The Office of Environmental Health Hazard Assessment (OEHHA) is releasing a revised draft document summarizing the carcinogenicity and derivation of an inhalation cancer unit risk factor (URF) for tertiary-Butyl Acetate (TBAc).  Inhalation cancer unit risk factors are used to estimate lifetime cancer risks associated with inhalation exposure to a carcinogen. These documents will be reviewed and discussed by the Scientific Review Panel on Toxic Air Contaminants (SRP) (link is external)at its meeting on December 14, 2016 in Sacramento, CA. 

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 develops URFs for many air pollutants. The TBAc URF was developed using the most recent “Air Toxics Hot Spots Program Technical Support Document for Cancer Potency Factors,” finalized by OEHHA in 2009.

A draft of the TBAc URF document was released for a 60-day public review and comment period on August 14, 2015.  One set of comments was received.  The TBAc URF document was revised in response to those comments. The values proposed are as follows:

• Unit Risk Factor: 1.9 X 10-6 (μg/m3)-1
• Inhalation Slope Factor: 6.7 X10-6 (mg/kg-day)-1
• Oral Slope Factor : 7.0 X10-3 (mg/kg-day)-1