1-ethyl-3-methyl-3H-imidazolium dicyanidoamide(1-)

Endpoint summary

Description of key information

The test substance showed an indication of skin sensitizing potential in an OECD 429 study.

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:

guideline study

Qualifier:

according to guideline

Guideline:

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

GLP compliance:

yes

Type of study:

mouse local lymph node assay (LLNA)

Specific details on test material used for the study:

- Name of test material (as cited in study report)t: EMIM Dicyanamid
- Purity: 97.4 g/100 g

Species:

mouse

Strain:

CBA

Sex:

female

Details on test animals and environmental conditions:

TEST ANIMALS
- Weight at study initiation: 0: 18.9 g – 21.8 g
- Housing: One animal per cage (type: Makrolon cage, type II).
- Diet: Kliba-Labordiaet (Maus / Ratte Haltung “GLP”), Provimi Kliba SA, Kaiseraugst, Basel, Switzerland, ad libitum
- Water: Tap water ad libitum
- Acclimation period: at least 5 days before the first test substance application
- Other: The single housed animals were identified by cage cards.

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 20 – 24
- Humidity (%): 30 – 70
- Photoperiod (hrs dark / hrs light): 12h light/12h darkmess

Vehicle:

other: 70% ethanol was used as the vehicle because good solubility of the preparation was achieved

Concentration:

Control group 1: 25 µL of 70% ethanol
Test group 2: 25 µL of 10% in 70% ethanol
Test group 3: 25 µL of 25% in 70% ethanol
Test group 4: 50% in 70% ethanol

No. of animals per dose:

5

Details on study design:

A solubility experiment was performed according to the recommendations given by OECD 429. The highest test-substance concentration which can be technically used was the undiluted test substance. The test-substance preparations/solutions at different concentrations were formulated in 70% ethanol. To determine the highest test-substance concentration that does not induce local signs of skin irritation and/or systemic toxicity, a pre-test (experimental conduct in accordance with GLP but without a GLP status) was performed. Two mice per dose group were treated with test substance concentrations of 25% and 50% or with the undiluted test substance on three consecutive days. The test-substance preparation was produced on a weight per weight basis shortly before the application by stirring with a magnetic stirrer. After stirring with a magnetic stirrer the test substance was soluble in the vehicle. Form of application: solution

Positive control substance(s):

other: Alpha-Hexylcinnamaldehyde, techn. 85%

Key result

Parameter:

EC3

Value:

26

Remarks on result:

other: 3H-thymidine incorporation

Parameter:

SI

Value:

2.27

Test group / Remarks:

10% in 70% ethanol

Remarks on result:

other: 3H-thymidine incorporation

Parameter:

SI

Value:

2.98

Test group / Remarks:

25% in 70% ethanol

Remarks on result:

other: 3H-thymidine incorporation

Parameter:

SI

Value:

3.53

Test group / Remarks:

50% in 70% ethanol

Remarks on result:

other: 3H-thymidine incorporation

Cellular proliferation data / Observations:

Beside slightly reduced mean body weights in test groups 3 and 4, no signs of systemic toxicity were noticed during general observation. When applied as 10%, 25% and 50% solution in 70% ethanol, the test substance induced a statistically significant increase of 3H-thymidine incorporation into the cells from the auricular lymph nodes, which was above the cut-off value for skin sensitization (increase above the cut off stimulation index (SI) of 3) at the 50% concentration. The 25% test substance preparation caused an increase of 3H-thymidine incorporation at the border of this value. Concomitantly, all concentrations induced statistically significant responses in the auricular lymph node cell counts, which failed the border of biological relevance (increase to 1.5fold or above of control value = stimulation index (SI) ≥ 1.5) at the 25% and 50% concentrations. In addition, both concentrations caused about the same statistically significant increase in lymph node weights. The ear weights of all concentrations showed some statistically significant increase as indication of slight ear skin irritation, but without a clear concentration response relation. Because the lymph node response cannot be fully attributed to the ear skin irritation observed, it is concluded that EMIM Dicyanamid exhibits a skin sensitizing potential in the Murine Local Lymph Node Assay under the test conditions chosen The threshold concentration for sensitization induction was ca. 25% for 3H-thymidine incorporation. Due to the difference in concentration-effect relationships of 3H-thymidine incorporation and cell count, no congruent estimated concentrations were obtained. The EC 3 (estimated concentration that leads to the SI of 3.0) for 3H-thymidine incorporation was calculated by linear regression from the results of the 25% and 50% concentrations to be 26%, while the SI of 1.5 for cell count was >50%.

Interpretation of results:

Category 1B (indication of skin sensitising potential) based on GHS criteria

Endpoint conclusion

Endpoint conclusion:

adverse effect observed (sensitising)

Additional information:

The potency to induce skin sensitisation was assessed in a study according to OECD 429 and in compliance with GLP criteria. In this study five female CBA mice per dose were exposed to 25 µL of the following test substance concentrations, 0 (control), 10%, 25% and 50%. A 70% ethanol solution was used as vehicle. These concentrations were based on a previously performed pre-test to determine the highest test-substance concentration that did not induce local signs of skin irritation and/or systemic toxicity. As a result, beside slightly reduced mean body weights in test groups 3 and 4, no signs of systemic toxicity were noticed during general observation. When applied as 10%, 25% and 50% solution in 70% ethanol, the test substance induced a statistically significant increase of 3H-thymidine incorporation into the cells from the auricular lymph nodes. The 50% concentration showed an SI > 3. The 25% test substance preparation caused an increase of 3H-thymidine incorporation at the border of an SI value of 3. The EC3 value was calculated by linear regression to be 26%.

Respiratory sensitisation

Endpoint conclusion

Endpoint conclusion:

no study available

Justification for classification or non-classification

Based on the available data, the test substance has to be classified as sensitising Category 1B, H317: May cause an allergic skin reaction according to EU Classification, Labelling and Packaging of Substances and Mixtures (CLP) Regulation (EC) No. 1272/2008.