TERTIARY BUTYL ALCOHOL (TBA)
Update: April 2006
Current Massachusetts Regulatory Limit
ORSGL = 0.12 mg/L.
Federal Regulatory Limit
No MCL available
Basis for Criteria
The ORS guideline for TBA was derived based on the RfD (presented below) derived by ORS for this chemical and assumes that a 70 kg adult ingests 2 L/day of drinking water. A relative source contribution factor of 20% and a 10-fold uncertainty factor to account for potential carcinogenicity are incorporated into the final value.
RfD: 0.175 mg/kg/day (MassDEP, 2006)
UF: 1000 (10 = LOAEL to NOAEL; 10 = interspecies; 10 = intraspecies)
Inhalation of high concentrations of TBA at prolonged exposures may produce transient effects on the central nervous system, as well as eye and mucous membrane irritation. Subchronic exposure studies have indicated that the urinary tract is the primary target system of TBA. Chronic exposure studies have also indicated adverse effects on the kidney, urinary bladder and thyroid gland.
In a 2-year chronic drinking water study conducted by NTP (NTP, 1995; Cirvello et al., 1995), TBA was administered to rats and mice using 60 animals per dose at doses of 0, 1250, 2500 or 5000 ppm (male rats); 0, 2500, 5000 or 10,000 ppm (female rats); and 1, 5000, 10,000, or 20,000 ppm (male and female mice). In female rats, the lowest concentration of 2500 ppm produced nephropathy and is a LOAEL for this effect. The concentration of 2500 ppm results in a dose of approximately 175 mg/kg/day (Cirvello et al., 1995). All exposure doses produced nephropathy in a dose-dependent manner in the female rat (MassDEP, 2006).
Cancer Assessment: The U.S. EPA has not classified TBA under either the old U.S. EPA carcinogen classification system or under their Proposed Guidelines for Carcinogen Risk Assessment (U.S. EPA, 1999a). Using the 1999 proposed guidelines, ORS would tentatively classify TBA as having suggestive evidence of carcinogenicity but not sufficient to assess human carcinogenic potential.
PQL: 50 ug/L
U.S. EPA Method 8260 and 524.2
PQLs and analytical methods may have been updated since this guidance value was last revised. Updated analytical methods for drinking water and their associated PQLs may be found at US EPA Drinking Water Analytical Methods .
Other Regulatory Data
Any Health Advisories, Reference Doses (RfDs), cancer assessments or Cancer Potency Factors (CPFs) referenced in this document pertain to the derivation of the current guidance value. Updated information may be obtained from the following sources:
Health Advisories - The U.S. EPA provides guidance for shorter-term exposures for chemicals based on their non-cancer effects. Current health advisories may be more current than those used to derive MCLs and may be found at US EPA Current Drinking Water Health Advisories .
RfDs, cancer assessments and CPFs - For specific information pertaining to derivation of drinking water criteria, consult the Federal Register notice that announces the availability of the most current guidance for that chemical. In addition, information on other current RfDs and CPFs as well as cancer assessments for specific chemicals may be found in the U.S. EPA Integrated Risk Information System (IRIS) at http://www.epa.gov/iris/. Please note that the information in IRIS may differ from that used in the derivation process as published in the Federal Register notice.
Cirvello, J. D.; Radovsky, A.; Heath, J. E.; Farnell, D. R., and Lindamood, C. 3rd. Toxicity and carcinogenicity of t-butyl alcohol in rats and mice following chronic exposure in drinking water. Toxicol Ind Health. 1995 Mar-1995 Apr 30; 11(2):151-65.NTP (National Toxicology Program). May 1995.
NTP Toxicology and Carcinogenesis Studies of t-Butyl Alcohol (CAS No. 75-65-0) in F344/N Rats and B6C3F1 Mice (Drinking Water Studies).
Massachusetts Department of Environmental Protection (MassDEP). March 27, 2006. Drinking Water Guideline for Tertiary Butyl Alcohol (TBA). Office of Research and Standards (ORS).
U.S. EPA (U.S. Environmental Protection Agency). July 1999a. Guidelines for Carcinogen Risk Assessment. Review Draft. NCEA-F-0644. Risk Assessment Forum.