Silicon dioxide

Skin sensitisation

Administrative data

Endpoint:

skin sensitisation: in vivo (LLNA)

Type of information:

experimental study

Adequacy of study:

key study

Study period:

28 January 2015 - 16 February 2015

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2015

Report date:

2015

Materials and methods

Test guideline

Test guideline 1

Qualifier:

according to guideline

Guideline:

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

Version / remarks:

July 2010

Deviations:

no

Test guideline 2

Qualifier:

according to guideline

Guideline:

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

Version / remarks:

May 2008, including most recent amendments

Deviations:

no

Test guideline 3

Qualifier:

according to guideline

Guideline:

EPA OPPTS 870.2600 (Skin Sensitisation)

Version / remarks:

March 2003

Deviations:

no

GLP compliance:

yes

Type of study:

mouse local lymph node assay (LLNA)

Test material

Test material information

Constituent 1

Reference substance name:

Silicon dioxide

EC Number:

231-545-4

EC Name:

Silicon dioxide

Cas Number:

7631-86-9

Molecular formula:

O2Si

IUPAC Name:

dioxosilane

Specific details on test material used for the study:

Appearance: Clear cloudy liquid
Batch: 15036
Purity/Composition: 28.0%
Test substance storage In refrigerator: 2-8°C
Stable under storage conditions: until 02 February 2016 (expiry date)

In vivo test system

Test animals

Species:

mouse

Strain:

other: CBA/J

Sex:

female

Details on test animals and environmental conditions:

- Source: Janvier, Le Genest-Saint-Isle, France.
- Age at study initiation: Young adult animals (approx. 10 weeks old)
- Weight at study initiation: 20 - 25 g
- Housing: Animals were group housed in labeled Makrolon cages. Paper and shelters were provided as cage-enrichment.
- Diet: Free access to pelleted rodent diet (SM R/M-Z from SSNIFF® Spezialdiäten GmbH, Soest, Germany).
- Water: Free access to tap water.
- Acclimation period: At least 5 days

ENVIRONMENTAL CONDITIONS (set to maintain)
- Temperature (°C): 18 – 24
- Humidity (%): 40 - 70
- Air changes (per hr): at least 10
- Photoperiod (hrs dark / hrs light): 12/12

IN-LIFE DATES: From: 28 January 2015 to 16 February 2015

Study design: in vivo (LLNA)

Vehicle:

dimethylformamide

Concentration:

0, 25, 50, 100% w/w

No. of animals per dose:

5

Details on study design:

RANGE FINDING TESTS:
In the pre-screen test another batch of the test substance was used since the test substance cannot be stored for more than three days. It was considered that this batch was representative for the batch used in the main study. Two test substance concentrations were tested; a 50% and 100% concentration of the test substance as delivered (corresponding to concentrations of the active ingredient of 14.0% and 28.0%, respectively).
The test system, procedures and techniques were identical to those used in the main study except that the animals were approximately 11 weeks (at initiation of treatment) and that the assessment of lymph node proliferation and necropsy were not performed. Two young adult animals per concentration were selected. Each animal was treated with one concentration on three consecutive days. Ear thickness measurements were conducted using a digital thickness gauge prior to dosing on days 1, 3 and 6.

MAIN STUDY
ANIMAL ASSIGNMENT AND TREATMENT
- Name of test method: Local Lymph Node Assay
- Criteria used to consider a positive response: DPM values are presented for each animal and for each dose group. A Stimulation Index (SI) is calculated for each group. The SI is the ratio of the DPM/group compared to DPM/vehicle control 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.

ANIMAL ASSIGNMENT
Three groups of five animals were treated with one test substance concentration per group. One group of five animals was treated with vehicle.

TREATMENT PREPARATION AND ADMINISTRATION:
Test substance preparation: The test substance preparations (w/w) were prepared within 4 hours prior to each dosing. No adjustment was made for specific gravity of the vehicle. Homogeneity was obtained to visually acceptable levels.
Rationale for vehicle: The vehicle was selected based on trial formulations performed at WIL Research Europe and on test substance data supplied by the sponsor.
Administration: 25 μL/ear

Induction - Days 1, 2 and 3; Excision of nodes - Day 6; Tissue processing for radioacitivity - Day 6; Radioactivity measurements - Day 7; Performed according to test guidelines.

Observations:
Mortality/Viability: Twice daily.
Body weights: On day 1 (pre-dose) and day 6 (prior to necropsy).
Clinical signs: Once daily on days 1-6 (on days 1-3 between 3 and 4 hours after dosing).
Irritation: Once daily on days 1-6 (on days 1 - 3 immediately after dosing) according to a numerical scoring system. Furthermore, a description of all other (local) effects was recorded according to guidelines.

Necropsy: No necropsy for gross macroscopic examination was performed according to protocol.

Interpretation:
DPM values are presented for each animal and for each dose group. A Stimulation Index (SI) is calculated for each group using the individual SI values. The individual SI is the ratio of the DPM/animal compared to DPM/vehicle control group.
If the results indicate a SI ≥ 3, the test substance may be regarded as a skin sensitizer.
The results are evaluated according to the Globally Harmonized System of Classification and Labelling of Chemicals (GHS) of the United Nations (2011) (including all amendments) and the Regulation (EC) No 1272/2008 of the European Parliament and of the Council of 16 December 2008 on classification, labelling and packaging of substances and mixtures, including all amendments.

Positive control substance(s):

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

Statistics:

Not performed.

Results and discussion

Positive control results:

The six-month reliability check with Alpha-hexylcinnamicaldehyde indicates that the Local Lymph Node Assay as performed at WIL Research Europe is an appropriate model for testing for contact hypersensitivity.

In vivo (LLNA)

Results

Results 1

Key result

Parameter:

SI

Value:

<= 0.9

Remarks on result:

other: The SI values calculated for the substance concentrations 25, 50 and 100% were 0.9, 0.8 and 0.7, respectively.

Results 2

Key result

Parameter:

SI

Value:

ca. 0.9

Test group / Remarks:

25%

Results 3

Key result

Parameter:

SI

Value:

ca. 0.8

Test group / Remarks:

50%

Results 4

Key result

Parameter:

SI

Value:

ca. 0.7

Test group / Remarks:

100%

Cellular proliferation data / Observations:

Mean DPM/animal values for the experimental groups treated with test substance concentrations 25, 50 and 100% were 532, 476 and 423 DPM, respectively. The mean DPM/animal value for the vehicle control group was 623 DPM.

Any other information on results incl. tables

Results Pre-screen test:

No irritation and no signs of systemic toxicity were observed in any of the animals examined. Variations in ear thickness during the observation period were less than 25% from Day 1 pre-dose values. Based on these results, the highest test substance concentration selected for the main study was a 100% concentration.

Other results - main study:

No irritation of the ears was observed in any of the animals examined.

All auricular lymph nodes of the animals of the experimental and control groups were considered normal in size. No macroscopic abnormalities of the surrounding area were noted for any of the animals.

No mortality occurred and no clinical signs of systemic toxicity were observed in the animals of the main study. Body weights and body weight gain of experimental animals remained in the same range as controls over the study period.

Applicant's summary and conclusion

Interpretation of results:

GHS criteria not met

Conclusions:

In an LLNA skin sensitisation study, performed according to OECD/EC test guidelines, Bindzil CC 301 was considered not to be a skin sensitiser, as the SI appeared not to be ≥ 3 when tested up to and including 100% w/w.