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Administrative data

Description of key information

The EC3 of the test chemical couldnot be calculated as the mean SI value was less than 3.0.

Based on the SI values, the test chemical was considered to be not sensitizing to skin.

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:
data from handbook or collection of data
Justification for type of information:
data is from peer reviewed journals
Qualifier:
according to
Guideline:
OECD Guideline 429 (Skin Sensitisation: Local Lymph Node Assay)
Principles of method if other than guideline:
To evaluate the potential of the test chemical for inducing allergic contact dermatitis in mice
GLP compliance:
not specified
Type of study:
mouse local lymph node assay (LLNA)
Species:
mouse
Strain:
CBA
Sex:
female
Details on test animals and environmental conditions:
Details on test animal
TEST ANIMALS
- Age at study initiation: 7-12 weeks
Vehicle:
dimethyl sulphoxide
Concentration:
25 µL of 1.0,10.0,25.0 w/v in vehicle
No. of animals per dose:
groups of female mice (number not specified)
Details on study design:
Details on study design

Pre –screen tests : No data

MAIN STUDY

ANIMAL ASSIGNMENT AND TREATMENT
- Name of test method: LLNA
- Criteria used to consider a positive response:
A substance was classified as a skin sensitizer if it induced a threefold or greater increase in local lymph node proliferative activity at one or more test concentrations when compared with concurrent vehicle-treated controls (SI≥3). Dose response data were used to measure the relative skin sensitization potency of all of the chemicals that were positive. When the LLNA dose-response curve included concentrations that induced at least one SI greater than 3 and one SI less than 3, EC3 values were calculated by linear interpolation. For chemicals that induced an SI greater than or equal to 3 at all concentrations tested, an EC3 value was extrapolated from the two lowest doses used. For this extrapolation method to work, a dose response should be evident. The relative sensitizing potencies of the chemical allergens were categorized via a recently proposed arbitrary classification scheme.

TREATMENT PREPARATION AND ADMINISTRATION: groups of CBA female mice (7–12 weeks of age) were exposed topically on the dorsum of both ears to 25 µL of test material or to an equal volume of the relevant vehicle alone. Treatment was performed daily for 3 consecutive days. Five days after the initiation of exposure, all mice were injected via the tail vein with 250 µL of phosphate buffered saline (PBS) containing 20 µCi of tritiated thymidine. 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 (dpm). A stimulation index (SI) was calculated for each chemical-treated group as the ratio of the dpm of the treated group (or mean dpm when individual animals were assessed) to the dpm or mean dpm of the concurrent vehicle control group.
Positive control substance(s):
not specified
Statistics:
no data available
Key result
Parameter:
EC3
Test group / Remarks:
test group
Remarks on result:
other: Couldnot be calculated as SI values were below 3
Remarks:
Not sensitizing
Cellular proliferation data / Observations:
The EC3 of the test chemical couldnot be calculated as the mean SI value was less than 3.0.

Table: Chemical Structures, Molecular Weights, LLNA Data, Potency Categorizations, and Reaction Mechanistic Domains

CAS

Vehicle

LLNA%

LLNA%

LLNA%

LLNA%

LLNA%

LLNA SI

LLNA SI

LLNA SI

LLNA SI

LLNA SI

LLNA EC3

Relative Potency

Reaction mechanism domain

67-71-0

DMSO

1.0

10.0

25.0

 

 

1.2

1.5

0.7

 

 

NC

Non sensitizer

NR

DMSO = Dimethylsulphoxide; LLNA – Local lymph node assay (LLNA% = weight per volume concentration); EC3 – Mathematically estimated concentration of the test chemical necessary to induce a threefold stimulation index; NR= non reactive

Interpretation of results:
other: not sensitizing
Conclusions:
The EC3 of the test chemical couldnot be calculated as the mean SI value was less than 3.0.
Based on the SI values, the test chemical was considered to be not sensitizing to skin.
Executive summary:

The dermal sensitization potential of the test chemicalwas evaluated in a mouse local lymphnode assay(LLNA). The study was performed as per OECD 429 Guidelines. Groups of female CBA mice (7-12 weeks of age) were exposed topically on the dorsum of both ears to 25µl of the test material or to an equal volume of relevant vehicle only. Treatment was performed daily for 3 consecutive days.Five days after the initiation of exposure, all mice were injected via the tail vein with 250 µL of phosphate buffered saline (PBS) containing 20 µCi of tritiated thymidine. 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 (dpm). A stimulation index (SI) was calculated for each chemical-treated group as the ratio of the dpm of the treated group (or mean dpm when individual animals were assessed) to the dpm or mean dpm of the concurrent vehicle control group.The approach to estimation of the relative skin sensitization potential was based on the mathematical estimation of the concentration of chemical necessary to obtain a threshold positive response (SI = 3); this is termed as the EC3 value.A substance was classified as a skin sensitizer if it induced a threefold or greater increase in local lymph node proliferative activity at one or more test concentrations when compared with concurrent vehicle-treated controls (SI≥3).

 

The EC3 of the test chemical couldnot be calculated as the mean SI value was less than 3.0.

Based on the SI values, the test chemical was considered to be not sensitizing to skin.
Endpoint conclusion
Endpoint conclusion:
no adverse effect observed (not sensitising)
Additional information:

Various studies have been reviewed to evaluate the dermal sensitization potential of the test chemical in living organisms. These include in vivo experimental studies performed on guinea pigs, mice for the testchemical. The results are summarized below:

The dermal sensitization potential of the test chemicalwas evaluated in a mouse local lymphnode assay(LLNA). The study was performed as per OECD 429 Guidelines. Groups of female CBA mice (7-12 weeks of age) were exposed topically on the dorsum of both ears to 25µl of the test material or to an equal volume of relevant vehicle only. Treatment was performed daily for 3 consecutive days.Five days after the initiation of exposure, all mice were injected via the tail vein with 250 µL of phosphate buffered saline (PBS) containing 20 µCi of tritiated thymidine. 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 (dpm). A stimulation index (SI) was calculated for each chemical-treated group as the ratio of the dpm of the treated group (or mean dpm when individual animals were assessed) to the dpm or mean dpm of the concurrent vehicle control group.The approach to estimation of the relative skin sensitization potential was based on the mathematical estimation of the concentration of chemical necessary to obtain a threshold positive response (SI = 3); this is termed as the EC3 value.A substance was classified as a skin sensitizer if it induced a threefold or greater increase in local lymph node proliferative activity at one or more test concentrations when compared with concurrent vehicle-treated controls (SI≥3).

The EC3 of the test chemical couldnot be calculated as the mean SI value was less than 3.0.

Based on the SI values, the test chemical was considered to be not sensitizing to skin.

This is suppprted by the results of a Guinea pig maximization test performed to determine the dermal sensitization potential of the test chemical.

Dunkin Hartley albino guinea pigs were sensitized by intradermal injection of a 4% solution of the test chemical. After a rest period of 2 weeks, the animals were subjected to the challenge exposure. The challenge was completed by epicutaneous application of the test article (16%) under occlusive dressing.

The injection of the test article at 4% caused slight irritation during the induction phase. No animals showed positive reactions at the challenge.

Hence, the test chemical can be considered to be not sensitizing to guinea pig skin.

These studies are further supported by the results of another guinea pig maximization test performed according to Magnusson and Kligman method to evaluate the sensitization potential of the test chemical. 10 Female albino guinea pigs of the Hartley strain were used in the study. 21 days after the initial intradermal injection (induction), 0.1 mL aliquots of various concentrations of the test substance were applied on the flank of each animal for challenge. The challenge was done by open patch test method, the chemical was left in place for 24h. For the induction phase, the undiluted DMSO was tested by intradermal injection whereas for challenge phase, the undiluted DMSO (0.1 mL aliquots) was tested by topical application. Dinitrochlorobenzene was used as positive control substance. Dermal response of each challenge site was evaluated 48 h after the challenge application.

No skin reactions were observed. Thus, from the study it can be considered that the test chemical was not sensitizing to skin.

Based on the available results, the test chemical can be considered to lack the potential to cause dermal sensitization. Hence, the test chemical can be considered to be not sensitizing to skin.

Respiratory sensitisation

Endpoint conclusion
Endpoint conclusion:
no study available

Justification for classification or non-classification

Based on the available results, the test chemical can be considered to lack the potential to cause dermal sensitization. Hence, the test chemical can be considered to be not sensitizing to skin.