Butyl (S)-2-hydroxypropionate

Endpoint summary

Description of key information

n-Butyl-S-lactate (target substance) is moderately irritating to the skin of rabbits when applied for 4 h under semi-occlusive conditions in an in vivo skin irritation test (OECD 404). In an in vitro chicken enucleated eye test (eq. to OECD 438), n-Butyl-S-lactate caused severe irritating effects. Moreover, slight irritating effects to the respiratory tract were seen in a sub-acute inhalation toxicity study (see IUCLID section 7.5.2).

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:

key study

Study period:

1996-08-26 to 1996-10-10

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 404 (Acute Dermal Irritation / Corrosion)

Version / remarks:

adopted in July 1992

Deviations:

yes

Remarks:

The relative humidity of the animal room was higher than the upper limit mentioned in the guidelines

GLP compliance:

yes

Specific details on test material used for the study:

- Name: PURASOLV BL (n-butyl lactate)
- Chemical name: butyl-S-(-)-2-hydroxy propionate
- Package: Plastic bottle
- Batch No: BU-6001K
- CAS. Reg. No: 138-22-7 (although this is the CAS number for butyl lactate of unspecified stereochemistry, the substance is clearly identified as the S-enatiomer)
- Labelling: Butyl lactate PURASOLV BL
- General appearance: Clear, colourless liquid
- Storage conditions: Ambient temperature

Species:

rabbit

Strain:

New Zealand White

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Broekman Institute, Someren, The Netherlands
- Age at study initiation: Young adults
- Weight at study initiation: 3350-3910 g
- Sex: Male
- Housing: Individually in stainless steel cages with perforated floor
- Diet: Ad libitum
- Water: Ad libitum
- Acclimation period: 54 days

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 20 ± 3
- Humidity (%): 60-87.5 % (upper limit higher than 70%, because of wet cleaning of the animal room and/or meteorological circumstances; the 87.5% peak occurred for some hours at most)
- Air changes (per hr): 10
- Photoperiod (hrs dark / hrs light): 12

Type of coverage:

semiocclusive

Preparation of test site:

other: removal of hair with electric clippers so as to avoid abrasions

Vehicle:

unchanged (no vehicle)

Controls:

not required

Amount / concentration applied:

TEST MATERIAL
- Amount(s) applied (volume or weight with unit): 0.5 mL

Duration of treatment / exposure:

4 h

Observation period:

14 days

Number of animals:

3

Details on study design:

TEST SITE
- Area of exposure: 2.5 × 2.5 cm

REMOVAL OF TEST SUBSTANCE
- Washing (if done): with a moistened tissue
- Time after start of exposure: 4 h

SCORING SYSTEM: Draize et al. (1944)

Irritation parameter:

erythema score

Basis:

animal #1

Time point:

24/48/72 h

Score:

3.33

Max. score:

5

Reversibility:

not fully reversible within: 7 days

Irritation parameter:

erythema score

Basis:

animal #2

Time point:

24/48/72 h

Score:

2

Max. score:

4

Reversibility:

fully reversible within: 7 days

Irritation parameter:

erythema score

Basis:

animal #3

Time point:

24/48/72 h

Score:

2

Max. score:

4

Reversibility:

fully reversible within: 7 days

Irritation parameter:

edema score

Basis:

animal #1

Time point:

24/48/72 h

Score:

2

Max. score:

4

Reversibility:

fully reversible within: 7 days

Irritation parameter:

edema score

Basis:

animal #2

Time point:

24/48/72 h

Score:

1.67

Max. score:

4

Reversibility:

fully reversible within: 7 days

Irritation parameter:

edema score

Basis:

animal #3

Time point:

24/48/72 h

Score:

1.67

Max. score:

4

Reversibility:

fully reversible within: 7 days

Irritant / corrosive response data:

The irritation scoring is presented in Table 1 below, section 'any other information on results incl. tables'. At 1 hour after treatment, very slight erythema was observed in the three rabbits. At 24 an 48 h post- treatment, well-defined erythema and slight oedema were observed in the three rabbits. One rabbit showed very slight incrustation and all three rabbits slight scaliness at 48 hours after treatment. At 72 hours after treatment, well-defined erythema and very slight or slight oedema were observed in the three rabbits. In addition, one rabbit showed very slight incrustation and all three rabbits slight scaliness. At 14 days after treatment all skin effects had cleared in the skin of all rabbits.

Table 1: Skin irritation scores for n-butyllactate after 4 -h dermal application in rabbits.

Rabbit No	1 h A B	24 h A B	48 h A B	72 h A B	7 d A B
8	1-0	2-2	4^2-2	4^2,3-2	4-0
10	1-0	2-2	2-2	2-1	0-0
12	1-0	2-2	2-2	2^3-1	0-0
Erytherma^1	1.0	2.0	3.0	3.0	n.r.
Oedema^1	0.0	2.0	2.0	1.5	n.r.

The average score is calculated for the two animals showing the strongest skin response

A: erythrema

B: oedema

¹ The average erythema and oedema score is calculated for the two animals showing the strongest skin response

² very slight incrustation in combination with well-defined erythema (erythema score = 4)

³ slight scaliness

⁴ very slight incrustation and slight scaliness (erythema score = 4), which had cleared completely at 14 days
after treatment

n.r. = not relevant; only scores 24-72 hours are used for classification

Interpretation of results:

Category 2 (irritant) based on GHS criteria

Conclusions:

n-Butyl-S-lactate is moderately irritating to the skin of rabbits when applied for 4 h under semi-occlusive conditions.

Executive summary:

A sample of n-Butyl-S-lactate was tested for acute skin irritating/corrosive properties in an experiment with three albino rabbits. The dermal exposure period was 4 hours under semi-occlusive conditions. The test substance caused well-defined erythema, very slight incrustation, slight scaliness and slight oedema in the rabbits. The study design was in accordance with OECD guideline 404 (adopted in July 1992). At 14 days after treatment, the skin effects had cleared completely. On the basis of the results obtained it was concluded that, under the conditions of this study, n-Butyl-S-lactate is moderately irritating to the skin of rabbits after a 4-hour dermal contact period. According to the EC-standards n-butyl-S-lactate is irritating, but not corrosive to (human) skin and it shall be classified as irritant Category 2 (CLP, Regulation EC No 1272/2008).

Endpoint conclusion

Endpoint conclusion:

adverse effect observed (irritating)

Eye irritation

Link to relevant study records

Reference

Endpoint:

eye irritation: in vitro / ex vivo

Type of information:

experimental study

Adequacy of study:

key study

Study period:

1995-03-02 to 1995-03-20

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study with acceptable restrictions

Qualifier:

equivalent or similar to guideline

Guideline:

OECD Guideline 438 (Isolated Chicken Eye Test Method for Identifying Ocular Corrosives and Severe Irritants)

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Specific details on test material used for the study:

- Name: n-butyl lactate
- Chemical name: butyl-(S)-2-hydroxypropionate
- CAS: 34451-19-9 (S-isomer), 138-22-7 (general)
- Labeling: Butyl lactate
- Package: White, plastic bottle
- Purity: 99.06 %
- General appearance: Clear, colourless liquid
- Storage conditions: Ambient

Species:

other: chicken eyes

Details on test animals or tissues and environmental conditions:

Approximately 7 weeks old, male or female chickens (ROSS, spring chickens), body weight range approximately 2.5–3.0 kg, were used as eye-donors. Heads of these animals were obtained from poultry slaughterhouse v.d. Bor, Amersfoortseweg 118, Nijkerkerveen, the Netherlands. Within 2 hours after kill, eyes were carefully dissected and placed in a supervision apparatus. The enucleated eyes were placed in a stainless steel clamp with the cornea positioned vertically and transferred to a chamber of the superfusion apparatus. The corneal integrity was assessed in all eyes. Eyes with a corneal thickness deviating more than 10 % of the average corneal thickness of the eyes, or eyes that were unacceptably stained with fluorescein (score higher than 0.5), indicating the cornea to be permeable, or eyes that showed any other signs of damage, were rejected as test eyes and replaced, if necessary. Four eyes were selected for testing.

Vehicle:

unchanged (no vehicle)

Controls:

other: 1 control eye treated with isotonic saline

Amount / concentration applied:

TEST MATERIAL
- Amount(s) applied (volume or weight with unit): 0.03 mL

Duration of treatment / exposure:

10 sec

Observation period (in vivo):

240 min

Number of animals or in vitro replicates:

not applicable

Details on study design:

REMOVAL OF TEST SUBSTANCE
- Washing (if done): each was washed out with 20 mL of isotonic saline; after rinsing the eyes were examined at 0, 30, 75, 120, 180 and 240 min.

ENDPOINTS MEASURED
Corneal opacity, swelling, fluorescein retention and morphological effects

SCORING SYSTEM
- Corneal swelling: [(CT at t - CT at t=0)/ CT at t=0] × 100%, where CT: corneal thickness
- Corneal opacity: Opacity degree of density (area most dense taken for scoring)
0 = no opacity; 0.5 = very faint opacity; 1 = scattered or diffuse areas, details of iris clearly visible; 2 = easily discernible translucent area, details of iris slightly obscured; 3 = severe corneal opacity, no specific details of iris visible, size of pupil barely discernible; 4 = complete corneal opacity, iris invisible

TOOL USED TO ASSESS SCORE: Slit lamp microscope

Irritation parameter:

percent corneal swelling

Remarks:

after 240 min

Run / experiment:

1

Value:

39

Vehicle controls validity:

not applicable

Negative controls validity:

valid

Positive controls validity:

not examined

Remarks on result:

positive indication of irritation

Irritation parameter:

percent corneal swelling

Remarks:

after 240 min

Run / experiment:

2

Value:

44

Vehicle controls validity:

not applicable

Negative controls validity:

valid

Positive controls validity:

not examined

Remarks on result:

positive indication of irritation

Irritation parameter:

percent corneal swelling

Remarks:

after 240 min

Run / experiment:

3

Value:

41

Vehicle controls validity:

not applicable

Negative controls validity:

valid

Positive controls validity:

not examined

Remarks on result:

positive indication of irritation

Irritation parameter:

cornea opacity score

Remarks:

after 240 min

Run / experiment:

1

Value:

3

Vehicle controls validity:

not applicable

Negative controls validity:

valid

Positive controls validity:

not examined

Remarks on result:

positive indication of irritation

Irritation parameter:

cornea opacity score

Remarks:

after 240 min

Run / experiment:

2

Value:

3

Vehicle controls validity:

not applicable

Negative controls validity:

valid

Positive controls validity:

not examined

Remarks on result:

positive indication of irritation

Irritation parameter:

cornea opacity score

Remarks:

after 240 min

Run / experiment:

3

Value:

3

Vehicle controls validity:

not applicable

Negative controls validity:

valid

Positive controls validity:

not examined

Remarks on result:

positive indication of irritation

Irritation parameter:

fluorescein retention score

Remarks:

after 30 min

Run / experiment:

1

Value:

3

Vehicle controls validity:

not applicable

Negative controls validity:

valid

Positive controls validity:

not examined

Remarks on result:

positive indication of irritation

Irritation parameter:

fluorescein retention score

Remarks:

after 30 min

Run / experiment:

2

Value:

3

Vehicle controls validity:

not applicable

Negative controls validity:

valid

Positive controls validity:

not examined

Remarks on result:

positive indication of irritation

Irritation parameter:

fluorescein retention score

Remarks:

after 30 min

Run / experiment:

3

Value:

3

Vehicle controls validity:

not applicable

Negative controls validity:

valid

Positive controls validity:

not examined

Remarks on result:

positive indication of irritation

Interpretation of results:

Category 1 (irreversible effects on the eye) based on GHS criteria

Conclusions:

n-Butyl-S-lactate is highly irritating and possibly corrosive to the eye of chicken when tested with a single application under the conditions of the present test. On the basis of these results, it is recommended not to perform the standard rabbit eye irritation test with n-butyl-S-lactate in rabbits, but to classify the test substance as an eye irritant Category 1.

Executive summary:

n-Butyl-S-lactate was examined for eye irritating/corrosive potential in an ex vivo bioassay, the enucleated eye test with chicken eyes (CEET). The chicken eyes were obtained from slaughter animals for human consumption. Four chicken eyes were used (one as a control, washed with physiological saline). Although the study was performed before the adoption of the OECD guideline 438 for this test, the design was very similar to the design proposed in the aforementioned guideline. The sample caused severe corneal swelling, severe corneal opacity and severe fluorescein retention of damaged corneal epithelium in the test eyes. On the basis of the results obtained with this investigation and according to the scheme for (EC) classification applied, it is concluded that n-butyl-S-lactate is severely irritating and possibly corrosive to eyes. On the basis of these results, it is recommended not to perform the standard rabbit eye irritation test with n-butyl-S-lactate in rabbits, but to classify the test substance as an eye irritant Category 1.

Endpoint conclusion

Endpoint conclusion:

adverse effect observed (irreversible damage)

Respiratory irritation

Endpoint conclusion

Endpoint conclusion:

adverse effect observed (irritating)

Additional information

Slightly irritating effects to the respiratory tract were seen in a sub-acute inhalation toxicity study (see IUCLID section 7.5.2).

Justification for classification or non-classification

According to the CLP Regulation 1272/2008, n-Butyl-S-lactate is irritating, but not corrosive to (human) skin and it shall be classified as Skin Irrit 2, H315. On the basis of the results obtained in an in vitro eye irritation study and according tothe CLP Regulation 1272/2008, it is concluded that n-Butyl-S-lactate is severely irritating and possibly corrosive to eyes (Eye Dam. 1, H318). Moreover, based on the irritating effects to the respiratory tract seen in sub-acute inhalation study classification as STOT SE3, H335 is warranted.