Tetradecyl laurate

Endpoint summary

Key value for chemical safety assessment

Skin sensitisation

Link to relevant study records

Reference

Endpoint:

skin sensitisation: in vivo (LLNA)

Type of information:

migrated information: read-across based on grouping of substances (category approach)

Adequacy of study:

key study

Study period:

26 May - 23 Jun 2010

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: see 'Remark'

Remarks:

GLP - Guideline study. According to the ECHA guidance document "Practical guide 6: How to report read-across and categories (March 2010)", the reliability was changed from Klimisch code 1 to Klimisch code 2 to reflect the fact that this study was conducted on a read-across substance.

Qualifier:

according to guideline

Guideline:

OECD Guideline 429 (Skin Sensitisation: Local Lymph Node Assay)

Version / remarks:

adopted 2002

Deviations:

no

Qualifier:

according to guideline

Guideline:

EU Method B.42 (Skin Sensitisation: Local Lymph Node Assay)

Deviations:

no

Qualifier:

according to guideline

Guideline:

EPA OPPTS 870.2600 (Skin Sensitisation)

Deviations:

no

GLP compliance:

yes

Type of study:

mouse local lymph node assay (LLNA)

Species:

mouse

Strain:

other: CBA/J

Sex:

female

Details on test animals and environmental conditions:

TEST ANIMALS
- Source: Janvier, Le Genest-Saint-Isle, France
- Age at study initiation: approximately 10 weeks
- Weight at study initiation: 22-25 g (range)
- Housing: animals were housed individually in labelled Makrolon cages (MI type, height 12.5 cm) containing sterilised sawdust as bedding material (Litalabo, S.P.P.S., Argenteuil, France) and paper as cage-enrichment (Enviro-dri, Wm. Lillico & Son (Wonham Mill Ltd.), Surrey, UK). The paper was removed on Day 1 prior to dosing and was supplied again after scoring of the ears on the third day 3. During the acclimation period the animals were housed in groups in Macrolon cages (MIII type, height 18 cm).
- Diet: pelleted rodent diet (SM R/M-Z from SSNIFF Spezialdiäten GmbH, Soest, Germany), ad libitum
- Water: tap water, ad libitum
- Acclimation period: at least 5 days

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 20.5-23.1
- Humidity (%): 41-68
- Air changes (per hr): approximately 15
- Photoperiod (hrs dark / hrs light): 12/12

IN-LIFE DATES: From: 26 May 2010 To: 23 Jun 2010

Vehicle:

acetone/olive oil (4:1 v/v)

Concentration:

25, 50 and 100% (w/w)

No. of animals per dose:

5

Details on study design:

RANGE FINDING TESTS:
- Irritation: A preliminary irritation study was performed according to the procedure of the main study. Two mice were treated daily for 3 consecutive days with either a 50% solution or 100% test substance. 3-4 hours after the last exposure, the irritation severity on the treated skin site was assessed. The body weight was recorded on Day 1 and 3. Very slight erythema (grade 1 of 4) was observed on both the treated sites in the animal exposed to 100% concentration. None of the animals exhibited signs of toxicity during the study period and the body weight was not affected by the treatment. Based on these results, the highest test substance concentration selected for the main study was 100%.

MAIN STUDY
ANIMAL ASSIGNMENT AND TREATMENT
- Name of test method: 3H-methyl thymidine incorporation determined by beta-scintillation counting
- Criteria used to consider a positive response: DMP values will be measured for each animal and for each dose group. The stimulation Index (SI) will be calculated for each group. The SI is the ratio of the DPM/group compared to DPM/vehicle control group. If the results indicate a SI ≥3, the test substance may be regarded as a skin sensitiser, based on the test guidelines and the recommendations done by ICCVAM.

TREATMENT PREPARATION AND ADMINISTRATION:
The test substance formulations (w/w) were prepared within 4 hours prior to each treatment. No adjustment was made for specific gravity of the vehicle. Homogeneity was obtained to visually acceptable levels.
During the induction phase (Day 1-3), the dorsal surface of both ears was epidermally treated (25µL/ear) with the vehicle control or 25, 50 and 100% test substance, at approximately the same time each day for 3 consecutive days. On Day 6, all the animals were injected via the tail vein with 0.25 mL sterile phosphate buffered saline (PBS), containing 20 µCi 3H-methyl thymidine. After approximately 5 hours, all the animals were sacrificed by intraperitoneal injection of Euthasol 20% and the draining (auricular) lymph node of both ears was excised. The relative size of the nodes (as compared to normal) was estimated by visual examination, and abnormalities of the nodes and surrounding area were recorded. The nodes were pooled for each animal in approximately 3 mL PBS. A single cell suspension of lymph node cells (LNC) was prepared the same day in PBS by gentle separation through a stainless steel gauze (diameter 125 µm).
A single cell suspension of LNCs was prepared in PBS by gentle separation through stainless steel gauze (diameter 125 µm). To precipitate the DNA, the LNCs were exposed to 5% trichloroacetic acid (TCA) and stored in the refrigerator until the next day.
Radioactivity measurements were performed on Day 7, using Ultima Gold cocktail as the scintillation fluid. The scintillation counter was programmed to automatically subtract background and convert Counts Per Minute (CPM) to Disintegrations Per Minute (DPM).

Positive control substance(s):

other: A reliability check was performed with alpha-hexylcinnamaldehyde every 6 months to demonstrate that the LLNA test system is reliable and sufficiently sensitive

Positive control results:

A reliability check with a positive control substance was performed every 6 months to demonstrate that the LLNA test system, as used by the test laboratory, is reliable and sufficiently sensitive. In the test performed in April 2010 (project No. 494039), 5, 10 and 25% alpha-hexylcinnamaldehyde, technical grade in acetone/olive oil (4:1 v/v) was used as the positive control. The SI values calculated for the substance concentrations 5, 10 and 25% were 1.7, 2.7 and 8.8 respectively. The SI-value for the vehicle control was 1.0. An EC3 value of 10.7% was calculated using linear interpolation. The calculated EC3 value was found to be in the acceptable range of 2 and 20%. The results of the 6 -monthly HCA reliability checks in CBA/J female mice of the recent years were 14.1, 13.8, 13.9, 16.0, 11.9 and 16.9%. Based on the results, it was concluded that the Local Lymph Node Assay in the mouse as supplied by Janvier performed at NOTOX is an appropriate model for testing for contact hypersensitivity.

Parameter:

SI

Remarks on result:

other: The mean SI for the control, 25, 50 and 100% groups was 1.0, 1.2, 2.0 and 2.1, respectively.

Parameter:

other: disintegrations per minute (DPM)

Remarks on result:

other: The mean DPM values for the control, 25, 50 and 100% groups were 488, 571, 951 and 1013, respectively (see Table 1). The slight increase in DPM with increasing dose level was not statistically significant.

Effects on the lymph nodes:

The right auricular node was enlarged in 1/5 mice in the highest dose group. As this was a single case, it is not considered to be a sensitivity reaction. No macroscopic abnormalitites were observed in the surrounding area.

Table 1: Individual values for radioactivity measurements (disintegrations per minute) and mean stimulation indices

Group	Animal No.	Concentration (% w/w)	DPM/animal	Stimulation index (mean± SEM)
1	1	0	480	-
	2	0	629	-
	3	0	367	-
	4	0	447	-
	5	0	515	-
Mean ± SEM			488 ± 43	1.0 ± 0.1
2	6	25	514	-
	7	25	516	-
	8	25	519	-
	9	25	817	-
	10	25	491	-
Mean ± SEM			571 ± 62	1.2 ± 0.2
3	11	50	928	-
	12	50	778	-
	13	50	589	-
	14	50	1084	-
	15	50	1376	-
Mean ± SEM			951 ± 134	1.0 ± 0.3
4	16	100	637	-
	17	100	796	-
	18	100	1137	-
	19	100	1013	-
	20	100	1483	-
Mean ± SEM			1013 ± 146	1.1 ± 0.1

DPM = disintegrations per minute

SEM = standard error of the mean

Skin irritation effects:

Slight erythema was observed at the test site on both ears in 5/5 mice exposed to 100% test substance. This was not considered to have affected the activity of the lymph nodes.

Systemic effects:

There was no mortality. No clinical signs were observed during the study period and there were no effects on body weight.

Interpretation of results:

not sensitising

Remarks:

Migrated information Criteria used for interpretation of results: EU

Conclusions:

CLP: not classified
DSD: not classified

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed (not sensitising)

Additional information:

A mouse Local Lymph Node Assay (LLNA) with the analogue decyl oleate (Cas# 3687-46-5) showed a mean SI for the control, 25, 50 and 100% groups of 1.0, 1.2, 2.0 and 2.1, respectively. Hence, the conclusion was that this fatty alkyl ester was not sensitizing. A traditional guinea pig test with intradermal exposure confirmed the lack of significant sensitization.

Justification for selection of skin sensitisation endpoint:
The key study is a mouse Local Lymph Node Assay (LLNA) with the analogue decyl oleate (Cas# 3687-46-5). Currently, the LLNA is the preferred and accepted method for assessing skin sensitization of most substances (ICCVAM Evaluations; ICCVAM Protocols; ECVAM ESAC Statement, 2000; OECD TG 429, 2010). Compared with e.g. the GPMT, the LLNA reduces animal use by 17% as well as animal pain and suffering as it evaluates the induction phase and doesn’t require the use of irritating adjuvants. Furthermore, the LLNA provides a quantitative endpoint, dose-responsive data, and allows for the prediction of potency.

Justification for classification or non-classification

The results of the cited studies showed no potency of sensitizing properties for fatty alkyl esters.