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Toxicological information

Skin sensitisation

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Administrative data

Endpoint:
skin sensitisation: in vivo (LLNA)
Type of information:
experimental study
Adequacy of study:
key study
Study period:
01 to 16 February 2012
Reliability:
1 (reliable without restriction)

Data source

Reference
Reference Type:
study report
Title:
Unnamed
Year:
2013
Report Date:
2013

Materials and methods

Test guideline
Qualifier:
according to
Guideline:
OECD Guideline 429 (Skin Sensitisation: Local Lymph Node Assay)
Deviations:
no
GLP compliance:
yes
Type of study:
mouse local lymph node assay (LLNA)

Test material

Reference
Name:
Unnamed
Type:
Constituent
Details on test material:
- Name of test material (as cited in study report): 2-(2-naphthoxy)ethanol
- Physical state: Light tan-coloured waxy solid
- Analytical purity: >98.5%
- Lot/batch No.: E00173-186
- Expiration date of the lot/batch: 31 July 2013
- Storage condition of test material: Ambient temperature, in the dark

In vivo test system

Test animals

Species:
mouse
Strain:
CBA
Sex:
female
Details on test animals and environmental conditions:
TEST ANIMALS
- Source: Charles River, Margate
- Age at study initiation: Between 8 and 10 weeks old
- Weight at study initiation: 16.6 to 21.0 g
- Housing: In groups of 2 or 3
- Diet (e.g. ad libitum): Ad libitum
- Water (e.g. ad libitum): Ad libitum
- Acclimation period: 8 days

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 21°C to 22°C
- Humidity (%): 48% to 70%
- Air changes (per hr): 10
- Photoperiod (hrs dark / hrs light): 12 hrs dark / 12 hrs light

IN-LIFE DATES: From: To: 01 to 13 February 2012

Study design: in vivo (LLNA)

Vehicle:
other: maize oil
Concentration:
0%, 2.5%, 10% and 50%
No. of animals per dose:
6 at 0% and 4 at each of 2.5%, 10% and 50%
Details on study design:
RANGE FINDING TESTS:
- Irritation and toxicity

MAIN STUDY
ANIMAL ASSIGNMENT AND TREATMENT
- Name of test method: Local Lymph Node Assay: dermal application
- Criteria used to consider a positive response: Stimulation Indices greater than or equal to 3 in groups treated at either 2.5%, 10% or 50%

TREATMENT PREPARATION AND ADMINISTRATION: No preparation. Dermal administration to dorsum of the ears by micropipette
Positive control substance(s):
hexyl cinnamic aldehyde (CAS No 101-86-0)
Statistics:
Dixon’s Q-test for the detection of a single outlier was performed on disintegrations per minute values

Results and discussion

Positive control results:
Stimulation index = 8.09

In vivo (LLNA)

Resultsopen allclose all
Parameter:
SI
Value:
1
Test group / Remarks:
Control
Parameter:
SI
Value:
1.25
Test group / Remarks:
Group 2 (2.5%)
Parameter:
SI
Value:
1.15
Test group / Remarks:
Group 3 (10%)
Parameter:
SI
Value:
1.59
Test group / Remarks:
Group 4 (50%)
Parameter:
other: disintegrations per minute (DPM)
Remarks on result:
other: Control group = 1533. Group 2 (2.5%) = 1916. Group 3 (10%) = 1766. Group 4 (50%) = 2440.

Applicant's summary and conclusion

Interpretation of results:
not sensitising
Remarks:
Migrated information Criteria used for interpretation of results: EU
Conclusions:
Under the conditions of the study, since treatment with 2-(2-naphthoxy)ethanol at concentrations of up to 50% did not achieve a stimulation index of =3, it was considered that the test item does not have the potential to cause skin sensitisation.
This study is considered to be relevant, reliable and adequate for risk assessment and for classification purposes.
Executive summary:

The objective of this study was to determine the delayed contact hypersensitivity potential of 2-(2-naphthoxy)ethanol. 

The study was performed using female CBA/Ca mice. A preliminary test was conducted by administering a 50% concentration of test item to two mice. Each mouse received an open application of 25 µL of test formulation onto the dorsum of each ear.

As a result of the findings from the preliminary test, formulation concentrations were selected for the main study. The study design for the main study was as follows:

Text Table1
Experimental Design

Group Number

Treatment

Formulation Concentration (%)

Animal Numbers

1

Vehicle Control

0

1 to 6

2

2-(2-naphthoxy)ethanol

2.5

7 to 10

3

2-(2-naphthoxy)ethanol

10

11 to 14

4

2-(2-naphthoxy)ethanol

50

15 to 18

5

Hexylcinnamicaldehyde (HCA)

50

49 to 52

 

The selected vehicle was corn oil and the vehicle control group received only this. Each mouse received an open application of 25 µL of the appropriate formulation onto the dorsum of each ear for 3 consecutive days. Three days after the final application each animal received an intravenous injection of [methyl-3H] thymidine into the lateral tail vein. Approximately 5 h later the draining auricular lymph nodes were collected in order that incorporation of tritiated thymidine could be assessed by scintillation counting.

The stimulation indices (SI) for groups of mice that received 2-(2-naphthoxy)ethanol at concentrations of 2.5%, 10% or 50%, when compared with controls, were 1.25, 1.15 and 1.59, respectively. The group treated with HCA, a chemical known to induce skin sensitisation, recorded a stimulation index of 8.09. This is considered to demonstrate competent performance of the test procedures.

Under the conditions of the study, since treatment with 2-(2-naphthoxy)ethanol at concentrations of up to 50% did not achieve a stimulation index of =3, it was considered that the test item does not have the potential to cause skin sensitisation.