Isobutyl alcohol (CASRN 78-83-1) | IRIS
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0169
Isobutyl alcohol;
CASRN 78-83-1
Health assessment information on a chemical substance is included in IRIS
only after a comprehensive review of chronic toxicity data by U.S. EPA
health scientists from several Program Offices and the Office of Research
and Development. The summaries presented in Sections I and II represent
a consensus reached in the review process. Background information and
explanations of the methods used to derive the values given in IRIS are
provided in the Background Documents.
STATUS OF DATA FOR Isobutyl alcohol
File First On-Line 03/31/1987
Category (section) |
Status |
Last Revised |
---|---|---|
Oral RfD Assessment (I.A.) | on-line | 04/01/1991 |
Inhalation RfC Assessment (I.B.) | no data | |
Carcinogenicity Assessment (II.) | no data |
_I. Chronic Health Hazard Assessments for Noncarcinogenic Effects
_I.A. Reference Dose for Chronic Oral Exposure (RfD)
Substance Name — Isobutyl alcohol
CASRN — 78-83-1
Last Revised — 04/01/1991
The oral Reference Dose (RfD) is based on the assumption that thresholds
exist for certain toxic effects such as cellular necrosis. It is expressed
in units of mg/kg-day. In general, the RfD is an estimate (with uncertainty
spanning perhaps an order of magnitude) of a daily exposure to the human
population (including sensitive subgroups) that is likely to be without
an appreciable risk of deleterious effects during a lifetime. Please refer
to the Background Document for an elaboration of these concepts. RfDs
can also be derived for the noncarcinogenic health effects of substances
that are also carcinogens. Therefore, it is essential to refer to other
sources of information concerning the carcinogenicity of this substance.
If the U.S. EPA has evaluated this substance for potential human carcinogenicity,
a summary of that evaluation will be contained in Section II of this file.
__I.A.1. Oral RfD Summary
Critical Effect |
Experimental Doses* |
UF
|
MF
|
RfD
|
---|---|---|---|---|
Hypoactivity and Rat Oral Subchronic U.S. EPA, 1986 |
NOEL: 316 mg/kg/day LOAEL: 1000 mg/kg/day |
1000
|
1
|
3E-1
mg/kg/day |
*Conversion Factors: none
__I.A.2. Principal and Supporting Studies (Oral RfD)
U.S. EPA. 1986. Rat oral subchronic toxicity study with isobutyl alcohol.
Office of Solid Waste, Washington, DC.
Animal toxicity studies indicate that butyl alcohol may produce liver/ kidney
effects and decreased red blood cell numbers. Using pathways similar to buty
alcohol, isobutyl alcohol is metabolized to its aldehydes and further
catabolized to carbon dioxide and water (Cornish, 1980).
To evaluate the toxicity of isobutyl alcohol, U.S. EPA (1986) conducted a
subchronic study in rats (30/sex/group). Animals were given oral doses of 0,
100, 316, and 1000 mg/kg/day of isobutyl alcohol for 13 weeks. This study
contained data on body weight changes, food consumption, ophthalmologic
examinations, clinical and biochemical parameters, and gross and microscopic
examinations. An evaluation of the data revealed no effect on body weight or
clinical and histopathologic parameters at doses less than or equal to 316
mg/kg/day. Treatment at the high dose (1000 mg/kg/day) resulted in a minor
decrease in body weight gain during week 2 and decreased serum potassium
levels and hypoactivity. Hypoactivity was the most frequently observed
clinical sign. It occurred in every rat in the 1000-mg/kg/day dose group
during week 1; hypoactivity was markedly decreased by week 4 and occurred only
sporadically thereafter. Ataxia was also seen at low incidence in the 1000-
mg/kg/day dose group throughout the study. The NOEL for this study is 316
mg/kg/day.
__I.A.3. Uncertainty and Modifying Factors (Oral RfD)
UF — An uncertainty factor of 1000 was applied: 10 for interspecies
extrapolation, 10 for intraspecies variability and 10 for extrapolating
subchronic exposure to chronic exposure.
MF — None
__I.A.4. Additional Studies/Comments (Oral RfD)
No adequate chronic toxicity studies have been conducted on isobutyl alcohol. Of the two other published subchronic (2- or 4-month) oral studies (Hillbom et al., 1974a,b), one was available only as an abstract (1974a) and contained insufficient information upon which to evaluate the adequacy of experimental design, etc. The second Hillbom et al. (1974b) study examined the effects of isobutanol only at a single concentration (1M), which could be considered a LOAEL for gastrointestinal damage for isobutanol. However, this study is not of appropriate design for risk assessment purposes, and histopathological examination of stomach, small and large intestine in the much more detailed and experimentally sound 1986 EPA study failed to reproduce the gastrointestinal effects reported by Hillbom et al. (1974b) at dosages five to six orders of magnitude greater than those used by Hillbom et al. (1974b). Isobutyl alcohol has not been scheduled for NTP testing for chronic toxicity, carcinogenicity, or other reproductive effects.
__I.A.5. Confidence in the Oral RfD
Study — Medium
Database — Low
RfD — Low
The oral subchronic study is a well-designed study which employed several dose levels and measured adequate toxicologic endpoints; thus, a medium to high confidence is recommended. The database lacks adequate supporting or chronic toxicity and reproduction studies; thus, low confidence is recommended. Low confidence in the RfD follows.
__I.A.6. EPA Documentation and Review of the Oral RfD
Source Document — This assessment is not presented in any existing U.S. EPA
document.
Other EPA Documentation — U.S. EPA, 1986
Agency Work Group Review — 05/14/1986
Verification Date — 05/14/1986
Screening-Level Literature Review Findings — A screening-level review conducted by an EPA contractor of the more recent toxicology literature pertinent to the RfD for Isobutyl alcohol conducted in September 2002 identified one or more significant new studies. IRIS users may request the references for those studies from the IRIS Hotline at hotline.iris@epa.gov or (202)566-1676.
__I.A.7. EPA Contacts (Oral RfD)
Please contact the IRIS Hotline for all questions concerning this assessment or IRIS, in general, at (202)566-1676 (phone), (202)566-1749 (FAX) or hotline.iris@epa.gov (internet address).
_I.B. Reference Concentration for Chronic Inhalation Exposure (RfC)
Substance Name — Isobutyl alcohol
CASRN — 78-83-1
Not available at this time.
_II. Carcinogenicity Assessment for Lifetime Exposure
Substance Name — Isobutyl alcohol
CASRN — 78-83-1
This substance/agent has not undergone a complete evaluation and determination under US EPA's IRIS program for evidence of human carcinogenic potential.
_III.
[reserved]
_IV. [reserved]
_V. [reserved]
_VI. Bibliography
Substance Name — Isobutyl alcohol
CASRN — 78-83-1
Last Revised — 04/01/1991
_VI.A. Oral RfD References
Cornish, H.H. 1980. Solvents and vapors. In: Casarett and Doull's
Toxicology, The Basic Science of Poisons, 2nd. ed., J. Doull, C.D. Klaassen
and M.O. Amdur, Ed. MacMillan Publishing Co., Inc., New York. p. 480-481.
Hillibom, M.E., K. Franssila and O.A. Forsander. 1974a. Effects of chronic
ingestion of some lower aliphatic alcohols in rats. Arukow Kenkyu. 9(2):
101-108. (Abstract)
Hillbom, M.E., K. Franssila and O.A. Forsander. 1974b. Effects of chronic
ingestion of some lower aliphatic alcohols in rats. Res. Commun. Chem.
Pathol. Pharmacol. 9(1): 177-180.
U.S. EPA. 1986. Rat oral subchronic toxicity study with isobutyl alcohol.
Office of Solid Waste, Washington, DC.
_VI.B. Inhalation RfC References
None
_VI.C. Carcinogenicity Assessment References
None
_VII. Revision History
Substance Name — Isobutyl alcohol
CASRN — 78-83-1
Date |
Section |
Description |
---|---|---|
09/30/1987 | I.A.2. | Citation corrected |
09/30/1987 | IV. | Regulatory Action section on-line |
03/01/1988 | I.A.5. | Confidence levels revised |
02/01/1989 | I.A.7. | Secondary contact's phone number corrected |
07/01/1989 | I.A.2. | 1st paragraph revised |
07/01/1989 | I.A.4. | Text revised |
07/01/1989 | VI. | Bibliography on-line |
04/01/1991 | I.A. | Text edited |
04/01/1991 | I.A.2. | Paragraph 1 - citation clarified |
04/01/1991 | I.A.7. | Primary and secondary contact changed |
04/01/1991 | VI.A. | Cassarett and Doul, 1980 corrected to Cornish, 1980 |
01/01/1992 | IV. | Regulatory actions updated |
04/01/1997 | III., IV., V. | Drinking Water Health Advisories, EPA Regulatory Actions, and Supplementary Data were removed from IRIS on or before April 1997. IRIS users were directed to the appropriate EPA Program Offices for this information. |
12/03/2002 | I.A.6. | Screening-Level Literature Review Findings message has been added. |
_VIII. Synonyms
Substance Name — Isobutyl alcohol
CASRN — 78-83-1
Last Revised — 03/31/1987
- 78-83-1
- ALCOOL ISOBUTYLIQUE
- FERMENTATION BUTYL ALCOHOL
- 1-HYDROXYMETHYLPROPANE
- ISOBUTANOL
- Isobutyl Alcohol
- ISOBUTYLALKOHOL
- ISOPROPYLCARBINOL
- 2-METHYL PROPANOL
- 2-METHYL-1-PROPANOL
- 2-METHYLPROPYL ALCOHOL
- 1-PROPANOL, 2-METHYL-
- RCRA WASTE NUMBER U140
- UN 1212