is adopting a new cancer inhalation unit risk factor (IUR) for tert-butyl acetate (TBAc).  IURs are used to estimate lifetime cancer risks associated with inhalation exposure to a carcinogen. 

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 implementing this requirement, OEHHA develops new IURs and revises existing IURs for many air pollutants.  The IUR for TBAc was developed using the most recent “Air Toxics Hot Spots Program Technical Support Document for Cancer Potency Factors,” finalized by OEHHA in 2009.

The values for TBAc are as follows:
Inhalation Unit Risk Factor    1.3 x 10-6 (µg/m3)-1
Inhalation Slope Factor         4.7 x 10-3 (mg/kg-day)-1
Oral Slope Factor                 5.0 x 10-3 (mg/kg-day)-1

A draft document for the TBAc IUR was released on August 14, 2015, to solicit public comment and was discussed at public workshops in Sacramento and Diamond Bar, CA during the subsequent 60-day public review period. The document was revised to reflect public comments, and peer-reviewed by the State’s Scientific Review Panel on Toxic Air Contaminants (SRP) in December 2016 and December 2017 before being finalized.

Please direct any inquiries concerning technical matters or availability of the document 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: (link sends e-mail)
Telephone: (510) 622-3145