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Description of key information

Key value for chemical safety assessment

Skin sensitisation

Link to relevant study records
Reference
Endpoint:
skin sensitisation: in vivo (LLNA)
Type of information:
experimental study
Adequacy of study:
key study
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
study well documented, meets generally accepted scientific principles, acceptable for assessment
Justification for type of information:
See Read Across Justification document in Section 13.2 of IUCLID
Reason / purpose:
read-across: supporting information
Reason / purpose:
read-across: supporting information
Qualifier:
equivalent or similar to
Guideline:
OECD Guideline 429 (Skin Sensitisation: Local Lymph Node Assay)
Version / remarks:
The lead author, G.F. Gerberick, is cited in the current OECD 429 guideline, and was involved in the establishment of the guideline. Therefore, this paper represents work done toward the development of the guideline.
GLP compliance:
not specified
Type of study:
mouse local lymph node assay (LLNA)
Species:
mouse
Strain:
CBA
Sex:
female
Details on test animals and environmental conditions:
TEST ANIMALS
- Source: Jackson Labs (Bar Harbor, ME) or NCI (Fredrick, MD)
- Age at study initiation: 6 - 9 weeks
- Weight at study initiation:
- Housing: in compliance with standards set by US Animal Welfare act
- Diet (e.g. ad libitum): in compliance with standards set by US Animal Welfare act
- Water (e.g. ad libitum): in compliance with standards set by US Animal Welfare act
- Acclimation period:


ENVIRONMENTAL CONDITIONS
- Temperature (°C): in compliance with standards set by US Animal Welfare act
- Humidity (%): in compliance with standards set by US Animal Welfare act
- Air changes (per hr): in compliance with standards set by US Animal Welfare act
- Photoperiod (hrs dark / hrs light):

Vehicle:
other: acetone
Concentration:
5% , 10% and 20%
No. of animals per dose:
5 female animals
Details on study design:
RANGE FINDING TESTS:

MAIN STUDY
ANIMAL ASSIGNMENT AND TREATMENT
- Name of the test method: local lymph node assay
- Criteria used to consider a positive response: DPM values are presented for each animal and for each dose group. A Stimulation Index (SI) is calculated for each group. The SI is the ratio of the DPM/group compared to DPM/vehicle group. If the results indicate a SI > 2 (but SI < 30), the test substance may be regarded as a weak to moderate skin sensitiser; if the results indicate a SI > 30, the test substance may be regarded as a strong skin sensitiser, based on the article.

TREATMENT PREPARATION AND ADMINISTRATION:
Groups of five experimental animals were treated with the test substance concentrations of 5%, 10% and 20% on four consecutive days, by open application on both ears (total 25 microliter/ear). Five vehicle control animals were similarly treated, but with vehicle alone (acetone). Eighteen to 24 hours after the last exposure, all animals were injected with 3H-methyl thymidine in phosphate-buffered saline into the tail vein and after five hours the test animals were euthanized and the bilateral auricular lymph nodes were excised. After precipitating the DNA of the lymph node cells, radioactivity measurements were performed.
Positive control substance(s):
not specified
Statistics:
None stated
Positive control results:
No information provided
Parameter:
SI
Value:
1
Test group / Remarks:
vehicle control
Parameter:
SI
Value:
0.8
Test group / Remarks:
test substance concentration: 5%
Parameter:
SI
Value:
0.9
Test group / Remarks:
test substance concentration: 10%
Parameter:
SI
Value:
0.8
Test group / Remarks:
test substance concentration: 20%
Parameter:
other: disintegrations per minute (DPM)
Remarks on result:
other: see Remark
Remarks:
The mean DPM/animal value for the vehicle control group was 5.42E-02 DPM. The mean DPM/animal value for the experimental group treated with test substance concentrations 5% was 4.20E-02 DPM. The mean DPM/animal value for the experimental group treated with test substance concentrations 10% was 5.00E-02 DPM. The mean DPM/animal value for the experimental group treated with test substance concentrations 20% was 4.27E-02 DPM.
Interpretation of results:
not sensitising
Remarks:
Migrated information Criteria used for interpretation of results: EU
Conclusions:
The SI values calculated for the test substance concentrations 5%, 10% and 20% were 0.8, 0.9 and 0.8 respectively.
There was no indication that the test substance could elicit an SI >=2 when tested on higher concentrations.
Therefore the test substance does not have to be classified and has no obligatory labeling requirement for sensitization by skin contact.
Executive summary:

This LLNA test was conducted according to a modification of a method described by kimber et al., 1989. Five CBA mice per dose were used.

The SI values calculated for the test substance concentrations 5%, 10% and 20% were 0.8, 0.9 and 0.8 respectively. There was no indication that the test substance could elicit an SI >=2 when tested on higher concentrations. Therefore the test substance does not have to be classified and has no obligatory labeling requirement for sensitization by skin contact.

Endpoint conclusion
Endpoint conclusion:
no adverse effect observed (not sensitising)
Additional information:

No studies on dermal sensitization with the test substance are available, but dermal sensitization studies with mice in a LLNA assay (Geberick, 1991) and with guinea pigs in a Buehler study (Bier, 1979) which were run on a structural analog substance Benzoic acid (65-85-0) are available. These studies were run to a method comparable with current guidelines and gave negative results.

The available case studies are too limited to allow conclusions on the toxicity of the test substance and to allow derivation of a NOAEL. Epidemiological studies (Brasch, 1993, Brasch 2010) are available that clearly indicate that the test substance does not induce sensitization. Many studies use the human patch test in a single challenge. The validity of this test design is not officially confirmed and therefore the results of the individual tests need to be considered as preliminary. However, in view of the consistence of the results, it can be concluded that based on the information available, no sensitizing properties are associated with the test substance in healthy subjects. In patients with frequent urticaria or asthma, symptoms or exacerbation of the symptoms were observed after challenge with the test substance. A study in healthy volunteers (Lucas 1909) showed effects at low doses, but deficiencies in the study design and bias prohibit proper evaluation of the results.

Migrated from Short description of key information:

Dermal sensitization studies with mice (Geberick, 1991) and with guinea pigs (Bier, 1979) which were run on structural analog substance Benzoic acid (65-85-0) are available. These studies gave negative results.

In addition to animal data, many human studies are available investigating effects of the test substance on skin, including immunological and non-immunological responses. Most studies are of limited quality and the test substance is used as a standard substance to elicit a skin reaction in humans. The test substance does induce skin effects in healthy adults and children after topical application.

Justification for selection of skin sensitisation endpoint:

This is a LLNA study read-across from Benzoic acid which is conducted with guinea pig.

Justification for classification or non-classification

As indicated in Annex VI report – Harmonisation of C&L for Benzoic acid, August 2011, Section 5.5.3 "Benzoic acids and its salts are not considered to be skin or respiratory sensitisers".