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Description of key information

LOAEL; OECD 429; GLP; skin sensitization was observed in mice (EC3 = 0.49%); reliability = 2.

CLASSIFIED: Cat 1

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:
comparable to guideline study with acceptable restrictions
Qualifier:
equivalent or similar to
Guideline:
OECD Guideline 429 (Skin Sensitisation: Local Lymph Node Assay)
Deviations:
no
GLP compliance:
not specified
Type of study:
mouse local lymph node assay (LLNA)
Species:
mouse
Strain:
CBA
Sex:
female
Vehicle:
acetone/olive oil (4:1 v/v)
Concentration:
2.5, 5, 10%
No. of animals per dose:
Not reported
Details on study design:
Animals were exposed topically on the dorsum of both ears to 25 microliters of test substance or to an equal volume of vehicle alone. Treatment was performed daily for three consecutive days. Five days after the initiation of exposure, all mice were injected via the tail vein with 250 microliters of phosphate-buffered saline containing 20 µCi if tritiated thymidine. The mice were sacrificed 5 hours later, and the draining auricular lymph nodes were excised and pooled for each experimental group or each individual animal. The incorporation of tritiated thymidine measured by beta scintillation counting was reported in disintegrations per minute. An SI was calculated for each chemical-treated group as the ratio of disintegrations per minute in the treated group (or mean disintegrations per minute when individual animals were assessed) to the disintegrations per minute or mean disintegrations per minute of the concurrent vehicle control group. The test substance was classified as a skin sensitizer if, at one or more test concentrations, it induced a threefold or greater incrrease in local lymph node proliferative activity when compared with concurrent vehicle-treated controls (SI ≥ 3).
Parameter:
EC3
Remarks on result:
other: 0.49% (estimated value derived by Gerberick GF, et al. (2005) from original data generated by Ashby J et al. (1995)).
Parameter:
SI
Test group / Remarks:
2%
Remarks on result:
other: test to control (T/C) ratio of 11.7
Parameter:
SI
Test group / Remarks:
5%
Remarks on result:
other: test to control (T/C) ratio of 15.4
Parameter:
SI
Test group / Remarks:
10%
Remarks on result:
other: test to control (T/C) ratio of 19.2
Parameter:
other: disintegrations per minute (DPM)
Remarks on result:
other: Not reported

The ratio of 3HTdR incorporation into test lymph nodes relative to that recorded for control nodes (T/C ratio) was calculated for each test group.

% Concentration

T/C Ratio

2.5

11.7

5

15.4

10

19.2

 

In this test, a T/C ratio of ≥3 has been the main criterion for classifying a substance as a sensitizer in the LLNA.

Interpretation of results:
Category 1 (skin sensitising) based on GHS criteria
Conclusions:
At three concentrations, 2%, 5%, and 10% the test substance is a sensitizing agent in the LLNA assay.
Executive summary:

The sensitizing activity of 106 chemicals was tested in the local lymph node assay. The policy is to classify a chemical as potential sensitizers if that chemical provokes, at least one concentration, a 3-fold or greater increase in isotope incorporation compared with vehicle-treated controls. The test substance was tested at concentrations of 2, 5, and 10% and was found to have test to control (T/C) ratios of 11.7, 15.4, and 19.2, respectively. The overall stimulation index (EC3) was calculated to be 0.49%. Thus the test substance is a sensitizing agent in the LLNA assay.

Endpoint conclusion
Endpoint conclusion:
adverse effect observed (sensitising)
Additional information:

The test substance was tested at concentrations of 2, 5, and 10% and was found to have test to control (T/C) ratio of 11.7, 15.4, and 19.2 respectively. The overall stimulation index (EC3) was calculated to be 0.49%. Based on this information, the substance is considered to be a sensitising agent in the LLNA assay.

Respiratory sensitisation

Endpoint conclusion
Additional information:

There were no observations of respiratory sensitisation during inhalation exposures with the substance.

Justification for classification or non-classification

Based on the overall stimulation index (EC3) from the local lymph node assay (LLNA), the substance is classified as Skin Sensitisation Category 1 (May cause an allergic skin reaction) according to EU Classification, Labelling and Packaging of Substances and Mixtures (CLP) Regulation (EC) No. 1272/2008.