Zinc bis(dibenzyldithiocarbamate)

Endpoint summary

Description of key information

The substance was studied in a GLP-compliant mouse Local Lymph Node assay (LLNA) and was concluded that is 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:

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)

Qualifier:

according to guideline

Guideline:

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

Qualifier:

according to guideline

Guideline:

EPA OPPTS 870.2600 (Skin Sensitisation)

GLP compliance:

yes (incl. QA statement)

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: approx. 11 weeks old)
- Weight at study initiation: within +/- 20% of the sex mean
- Housing: Individually in labeled Macrolon cages (MI type; height 12.5 cm) containing sterilized sawdust as bedding material (Litalabo, S.P.P.S., Argenteuil, France). Paper (Enviro-dri, Wm. Lillico & Son (Wonham Mill Ltd), Surrey, United Kingdom) was supplied as cage-enrichment. The paper was removed on Day 1 prior to dosing and was supplied again after scoring of the ears on Day 3.
- 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): 19.7– 22.9
- Humidity (%): 43 - 62
- Air changes (per hr): 15
- Photoperiod (hrs dark / hrs light): 12/12

Vehicle:

dimethyl sulphoxide

Concentration:

0, 10, 25 and 50% in DMSO

No. of animals per dose:

5 females/dose

Details on study design:

RANGE FINDING TESTS:
- Compound solubility: the vehicle (DMSO) was selected based on trial formulations performed at NOTOX and on test substance data supplied by the sponsor. Homogeneity was obtained to visually acceptable levels.
- Irritation: a preliminary irritation study was conducted in order to select the highest test substance concentration to be used in the main study. In principle, this concentration should be well tolerated systemically by the animals and may give moderate irritation (maximally grade 2) at the highest concentration.
Two test substance concentrations were tested; a 25% and 50% concentration. The highest concentration was the maximum concentration as required in the test guidelines (50% for solids).
- Lymph node proliferation response: no necropsy performed

MAIN STUDY
ANIMAL ASSIGNMENT AND TREATMENT
- Name of test method: LLNA
- Criteria used to consider a positive response: Stimulation Index (SI) calculated for each group. If the results indicate a SI ≥ 3, the test substance may be regarded as a skin sensitizer, based on the test guideline and recommendations done by ICCVAM

TREATMENT PREPARATION AND ADMINISTRATION: the dorsal surface of both ears was epidermally treated (25 μL/ear) with the test substance
concentration, at approximately the same time per day. The concentrations were mixed thoroughly using a vortex mixer immediately prior to dosing. The control animals were treated the same as the experimental animals, except that the vehicle was administered instead of the test substance.

Positive control substance(s):

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

Key result

Parameter:

SI

Value:

0.7

Test group / Remarks:

substance concentration 10%

Key result

Parameter:

SI

Value:

0.8

Test group / Remarks:

substance concentration 25%

Key result

Parameter:

SI

Value:

0.9

Test group / Remarks:

substance concentration 50%

Parameter:

other: disintegrations per minute (DPM)

Remarks on result:

other: 1058, 706, 880 and 975 DPM (mean/animal) for concentrations 0 (vehicle), 10, 25 and 50% test substance, respectively.

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed (not sensitising)

Additional information:

Skin sensitizing potential of zinc bis(dibenzyldithiocarbamate) (ZBEC) was studied in a GLP-compliant mouse Local Lymph Node assay (LLNA) (Notox B.V., 2010c). Groups of 5 female CDA/J mice were epidermally treated (25 μL/ear) with 10, 25 and 50% of the test substance in DMSO. The control group was treated with the same amount of vehicle only. Each animal was injected via the tail vein with 0.25 mL of sterile phosphate buffered saline (PBS) containing 20 μCi of 3H-methyl thymidine. After approximately five hours, all animals were sacrificed and the draining lymph node of each ear was excised to determine the number of desintegrations per minute (DPM) by scintillation counter. The stimulation indices (SI; ratio DPM for test group to DPM for control group) were determined for each dose level. The SI were 0.7, 0.8 and 0.9 for 10, 25 and 50% test concentrations of the substance in DMSO, respectively, suggesting that zinc bis(dibenzyldithiocarbamate) is not sensitizing to skin.

Justification for classification or non-classification

Based on the stimulation indices < 3 for 50% concentration of the test substance in DMSO in mouse LLNA, classification of zinc bis(dibenzyldithiocarbamate) (ZBEC) as sensitizing is not warranted in accordance with Directive 67/548/EEC and EU Classification, Labelling and Packaging of Substances and Mixtures (CLP) Regulation (EC) No. 1272/2008.