Isobutyl acetate

Endpoint summary

Description of key information

For isobutyl acetate, no data on repeated dose toxicity could be located.
To compensate for this lack of data, information resulting from isobutanol and isobutyl isobutyrate as supporting substances will be used as substitute. Data are available for oral and inhalation repeated dose toxicity.
Repeated dose toxicity: oral (gavage)
Supporting substance isobutanol: In a valid subchronic (90 d) toxicity studies, a NOAEL of 316 mg/kg bw/day has been observed (EPA/Res. Triangle Inst. 1987).
The NOAEL for isobutyl acetate (conversion using the respective molecular weight) is 495 mg/kg bw/day.
Supporting substance isobutyl isobutyrate: In a valid subchronic (90 d) toxicity studies, a NOAEL of 1000 mg/kg bw/day has been observed (Drake 1978).
The NOAEL for isobutyl acetate (conversion using the respective molecular weight) is 805 mg/kg bw/day
Repeated dose toxicity: inhalation
Supporting subsance n-butyl acetae: In a valid subchronic (90 d) toxicity study, the NOAEL was considered to be 2410 mg/m³ (OPP/CMA, 1998 and 2001)
Supporting substance isobutanol: In a valid subchronic (90 d) toxicity study, the NOAEL was considered to be 7700 mg/m³ (Li/Monsanto 1999). 
The NOAEC for isobutyl acetate (conversion using the respective molecular weight) is 12067 mg/m³.
The findings of these studies indicate that the substance is neurotoxic and may induce narcosis. 

Key value for chemical safety assessment

Repeated dose toxicity: via oral route - systemic effects

Link to relevant study records

Reference

Endpoint:

sub-chronic toxicity: oral

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: comparable to guideline study, but as read-across from supporting substance maximum reliability is 2. Read-across hypothesis: for details please see read-across report in section 13.

Qualifier:

equivalent or similar to guideline

Guideline:

OECD Guideline 408 (Repeated Dose 90-Day Oral Toxicity Study in Rodents)

Deviations:

yes

Remarks:

; no special functional observations

Principles of method if other than guideline:

no guideline stated, but study design is comparable to the procedure of OECD test guidelin 408 (Repeated dose 90-day Oral Toxicity in Rodents)

GLP compliance:

not specified

Species:

rat

Strain:

Crj: CD(SD)

Sex:

male/female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Charles River Breeding Laboratories Inc., Portage, MI, USA
- Age at study initiation: 22 - 23 days
- Weight at study initiation: 45-55 g
- Fasting period before study: no
- Housing: individually in wire-bottom cages
- Diet (e.g. ad libitum): Purina Certified Rodent Laboratory Chow No. 5002 (pellet)
- Water (e.g. ad libitum): filtered municipal water
- Acclimation period: 7days

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 22 ± 1
- Humidity (%): 43 ± 5
- Air changes (per hr): no data
- Photoperiod (hrs dark / hrs light): 12 /12

Route of administration:

oral: gavage

Vehicle:

water

Details on oral exposure:

PREPARATION OF DOSING SOLUTIONS: dissolution in water

DIET PREPARATION
- Rate of preparation of dosing solution (frequency): weekly

VEHICLE
- Justification for use and choice of vehicle (if other than water):
- Concentration in vehicle: as required by dose
- Amount of vehicle (if gavage): 10 ml/kg bw

Analytical verification of doses or concentrations:

yes

Details on analytical verification of doses or concentrations:

GC analysis with a Varian 2100 GC with flame ionization detector connected to a Spectra Physics Model 4100 recording integrator.
Analysis of the test material was performed at week 1, 3, 8, 9, and 13. Measured concentrations were found to in acceptable accordance with nominal values.

Duration of treatment / exposure:

92 days

Frequency of treatment:

daily

Dose / conc.:

100 mg/kg bw/day (actual dose received)

Dose / conc.:

316 mg/kg bw/day (actual dose received)

Dose / conc.:

1 000 mg/kg bw/day (actual dose received)

No. of animals per sex per dose:

30 in total (10 for interim sacrifice)
In addition, one group of 10 animals per sex (group V) for baseline observation (sacrifice prior to initiation of dosing)

Control animals:

yes, concurrent vehicle

Details on study design:

- Dose selection rationale: preceding rage finding toxicity study (TLR study #032-001)
- Rationale for animal assignment (if not random): random
- Rationale for selecting satellite groups: no satellite groups

Observations and examinations performed and frequency:

CAGE SIDE OBSERVATIONS: Yes
- Time schedule: twice daily

DETAILED CLINICAL OBSERVATIONS: No data
- Time schedule:

BODY WEIGHT: Yes
- Time schedule for examinations: weekly

FOOD CONSUMPTION: Yes
- Time schedule for examinations: weekly

FOOD EFFICIENCY: No

OPHTHALMOSCOPIC EXAMINATION: Yes
- Time schedule for examinations: during pretreatment period and at week 13
- Dose groups that were examined: all rats were examined

HAEMATOLOGY: Yes
- Time schedule for collection of blood: prior to initiation of dosing, at week 4 or 5, and at week 13 or 14
- Anaesthetic used for blood collection: Yes, CO2
- Animals fasted: No data
- How many animals: prior to dosing 10 animals per sex ( group V), at week 4 or 5 (interim sacrifice) and at week 13 or 14 (final sacrifice) 10 animals per sex from each group
- Parameters examined: hemoglobin (HGB), hematocrit (PCV), erythrocyte count (RBC), mean cell volume (MCV), mean cell hemoglobin (MCH), mean cell hemoglobin concentration (MCHC), total and differential leucocyte counts (WBC), estimated platelet count (PLT)

CLINICAL CHEMISTRY: Yes
- Time schedule for collection of blood: prior to initiation of dosing, at week 4 or 5, and at week 13 or 14
- Anaesthetic used for blood collection: Yes, CO2
- Animals fasted: No data
- How many animals: prior to dosing 10 animals per sex ( group V), at week 4 or 5 (interim sacrifice) and at week 13 or 14 (final sacrifice) 10 animals per sex from each group
- Parameters examined: alkaline phosphatase (Alk phos), blood urea nitrogen (BUN), glutamate pyruvate transaminase (SGPT), glutamate oxaloacetate transaminase (SGOT), glucose (Gluc), total protein (TP), albumin (Alb), A/G ratio (calculated), globulin (calculated), total bilirubin (Tot. bili.), sodium (Na), potassium (K), chloride (Cl), calcium (Ca), creatinine, inorganic phosphate (phos.), total carbon dioxide (TCO2), total serum cholesterol (Chol)

URINALYSIS: Yes
- Time schedule for collection of urine: prior to initiation of dosing, at week 4 or 5, and at week 13 or 14
- Metabolism cages used for collection of urine: Yes
- Animals fasted: No data
- Parameters examined. pH, specific gravity, glucose, protein, ketones, bilirubin, urobilinogen, microscopy of sediment.

NEUROBEHAVIOURAL EXAMINATION: No special examinations

Sacrifice and pathology:

GROSS PATHOLOGY: Yes
HISTOPATHOLOGY: Yes

Statistics:

body weight, food consumption, clinicopathologic, and organ weight data were tested for homogeneity of variance by Bartlett's method (Steel and Torrie, 1980).
If the data were found to be homogeneous, differences between control and treatment means were tested for statistical significance by the method of Dunnett (Dunnett, 1964).
If the data were found not to be homogeneous, the method of Gill (modified Dunnett's) was employed (Gill, 1977)

Clinical signs:

effects observed, treatment-related

Mortality:

mortality observed, treatment-related

Body weight and weight changes:

effects observed, treatment-related

Food consumption and compound intake (if feeding study):

effects observed, treatment-related

Food efficiency:

not examined

Water consumption and compound intake (if drinking water study):

not examined

Ophthalmological findings:

no effects observed

Haematological findings:

no effects observed

Clinical biochemistry findings:

effects observed, treatment-related

Urinalysis findings:

no effects observed

Behaviour (functional findings):

not examined

Organ weight findings including organ / body weight ratios:

no effects observed

Gross pathological findings:

no effects observed

Histopathological findings: non-neoplastic:

no effects observed

Histopathological findings: neoplastic:

not examined

Details on results:

CLINICAL SIGNS AND MORTALITY
Treatment related clinical signs were restricted to the high-dose group and included hypoactivity, ataxia, and salivation. Hypoactivity decreased in the course of the experiment and was only sporadically observed after week 4.
The mortality rate was 1/60, 1/60, 2/60 and 11/60 for the control, 100, 316, and 1000 mg/kg/day dose group, respectively. In combination with the results of the gross necropsy and histologic findings, the increased number of death in the high-dose group are not related to a systemic toxicity of orally administered isobutyl alcohol.

BODY WEIGHT AND WEIGHT GAIN
During week 1 the males of the 1000 mg/kg/day dose group gained 10% less body weight than the controls.

FOOD CONSUMPTION
For the first two weeks of the study, food consumption averages of the 1000 mg/kg day dose group males and females were significantly lower than controls ( p ≤ 0.01 - males, p ≤ 0.05 - females week 1 and p ≤ 0.01 - males/females week 2).

FOOD EFFICIENCY
no examined

WATER CONSUMPTION
not examined

OPHTHALMOSCOPIC EXAMINATION
no effects

HAEMATOLOGY
no effects

CLINICAL CHEMISTRY
There was no definite treatment related effect on clinical pathologic parameters. However, the possibility of treatment-related effects was suggested by differences between control and treatment group mean serum potassium, albumin, and total protein concentrations. Group mean serum potassium concentration for males and females in the 1000 mg/kg/day group was 11-15% lower than the control group means at the interim evaluation, but it was similar for treated and control groups at the final clinical pathologic evaluation. Slightly lower than control group means for femals of the 316 mg/kg/day dose group (7%, p ≤ 0.05)and for females of the 1000 mg/kg/day dose group (9% p ≤ 0.01) appeare to be a result of higher than expected values in the control group rather than abnormally low values in the treated groups.

URINALYSIS
no effects

NEUROBEHAVIOUR
not examined

ORGAN WEIGHTS
no effects

GROSS PATHOLOGY
no effects

HISTOPATHOLOGY: NON-NEOPLASTIC
no effects

HISTOPATHOLOGY: NEOPLASTIC (if applicable)
not examined

HISTORICAL CONTROL DATA (if applicable)

Dose descriptor:

NOAEL

Effect level:

316 mg/kg bw/day (actual dose received)

Sex:

male/female

Basis for effect level:

other: overall effects in high dose group clinical signs (hypoactivity, ataxia); body weight; food consumption; clinical chemistry

Critical effects observed:

not specified

Read-across justification: for details please see read-across report in section 13.

Four rats were determined to have died from perforation of the esophagus (incurred during dosing). The case of death of another ten rats was acute tracheitis (or bronchial hemmorhage), which was apparently due to the regurgitation and subsequent aspiration of the isobutyl alcohol and/or its vapors into the trachea (and probably the nasal cavity). The acute lesions of the trachea (inflammation and/or necrosis) seen histologically support this theory.

Executive summary:

In a subchronic toxicity study (90 days), isobutanol (purity not stated) was administered to 30 rats/sex/dose by gavage at dose levels of 0, 100, 316, and 1000 mg/kg bw/day on the basis of a preliminary range finding study.

 

Treatment related effects were seen only at a dose level of 1000 mg/kg bw/day, but not at dose levels of 100 or 316 mg/kg bw/day. At the 1000 mg/kg bw/day dose level, hypoactivity was observed in all rats and body weight gain in the males was 18% below the control average during week 1. Food consumption averages were below those of the controls for both males and females during week 1 and 2. In addition, serum potassium averages (both sexes) were 11-15% below control averages at the interim evaluation (day 29) only and this may have been related to treatment.

No difference between dosed groups and controls were found for ophthalmoscopic examination, haematology, urinalysis, organ weights, gross pathology and histopathology.

The NOAEL is 316 mg/kg bw/day for males and females (EPA/Res. Triangle Inst. 1987)

This subchronic toxicity study in the rat is acceptable and satisfies the guideline requirements for a subchronic oral study (OECD 408).

Endpoint conclusion

Endpoint conclusion:

adverse effect observed

Dose descriptor:

NOAEL

495 mg/kg bw/day

Study duration:

subchronic

Species:

rat

Quality of whole database:

sufficiently reliable studies available for read-across substance

Repeated dose toxicity: inhalation - systemic effects

Link to relevant study records

Reference

Endpoint:

sub-chronic toxicity: inhalation

Type of information:

experimental study

Adequacy of study:

key study

Study period:

From 12 SEP 1994 to 16 AUG 1996

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: Guideline Study (EPA OTS 798.2450), but as read-across from supporting substance maximum reliability is 2 Read-across hypothesis: for details please see read-across report in section 13

Qualifier:

according to guideline

Guideline:

EPA OTS 798.2450 (90-Day Inhalation Toxicity)

Deviations:

no

GLP compliance:

yes

Limit test:

no

Species:

rat

Strain:

Sprague-Dawley

Sex:

male/female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Charles River Kingston (Stone ridge, NY)
- Age at study initiation: 60 days
- Weight at study initiation: 271 +/- 7 g (males); 215 +/- 8 g (females)
- Fasting period before study: no
- Housing: individually during non expsure periods
- Diet: Certified Rodent Diet (Agway Prolab RMH 3200, ground chow), ad libitum except during exposure
- Water: ad libitum, except during exposure
- Acclimation period: 12 days


ENVIRONMENTAL CONDITIONS
- Temperature: 67-75°F
- Humidity: 46-60%
- Photoperiod (hrs dark / hrs light): 12/12

Route of administration:

inhalation: vapour

Type of inhalation exposure:

whole body

Vehicle:

other: unchanged (no vehicle)

Details on inhalation exposure:

GENERATION OF TEST ATMOSPHERE / CHAMBER DESCRIPTION
- Exposure apparatus: 4200 L stainless-steel and glass inhalation chambers
- Method of holding animals in test chamber: cages
- System of generating vapour: test substance was metered into glass distillation columns packed with glass beads; filtered, compressed air was passed through the glass bead-packed columns to evaporate the test substance; distillation columns were heated to about 50°C to enhance vaporization; the resultant vapour was directed via glass tubing to a tee just upstream of the inhalation chamber where it was mixed with filtered, conditioned outside air
- Temperature, humidity in air chamber: 21.1-24.7°C; 36.7-68.7%
- Air flow rate: 836 to 965 Lpm
- Air change rate: 12 to 14 air changes per hour
- Method of particle size determination: Micro Laser Particle counter (µLPC-301, Particle Measuring Systems, Inc, Coulder, USA); indicating that an aerosol fo the test subsance was not present



TEST ATMOSPHERE
- Brief description of analytical method used: MIRAN IA infrared gas analyzer (Wilks Foxboro Analytical, South Norwalk, CT) set at a wavelength of 3.38 µM
- Samples taken from breathing zone: no; collection of chamber vapour samples

Analytical verification of doses or concentrations:

yes

Details on analytical verification of doses or concentrations:

- MIRAN IA infrared gas analyzer (Wilks Foxboro Analytical, South Norwalk, CT) set at a wavelength of 3.38 µM
- chamber vapour samples were continuously collected from each chamber throught TEFLON tubing (3/16" i.d.)
- valve position was pepriodically changed to sample from each chamber at least once each hour

Duration of treatment / exposure:

13 weeks

Frequency of treatment:

6 hours per day, 5 days per week

Dose / conc.:

500 ppm (nominal)

Dose / conc.:

1 500 ppm (nominal)

Dose / conc.:

3 000 ppm (nominal)

No. of animals per sex per dose:

15

Control animals:

yes, sham-exposed

Details on study design:

- Dose selection rationale: Range finding study: 2-Weeks repeated exposure in which animals were exposed to 0, 750, 1500 or 3000 ppm n-butyl acetate. The test substance produced concentration-related reductions in general activity levels during exposure periods. Animals appeared to acclimate to the 750 and 1500 ppm concentrations but not to 3000 ppm. Mean body weights for the female 1500 ppm animals and for the 3000 ppm male and female animals were lower than the control group on Days 7 and 14, but no statistically significant differences were noted. 3000 ppm was selected as an exposure concentration that would produce overt signs of toxicity, and 500 ppm was selected as an exposure concentration that was expected to have no effect. An exposure concentration of 1500 ppm was selected as the intermediate exposure concentration.

Positive control:

none

Observations and examinations performed and frequency:

CAGE SIDE OBSERVATIONS: Yes
- Time schedule: during exposure and once per day on weekends
- Cage side observations checked were included.


DETAILED CLINICAL OBSERVATIONS: Yes
- Time schedule: before and after exposure


BODY WEIGHT: Yes
- Time schedule for examinations: weekly


FOOD CONSUMPTION: YES
- Time schedule for examinations: weekly

FOOD EFFICIENCY:
- Body weight gain in kg/food consumption in kg per unit time X 100 calculated as time-weighted averages from the consumption and body weight gain data: No


WATER CONSUMPTION: No


OPHTHALMOSCOPIC EXAMINATION: Yes
- Time schedule for examinations: prior to the start of the study and during the last week of exposure
- Dose groups that were examined: all animals prior to the start of the study; animals from the control and high-concentration group during the last week of exposure


HAEMATOLOGY: Yes
- Time schedule for collection of blood: day 30 and 90 of the study
- Anaesthetic used for blood collection: Yes (Metofane)
- Animals fasted: Yes
- How many animals: 5 per sex per dose group
- Parameters checked:
Whole blood: hemoglobin concentration, red blood cell count, white blood cell count, hematocrit, red blood cell indices, prothrombin time
Blood smears: cellular morphology and differential white blood cell count


CLINICAL CHEMISTRY: Yes
- Time schedule for collection of blood: day 30 and 90 of the study
- Anaesthetic used for blood collection: Yes (Metofane)
- Animals fasted: Yes
- How many animals: 5 per sex per dose group
- Parameters checked:
Blood serum: aspartate aminotransferase, sorbitol dehydrogenase, alkaline phosphatase, creatinine, albumin, total protein, total bilirubin, alanine aminotransferase, gamma glutamyltranspeptidase, urea nitrogen, glucose, calcium, phosphorus


URINALYSIS: No

NEUROBEHAVIOURAL EXAMINATION: No

OTHER: Organ weights (liver, kidneys, testes or ovaries, spleen adrenal glands, lungs, brain)

Sacrifice and pathology:

GROSS PATHOLOGY: Yes

HISTOPATHOLOGY: Yes (embedded in paraffin, sectioned at 5 µm and stained with hematoxylin and eosin; nasal passages were decalcified prior to being embedded and sectioned); all tissues (see below) were examined microscopically from the control and high-concentration groups, in addition, the lungs, nasal passages, thymus (males only), stomach (females only), and gross lesions were examined from the mid- and low concentration group
- tissues examined: nasal passages, trachea, larynx, lungs, esophagus, stomach, duodenum, jejunum, ileum, cecum, colon, rectum, heart, aorta, adrenal glands, pituitary gland, thymus, pancreas, urinary bladder, thyroid gland, parathyroid gland, spleen, liver, kidneys, mesenteric lymph nodes, sternum (with bone marrow), right testis, right epididymis, male accessory sex glands, ovaries, vagina, uterus, fallopian tubes, salivary glands, gross lesions

Other examinations:

- assessment of sperm morphology and development (reported in section 7.8)

Statistics:

Bartlett's test, one-way analysis of variance, duncan's multiple range test, Kruskal-Wallis H-test and Mann-Whitney U-test

Clinical signs:

effects observed, treatment-related

Mortality:

mortality observed, treatment-related

Body weight and weight changes:

effects observed, treatment-related

Food consumption and compound intake (if feeding study):

effects observed, treatment-related

Food efficiency:

not specified

Water consumption and compound intake (if drinking water study):

not specified

Ophthalmological findings:

no effects observed

Haematological findings:

effects observed, treatment-related

Clinical biochemistry findings:

effects observed, treatment-related

Urinalysis findings:

not examined

Behaviour (functional findings):

not examined

Organ weight findings including organ / body weight ratios:

effects observed, treatment-related

Gross pathological findings:

effects observed, treatment-related

Histopathological findings: non-neoplastic:

effects observed, treatment-related

Histopathological findings: neoplastic:

not examined

Details on results:

CLINICAL SIGNS AND MORTALITY
- no spontaneous mortality occurred during the study

3000 ppm group:
- reduced activity levels of generally minor severity during exposure (less movement, decreased alertness, slower response to tapping on the chamber wall)
- Sialorrhea was observed in three animals for no more than one or two exposure days
- red discoloration of the chin hair occurred in several females for no more than one or two exposure days

1500 ppm group:
- reduced activity of generally minimal severity during exposure periods (except the first 5 hours of Day 0 and the first hour or two of Days 1 and 2)

Animals in all groups had prophyrin nasal discharges and dried porphyrin stains around the nose, which occasionally persisted till the next morning. Animals from all groups exhibited discolored-red facial hair, usually the chin hair (slightly higher in the 3000 ppm group than in other groups)

BODY WEIGHT AND WEIGHT GAIN

3000 ppm group:
- significantly reduced mean body weights and body weight gains in males and females; overall weight gains were 62% and 78% of weight gains for the control group (males and females, respectively)

1500 ppm group:
- significantly reduced mean body weights and body weight gains in males and females; overall weight gains were 77% and 70% of weight gains for the control group (males and females, respectively)

500 ppm group:
- body weights and body weight gains were not affected; overall weight gains were 90% and 107% of weight gains for the control group (males and females, respectively)

FOOD CONSUMPTION

3000 ppm group:
- significantly lower than for the control group
- mean weekly feed consumption values were 14-25% or 6-16% lower than the control group in male and female rats, respectively

1500 ppm group:
- significantly lower than for the control group
- mean weekly feed consumption values were 4-17% or 10-15% lower than the control group in male and female rats, respectively
500 ppm group:
- significantly (p - mean weekly feed consumption values were 3-12% lower than the control group in male rats and from 2% higher to 7% lower than the control group for female rats
FOOD EFFICIENCY
- no data

WATER CONSUMPTION
- no data

OPHTHALMOSCOPIC EXAMINATION
- no effects

HAEMATOLOGY
No significant differences in hematologic parameters were seen after 30 days on test. Significantly higher (p Evaluation of blood cell morphology did not suggest any compound-related effects. After 30 days on test, spherocytosis and poikilocytosis were seen in blood smears of animals from most groups. Increased polychromasia was observed in one male control rat (# 613), while decreased polychromasia was see in two female 3000 ppm rats (# 719 and 720). Howell-Jolly bodies in the blood and anisocytosis were also noted for Rat # 720. After 90 days on test, poikilocytosis was seen in animals from all groups. Anisocytosis was noted in animals from the control, 500, and 1500 ppm groups. Microcytosis was seen in one male 1500 ppm rat (# 632) and in one male 500 ppm rat (#624) and spherocytosis was seen in two male 1500 ppm rats (# 631 and 638).

CLINICAL CHEMISTRY
After 30 days on test, mean sodium concentrations for the male and female 3000 ppm groups were significantly lower (p After 90 days on test, mean albumin and total protein concentrations for the 3000 ppm female group were significantly lower (p
URINALYSIS
- not examined

NEUROBEHAVIOUR
- not examined

ORGAN WEIGHTS
Mean terminal body weights measured after exsanguination were significantly lower (p kidney weights for the 1500 female and 3000 ppm male and female groups were also significantly lower (p

GROSS PATHOLOGY
- no exposure related effects were observe in male rats.
- Two females of the 3000 ppm group showed hemorrhage involving the glandular stomach (minimal severity). White discoloration in the non-glandular stomach was also observe for these animals.
- No changes were seen in female rats from the 1500 and 500 ppm groups.

HISTOPATHOLOGY: NON-NEOPLASTIC
- exposure related changes were observed in the nasal passages and stomach of 1500 and 3000 ppm rats
- all male and female 3000 ppm rats and 4/10 male and 6/10 female 1500 ppm rats had necrosis of the olfactory epithelium (mild to moderate for the 3000 ppm group, mild for the 1500 ppm group).
- no lesions were observed in the nasal passages of the 500 ppm group
- 3/10 female rats of the 3000 ppm group had inflammation of the stomach mucosa (glandular or forestomach) of mild to minimal severity; the pathologist concluded that this effect was probably due to stress
- no effects were seen in the low- and mid concentration group
- thymus atrophy was observed in one male of the 3000 ppm group, this lesion was attributed to stress by the pathologist

HISTOPATHOLOGY: NEOPLASTIC (if applicable)
- not examined


OTHER FINDINGS
- No exposure-related effect on epidydimidal or testicular sperm count was observed. Effects on testicular staging or spermatogenic were not evaluated due to the unacceptable condition of tissue.

Dose descriptor:

NOAEC

Effect level:

500 ppm

Based on:

test mat.

Remarks:

n-butyl acetate

Sex:

male/female

Basis for effect level:

other: see 'Remark'

Critical effects observed:

not specified

Read-across justification: for details please see read-across report in section 13.

- overall time-weighted average analytical concentrations:

548.4; 1487.5, 3009.6 ppm for males

547.9, 1487.6, 3008.8 ppm for females

- target analytical concentration for the 500 ppm group was increased to 550 ppm to ensure that exposure concentration was at least 500 ppm at all locations of the eposure chamber

Conclusions:

Subchronic exposure of rats to n-butyl acetate vapour resulted in acute, transient signs of reduced activity levels during exposure to 1500 and 3000 ppm. Decreased body weight and feed consumption were noted for the 1500 and 3000 ppm groups, but there was no systemic or organ-specific toxicity. Signs of upper respiratory tract irritation were seen in the nasal passages of 1500 and 3000 ppm animals, but there was no evidence of pulmonary toxicity. The no-observed-adverse-effect concentration (NOAEC) for this study is considered to be 500 ppm (2.4 mg/L).

Executive summary:

Male and female Sprague-Dawley rats (15 animals/sex/dose group) were exposed to nominal concentrations of 0, 500, 1500 or 3000 ppm of n-butyl acetate for 6 hours per day, 5 days per week for 13 consecutive weeks. The time-weighted average analytical concentrations were within 10% of the target concentrations. Transient signs of sedation were observed during exposure to the 1500 and 3000 ppm concentrations. Body weights were significantly reduced in the mid and high concentration groups. Feed consumption was significantly lower in the 1500 and 3000 ppm group in comparison to the control group. Organ weights affected: weights of liver, kidneys and spleen were significantly lower for the males of the highest concentration goup. Testes and adrenal gland weights for the mid and high concentration groups and the lung weights for the 3000 ppm males were significantly higher than for the control group. Additionally, effects on the stomach (probably stress related) and pulmonary system were observed: Females of the highest concentration group showed signs of irritation of the glandular stomach and necrosis in the non-glandular stomach. Some rats of the 1500 and 3000 ppm group showed degeneration of the olfactory epithelium along the dorsal medial meatus and ethomtubinates of the nasal passages. The severity was mild to moderate for the 3000 ppm group and minimal to mild for the 1500 ppm group. There was no systemic, organ specific toxicity. The no-observed-adverse-effect concentration (NOAEC) for this study is 500 ppm (2.4 mg/L) (Bernard and David, 1996; David et al., 2001).

The study is reliable with restriction (RL2) as maximum reliability for read across from supporting substances is 2.

Endpoint conclusion

Endpoint conclusion:

adverse effect observed

Dose descriptor:

NOAEC

2 410 mg/m³

Study duration:

subchronic

Species:

rat

Quality of whole database:

sufficiently reliable studies available for read-across substances

Repeated dose toxicity: inhalation - local effects

Link to relevant study records

Reference

Endpoint:

sub-chronic toxicity: inhalation

Type of information:

experimental study

Adequacy of study:

key study

Study period:

From 12 SEP 1994 to 16 AUG 1996

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: Guideline Study (EPA OTS 798.2450), but as read-across from supporting substance maximum reliability is 2 Read-across hypothesis: for details please see read-across report in section 13

Qualifier:

according to guideline

Guideline:

EPA OTS 798.2450 (90-Day Inhalation Toxicity)

Deviations:

no

GLP compliance:

yes

Limit test:

no

Species:

rat

Strain:

Sprague-Dawley

Sex:

male/female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Charles River Kingston (Stone ridge, NY)
- Age at study initiation: 60 days
- Weight at study initiation: 271 +/- 7 g (males); 215 +/- 8 g (females)
- Fasting period before study: no
- Housing: individually during non expsure periods
- Diet: Certified Rodent Diet (Agway Prolab RMH 3200, ground chow), ad libitum except during exposure
- Water: ad libitum, except during exposure
- Acclimation period: 12 days


ENVIRONMENTAL CONDITIONS
- Temperature: 67-75°F
- Humidity: 46-60%
- Photoperiod (hrs dark / hrs light): 12/12

Route of administration:

inhalation: vapour

Type of inhalation exposure:

whole body

Vehicle:

other: unchanged (no vehicle)

Details on inhalation exposure:

GENERATION OF TEST ATMOSPHERE / CHAMBER DESCRIPTION
- Exposure apparatus: 4200 L stainless-steel and glass inhalation chambers
- Method of holding animals in test chamber: cages
- System of generating vapour: test substance was metered into glass distillation columns packed with glass beads; filtered, compressed air was passed through the glass bead-packed columns to evaporate the test substance; distillation columns were heated to about 50°C to enhance vaporization; the resultant vapour was directed via glass tubing to a tee just upstream of the inhalation chamber where it was mixed with filtered, conditioned outside air
- Temperature, humidity in air chamber: 21.1-24.7°C; 36.7-68.7%
- Air flow rate: 836 to 965 Lpm
- Air change rate: 12 to 14 air changes per hour
- Method of particle size determination: Micro Laser Particle counter (µLPC-301, Particle Measuring Systems, Inc, Coulder, USA); indicating that an aerosol fo the test subsance was not present



TEST ATMOSPHERE
- Brief description of analytical method used: MIRAN IA infrared gas analyzer (Wilks Foxboro Analytical, South Norwalk, CT) set at a wavelength of 3.38 µM
- Samples taken from breathing zone: no; collection of chamber vapour samples

Analytical verification of doses or concentrations:

yes

Details on analytical verification of doses or concentrations:

- MIRAN IA infrared gas analyzer (Wilks Foxboro Analytical, South Norwalk, CT) set at a wavelength of 3.38 µM
- chamber vapour samples were continuously collected from each chamber throught TEFLON tubing (3/16" i.d.)
- valve position was pepriodically changed to sample from each chamber at least once each hour

Duration of treatment / exposure:

13 weeks

Frequency of treatment:

6 hours per day, 5 days per week

Dose / conc.:

500 ppm (nominal)

Dose / conc.:

1 500 ppm (nominal)

Dose / conc.:

3 000 ppm (nominal)

No. of animals per sex per dose:

15

Control animals:

yes, sham-exposed

Details on study design:

- Dose selection rationale: Range finding study: 2-Weeks repeated exposure in which animals were exposed to 0, 750, 1500 or 3000 ppm n-butyl acetate. The test substance produced concentration-related reductions in general activity levels during exposure periods. Animals appeared to acclimate to the 750 and 1500 ppm concentrations but not to 3000 ppm. Mean body weights for the female 1500 ppm animals and for the 3000 ppm male and female animals were lower than the control group on Days 7 and 14, but no statistically significant differences were noted. 3000 ppm was selected as an exposure concentration that would produce overt signs of toxicity, and 500 ppm was selected as an exposure concentration that was expected to have no effect. An exposure concentration of 1500 ppm was selected as the intermediate exposure concentration.

Positive control:

none

Observations and examinations performed and frequency:

CAGE SIDE OBSERVATIONS: Yes
- Time schedule: during exposure and once per day on weekends
- Cage side observations checked were included.


DETAILED CLINICAL OBSERVATIONS: Yes
- Time schedule: before and after exposure


BODY WEIGHT: Yes
- Time schedule for examinations: weekly


FOOD CONSUMPTION: YES
- Time schedule for examinations: weekly

FOOD EFFICIENCY:
- Body weight gain in kg/food consumption in kg per unit time X 100 calculated as time-weighted averages from the consumption and body weight gain data: No


WATER CONSUMPTION: No


OPHTHALMOSCOPIC EXAMINATION: Yes
- Time schedule for examinations: prior to the start of the study and during the last week of exposure
- Dose groups that were examined: all animals prior to the start of the study; animals from the control and high-concentration group during the last week of exposure


HAEMATOLOGY: Yes
- Time schedule for collection of blood: day 30 and 90 of the study
- Anaesthetic used for blood collection: Yes (Metofane)
- Animals fasted: Yes
- How many animals: 5 per sex per dose group
- Parameters checked:
Whole blood: hemoglobin concentration, red blood cell count, white blood cell count, hematocrit, red blood cell indices, prothrombin time
Blood smears: cellular morphology and differential white blood cell count


CLINICAL CHEMISTRY: Yes
- Time schedule for collection of blood: day 30 and 90 of the study
- Anaesthetic used for blood collection: Yes (Metofane)
- Animals fasted: Yes
- How many animals: 5 per sex per dose group
- Parameters checked:
Blood serum: aspartate aminotransferase, sorbitol dehydrogenase, alkaline phosphatase, creatinine, albumin, total protein, total bilirubin, alanine aminotransferase, gamma glutamyltranspeptidase, urea nitrogen, glucose, calcium, phosphorus


URINALYSIS: No

NEUROBEHAVIOURAL EXAMINATION: No

OTHER: Organ weights (liver, kidneys, testes or ovaries, spleen adrenal glands, lungs, brain)

Sacrifice and pathology:

GROSS PATHOLOGY: Yes

HISTOPATHOLOGY: Yes (embedded in paraffin, sectioned at 5 µm and stained with hematoxylin and eosin; nasal passages were decalcified prior to being embedded and sectioned); all tissues (see below) were examined microscopically from the control and high-concentration groups, in addition, the lungs, nasal passages, thymus (males only), stomach (females only), and gross lesions were examined from the mid- and low concentration group
- tissues examined: nasal passages, trachea, larynx, lungs, esophagus, stomach, duodenum, jejunum, ileum, cecum, colon, rectum, heart, aorta, adrenal glands, pituitary gland, thymus, pancreas, urinary bladder, thyroid gland, parathyroid gland, spleen, liver, kidneys, mesenteric lymph nodes, sternum (with bone marrow), right testis, right epididymis, male accessory sex glands, ovaries, vagina, uterus, fallopian tubes, salivary glands, gross lesions

Other examinations:

- assessment of sperm morphology and development (reported in section 7.8)

Statistics:

Bartlett's test, one-way analysis of variance, duncan's multiple range test, Kruskal-Wallis H-test and Mann-Whitney U-test

Clinical signs:

effects observed, treatment-related

Mortality:

mortality observed, treatment-related

Body weight and weight changes:

effects observed, treatment-related

Food consumption and compound intake (if feeding study):

effects observed, treatment-related

Food efficiency:

not specified

Water consumption and compound intake (if drinking water study):

not specified

Ophthalmological findings:

no effects observed

Haematological findings:

effects observed, treatment-related

Clinical biochemistry findings:

effects observed, treatment-related

Urinalysis findings:

not examined

Behaviour (functional findings):

not examined

Organ weight findings including organ / body weight ratios:

effects observed, treatment-related

Gross pathological findings:

effects observed, treatment-related

Histopathological findings: non-neoplastic:

effects observed, treatment-related

Histopathological findings: neoplastic:

not examined

Details on results:

CLINICAL SIGNS AND MORTALITY
- no spontaneous mortality occurred during the study

3000 ppm group:
- reduced activity levels of generally minor severity during exposure (less movement, decreased alertness, slower response to tapping on the chamber wall)
- Sialorrhea was observed in three animals for no more than one or two exposure days
- red discoloration of the chin hair occurred in several females for no more than one or two exposure days

1500 ppm group:
- reduced activity of generally minimal severity during exposure periods (except the first 5 hours of Day 0 and the first hour or two of Days 1 and 2)

Animals in all groups had prophyrin nasal discharges and dried porphyrin stains around the nose, which occasionally persisted till the next morning. Animals from all groups exhibited discolored-red facial hair, usually the chin hair (slightly higher in the 3000 ppm group than in other groups)

BODY WEIGHT AND WEIGHT GAIN

3000 ppm group:
- significantly reduced mean body weights and body weight gains in males and females; overall weight gains were 62% and 78% of weight gains for the control group (males and females, respectively)

1500 ppm group:
- significantly reduced mean body weights and body weight gains in males and females; overall weight gains were 77% and 70% of weight gains for the control group (males and females, respectively)

500 ppm group:
- body weights and body weight gains were not affected; overall weight gains were 90% and 107% of weight gains for the control group (males and females, respectively)

FOOD CONSUMPTION

3000 ppm group:
- significantly lower than for the control group
- mean weekly feed consumption values were 14-25% or 6-16% lower than the control group in male and female rats, respectively

1500 ppm group:
- significantly lower than for the control group
- mean weekly feed consumption values were 4-17% or 10-15% lower than the control group in male and female rats, respectively
500 ppm group:
- significantly (p - mean weekly feed consumption values were 3-12% lower than the control group in male rats and from 2% higher to 7% lower than the control group for female rats
FOOD EFFICIENCY
- no data

WATER CONSUMPTION
- no data

OPHTHALMOSCOPIC EXAMINATION
- no effects

HAEMATOLOGY
No significant differences in hematologic parameters were seen after 30 days on test. Significantly higher (p Evaluation of blood cell morphology did not suggest any compound-related effects. After 30 days on test, spherocytosis and poikilocytosis were seen in blood smears of animals from most groups. Increased polychromasia was observed in one male control rat (# 613), while decreased polychromasia was see in two female 3000 ppm rats (# 719 and 720). Howell-Jolly bodies in the blood and anisocytosis were also noted for Rat # 720. After 90 days on test, poikilocytosis was seen in animals from all groups. Anisocytosis was noted in animals from the control, 500, and 1500 ppm groups. Microcytosis was seen in one male 1500 ppm rat (# 632) and in one male 500 ppm rat (#624) and spherocytosis was seen in two male 1500 ppm rats (# 631 and 638).

CLINICAL CHEMISTRY
After 30 days on test, mean sodium concentrations for the male and female 3000 ppm groups were significantly lower (p After 90 days on test, mean albumin and total protein concentrations for the 3000 ppm female group were significantly lower (p
URINALYSIS
- not examined

NEUROBEHAVIOUR
- not examined

ORGAN WEIGHTS
Mean terminal body weights measured after exsanguination were significantly lower (p kidney weights for the 1500 female and 3000 ppm male and female groups were also significantly lower (p

GROSS PATHOLOGY
- no exposure related effects were observe in male rats.
- Two females of the 3000 ppm group showed hemorrhage involving the glandular stomach (minimal severity). White discoloration in the non-glandular stomach was also observe for these animals.
- No changes were seen in female rats from the 1500 and 500 ppm groups.

HISTOPATHOLOGY: NON-NEOPLASTIC
- exposure related changes were observed in the nasal passages and stomach of 1500 and 3000 ppm rats
- all male and female 3000 ppm rats and 4/10 male and 6/10 female 1500 ppm rats had necrosis of the olfactory epithelium (mild to moderate for the 3000 ppm group, mild for the 1500 ppm group).
- no lesions were observed in the nasal passages of the 500 ppm group
- 3/10 female rats of the 3000 ppm group had inflammation of the stomach mucosa (glandular or forestomach) of mild to minimal severity; the pathologist concluded that this effect was probably due to stress
- no effects were seen in the low- and mid concentration group
- thymus atrophy was observed in one male of the 3000 ppm group, this lesion was attributed to stress by the pathologist

HISTOPATHOLOGY: NEOPLASTIC (if applicable)
- not examined


OTHER FINDINGS
- No exposure-related effect on epidydimidal or testicular sperm count was observed. Effects on testicular staging or spermatogenic were not evaluated due to the unacceptable condition of tissue.

Dose descriptor:

NOAEC

Effect level:

500 ppm

Based on:

test mat.

Remarks:

n-butyl acetate

Sex:

male/female

Basis for effect level:

other: see 'Remark'

Critical effects observed:

not specified

Read-across justification: for details please see read-across report in section 13.

- overall time-weighted average analytical concentrations:

548.4; 1487.5, 3009.6 ppm for males

547.9, 1487.6, 3008.8 ppm for females

- target analytical concentration for the 500 ppm group was increased to 550 ppm to ensure that exposure concentration was at least 500 ppm at all locations of the eposure chamber

Conclusions:

Subchronic exposure of rats to n-butyl acetate vapour resulted in acute, transient signs of reduced activity levels during exposure to 1500 and 3000 ppm. Decreased body weight and feed consumption were noted for the 1500 and 3000 ppm groups, but there was no systemic or organ-specific toxicity. Signs of upper respiratory tract irritation were seen in the nasal passages of 1500 and 3000 ppm animals, but there was no evidence of pulmonary toxicity. The no-observed-adverse-effect concentration (NOAEC) for this study is considered to be 500 ppm (2.4 mg/L).

Executive summary:

Male and female Sprague-Dawley rats (15 animals/sex/dose group) were exposed to nominal concentrations of 0, 500, 1500 or 3000 ppm of n-butyl acetate for 6 hours per day, 5 days per week for 13 consecutive weeks. The time-weighted average analytical concentrations were within 10% of the target concentrations. Transient signs of sedation were observed during exposure to the 1500 and 3000 ppm concentrations. Body weights were significantly reduced in the mid and high concentration groups. Feed consumption was significantly lower in the 1500 and 3000 ppm group in comparison to the control group. Organ weights affected: weights of liver, kidneys and spleen were significantly lower for the males of the highest concentration goup. Testes and adrenal gland weights for the mid and high concentration groups and the lung weights for the 3000 ppm males were significantly higher than for the control group. Additionally, effects on the stomach (probably stress related) and pulmonary system were observed: Females of the highest concentration group showed signs of irritation of the glandular stomach and necrosis in the non-glandular stomach. Some rats of the 1500 and 3000 ppm group showed degeneration of the olfactory epithelium along the dorsal medial meatus and ethomtubinates of the nasal passages. The severity was mild to moderate for the 3000 ppm group and minimal to mild for the 1500 ppm group. There was no systemic, organ specific toxicity. The no-observed-adverse-effect concentration (NOAEC) for this study is 500 ppm (2.4 mg/L) (Bernard and David, 1996; David et al., 2001).

The study is reliable with restriction (RL2) as maximum reliability for read across from supporting substances is 2.

Endpoint conclusion

Endpoint conclusion:

adverse effect observed

Dose descriptor:

NOAEC

2 410 mg/m³

Study duration:

subchronic

Species:

rat

Quality of whole database:

sufficiently reliable studies available for read-across substances

Repeated dose toxicity: dermal - systemic effects

Endpoint conclusion

Endpoint conclusion:

no study available

Repeated dose toxicity: dermal - local effects

Endpoint conclusion

Endpoint conclusion:

no study available

Additional information

For isobutyl acetate, no study concerning repeated dose toxicity could be identified. As substitute, data for isobutanol and isobutyl isobutyrate will be used (read-across from supporing substance). For details on read-across hypothesis and justification please see read-across report in IUCLID section 13..

 

Effect levels derived for the supporting substances isobutanol and isobutyl isobutyrate will be transformed to effects levels for isobutyl acetate using the respective molecular weights. These values are used to evaluate the toxic potential of isobutyl acetate.

 

The repeated dose toxicity of isobutanol has been evaluated in two valid studies of high reliability which are used as key studies (oral administration: EPA/Res. Triangle Inst. 1987 and inhalation exposure: Li/Monsanto 1999). The study with isobutyl isoburate (oral exposure: Drake 1978) is used as supporting study.

 

Oral administration (gavage)

Supporting substance: isobutanol

In a valid subchronic toxicity study (90 days) similar to OECD TG 408, isobutanol (purity not stated) was administered to 30 rats/sex/dose by gavage at dose levels of 0, 100, 316, and 1000 mg/kg bw/day on the basis of a preliminary range finding study.

  

Treatment related effects were seen only at a dose level of 1000 mg/kg bw/day, but not at dose levels of 100 or 316 mg/kg bw/day. At the 1000 mg/kg bw/day dose level, hypoactivity and ataxia was observed in all rats and body weight gain in the males was 18% below the control average during week 1. Food consumption averages were below those of the controls for both males and females during week 1 and 2. In addition, serum potassium averages (both sexes) were 11-15% below control averages at the interim evaluation (day 29) only and this may have been related to treatment.

No difference between dosed groups and controls were found for ophthalmoscopic examination, haematology, urinalysis, organ weights, gross pathology and histopathology.

Based on these results (transient neurotoxic effects: hypoactivity and ataxia) the neurologic system was identified as target organ.

The NOAEL of isobutanol is 316 mg/kg bw/day for males and females (EPA/Res. Triangle Inst. 1987)

Deduction of the NOAEL (oral) for isobutyl acetate

The NOAEL of isobutyl acetate will be calculated on basis of the NOAEL of isobutanol (EPA/Res. Triangle Inst. 1987) using the respective molecular weights (116.16 and 74.12).

The deduced oral NOAEL for isobutyl acetate is 495 mg/kg bw/day.

 

Supporting substance: isobutyl isobutyrate

In a valid subchronic toxicity study (18 weeks) similar to OECD TG 408, isobutyl isobutyrate (purity >= 98%) was administered to 15 male and female Wistar rats per group by gavage at dose levels of 0, 10, 100, and 1000 mg/kg bw/day. Observation parameters were slightly reduced compared to OECD TG 408 (no behavioral/neurological observations, limited blood parameters, no clinical chemistry).

No treatment related effects were observed even at the highest dose level in male and female rats.

Results do not indicate a specific target organ.

The NOAEL is 1000 mg/kg bw/day for males and females based on overall effects (Drake 1978)

Deduction of the NOAEL (oral) for isobutyl acetate

The NOAEL of isobutyl acetate will be calculated on basis of the NOAEL of isobutyl isobutyrate (Drake 1978) using the respective molecular weights (116.16 and 144.21).

The deduced oral NOAEL of isobutyl acetate is 805 mg/kg bw/day.

 

Inhalation exposure

Supporting substance: n-butyl acetate

In a valid subchronic (13 weeks) inhalation toxicity study according to EPA OTS 798.2450, n-butyl acetate (purity > 99%) was administered to 15 Sprague-Dawley rats/sex/dose by whole body exposure at dose levels of 0, 500, 1500, and 3000 ppm for 6 hours per day, 5 days/week. Transient signs of sedation were observed during exposure to the 1500 and 3000 ppm. Body weights were significantly reduced in the mid and high concentration groups. Further, some effects on food consumption, stomach (only high concentration) as well as on organ weights were observed in the mid and high dose group. Some rats of the mid and high concentration group showed degeneration fo the olfactory epithelium along the dorsal medial meatus and ethomtubinates of the nasal passages. The severity was mild to moderate for the 3000 ppm group and minmal to mild for the 1500 ppm group (Bernard and David, 1996; David et al., 2001; corresponds to IUCLID study record OPP/CMA, 1996). These effects were confirmed by a 13 -week neurotoxicity study of the same research group (David et al., 1998; corresponds to IUCLID study record OPP/CMA, 1998).

Based on these findings, the NOAEC for repeated dose toxicity is considered to be 500 ppm (ca. 2410 mg/m³) for males and females.

Based on neurobehavioral observation tests performed in this study, a NOAEC for neurotoxicity of 500 ppm (ca. 2410 mg/m³) for males and females can be deduced (David et al., 1998).

Deduction of the NOAEC (inhalation ) for isobutyl acetate

The NOAEC of isobutyl acetate will be calculated on basis of the NOAEC of n-butyl acetate (David et al., 1998 and 2001) using the mass concentration /m³ and the respective molecular weights (116.16 and 116.16).

The deduced NOAEC for isobutyl acetate is 2.4 mg/L (500 ppm).

Supporting substance: isobutanol

In a valid subchronic (14 weeks) inhalation toxicity study similar to OECD TG 413, isobutanol (purity 99%) was administered to 20 or 10 Sprague-Dawley rats/sex/dose (controls and 2500 ppm group 20 animals, 250 and 1000 ppm group 10 animals) by dynamic whole body exposure at dose levels of 0, 250, 1000, and 2500 ppm for 6 hours per day, 5 days/week. Doses were selected on the basis of a preliminary range finding study.

  

Unspecific treatment related effects (decreased response to external stimuli on the exposure chamber) were seen for all dose levels only during exposure. This effect disappeared immediately after exposure. It is regarded as a non-specific acute effect due to the narcotic properties of isobutanol. It was very slight and transient, and therefore it is not regarded as an adverse effect under the conditions of this study.

   In the female 2500 ppm dose group, total erythrocyte count, hemoglobin, and hematocrit were slightly elevated statistically different from controls (p ≤ 0.05). The changes were however small and the biological significance is low. This effect was not seen in any of the other groups and is estimated not to be of biological significance.

   All other observed parameters did not show any statistically significant effects. No differences between dosed groups and controls were found for body weight, food consumption, ophthalmoscopic examination, clinical observation, clinical chemistry, neurobehavioral observations, organ weights, gross pathology, and histopathology.

  

Based on these findings, the NOAEC for repeated dose toxicity is considered to be 2500 ppm (ca. 7700 mg/m³) for males and females.

  

Based on neurobehavioral observation tests performed in this study, a NOEC for neurotoxicity of 2500 ppm (ca. 7700 mg/m³) for males and females can be deduced (Li/Monsanto 1999).

These findings for isobutanol are supported by a developmental toxicity study in rabbits. Rabbits (15 females) were exposed to isobutanol (purity 99.8%) concentrations of 0, 500, 2500 and 10000 ppm (6 h/d) from day 7 through 19 of gestation. All animals were killed on day 29 of gestation. The fetuses were removed and examined for compound related effects. There were no develpmental effects observed in the fetuses. Maternal animals of the highest concentration showed retardation in body weight change, expecially during the firt phase of the exposure, indicating maternal toxicity (Klimisch/BASF, 1990). The maternal NOAEC was 2500 ppm in this study and supports the findings in rats discussed above.

Deduction of the NOAEC (inhalation ) for isobutyl acetate

The NOAEC of isobutyl acetate will be calculated on basis of the NOAEC of isobutanol (Li/Monsanto 1999) using the mass concentration /m³ and the respective molecular weights (116.16 and 74.12).

The deduced NOAEC for isobutyl acetate is 12 mg/L (2500 ppm).

Justification for selection of repeated dose toxicity via oral route - systemic effects endpoint:
Reliable study with read-accross substance isobutanol

Justification for selection of repeated dose toxicity inhalation - systemic effects endpoint:
Reliable study with read-accross substance n-butyl acetate

Justification for selection of repeated dose toxicity inhalation - local effects endpoint:
Reliable study with read-accross substance n-butyl acetate

Justification for selection of repeated dose toxicity dermal - systemic effects endpoint:
Inhalation exposure is the most relevant route of exposure based on the vapour pressure of the substance. Adequate studies with supporting substance isobutanol (relevant metabolite) using this route of exposure are available.

Justification for selection of repeated dose toxicity dermal - local effects endpoint:
Inhalation exposure is the most relevant route of exposure based on the vapour pressure of the substance. Adequate studies with supporting substance isobutanol (relevant metabolite) using this route of exposure are available.

Repeated dose toxicity: via oral route - systemic effects (target organ) neurologic: central nervous system

Repeated dose toxicity: inhalation - systemic effects (target organ) neurologic: central nervous system

Justification for classification or non-classification

On the basis of results originating from the supporting substances isobutanol and n-butyl acetate, isobutyl acetate should be classified for Specific Target Organ Toxicity Category 3 (STOT SE 3; H336) according to Regulation (EC) No 1272/2008 as transient narcotic effects may occur during exposure. No additional classification is necessary for repeated exposure as other effects after repeated exposure were only observed at doses above the guidance values for classification.

 

For oral application, a NOAEL of 495 mg/kg bw/day for isobutyl acetate was derived based on the 90 day study for isobutanol.

 

A NOAEC of 2.4 mg/L for isobutyl acetate was derived based on a 90 day repeated dose toxicity inhalation study with n-butyl acetate.

For dermal application, no data have been located.