2-methylpropan-1-ol

Endpoint summary

Description of key information

Skin 
In vivo
Rabbit, 4 h, semiocclussive: not irritating (OECD 404, GLP; Hoechst 1988)
Rabbit, 4 h, occlusive: irritating (superficial necrosis in 2/6 animals; OECD 404, GLP; Union Carbide Corporation 1993)
Rabbit, 4h, occlusive, corrosive (necrosis in 2/6 rabbits, D.O.T guideline, UCC 1981)
Rabbit, 24h, occlusive, not irritating (Federal Register 38, No. 187, § 1500.41, BASF 1978)
Rabbit, 24h, occlusive, irritating (Code of Federal Regulations, Title 16, Section 1500.41, BASF 1979)
Rabbit, 2h, occlusive, irritating (US Fed eral register, BASF 1979)
Eye
In vivo
Rabbit: serious risk of eye damage (irreversible corneal opacity and conjunctivae redness; OECD 405, GLP, Hoechst AG 1988)
Respiratory tract
Acute inhalation study, rat: Irritating to the respiratory tract (Kushneva et al. 1983; Val. 4)

Key value for chemical safety assessment

Skin irritation / corrosion

Link to relevant study records

Reference

Endpoint:

skin irritation: in vivo

Type of information:

experimental study

Adequacy of study:

weight of evidence

Study period:

15 December 1992 - 29 December 1992

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

EPA OTS 798.4470 (Acute Dermal Irritation)

Deviations:

no

Qualifier:

according to guideline

Guideline:

OECD Guideline 404 (Acute Dermal Irritation / Corrosion)

Deviations:

no

GLP compliance:

yes

Specific details on test material used for the study:

A sample of isobutanol, Lot No. TS3370114, CAS No. 78-83-1, was used. The test substance was a colorless, transparent, low viscosity liquid.
Gas chromatography-mass spectrometry (GC/MS) and nuclear magnetic resonance spectroscopy (NMR) techniques were independently used to confirm the sample's identity. Sample purity, measured by capillary GC, is ~ 99.9%.

Species:

rabbit

Strain:

New Zealand White

Details on test animals or test system and environmental conditions:

Male and female New Zealand White rabbits were received from Hazleton Research Products, Inc. (Denver, PA). The strain and species were selected because of their availability and existing historical data. Rabbits were ordered to be between 2.0 and 2.3 kg (designated by the supplier to be approximately 12 to 14 weeks of age). The females were nulliparous and nonpregnant.

Periodically, a Clinical Veterinarian examined rabbits for any signs of health deficiencies. Within 1 or 2 days of receipt, all animals were assigned a unique number which was marked on the animal cage card. The rabbit number was also marked in indelible ink on 1 ear at the time of dosing.

The rabbits were housed individually in cages with wire floors (approximately 61.0 x 46.0 x 36.0 cm.). DACBQ (Deotized Animal Cage Board; Shepherd Specialty Papers, Inc.) was placed under each cage and changed regularly. An automatic timer was set to provide fluorescent lighting for a 12-hour photoperiod (approximately 0500 to 1700 hours for the light phase). Temperature and relative humidity were recorded (Cole-Parmer Hygrothermograph Seven-Day Continuous Recorder, Model No. 8368-00, Cole-Parmer Instrument Co., Chicago, IL). Temperature was routinely maintained at 61-70°F during the test period; relative humidity was routinely maintained at 40-70%. Any minor exceptions to these specified ranges were noted in the raw data.

Tap water (Municipal Authority of Westmoreland County, Greensburg, PA) was available ad libitum (except during dosing) and was delivered by an automatic watering system with demand control valves mounted on each rack. Water analyses were provided by the supplier, Halliburton NUS Environmental Laboratories, Materials Engineering & Testing Company, and Lancaster Laboratories, Inc. at regular intervals. EPA standards for maximum levels of contaminants were not exceeded. As available, water analysis reports were reviewed by the Study Director. AGWAYe PROLABe Animal Diet High Fiber Rabbit (Agway Inc.) was available ad libitum except during the actual dosing period. No analyses of chemical composition and possible contaminants of the feed were conducted by the supplier.

Animal Acclimation
The animals were acclimated for at least 5 days before dosing. Detailed clinical observations were conducted twice, at the time of receipt and during animal identification and/or dosing. In addition, rabbits were examined and weighed twice prior to dosing. Cage-side observations and mortality checks were conducted at least once daily. Animals considered unacceptable for the study, based on the clinical signs or body weights (rabbits), were rejected for use on this study.

Study Organization
The animals were weighed and inspected for health on the day of the test. Only those exhibiting a healthy state were used. Healthy animals appeared alert, active and well groomed, with no evidence of discharge, diarrhea, breathing difficulties or locomotor abnormalities. A BRRC veterinarian was available for consultation regarding any animal health concerns. Animals were randomly assigned to cages and were designated for dosing according to need and availability.

Type of coverage:

occlusive

Preparation of test site:

shaved

Vehicle:

unchanged (no vehicle)

Controls:

not specified

Amount / concentration applied:

0.5 ml

Duration of treatment / exposure:

4 hours

Observation period:

Readings were made at 1, 24, 48 and 72 hours and at 7 and 14 days, after the end of the contact period.

Number of animals:

3 males and 3 females

Details on study design:

The fur was removed from the dorsal area of the trunk of each rabbit using veterinary clippers a few days before dosing and the dose area was trimmed carefully (avoiding skin abrasion), as necessary, up to the day before application of the test substance. A 1-inch square gauze patch was placed over 1 intact (nonabraded) site/rabbit and secured by adhesive tape. A volume of 0.5 ml was then applied under the patch. Polyethylene sheeting was placed loosely around the trunk and secured. The animal was placed in a restraining device for the 4-hour contact period after which the coverings and as much excess test substance as possible were removed.

The test substance was applied to each of 6 rabbits (3 males, 3 females). Readings were made at 1, 24, 48 and 72 hours and at 7 and 14 days, after the end of the contact period according to the method of Draize, 1959. All rabbits were sacrificed at 14 days (ear vein injection using Euthanasia-6 Solution).

Reference
Draize, J. H. (1959). The Appraisal of Chemicals in Foods, Drugs and Cosmetics. Tbe Association of Food and Drug Officials of the United States.

Irritation parameter:

erythema score

Basis:

mean

Time point:

24/48/72 h

Score:

1.2

Max. score:

2

Reversibility:

not fully reversible within: 14 days

Remarks on result:

other: Maximum score observed. One animal had a score of 1 on day 14.

Irritation parameter:

edema score

Basis:

mean

Time point:

24/48/72 h

Score:

1

Max. score:

2

Reversibility:

not fully reversible within: 14 days

Remarks on result:

other: Maximum score observed. One animal had a score of 1 on day 14.

Irritant / corrosive response data:

Application of 0.5 ml of isobutanol to covered rabbit skin for a 4-hour contact period produced minor to moderate erythema and edema on 6 of 6 rabbits within 1 day. (Maximum score noted on any animal for erythema or edema was 2). One rabbit had a light brown discoloration on the dose site at 1 hour. Superficial necrosis developed on this animal by 1 day; another rabbit had superficial necrosis at 7 days. Ecchymoses were apparent on 1 animal within 1 day. At 7 days, fissuring was observed on 1 animal. Four rabbits had desquamation at this time. By 14 days, alopecia was observed on 2 rabbits. Erythema and edema subsided on 5 of 6 rabbits within 14 days; minor erythema and edema persisted on 1 rabbit. Two rabbits had a normal appearance at this time.

Other effects:

No additional information available.

No additional information available

Interpretation of results:

Category 3 (mild irritant) based on GHS criteria

Conclusions:

Minor to moderate erythema and edema on 6 of 6 rabbits, superficial necrosis on 2, ecchymoses on 1, fissuring on 1, desquamation on 4 and alopecia on 2 from 0.5 ml. Two rabbits had a normal appearance within 14 days; minor irritation persisted on the remaining 4 rabbits.

Executive summary:

The acute dermal irritation of isobutanol was examined in a 4 -hour exposure. Minor to moderate erythema and edema on 6 of 6 rabbits, superficial necrosis on 2, ecchymoses on 1, fissuring on 1, desquamation on 4 and alopecia on 2 from 0.5 ml. Two rabbits had a normal appearance within 14 days; minor irritation persisted on the remaining 4 rabbits.

Endpoint conclusion

Endpoint conclusion:

adverse effect observed (irritating)

Eye irritation

Link to relevant study records

Reference

Endpoint:

eye irritation: in vivo

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 405 (Acute Eye Irritation / Corrosion)

GLP compliance:

yes

Specific details on test material used for the study:

- Name of test material (as cited in study report): Isobutanol
- Physical state: liquid
- Analytical purity: at least 99.5 %

Species:

rabbit

Strain:

New Zealand White

Details on test animals or tissues and environmental conditions:

TEST ANIMALS
- Source: Hoechst AG, Kastengrund, own breeding facilities
- Age at study initiation: 3-5 months
- Weight at study initiation: 2.6-3.1 kg
- Housing: individually
- Diet: ad libitum
- Water: ad libitum ad libitum


ENVIRONMENTAL CONDITIONS
- Temperature (°C): 20 +/- 3 °C
- Humidity (%): 50 +/- 20 %
- Photoperiod (hrs dark / hrs light): 12/12

Vehicle:

unchanged (no vehicle)

Controls:

other: untreated eyes of the same animals

Amount / concentration applied:

TEST MATERIAL
- Amount(s) applied (volume or weight with unit): 0.1 ml

Duration of treatment / exposure:

24 hours

Observation period (in vivo):

14 days

Number of animals or in vitro replicates:

3

Details on study design:

REMOVAL OF TEST SUBSTANCE
- Washing (if done): with physiological sodium chloride solution (37 °C)
- Time after start of exposure: 24 hours


SCORING SYSTEM: according to OECD 405 guidelines


TOOL USED TO ASSESS SCORE: fluorescein

Irritation parameter:

cornea opacity score

Basis:

mean

Time point:

24/48/72 h

Score:

1

Max. score:

4

Reversibility:

not fully reversible within: 14 days

Irritation parameter:

cornea opacity score

Basis:

animal #1

Time point:

24/48/72 h

Score:

1.67

Max. score:

4

Reversibility:

not fully reversible within: 14 d

Remarks on result:

other: score 3 after 14 d; fluorescein test positive at d 14

Irritation parameter:

cornea opacity score

Basis:

animal #2

Time point:

24/48/72 h

Score:

1.33

Max. score:

4

Reversibility:

fully reversible within: 14 d

Irritation parameter:

cornea opacity score

Basis:

animal #3

Time point:

24/48/72 h

Score:

0

Max. score:

4

Reversibility:

other: no efects

Irritation parameter:

iris score

Basis:

mean

Time point:

24/48/72 h

Score:

0.33

Max. score:

2

Reversibility:

fully reversible within: 14 days

Irritation parameter:

iris score

Basis:

animal #1

Time point:

24/48/72 h

Score:

1

Max. score:

2

Reversibility:

fully reversible within: 14 d

Irritation parameter:

iris score

Basis:

animal #2

Time point:

24/48/72 h

Score:

0

Max. score:

2

Reversibility:

other: no effects

Irritation parameter:

iris score

Basis:

animal #3

Time point:

24/48/72 h

Score:

0

Max. score:

2

Reversibility:

other: no effects

Irritation parameter:

conjunctivae score

Basis:

mean

Time point:

24/48/72 h

Score:

2.55

Max. score:

3

Reversibility:

not fully reversible within: 14 days

Irritation parameter:

conjunctivae score

Basis:

animal #1

Time point:

24/48/72 h

Score:

3

Max. score:

3

Reversibility:

not fully reversible within: 14 d

Remarks on result:

other: score 1 after 14 d

Irritation parameter:

conjunctivae score

Basis:

animal #2

Time point:

24/48/72 h

Score:

2.33

Max. score:

3

Reversibility:

fully reversible within: 14 d

Irritation parameter:

chemosis score

Basis:

animal #3

Time point:

24/48/72 h

Score:

2.33

Max. score:

3

Reversibility:

fully reversible within: 14 d

Irritation parameter:

chemosis score

Basis:

mean

Time point:

24/48/72 h

Score:

1.55

Max. score:

4

Reversibility:

fully reversible within: 14 days

Irritation parameter:

chemosis score

Basis:

animal #1

Time point:

24/48/72 h

Score:

2.33

Max. score:

4

Reversibility:

fully reversible within: 14 d

Irritation parameter:

chemosis score

Basis:

animal #2

Time point:

24/48/72 h

Score:

1

Max. score:

4

Reversibility:

fully reversible within: 14 d

Irritation parameter:

chemosis score

Basis:

animal #3

Time point:

24/48/72 h

Score:

1.33

Max. score:

4

Reversibility:

fully reversible within: 14 d

Corneal opacity grade 3 and conjunctival redness grade 1 was observed in 1/3 rabbits at the end of the observation period (day 14). The other two rabbits were free of any signs of irritation.

 

Scores of the individual animals:

cornea score: 0 in 1/3; 1.33 in 1/3; 1.67 in 1/3

iris score: 0 in 2/3; 1 in 1/3

conjunctivae score: 2.33 in 2/3, 3 in 1/3

chemosis score: 1 in 1/3; 1.33 in 1/3; 2.33 in 1/3

 

 

 

Interpretation of results:

other: corrosive

Endpoint conclusion

Endpoint conclusion:

adverse effect observed (irritating)

Respiratory irritation

Endpoint conclusion

Endpoint conclusion:

adverse effect observed (irritating)

Additional information

There are valid in vivo data available for the assessment of the irritation potential of isobutanol.

 

Skin

The results of various reliable studies, mainly performed under occlusive conditions, vary. Overall, the results indicate that isobutanol has skin irritating properties.

 

A GLP and OECD TG 404 conform acute dermal irritation/corrosion study was performed in three rabbits (Hoechst 1988). A 4-hour semiocclusive exposure to 0.5 ml of the test substance produced slight to marked erythema after 30-60 minutes and minor to moderate erythema and slight edema in the 24 h reading, which were fully reversible within 48 h. Mean scores were 0.44 for erythema and 0.11 for edema in the 24 -72 h reading. (The individual mean animal scores (24/48/72 hours) were: erythema: 0.0 in 1/3 animals, 0.67 in 2/3 animals; edema: 0.0 in 2/3 animals; 0.33 in 1/3 animals).

In a second GLP conform study according to OECD TG 404, three New Zealand White rabbits were exposed to 0.5 mL isobutanol (purity 99.9%) for 4 hours under occlusive conditions (Union Carbide Corporation 1993). Here, the mean scores of the 24-72h readings were 1.2 for erythema and 1.0 for edema. Superficial necrosis was observed on 2 animals, ecchymoses on 1, fissuring on 1, desquamation on 4 and alopecia on 2. Two rabbits had a normal appearance within 14 days at the final reading; minor irritation persisted on the remaining 4 rabbits.

Several further non-GLP studies according to different guidelines exist. In one study by UCC (1981), 6 rabbits were treated with 0.5ml of the test substance for 4h under occlusive conditions. Necrosis was observed in 2 of these animals, but no further data was provided on the type of necrosis (superficial or not), and the observation ended after 48h. Due to these limits in reporting, occlusive versus semiocclusive conditions, and the fact that exposure for 24h in two additional studies (BASF 1978 / 1979) did not cause necrosis (and not even irritation in one case), classification as corrosive to the skin does not seem warranted.

 

Eye

The most severe effects were observed in a study conducted by Hoechst AG (1988) in accordance with GLP requirements and OECD guideline 405 (single application of 0.1 ml test substance, eyes were washed 24 hours after application) with three rabbits. Application of the test substance led to corneal opacity grade 3 and conjunctivae redness grade 1 in one rabbit at the end of the observation period (day 14). The other two rabbits showed moderate to severe conjunctivae redness and chemosis during the first 72 h, but were free of any signs of irritation after 14 d. (The mean cornea score (24/48/72 hours) was 1, the mean iris score (24/48/72 hours) was 0.33, the mean conjunctivae score (24/48/72 hours) was 2.55 and the mean chemosis (edema) score (24/48/72 hours) was 1.55.  Individual mean animal scores (24/48/72 hours) were: cornea score: 0 in 1/3 animals; 1.33 in 1/3 animals; 1.67 in 1/3 animals; iris score: 0 in 2/3 animals; 1 in 1/3 animals; conjunctivae score: 2.33 in 2/3 animals, 3 in 1/3 animals; chemosis score: 1 in 1/3 animals; 1.33 in 1/3 animals; 2.33 in 1/3 animals.

Additionally, in some other guideline conform studies, instillation of 0.1 mL isobutanol caused slight, but irreversible effects after 21 days (Union Carbide Corporation 1993) or 8 days (BASF SE 1978, 1979).

Due to these observations, the test substance has to be classified as posing the risk of serious eye damage according to 67/548/EEC (R41) and as eye irritant Cat. 1 according to 1272/2008/EC (CLP).

 

Respiratory tract

Irritating effects on the respiratory tract were observed in an acute inhalation study in rats (Kushneva et al. 1983; Val. 4, see IUCLID chapter 7.2.2)

Relevant data on human occupational hazard were provided for n-butanol by Sterner et al. (1949; see chapter 7.10.5). In a longitudinal study over 10 years, measured exposure levels of up to 99 workers were correlated with findings of clinical signs, lung X-ray and clinical chemistry. No eye injuries or symptoms were found in any individual at concentrations averaging 310 mg/m3 (= 100 ppm), while average concentrations of 620 mg/m3 (200 ppm) caused transient corneal inflammation, with associated burning sensation, lacrimation, and photophobia. No systemic effects have been observed.

 

Effects on skin irritation/corrosion: moderately irritating

Effects on eye irritation: corrosive

Effects on respiratory irritation: irritating

Justification for classification or non-classification

Skin

In summary, results of the available studies led to the classification as a skin irritant Cat. 2 according to 1272/2008/EC (CLP) requirements.

 

Eye

Due to the irreversible irritation effects on rabbit eyes, isobutanol has to be classified as posing the risk of serious eye damage Cat. 1 according to 1272/2008/EC (CLP) criteria.

 

Respiratory tract

Due to the effects observed in an acute inhalation study in rats and with n-butanol in humans, isobutanol has to be classified as irritant to the respiratory tract (STOT SE Cat. 3) according to 1272/2008/EC (CLP) requirements.