Magnesium zirconium oxide

Skin sensitisation

Administrative data

Endpoint:

skin sensitisation: in vivo (LLNA)

Type of information:

experimental study

Adequacy of study:

weight of evidence

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2010

Materials and methods

Test guideline

Test guideline 1

Qualifier:

according to guideline

Guideline:

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

Deviations:

not specified

Test guideline 2

Qualifier:

according to guideline

Guideline:

EPA OPPTS 870.2600 (Skin Sensitisation)

Deviations:

not specified

Test guideline 3

Qualifier:

according to guideline

Guideline:

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

Deviations:

not specified

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:

Magnesium hydroxide

EC Number:

215-170-3

EC Name:

Magnesium hydroxide

Cas Number:

1309-42-8

Molecular formula:

H2MgO2

IUPAC Name:

magnesium dihydroxide

Details on test material:

Identification: Magnesium hydroxide
Molecular formula: Mg(OH)2
Molecular weight: 58.32
CAS Number: 1309-42-8
Stable under storage conditions: Stable

In vivo test system

Test animals

Species:

mouse

Strain:

CBA

Sex:

female

Details on test animals and environmental conditions:

TEST ANIMALS
- Source: Charles River France, L'Arbresle Cedex, France
- Age at study initiation: Aprrox 9 weeks old.
- Weight at study initiation: Body weight variation was within +/- 20% of the sex mean.
- Housing: Individual housing in labelled Macrolon cages containing sterilised sawdust as bedding material. Paper 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: Free access to pelleted rodent diet.
- Water: Free access to tap water.
- Acclimation period: At least 5 days before the start of treatment.

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 21.0 ± 3.0°C
- Humidity (%): A relative humidity of 40-70%
- Air changes (per hr): 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: 14 April 2010 To: 17 May 2010

Study design: in vivo (LLNA)

Vehicle:

propylene glycol

Concentration:

The test animals were treated with test substance concentrations of 10, 25 or 50% w/w on three consecutive days, by open application on the ears. Five vehicle control animals were similarly treated, but with vehicle alone (propylene glycol). For allocation of the doses see Table 1.

No. of animals per dose:

3 groups of 5 female CBA/J mice were treated with one test substance concentration per group. One group of 5 female CBA/J mice were treated with vehicle.

Details on study design:

MAIN STUDY
A. INDUCTION EXPOSURE
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 control animals were treated the same as the experimental animals, except that, instead of the test substance, the vehicle alone was administered.

B. EXCISION OF THE NODES
- All animals: Each animal was injected via the tail vein with 0.25 mL of sterile phosphate buffered saline containing 20 µCi of 3 H-methylthymidine. After approximately five hours, all animals were killed by intraperitoneal injection with Euthasol 20%. The draining lymph node of each ear was excised. The relative size of the nodes 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
A single suspension of lymph node cells 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 200 g for 10 minutes at 4°C. To precipitate the DNA, the LNC were exposed to 5% trichloroacetic acid and stored in the refrigerator until the next day.

Results and discussion

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 2.0, 3.6 and 5.9 respectively. These results indicate that the test substance could elicit an SI >=3.

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 564, 1046 and 1690 DPM respectively. The mean DPM/animal value for the vehicle control group was 288 DPM.

Results 3

Parameter:

SI

Remarks:

10%

Value:

2

Results 4

Parameter:

SI

Remarks:

25%

Value:

3.6

Results 5

Parameter:

SI

Remarks:

50%

Value:

5.9

Any other information on results incl. tables

Skin reactions / Irritation (table 2):

- Very slight erythema was observed for all animals treated at 50%. No oedema was observed in any of the animals examined. White staining on the ears was observed at 10, 25 and 50%, which did not hamper the scoring of any skin reactions.

Macroscopy of the auricular lymph nodes and surrounding area:

- 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 in any of the animals.

Body weights (table 2):

- 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.

Toxicity and Mortality:

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

Table 2: Skin reactions after epidermal exposure and body weights

 

		Day 1	Day 3
Animal Number	Test substance (% w/w)	Body weight (g)	Skin reactions dorsal surface ear				Body weight (g)
			Left		Right
			Erythema	Oedema	Erythema	Oedema
1	25	22	0^2	0	0^2	0	21
2	20	22	1^2	0	1^2	0	22

 

Table 3: Disintegrations Per Minute (DPM) and Stimulation Index (SI)

 

Group	Test Substance (% w/w)	Mean DPM ±SEM	SI± SEM
2	10%	564 ± 121	2.0 ± 0.5
3	25%	1046 ± 313	3.6 ± 1.3
4	50%	1690 ± 258	5.9 ± 1.4
1	0%	288 ± 50	1.0 ± 0.2

Applicant's summary and conclusion

Interpretation of results:

other: sensitising

Conclusions:

According to the recommendations made in the test guidelines, magnesium hydroxide would be regarded as a skin sensitiser.

Executive summary:

The SI values calculated for the substance concentrations 10, 25 and 50% were 2.0, 3.6 and 5.9, respectively. These results indicate that the test substance could elicit an SI >= 3. The data showed a dose-response relationship and an EC3 value (the estimated test substance concentration that will give an SI = 3) of 19.4% was calculated.