3-hydroxy-2,2-dimethylpropyl 3-hydroxy-2,2-dimethylpropionate

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:

experimental study

Adequacy of study:

key study

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: Guideline conform GLP study

Qualifier:

according to guideline

Guideline:

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

Deviations:

no

GLP compliance:

yes

Type of study:

mouse local lymph node assay (LLNA)

Species:

mouse

Strain:

CBA

Sex:

female

Details on test animals and environmental conditions:

TEST ANIMALS
- Test system / strain / quality: Mouse / CBA/J
- Age on day 0: 8 – 12 weeks
- Sex: Female
- Supplier: Charles River Laboratories, Research Models and Services, Germany GmbH, Sandhofer Weg 7, 97633 Sulzfeld
- Acclimatization period: 14 days before the first test-substance application
- Body weight on day 0: 17.4 g – 21.5 g
- Housing: single in Makrolon cage, type II
- Diet (e.g. ad libitum): Kliba-Labordiät (Maus / Ratte Haltung “GLP”), Provimi Kliba SA, Kaiseraugst, Basel, Switzerland, ad libitum
- Water (e.g. ad libitum): Tap water; ad libitum

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 20 – 24°C
- Humidity (%): 30 – 70%
- Photoperiod (hrs dark / hrs light): 12 h /12 h
- Bedding: Lignocel PS14; SSNIFF

Vehicle:

propylene glycol

Concentration:

50 % ; The 50% preparation was the maximum technically applicable concentration. The study was carried out as a limit test, using 1 test group and 1 control group.

No. of animals per dose:

5

Details on study design:

RANGE FINDING TESTS:
- Compound solubility: A solubility experiment was performed according to the recommendations given by OECD 429. The highest test-substance concentration, which can be technically used, was a 50% test-substance preparation.
- Irritation: none
- Lymph node proliferation response: none

MAIN STUDY
The study was carried out as a limit test, using 1 test group and 1 control group. Each test animal was applied with 25 μL per ear of the test-substance preparation to the dorsum of both ears for three consecutive days. The control group was treated with 25 μL per ear of the vehicle alone.
Three days after the last application the mice were injected intravenously with 20 μCi of 3H-thymidine in 250 μL of sterile saline into a tail vein. About 5 hours after the 3H-thymidine injection, the mice were sacrificed and the auricular lymph nodes were removed. The weights of each animal’s pooled lymph nodes were determined. Thereafter lymph nodes were pooled group wise and further evaluated by measuring their cellular content and 3H-thymidine incorporation into the lymph node cells (indicators of cell proliferation). Moreover, a defined area with a diameter of 0.8 cm was punched out of the apical part of each ear and for each test group the weight of the pooled punches was determined in order to obtain an indication of possible skin irritation.
The stimulation indices (fold of change as compared to the vehicle control) for cell count, 3H-thymidine incorporation, lymph node weight and ear weight were measured. The increase SI of cell count by a factor of ≥ 1.5 and/or of 3H-thymidine incorporation by a factor of ≥ 3 as compared to the concurrent vehicle control group is generally considered as indicating a sensitizing potential of a test substance.

Positive control substance(s):

hexyl cinnamic aldehyde (CAS No 101-86-0)

Statistics:

mean velues, and standard diviation

Positive control results:

A concurrent positive control (reliability check) with a known sensitizer was not included into this study. Studies using the positive control substance Alpha-Hexylcinnamaldehyde, techn. 85% are performed twice a year in the laboratory in order to show that the test system is able to detect sensitizing compounds under the test conditions chosen. Positive controls in these experiments gave the expected results.

Parameter:

SI

Value:

0.83

Remarks on result:

other: 0.83 (compared to the concurrent control) 2 .04 (compared to the historical control)

Parameter:

other: disintegrations per minute (DPM)

Remarks on result:

other: vehicle propylene glycol 1,380.9 (SI =1); historical control (mean value) 561.2 50% test substance in propylne glycol: 1,143.3

CELL COUNT, 3H-THYMIDINE INCORPORATION AND LYMPH NODE WEIGHT:

TEST GROUP MEAN VALUES AND STIMULATION INDICES

 

Test group	Treatment	Cell Counts
		[Counts/Lymph Node Pair]	Stimulation Index
1	vehicle propylene glycol historical control (mean)	8 634 667 6 809 867	1.00
2	50% in propylene glycol	7 776 000	0.90 1.14

 

Test group	Treatment	³H-thymidine incorporation
		[DPM/Lymph Node Pair]	Stimulation Index
1	vehicle propylene glycol historical control (mean)	1 380.9 561.2	1.00
2	50% in propylene glycol	1 143.3	0.83 2.04

 

Test group	Treatment	Lymph Node Weight
		[mg/Lymph Node Pair]	Stimulation Index
1	vehicle propylene glycol	5.4	1.00
2	50% in propylene glycol	4.8	0.90

 

EAR WEIGHT: TEST GROUP MEAN VALUES AND STIMULATION INDICES

Test group	Treatment	Ear weight
		[mg/animal]	Stimulation Index
1	vehicle propylene glycol	32.3	1.00
2	50% in propylene glycol	34.5	1.06

Interpretation of results:

not sensitising

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed (not sensitising)

Additional information:

In an GLP guideline study (BASF SE. 2010), the skin sensitizing potential of Hydroxypivalic acid neopentylglycol ester flakes was assessed in the LLNA. Groups of 5 female CBA/J mice each were treated with a 50% w/w preparation of the test substance in propylene glycol (maximum technically applicable concentration) or with the vehicle alone (Limit test).

Weights of the pooled auricular LNs and of ear punches (0.8 cm diameter) were determined per animal. Cellular content and 3H-thymidine incorporation was determined after pooling per group. Compared to the control the test substance did no increase 3H-thymidine incorporation, lymph node cell counts, lymph node weights or ear weights.

Because the current vehicle values were considerably higher than the historical control data, the stimulation indices were additionally calculated in relation to the mean historical control values. The resulting stimulation indices are still below the threshold of biological relevance for cell count and 3H-thymidine incorporation.

Besides a slight reduction of the mean body weights in both test groups, no signs of systemic toxicity were noticed.

Conclusion: The substance does not show a skin sensitizing effect.

Justification for classification or non-classification

Due to the negative LLNA results, classification and labelling according to Annex VI of Directive 67/548/EWG or Annex I of Directive 1272/2008 (EU-GHS) is not required for 3-hydroxy-2,2-dimethyl-propyl- 3'-hydroxy-2',2'dimethylpropionate.