butyl 4-hydroxybenzoate

Endpoint summary

Description of key information

A read-across approach was conducted on source substance isobutyl 4-hydroxybenzoate:

LLNA (OECD 429): not sensitising

Data on target substance:

GPMT (OECD 406): inconclusive

Overall conclusion: not sensitising

Key value for chemical safety assessment

Skin sensitisation

Link to relevant study records

Reference

Reference 1

Endpoint:

skin sensitisation: in vivo (LLNA)

Type of information:

read-across from supporting substance (structural analogue or surrogate)

Adequacy of study:

weight of evidence

Justification for type of information:

refer to analogue justification provided in IUCLID section 13

Reason / purpose for cross-reference:

read-across source

Key result

Parameter:

SI

Value:

1

Test group / Remarks:

10%

Key result

Parameter:

SI

Value:

0.8

Test group / Remarks:

25%

Key result

Parameter:

SI

Value:

1.1

Test group / Remarks:

60%

Key result

Parameter:

other: disintegrations per minute (DPM)

Value:

795

Test group / Remarks:

10%

Key result

Parameter:

other: disintegrations per minute (DPM)

Value:

613

Test group / Remarks:

25%

Key result

Parameter:

other: disintegrations per minute (DPM)

Value:

862

Test group / Remarks:

60%

Interpretation of results:

other: CLP/EU GHS criteria not met, no classification required according to Regulation (EC) No 1272/2008

Conclusions:

In an LLNA skin sensitisation study with source substance isobutyl 4-hydroxybenzoate, performed according to OECD 429 test guideline and GLP principles, the source substance was considered not to be a skin sensitiser, as the SI appeared not to be ≥ 3 when tested up to and including 60% (v/v). Therefore, as explained in the analogue justification, the target substance butyl 4-hydroxybenzoate is considered to be not skin sensitising.

Reference 2

Endpoint:

skin sensitisation: in vivo (non-LLNA)

Type of information:

experimental study

Adequacy of study:

weight of evidence

Reliability:

4 (not assignable)

Rationale for reliability incl. deficiencies:

documentation insufficient for assessment

Remarks:

epicutaneous induction with test substance only; no controls, no data on purity and specification of the test substance, no single scores

Qualifier:

equivalent or similar to guideline

Guideline:

OECD Guideline 406 (Skin Sensitisation)

Version / remarks:

adopted: 12 May 1981

Deviations:

yes

Remarks:

epicutaneous induction with test substance only; no controls

Principles of method if other than guideline:

- Principle of test: Sensitisation in the guinea-pig is induced by two intradermal injections of Freund's adjuvant and 10 topical applications of the test substance under occlusive dressings over a period of 23 days. After a rest period of 12 days a single challenge application of the test substance under occlusive dressing is applied.
- Parameters analysed / observed: Erythema and Eschar formation is observed according to Draize score. Any other anomalities at the challenge site is noted.

GLP compliance:

no

Type of study:

guinea pig maximisation test

Justification for non-LLNA method:

The test was done before LLNA as first-choice method for in-vivo testing was set into force.

Species:

guinea pig

Strain:

Dunkin-Hartley

Sex:

male/female

Details on test animals and environmental conditions:

TEST ANIMALS
- Weight at study initiation: 300 - 400 g
- Housing: Animals were kept in cages measuring 600 x 540 x 315 mm with grilled bases
- Diet: granulated animal diet (granulés Cobaye U.A.R.N. No 114 ), 50 g/day, supplemented with carrots
- Water: ad libitum
- Acclimation period: two weeks

Route:

epicutaneous, occlusive

Vehicle:

unchanged (no vehicle)

Concentration / amount:

100%

Day(s)/duration:

day 0, 2, 4, 7, 9, 11, 14, 16, 18 and 21

Adequacy of induction:

highest technically applicable concentration used

No.:

#1

Route:

epicutaneous, occlusive

Vehicle:

olive oil

Concentration / amount:

5%

Day(s)/duration:

day 35

Adequacy of challenge:

highest non-irritant concentration

No. of animals per dose:

20

Details on study design:

RANGE FINDING TESTS:
Preliminary irritation test was conducted in 6 animals. On day 0, 0.5 g or 0.5 ml of the test substance (or the dilution to be used for the challenge application) is applied under occlusive conditions to the back of the animal immediately behind the left scapulum for 48 h. Skin side was examined for irritation and anomalities at 1, 7, 24 and 48 h following the removal of the patch. The minimum dilution which does not cause irritation is determined and used for the challenge application.

MAIN STUDY
A. INDUCTION EXPOSURE
- No. of exposures: 10 (test substance); 2 (FCA)
- Exposure period: Day 0 - 23
- Test groups: FCA (50% in saline; intradermal) and undiluted test substance (epidermal, occlusive)
- Control group: not specified
- Site: right scapula
- Frequency of applications: every second day (test substance); every 9 days (FCA)
- Concentrations: undiluted

B. CHALLENGE EXPOSURE
- No. of exposures: 1
- Day(s) of challenge: 35
- Exposure period: 48 h
- Test groups: test substance and vehicle
- Control group: not specified
- Site: area on the adomen side above the left groin
- Concentrations: 5% in olive oil
- Evaluation (hr after challenge): 1, 7, 24 and 48 h after patch removal

OTHER:
Erythematous reaction and eschar formation are evaluated using the following scale:
no erythema . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0
slight erythema (hardly visible) . . . . . . . . . . 1
erythema distinct . . . . . . . . . . . . . . . . . . . . . . 2
erythema moderate to severe ............ 3
erythema severe (red/purple) with the formation of light eschars (profound lesions) 4

Any other anomaly occurring at the challenge site (eg. papules, vesicles, oedema exfoliation) were noted.
The animals counted as positive are those which, (a) present at least once in four readings a reaction scoring two or more, or (b) present focal reactions whatever the reaction observed at the challenge site, or (c) present vesicles.

Histological examination
About 6-7 h after removing the dressing samples of skin for histological examination are taken from the challenge sites of those animals showing distinct macroscopic reactions. Samples are taken immediately after the readings which demonstrate these reactions. After fixing fragments of skin in Bouin's solution they are embedded in paraffin, sectioned at five µm and stained with haematoxylin and eosin.

Challenge controls:

not specified

Positive control substance(s):

not specified

Key result

Reading:

1st reading

Group:

test chemical

Dose level:

5%

No. with + reactions:

6

Total no. in group:

20

Clinical observations:

2/6 animals showed pathological aspects. The worst showed spongiosis, weeping, sqamous crust and moist lymphocyte infiltration.

Group:

negative control

Remarks on result:

not measured/tested

Group:

positive control

Remarks on result:

not measured/tested

The mean erythema score was 1.7 (maximum score 4). Microscopic examination of tissue from two of the six animals showed lesions considered allergic. For the 4 remaining animals it is not clearly stated if skin reactions are considered allergic.

Interpretation of results:

other: inconclusive

Conclusions:

Under conditions of this skin sensitisation test in guinea pigs the test substance induced skin reactions in 6/20 animals, causing slight to distinct erythema (mean erythema score of 1.7) and microscopic lesions considered allergic in 2 of 6 sensitised animals.For the 4 remaining animals it is not clearly stated if skin reactions are considered allergic. With regard to the criteria for skin sensitisation (threshold ≥ 30%) defined in the Guidance to Regulation (EC) No 1272/2008 on classification, labelling and packaging (CLP) positive results in 6/20 animals are a border-line case.

Executive summary:

The skin sensitising potential of butyl 4-hydroxybenzoate was investigated in a guinea pig maximisation test (GPMT) similar to OECD Guideline 406 (Brulos, 1977). 20 Albino Hartley guinea pigs were induced by two intradermal injections of Freund's adjuvant and 10 epicutaneous applications of the undiluted test substance under occlusive dressings over a period of 24 days. After a rest period of 12 days animals were challenged by a single application of the test substance at 5% in olive oil under occlusive dressing. Six of the 20 animals tested reacted to the challenge patch. The mean erythema score was 1.7 (maximum score 4). Microscopic examination of tissue from two of the six animals showed lesions (spongiosis, squamous crust and lymphocytic infiltration) considered allergic. For the 4 remaining animals it is not clearly stated if skin reactions are considered allergic.

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed (not sensitising)

Respiratory sensitisation

Endpoint conclusion

Endpoint conclusion:

no study available

Additional information:

Read-across justification

In addition to data on skin sensitisation available for butyl 4-hydroxybenzoate, the assessment was based on studies conducted with source substance isobutyl 4-hydroxybenzoate as part of a read across approach, which is in accordance with Regulation (EC) No. 1907/2006, Annex XI, 1.5. For each specific endpoint the source substance structurally closest to the target substance is chosen for read-across, with due regard to the requirements of adequacy and reliability of the available data. Structural similarities and similarities in properties and/or activities of the source and target substance are the basis of read-across. A detailed justification for the read across approach is provided in the technical dossier (see IUCLID Section 13).

Skin sensitisation in vivo

CAS 4247-02-3

In a LLNA skin sensitisation study (WIL research, 2016), performed according to OECD 429 test guideline and GLP principles, isobutyl 4-hydroxybenzoate was considered not to be a skin sensitiser, as the SI appeared not to be ≥ 3 when tested up to and including 60% (v/v) isobutyl 4-hydroxybenzoate.

CAS 94 -26 -8

The skin sensitising potential of butyl 4 -hydroxybenzoate was investigated in a guinea pig maximisation test (GPMT) similar to OECD Guideline 406 (Brulos, 1977). 20 Albino Hartley guinea pigs were induced by two intradermal injections of Freund's adjuvant and 10 epicutaneous applications of the undiluted test substance under occlusive dressings over a period of 24 days. After a rest period of 12 days animals were challenged by a single application of the test substance at 5% in olive oil under occlusive dressing. Six of the 20 animals tested reacted to the challenge patch. The mean erythema score was 1.7 (maximum score 4). Microscopic examination of tissue from two of the six animals showed lesions (spongiosis, squamous crust and lymphocytic infiltration) considered allergic. For the 4 remaining animals it is not clearly stated if skin reactions are considered allergic.

Overall conclusion on skin sensitisation

Data on skin sensitisation for parabens are heterogeneous. A skin sensitising potential was frequently discussed for parabens. As reviewed by the Cosmetic Ingredient Review (CIR) Expert Panel, available data on skin sensitisation indicate that the parabens are non-sensitising on intact skin. Parabens are reported to occasionally cause skin sensitisation when applied to damaged or broken skin (CIR, 2008).

Reliable data from a LLNA on source substance isobutyl 4-hydroxybenzoate did not show skin sensitising effects in the animals (LLNA; WIL research, 2016). In this study the test substance did not provoke skin irritation, thus skin was proved to be intact.

In a guinea pig maximisation test butyl 4-hydroxybenzoate showed skin reactions in 6/20 animals, with slight to distinct erythema (mean erythema score of 1.7) and microscopic lesions considered allergic in 2 of the 6 animals. For the 4 remaining animals it is not clearly stated if skin reactions are considered allergic. Since the test substance is irritating to the skin, it cannot be excluded that the observed skin reactions are related to skin damage by irritation. In addition, erythema was observed in 30% (6/20) of the animals only. Thus, with regard to the criteria for skin sensitisation (threshold ≥ 30%) defined in the Guidance to Regulation (EC) No 1272/2008 on classification, labelling and packaging (CLP) results are a border-line case even if skin sensitisation is assumed for all 6 animals with skin reactions.

Thus, based on aforementioned reasons butyl 4-hydroxybenzoate is not classified for skin sensitisation according to regulation (EC) No 1272/2008.

References

CIR (2008) Final Amended Report on the Safety Assessment of Methylparaben, Ethylparaben, Propylparaben, lsopropylparaben, Butylparaben, lsobutylparaben, and Benzylparaben as used in Cosmetic Products. International Journal of Toxicology, 27(Suppl. 4):1-82, 2008

Justification for classification or non-classification

Based on the read-across approach, the available data on skin sensitisation do not meet the criteria for classification according to Regulation (EC) 1272/2008 and are threrefore conclusive but not sufficient for classification.