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Description of key information

Niobium was negative in the murine LLNA.

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
Study period:
2009-08-31 to 2009-10-23
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)
Deviations:
no
GLP compliance:
yes (incl. QA statement)
Type of study:
mouse local lymph node assay (LLNA)
Species:
mouse
Strain:
CBA
Sex:
female
Details on test animals and environmental conditions:
TEST ANIMALS
- Source: Harlan Winkelmann, Borchen, Germany
- Age at study initiation: 8-9 weeks
- Weight at study initiation: 15-22 g
- Housing: in groups of 5 in IVC cages, type II L, polysulphone cages on Altromin saw fibre bedding
- Diet (ad libitum): ad libitum
- Water (ad libitum): ad libitum
- Acclimation period: 5 days

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 22+-3
- Humidity (%): 55+-10
- Air changes (per hr): 10
- Photoperiod (hrs dark / hrs light):12/12

IN-LIFE DATES: From: 2009-09-11 To: 2009-10-01
Vehicle:
other: acetone / oilive oil 3:1 (v/v)
Concentration:
25%, 50%, 100% (based on the results of the preliminary test)
No. of animals per dose:
5
Details on study design:
Preliminary test to test the highest tolerable and non-irritant dose (two animals used).
Two animals were treated by topical application of the test substance onto the entire dorsal surface of each ear for 3 consecutive days with 100% test item diluted in vehicle. An additional animal were treated with 100% vehicle and served as negative control. From day 1 to day 4 the ear thickness of each animal was measured.

MAIN STUDY
Each mouse was treated by topical application of 25 µL of the respective test substance solution or negative (vehicle) control onto the entire dorsal surface of the ear.
Topical applications were perforemed once daily for three consecutive days.
5 days after the first topical application all miced received 20 µCi 3H-methyl thymidine by intravenous injection.
5 hours later all mice were sacrificed. The draining auricular lymph nodes were excised, individually pooled for each animal and collected in PBS.
A single cell suspension of pooled lymphe node cells were prepared, washed and prepared for scintillation counting.
Incorporated 3H-methyl thymidine was measured by scintillatzion counting, and stimulation indices were determined.

OTHER:
Reliability checks with a positive control substance was performed periodically in the performing laboratory.
Positive control substance(s):
other: P-Phenylenediamine (CAS 106-50-3)
Positive control results:
Reliability checks with a positive control substance was performed periodically in the performing laboratory. The mean SI-value of the latest reliability check was 13.8.
Parameter:
SI
Value:
1.2
Test group / Remarks:
25%
Parameter:
SI
Value:
1.1
Test group / Remarks:
50%
Parameter:
SI
Value:
2.1
Test group / Remarks:
100%
Cellular proliferation data / Observations:
DPM (mean values):
DPM for negative control: 1251.5 DPM at an extract concentration of 25%: 1507.3 DPM at an extract concentration of 50%: 1428.4 DPM at an extract concentration of 100%: 2618.6

All animals survived throughout the test period without showing any clinical signs. All animals gained weight as expected.

Interpretation of results:
other: CLP/EU GHS criteria not met, no classification according to Regulation (EC) No 1272/2008
Conclusions:
According to OECD guideline 429 and EU criteria the test substance should not be classified for dermal sensitization.
CLP: not classified
Endpoint conclusion
Endpoint conclusion:
no adverse effect observed (not sensitising)
Additional information:

Niobium did not stimulate lymphocyte proliferation. In a murine LLNA a maximum SI of 2.1 was observed.

Respiratory sensitisation

Endpoint conclusion
Endpoint conclusion:
no study available

Justification for classification or non-classification

No classification as skin sensitizer is warranted.