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EC number: 201-148-0
CAS number: 78-83-1
Inhalation90 d, rat: NOAEC neurotoxicity >= 7.5 mg/L (2500 ppm;GLP, neurotoxicity guideline 82-7 F, CMA 1996a). 90 d, rat: NOAEC neurotoxicity/behaviour >= 7.5 mg/L (2500 ppm;GLP, neurotoxicity guideline 85 F, CMA 1996b). Acute, rat: LOEC neurotoxicity = 4.5 mg/L (1500 ppm; slight hypoactivation during exposure; EPA guidelines 798.6050 & 789.6200; CMA 1994)
There were no behavioral or morphological effects indicative of a
persistent or progressive action of isobutanol on the nervous system at
exposure concentrations up to 2500 ppm. However, a slight, transient
decrease in response to external stimuli was observed during exposures
to all concentrations. This effect is likely an acute effect of exposure
to isobutanol and is consistent with known effects of solvents which
cause a general and non-specific depression of the nervous system.
Under the conditions of this study, there were no effects on performance
under a 4 FR 20 - 2 FI 120 second schedule of food reinforcement after
subchronic exposure to isobutanol at concentrations up to 2500 ppm (ca.
Two GLP conform 13-week inhalation studies were performed with
Sprague-Dawley rats exposed to 0, 250, 1,000 or 2,500 ppm (ca. 0, 0.75,
3.0, 7.5 mg/L), 6 hours/day, 5 days/week either following U.S.
neurotoxicity guideline 82 -7, subdivision F (CMA 1996a) or following
U.S. neurotoxicity guideline 85, subdivision F (CMA 1996b). These
studies included expanded neurotoxicity endpoints (functional
observational battery, motor activity, scheduled-control operant
behavior, and neuropathology endpoints) as well as the standard
parameters for subchronic studies. Intensive investigations of
testicular parameters (homogenization-resistant spermatid head counts)
were collected at necropsy. The highest exposure concentration (2500
ppm; 7.5 mg/L) did not have any adverse effects demonstrating a
persistent or progressive effect of isobutanol on the central or
peripheral nervous system in both studies. A slight reduction in
responsiveness to external stimuli was noted during exposure in all
treatment groups. Slight increases (9%) in red blood cell parameters
(count, hematocrit, hemoglobin) were noted in female rats exposed to
2500 ppm (7.72 mg/L) in the first study but the slight nature of these
findings made them of questionable biological significance. There were
no changes in any other parameters in both studies. Based on the results
of both studies, the NOAEL for neurotoxicity (and repeated dose
toxicity) was at least 7.5 mg/L (2500 ppm).
An acute inhalation neurotoxicity study was performed with rats
following GLP requirements and EPA guidelines 798.6050 & 789.6200 (CMA
1994). 10 male and 10 female rats were exposed to 0, 1500, 3000 and 6000
ppm isobutanol (corresponding to ca. 4.5, 9.0 and 18.0 mg/L).
Neurobehaviour tests (functional observational battery and motor
activity) were conducted prior to exposure (pretest), immediately after
exposure (day 0), the day after exposure (day 1), and 7 and 14 days
after dosing. 3000 and 6000 ppm vapours of isobutanol caused rapidly
reversible narcosis, 1500 ppm caused slight hypoactivation in rats
during, but not after exposure. No treatment-related effects were
observed in gross necropsy. Therefore, only a LOEL of 1500 ppm (ca. 4.5
mg/L) was determined.
Effects indicative for
CNS depression were observed after single and repeated application (see
also chapters Acute Toxicity and Repeated Dose Toxicity). Therefore, the
substance has to be classified with R67 according to 67/548/EEC critera
and STOT single exposure, Cat. 3 (for narcotic effects) according to
1272/2008/EC (CLP) criteria, respectively.
Information on Registered Substances comes from registration dossiers which have been assigned a registration number. The assignment of a registration number does however not guarantee that the information in the dossier is correct or that the dossier is compliant with Regulation (EC) No 1907/2006 (the REACH Regulation). This information has not been reviewed or verified by the Agency or any other authority. The content is subject to change without prior notice.Reproduction or further distribution of this information may be subject to copyright protection. Use of the information without obtaining the permission from the owner(s) of the respective information might violate the rights of the owner.
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