SUBJECT: EXPEDITED EVALUATION OF RISK ASSESSMENT FOR TERTIARY BUTYL ALCOHOL IN DRINKING WATER.

In response to your request of May 19, 1999, we have summarized an interim assessment that the Office ofEnvironmental Health Hazard Assessment (OEHHA) staff made last year in connection with our assessment of methyl, tertiary butyl ether (MTBE) and based on limited data available at that time. While this is still an interim assessment with preliminary calculations, and by no means represents a full risk assessment, it may be suitable for the purposes stated in your request. Tertiary butyl alcohol (TBA) has been used as a gasoline octane booster and may be a food contaminant when used in coatings for metallic items that contact food, or as a coating for paperboard food containers. Human exposure can occur via skin contact, inhalation, or ingestion. The Occupational Safety and Health Administration has established a permissible exposure limit of 100 ppm or 300 mg/m3 for TBA. TBA is partially metabolized via demethylation in rats to acetone and formaldehyde. TBA is a metabolite of MTBE and exposure may occur through inhalation ofMTBE fumes. Compared to MTBE, relatively little toxicity data are available for TBA. A bioassay was conducted by the National Toxicology Program (NTP) in Fischer 344 rats and B6C3F1 mic