N-butyl acetate

Endpoint summary

Description of key information

Oral LD50 values of 12790 mg/kg bw and 10760 mg/kg bw have been reported for male and female rats, respectively (key study, RL2). The oral LD50 value for rabbits is 7400 mg/kg bw as reported in a less reliable study (RL3). Dermal LD50 values for rabbits in reliable studies were > 14000 mg/kg bw (i.e. no animal died during the study thefore LD0 = 14000 mg/kg bw). Data on acute toxicity of n-butyl acetate after inhalation exposure are inconsistent. No definite LC50 value can be stated. In a weight of evidence approach it has been concluded that the inhalatory LC50 is probably above the limit for classification (20 mg/L).

Key value for chemical safety assessment

Acute toxicity: via oral route

Link to relevant study records

Reference

Endpoint:

acute toxicity: oral

Type of information:

experimental study

Adequacy of study:

key study

Study period:

1987

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: Was not conducted under GLP but has sufficient data for interpretation of results.

Reason / purpose for cross-reference:

reference to same study

Reason / purpose for cross-reference:

reference to other study

Qualifier:

equivalent or similar to guideline

Guideline:

OECD Guideline 423 (Acute Oral toxicity - Acute Toxic Class Method)

Deviations:

yes

Remarks:

(too many animals per dose group; doses tested choosen too high)

GLP compliance:

no

Test type:

acute toxic class method

Limit test:

no

Species:

rat

Strain:

Sprague-Dawley

Sex:

male/female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Weight at study initiation: 200 to 300 g
- Fasting period before study: overnight before dosing
- Diet: commercial available diet, ad libitum
- Water: municipal water, ad libitum

Route of administration:

oral: gavage

Vehicle:

unchanged (no vehicle)

Doses:

males: 16.0, 11.3 & 8.0 ml/kg.
females: 16.0, 11.3, 8.0 & 4.0 ml/kg.

No. of animals per sex per dose:

5 rats per sex at 16.0, 11.3, 8.0 ml/kg.
2 rats (female only) at 4.0 ml/kg.

Control animals:

no

Details on study design:

- Duration of observation period following administration: 14 days
- Frequency of observations and weighing: day 0, 7 and 14.
- Necropsy of survivors performed: yes
- Other examinations performed: clinical signs, body weight, gross pathology:

Statistics:

LD50's and the estimated LD50 slopes are calculated by the moving average method (Thompson, 1947; Weil, 1983).

Preliminary study:

none.

Sex:

male

Dose descriptor:

LD50

Effect level:

14.5 mL/kg bw

95% CL:

9.3 - 22.7

Remarks on result:

other: LD50 (calculated 12789 mg/kg, based on specific gravity of 0.882)

Sex:

female

Dose descriptor:

LD50

Effect level:

12.2 mL/kg bw

95% CL:

9.2 - 16.1

Remarks on result:

other: LD50 (calculated 10760 mg/kg, based on specific gravity of 0.882)

Mortality:

16.0 ml/kg: 3 of 5 males, 4 of 5 females
11.3 ml/kg: 1 of 5 males, 2 of 5 females

Clinical signs:

other: 16.0 ml/kg male: Sluggishness at 30 min; moribund appearance at 2 hr. Survivors recovered at 1 day. 16.0 ml/kg female: Sluggishness at 30 min to 1 hr; prostration in 2 at 1 hr; moribund appearance in 1 at 2 hr. Death of 2 at 3 hr. Survivor recovered at 1

Gross pathology:

16.0 ml/kg male: In victims, ventral surface of liver of 1 pale tan; stomachs tan or red, liquid or gas-filled. In survivors, nothing
remarkable.
16.0 ml/kg female: In victims, ventral surface of livers of 2 pale tan; stomachs of 2 filled with clear liquid. In survivor, nothing remarkable.
11.3 ml/kg male: In victim, stomach tan and red, distended, gas-filled. In survivors, lungs of 2 mottled light and dark red; kidneys of 2 mottled tan and brown.
11.3 ml/kg female: In victims, ventral surface of liver of 1 pale tan; stomachs distended, gas-filled. In survivors, lungs of 2 dark red.

Other findings:

None.

None.

Interpretation of results:

not classified

Remarks:

Migrated information Criteria used for interpretation of results: EU

Conclusions:

N-Butyl Acetate was slightly toxic following its administration by single peroral intubation. The acute oral LD50 for n-Butyl Acetate in male rats is 14.5 ml/kg bwt (9.3 - 22.7 ml/kg; calculated 12789 mg/kg, based on specific gravity of 0.882). The acute oral LD50 for n-Butyl Acetate in female rats is 12.2 ml/kg bwt (9.2 - 16.1; ml/kg; calculated 10760 mg/kg, based on specific gravity of 0.882 .

Executive summary:

N-Butyl Acetate was tested for acute oral toxicity in 5 male rats/dose at doses of 16.0, 11.3 and 8.0 ml/kg. Male dosing killed 3 out of 5 rats at 16.0 ml/kg, 1 of 5 at 11.3 ml/kg and 0 of 5 at 8.0 ml/kg. Acute oral toxicity in 5 female rats/dose at doses of 16.0, 11.3, 8.0 and 4.0 ml/kg resulted in 4 of 5 deaths at 16.0 ml/kg, 2 of 5 at 11.3 ml/kg, 0 of 5 at 8.0 ml/kg and 0 of 2 at 4.0 ml/kg.

Based on the results obtained, the LD50 was 14.5 ml/kg for male rats (calculated 12789 mg/kg, based on specific gravity of 0.882) and 12.2 ml/kg for female rats (calculated 10760 mg/kg) under the study conditions (Myers et al., 1987).

This study was judged to be reliable (RL2) and therefore was selected as key study.

Endpoint conclusion

Endpoint conclusion:

adverse effect observed

Dose descriptor:

LD50

Value:

10 760 mg/kg bw

Quality of whole database:

Two studies with high reliability show comparable results. Additional less reliable studies support the findings. The quality of the database is high.

Acute toxicity: via inhalation route

Endpoint conclusion

Endpoint conclusion:

adverse effect observed

Quality of whole database:

A huge database is available on acute inhalation toxicity. No definite study can be chosen and the endpoint is assessed in a Weight-of-evidence approach. The quality of the database is high.

Acute toxicity: via dermal route

Link to relevant study records

Reference

Endpoint:

acute toxicity: dermal

Type of information:

experimental study

Adequacy of study:

key study

Study period:

1987

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: Was not conducted under GLP but has sufficient data for interpretation of results.

Reason / purpose for cross-reference:

reference to same study

Reason / purpose for cross-reference:

reference to other study

Qualifier:

equivalent or similar to guideline

Guideline:

OECD Guideline 402 (Acute Dermal Toxicity)

Deviations:

not specified

GLP compliance:

no

Test type:

standard acute method

Limit test:

yes

Species:

rabbit

Strain:

New Zealand White

Sex:

male/female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Weight at study initiation: 2 to 3 kg
- Diet: commercial available diet, ad libitum
- Water: municipal water, ad libitum

Type of coverage:

occlusive

Vehicle:

unchanged (no vehicle)

Details on dermal exposure:

REMOVAL OF TEST SUBSTANCE
- excess fluid is removed to diminish ingestion

Duration of exposure:

24 hours

Doses:

16.0 mL/kg

No. of animals per sex per dose:

5 rabbits per sex/dose

Control animals:

no

Details on study design:

- Duration of observation period following administration: 14 days
- Frequency of observations and weighing: 1 hour, day 7 and 14.
- Necropsy of survivors performed: yes
- Other examinations performed: clinical signs, body weight, gross pathology

Statistics:

LD50's and the estimated LD50 slopes are calculated by the moving average method (Thompson, 1947; Weil, 1983).

Preliminary study:

none.

Sex:

male/female

Dose descriptor:

LD0

Effect level:

16 mL/kg bw

Remarks on result:

other: (16 mL/kg calculated 14112 mg/kg, based on specific gravity of 0.882; none of the animals died during the 14 days observation period)

Sex:

male/female

Dose descriptor:

LD50

Effect level:

> 16 mL/kg bw

Remarks on result:

other: none of the animals died during the 14 days observation period

Mortality:

16 mL/kg - 0/5 rabbits, both sexes.

Clinical signs:

other: Male: No signs of toxicity. Ecchymosis at 1 day; erythema at 1 to 7 days; edema, necrosis at 1 to 14 days; fissuring at 7 days; desquamation at 7 to 14 days; scabs, ulcerations, alopecia at 14 days. Female: Diarrhea in 1 at 14 days; emaciation in 1 at 14

Gross pathology:

Male: Lungs light pink to dark red.
Female: Lungs mottled light to dark red; intestines of 1 gas-filled.

Other findings:

None.

None.

Interpretation of results:

not classified

Remarks:

Migrated information Criteria used for interpretation of results: EU

Conclusions:

N-Butyl Acetate has an extremely low order of acute toxicity following single dermal application. The dermal LD0 was > 16 mL/kg (calculated 14112 mg/kg, based on specific gravity of 0.882) under the study conditions.

Executive summary:

N-Butyl Acetate was tested for dermal toxicity in rabbits (5 male and 5 female rabbits/dose) at a dose of 16.0 ml/kg and killed 0 of 5 rabbits/sex (during 14 days observation period). Based on the results obtained, the LD0 was 16 mL/kg (calculated 14112 mg/kg, based on specific gravity of 0.882) under the study conditions, the estimated LD50 thus was > 16 mL/kg (Myers et al. 1987).

This study was judged to be reliable (RL2) and therefore selected as key study.

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed

Dose descriptor:

discriminating dose

Value:

14 112 mg/kg bw

Quality of whole database:

Two studies with high reliability show comparable results. Additional less reliable studies support the findings. The quality of the database is high.

Additional information

n-Butyl acetate was tested for acute oral toxicity (RL2, similar to OECD TG 423) in 5 male rats/dose at doses of 16.0, 11.3 and 8.0 mL/kg. Male dosing killed 3 out of 5 rats at 16.0 mL/kg, 1 of 5 at 11.3 mL/kg and 0 of 5 at 8.0 mL/kg. Acute oral toxicity in 5 female rats/dose at doses of 16.0, 11.3, 8.0 and 4.0 ml/kg resulted in 4 of 5 deaths at 16.0 mL/kg, 2 of 5 at 11.3 mL/kg, 0 of 5 at 8.0 mL/kg and 0 of 2 at 4.0 mL/kg. Based on the results obtained, the LD50 was 14.5 mL/kg for male rats (calculated 12789 mg/kg, based on specific gravity of 0.882) and 12.2 mL/kg for female rats (calculated 10760 mg/kg) under the study conditions (Myers et al., 1987; corresponds to IUCLID study record DCC/Bushy Run Research Center, 1987).

These findings are supported by another study which reported an acute oral LD 50 value for male and female rats of about 14130 mg/kg bw (Smyth et al., 1954; reliable with restrictions (RL2)). Another less reliable study (Munch, 1972: RL3) documented an acute oral LD50 for rabbits of 7437 mg/kg bw. Data from secondary literature (RL4) reported oral LD50 values for mouse (6000 mg/kg bw) and guinea pig (4700 mg/kg bw) which confirmed the findings from the key study (WHO, 2005, corresponds to IUCLID study record CICAD, 2005).

In a reliable study (RL2, similar to OECD TG 402) which was selected as key study, the dermal LD50 in male and female rabbits was > 16 ml/kg bw (corresponding to > 14112 mg/kg bw, based on specific gravity of 0.882) under the study conditions (Myers et al., 1987, corresponds to IUCLID study record DCC/Bushy Run Research Center, 1987).

As no animal died during this study the results can be expressed as LD0 value of 14112 mg/kg bw, as well.

Another reliable study reported a value > 17600 mg/kg bw as acute dermal LD50 dose in rabbits (Smyth et al., 1954, RL2).

Two other studies also conducted in rabbits support this finding giving acute dermal LD50 values >5000 mg/kg bw (Blaszcak, 1987, RL3, corresponds to IUCLID study record Hoechst-Celanese, 1987 and Opdyke, 1976, RL4).

A series of studies on acute toxicity of n-butyl acetate in rats after inhalation exposure is existing, however the results of the studies are inconsistent. One study reported an LC50 value of 0.74 mg/L (Debets, 1986; corresponds to IUCLID study record 3M/NOTOX). Several follow up studies have been performed in an attempt to reproduce this value. Two other studies reported LC50 values of 1.8 mg/L and 5.3 mg/L (Nachreiner, 1987 and Norris et al., 1997, respectively; correspond to IUCLID study records UCC/BRRC or UCC/BRRC-Norris). No mortality was observed in several other studies in different laboratories (BASF, BRRC, NOTOX) with much higher exposure concentrations (up to 6867 ppm, equivalent to 33 mg/L) (Klimisch, 1988a, b, c (cf. IUCLID study records BASF 1988 a, b, c); Bogers, 1988 (cf. IUCLID study record BASF/NOTOX 1988 d); Nachreiner, 1987; Norris et al., 1997; Smyth et al., 1954). Nearly all the studies were performed according to existing guidelines without any obvious flaws and were judged to be reliable (RL1) or reliable with restrictions (RL2). As the results of the studies are inconsistent evaluation of the acute toxicity of n-butyl acetate after inhalation exposure is performed in a weight of evidence approach. The following table summarises the data on acute toxicity of n-butyl acetate after inhalation exposure.

Nr.

Study

Endpoint

Purity of TS [%]

Atmosphere

PSA

Dose [mg/L]

LC50 [mg/L]

NOEL

RL

Laboratory

Generation

Vapour

Aerosol

nominal

measured

1

3M/NOTOX (08/1986) Debets, 1986

acute tox.: inhalation (standard method) 4h (head only)

“pure“

spraying nozzle (0.4 mm)

predominant

only at highest dose. 0.09% of total TS was present as aerosol

yes

3.1, 7.1, 14.1

0.8, 2.2, 5.2

0.74

1

NOTOX B.V.

2

BASF/NOTOX (05/1988) Bogers, 1988

acute tox.: inhalation (limit test) 4h (head only)

99.3 (information of sponsor)

spraying nozzle (0.4 mm)

predominant

0.11% of total TS was present as aerosol

yes

6.6

4.9

> 4.9 (no mortality)

1

NOTOX B.V.

3

BASF a (11/1987) Klimisch, 1988a

acute tox.: inhalation (limit test) 4h (nose only)

99.5 (characterization from sponsor)

glass evaporizer with thermostat

yes

-

no

25

21.0 ± 0.36

> 21.0 (no mortality)

1

BASF, Dep. of Tox.

4

BASF b (12/1987) KS Klimisch, 1988b

acute tox.: inhalation 4h (nose only)

99.5 (statement of producer)

two component atomizer

yes

no aerosol detectable

yes

2.7 and 31.5

1.97 ± 0.09 and 23.4 ± 1.35

> 23.4  (no mortality)

1

BASF, Dep. of Tox.

5

BASF c (02/1988) Klimisch, 1988c

acute tox.:inhalation (limit test) 4h (nose only)

99.3 (analyt. data of sponsor)

two component atomizer

yes

no aerosol detectable

yes

22.9

21.1 ± 3.05

> 21.1  (no mortality)

1

BASF, Dep. of Tox.

6a

UCC Nachreiner, 1987

acute inhalation (limit test) 4h (whole body)

99.6 (analytical data)

Statically- generated nearly saturated

yes

-

no

6867 ± 427 ppm (33.2 mg/L)

no mortality

1

BRRC

6b

UCC Nachreiner, 1987

acute inhalation 4h (whole body)

99.6 (analytical data)

heated evaporator

yes

-

no

ratio anal./ measured 0.89, 0.88, 0.92 2278, 3424, 6886 ppm

2027 ± 69, 3013 ± 127, 6335 ± 522 ppm (9.8, 14.6, 30.6 mg/L)

no mortality

1

BRRC

6c

UCC Nachreiner, 1987

acute inhalation 4h (whole body)

99.6 (analytical data)

atomizer

No particle size analysis performed, no aerosol visible in the breathing zone of the exposed animals visible

no

ratio anal./ measured 0.89, 0.91 607, 311 ppm

540 ± 34, 283 ± 20 ppm (2.5, 1.3 mg/L)

391 ppm 1.8 mg/L

1

BRRC

7

UCC Norris et al., 1997

acute tox.: inhalation 4h (whole body)

99.7

atomizer with liquid nozzle

yes

yes

798, 1411, 1442, 1517, 1575, 5082, 9312 ppm (current material)1514, 1549 ppm (old material)

no mortality

2

BRRC

8

UCC Norris et al., 1997

acute tox.: inhalation 4h (whole body)

99.75

atomizer with liquid nozzle

yes

yes

865, 1243, 1256, 1423 ppm (old material)

5.3 mg/L

2

BRRC

9

Smyth et al., 1954

acute inhalation 4h (whole body)

no data

yes

no

"saturated vapour" (about 71 mg/L)

no mortality

71 mg/L

2

PSA: Particle size analysis performed

The LC50 value of 0.74 mg/L observed in the study performed at the NOTOX laboratory (Debets, 1986) was much lower than the LC50 values reported in older studies which are not included in the IUCLID file because the purity of the test item used was unknown and the exposure concentrations were not verified analytically. Union Carbide Corporation (UCC) and BASF initiated a series of further studies which were performed at the NOTOX, BASF or Bushy Run Research Center (BRRC) laboratories to reproduce the finding of the study of Debets (1986) and to investigate the difference between vapour exposure versus aerosol exposure.

The study initiated by BASF at NOTOX (Bogers, 1988) used the same equipment and generation procedures as described in the initial 3M study (Debets, 1986). In this limit test with the exposure concentration of 4.9 mg/L no lethality occurred and no macroscopic or microscopic findings in the lungs were observed, i.e. the initial findings at the NOTOX laboratory were not reproducible. As in the study of Debets (1986) only a minimal amount of the test substance (about 0.1%) was present as aerosol.

Three further studies were initiated by BASF at the BASF laboratories. In two studies which used a two component atomizer for the generation of the test atmosphere no aerosol was detectable (Klimisch, 1988b, c, correspond to IUCLID study records BASF b and c), exposure was mainly against n-butyl acetate vapour as in the study which used a glass evaporizer for the generation of the test atmosphere (Klimisch, 1988a, cf. IUCLID study record BASFa). No lethal effects were observe in these three studies, even not at the highest concentrations tested (21 or 23 mg/L).

In a study initiated by UCC at the BRRC laboratory three different methods for the generation of the test atmosphere were used: a) statically generated nearly saturated vapour exposure, b) dynamic vapour generation by a heated evaporator and c) dynamic aerosol generation with an atomizer. But no particles size analysis was performed in these experiments and no aerosol was detectable in the breathing zone of the animals in the test using an atomizer. No lethality was observed in the tests using a statically generated vapour atmosphere (33.2 mg/L) and in the test using a heated evaporator (maximal concentration tested: 30.6 mg/L). In the tests using an atomizer no lethality occurred at the test concentration of 1.3 mg/L, but all animals of the 2.5 mg/L group died, resulting in an LC50 of 1.8 mg/L. The study author had no explanation for the observed differences (Nachreiner, 1987).

Two further studies were performed at the BRRC laboratories on behalf of UCC using current production process test material and old production process material which was aerosolized with an atomizer with liquid nozzle. Additionally, the influence of the test atmosphere humidity on the result and the influence of particle size/concentration were investigated. One test using old production process material reported an LC50 value of 5.3 mg/L. In the second test these findings could not be reproduced, no mortalities occurred in the presence of old or new production process material, tested at even higher concentrations than in the first test. Humidity and particle size/concentration appeared to be unrelated to toxicity (Norris et al., 1997).

All efforts to reproduce the data on acute inhalation toxicity of n-butyl acetate reported by Debets (1986) were not successful. Inconsistencies of the results occurred not only between laboratories but also within the same laboratory. No differences in lethality were observed in experiments with whole-body and head-only exposure. So the reasons for the observed differences remain unclear. An extensive discussion of the test results can be found in Norris et al. (1997) and WHO (2005).

Smyth et al.(1954) also did not observe any lethality in animals exposed for 4 hours to a saturated vapour atmosphere.

Taking into account not only the data on acute toxicity of n-butyl acetate after inhalation exposure but also data obtained after repeated inhalation exposure (e.g. subchronic neurotoxicity study, subchronic toxicity study, two-generation study) which did not reveal test item related lethality in animals exposed to concentrations up to 3000 ppm (14.5 mg/L) it seems to be justified to interpret the results which revealed LC50 values in the range of 0.74 to 5.3 mg/L as outliers. The lethal concentration of n-butyl acetate seems to be much higher, Klimisch (1988 a, b, c) reported values of > 21 mg/L. Although currently no definite LC50 value for n-butyl acetate can be determined, it seems to be higher than the limit for classification of 20 mg/L. It is recommended not to classify n-butyl acetate for acute toxicity after inhalation exposure.

Justification for selection of acute toxicity – oral endpoint
Low LD50 reported from adequate study of high reliability (Klimisch score 2). Even though the study was not conducted under GLP it has sufficient data for interpretation of results.

Justification for selection of acute toxicity – inhalation endpoint
No single study was selected as endpoints conclusion was reached in a weighth-of-evidence approach based on the results obtained in various studies of high reliability (Klimisch score 1 and 2).

Justification for selection of acute toxicity – dermal endpoint
Low LD0 reported from adequate study of high reliability (Klimisch score 2). Even though the study was not conducted under GLP it has sufficient data for interpretation of results.

Justification for classification or non-classification

According to criteria in Regulation (EC) No.1272/2008 the substance does not have to be classified for acute oral, dermal or inhalation toxicity, based on the observed LD50 values (acute oral toxicity: LD50 = 12700 mg/kg bw male rats and 10760 mg/kg bw female rats ; acute dermal toxicity: LD50 > 16 mL/kg bw (~ 14000 mg/kg bw = LD0)) and the results from the acute and repeated inhalation exposure studies.