Silicic acid (H2Si2O5), barium salt (1:1), lead-doped

Skin sensitisation

Administrative data

Endpoint:

skin sensitisation: in vivo (LLNA)

Type of information:

experimental study

Adequacy of study:

key study

Study period:

30 November 2009 - 14 December 2009

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: This study has been performed according to OECD and/or EC guidelines and according to GLP principles.

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2010

Report date:

2010

Materials and methods

Test guideline

Test guideline 1

Qualifier:

according to guideline

Guideline:

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

Deviations:

no

Test guideline 2

Qualifier:

according to guideline

Guideline:

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

Deviations:

no

Test guideline 3

Qualifier:

according to guideline

Guideline:

EPA OPPTS 870.2600 (Skin Sensitisation)

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Type of study:

mouse local lymph node assay (LLNA)

Test material

Test material information

Constituent 1

Reference substance name:

Silicic acid (H2Si2O5), barium salt (1:1), lead-doped

EC Number:

272-271-5

EC Name:

Silicic acid (H2Si2O5), barium salt (1:1), lead-doped

Cas Number:

68784-75-8

Molecular formula:

BaSi2O5::Pb

IUPAC Name:

barium(2+) {[oxido(oxo)silyl]oxy}silanoylolate λ²-plumbane

Details on test material:

- Name of test material (as cited in study report): Silicic acid(H2Si2O5), barium salt(1:1), lead-doped
- Substance type: White powder
- Physical state: Solid
- Molecular formula: BaSi2O5:Pb
- Molecular weight: 275.6 (based on theoretical value)
- Analytical purity: 100%
- Purity test date: 20-oct-2010
- Lot/batch No.: NP-800-11-232
- Expiration date of the lot/batch: 16 October 2010
- Stability under storage conditions: Stable
- Storage condition of test material: At room temperature in the dark
- General information: Keep away from acid
- pH (1% in water, indicative range): 9.5 – 9.6 (determined at NOTOX)
- Stability in propylene glycol: Unknown
- Solubility in propylene glycol: Not indicated

In vivo test system

Test animals

Species:

mouse

Strain:

other: CBA/J

Sex:

female

Details on test animals and environmental conditions:

TEST ANIMALS
- Source: Charles River France, L’Arbresle Cedex, France.
- Age at study initiation: approx. 11 weeks old
- Weight at study initiation: Body weight variation was within +/- 20% of the sex mean.
- Housing: Individual housing 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 (e.g. ad libitum): Free access to pelleted rodent diet (SM R/M-Z from SSNIFF® Spezialdiäten GmbH, Soest, Germany).
- Water (e.g. ad libitum): Free access to tap water.
- Acclimation period: The acclimatization period was at least 5 days before the start of treatment under laboratory conditions.
- Health inspection: A health inspection was performed prior to treatment, to ensure that the animals are in a good state of health. Special attention was paid to the ears, which were intact and free from any abnormality.

Results of analysis for diet (nutrients and contaminants), sawdust, paper and water were assessed and did not reveal any findings that were considered to have affected the study integrity. All certificates and results of analysis are retained in the NOTOX archives.

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 16.6 – 22.2ºC
- Humidity (%): 37 - 73%
Cleaning procedures in the room might have caused the temporary fluctuations above the optimal maximum level of 70% for relative humidity.
Temporary deviations from the minimum level of temperature and relative humidity occurred. Based on laboratory historical data, these fluctuations were considered not to have affected the study integrity.
- Air changes (per hr): approximately 15 air changes per hour
- Photoperiod (hrs dark / hrs light): 12 hours artificial fluorescent light and 12 hours darkness per day.

IN-LIFE DATES: From: 30 November 2009 To: 14 December 2009

Study design: in vivo (LLNA)

Vehicle:

propylene glycol

Concentration:

0 - 10 - 25 - 50%

No. of animals per dose:

5

Details on study design:

RANGE FINDING TESTS:
- Compound solubility: The vehicle was selected based on trial formulations performed at NOTOX and on test substance data supplied by the sponsor.
- 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 (undiluted for liquids, 50% for solids).
The test system, procedures and techniques were identical to those used during Days 1 to 3 of the main study unless otherwise specified. Two young adult animals were selected (8-14 weeks old. Each animal was treated with one concentration on three consecutive days. Approximately 3-4 hours after the last exposure, the irritation of the ears was assessed. Bodyweights were determined on Day 3. The animals were sacrificed after the final observation and no necropsy was performed.
- Lymph node proliferation response: Not determined in the preliminary irritation study.

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 (Ref 1).
Consideration was given to the EC3 value (the estimated test substance concentration that will give a SI =3) (Ref 2).

Ref 1. National Institute of Environmental Health Sciences, The Murine Lymph Node Assay: A test method for assessing the allergic contact dermatitis potential of chemicals/compounds. Independent peer review by the Interagency Coordinating Committee on the Validation of Alternative Methods (ICCVAM) and the National Toxicology Program Center for the Evaluation of Alternative Toxicological Methods (NICEATM), NIH publication; No 99-4494, February 1999.
Ref 2. Basketter DA, Lea LJ, Dickens A, Briggs, D, Pate I, Dearman RJ and Kimber I. A comparison of statistical approaches to the derivation of EC3 values from local lymph node assay dose responses. J Appl Toxicol 1999;19:261-266.

TREATMENT PREPARATION AND ADMINISTRATION:
Test substance preparation: The test substance formulations (w/w) were prepared within 4 hours prior to each treatment. 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 NOTOX and on test substance data supplied by the sponsor.

Induction - Days 1, 2 and 3:
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.

Excision of the nodes - Day 6:
Each animal was injected via the tail vein with 0.25 mL of sterile phosphate buffered saline (PBS) (Merck, Darmstadt, Germany) containing 20 μCi of 3H-methyl thymidine (PerkinElmer Life and Analytical Sciences, Boston, MA, US). After approximately five hours, all animals were killed by intraperitoneal injection with Euthasol® 20% (AST Farma BV, Oudewater, The Netherlands).
The draining (auricular) lymph node of each ear was excised. The relative size of the nodes (as compared to normal) was estimated by visual examination and abnormalities of the nodes and surrounding area were recorded. The nodes were pooled for each animal in approximately 3 mL PBS.

Tissue processing for radioactivity - Day 6:
A single cell suspension of lymph node cells (LNC) was prepared in PBS by gentle separation through stainless steel gauze (diameter 125 μm). LNC were washed twice with an excess of PBS by centrifugation at 200g for 10 minutes at 4ºC. To precipitate the DNA, the LNC were exposed to 5% trichloroacetic acid (TCA) (Merck, Darmstadt, Germany) stored in the refrigerator until the next day.

Radioactivity measurements - Day 7
Precipitates were recovered by centrifugation, resuspended in 1 mL TCA and transferred to 10 mL of Ultima Gold cocktail (PerkinElmer Life and Analytical Sciences, Boston, MA, US) as the scintillation fluid. Radioactive measurements were performed using a Packard scintillation counter (2800TR). Counting time was to a statistical precision of ± 0.2% or a maximum of 5 minutes whichever came first. The scintillation counter was programmed to automatically subtract background and convert Counts Per Minute (CPM) to Disintegrations Per Minute (DPM).

Observations:
Mortality/Viability: Twice daily.
Toxicity: At least once daily.
Body weights: On Days 1 (pre-treatment) and 6.
Necropsy: No necropsy was performed according to protocol.
Irritation: On Day 3 (3-4 hours after treatment), the skin reactions were assessed. Skin reactions were graded according to the following numerical scoring system. Furthermore descriptions of all other (local) effects were recorded.

Grading Irritation Reactions:
Erythema and eschar formation:
0: No erythema
1: Slight erythema (barely perceptible)
2: Well-defined erythema
3: Severe erythema (beef redness) to slight eschar formation (injuries in depth)

Oedema formation:
0: No oedema
1: Slight oedema (barely perceptible)
2: Moderate oedema
3: Severe oedema

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 NOTOX is an appropriate model for testing for contact hypersensitivity. See attached document 'Reliability check'.

In vivo (LLNA)

Results

Results 1

Parameter:

SI

Remarks on result:

other: The SI values calculated for the substance concentrations 10, 25 and 50% were 1.0, 1.4 and 1.1 respectively.

Results 2

Parameter:

other: disintegrations per minute (DPM)

Remarks on result:

other: Mean DPM/animal values for the experimental groups treated with test substance concentrations 10, 25 and 50% were 276, 377 and 295 respectively. The mean DPM/animal value for the vehicle control group was 268.

Any other information on results incl. tables

Tables and figures have been included in the attached document "LLNA tables and figures".

 

Preliminary irritation study:

At a 50% test substance concentration no signs of systemic toxicity were noted and no irritation was observed. Based on the results, the highest test substance concentration selected for the main study was a 50% concentration.

See also Table 1 in the attached document LLNA tables and figures

 

Main study:

No irritation of the ears and no oedema was observed in any of the animals examined. White staining of the dorsal surface of the ears was observed among all animals at a 25 and 50% test substance concentration, which did not hamper scoring of the skin reactions. 

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.

Body weights and body weight gain of experimental animals remained in the same range as controls over the study period. The slight body weight loss, noted in some animals, was considered not toxicologically significant.

No mortality occurred and no symptoms of systemic toxicity were observed in the animals of the main study.

Applicant's summary and conclusion

Interpretation of results:

not sensitising

Remarks:

Migrated information

Conclusions:

Since there was no indication that the test substance elicits an SI ≥ 3 when tested up to 50%, Silicic acid (H2Si2O5), barium salt (1:1), lead-doped was considered not to be a skin sensitizer. It was established that the EC3 value (the estimated test substance concentration that will give a SI =3) (if any) exceeds 50%.

Based on these results Silicic acid (H2Si2O5), barium salt (1:1), lead-doped would not be regarded as skin sensitizer according to the recommendations made in the test guidelines and does not have to be classified and has no obligatory labeling requirement for sensitization by skin contact according to the Globally Harmonized System of Classification and Labeling of Chemicals (GHS) of the United Nations (2007) and the Regulation (EC) No 1272/2008 on classification, labeling and packaging of substances and mixtures.