Magnesium zirconium oxide

Endpoint summary

Description of key information

1. Information on zirconium dioxide
In a Guinea Pig Maximisation Test (Hartley strain), yttrium zirconium dioxide was observed to be not sensitising to the skin (Chemicals Inspection and Testing Institute, 1999).

2. Information on magnesium oxide
In the absence of data for magnesium oxide, the approach followed in the REACH dossier for magnesium hydroxide was included, which consists of a positive Local Lymph Node Assay with magnesium hydroxide (van Otterdijk, 2010c), which is considered as a false positive, and a negative Guinea Pig Maximisation Test with magnesium chloride (Ahuja, 2010), which is used to overrule the positive results obtained in the LLNA study with magnesium hydroxide. Based on thorough interpretation of these studies, magnesium hydroxide was considered as not sensitising to skin. These results are considered appliable to magnesium oxide too.

3. Conclusion on magnesium zirconium oxide
Based on the available data and information on the individual substances zirconium dioxide and magnesium oxide, magnesium zirconium oxide is not expected to cause sensitising effects in skin.

Key value for chemical safety assessment

Skin sensitisation

Link to relevant study records

Reference

Reference 1

Endpoint:

skin sensitisation: in vitro

Data waiving:

study scientifically not necessary / other information available

Justification for data waiving:

an in vitro skin sensitisation study does not need to be conducted because adequate data from an in vivo skin sensitisation study are available

Reference 2

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

Qualifier:

according to guideline

Guideline:

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

Deviations:

not specified

Qualifier:

according to guideline

Guideline:

EPA OPPTS 870.2600 (Skin Sensitisation)

Deviations:

not specified

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)

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

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.

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.

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.

Parameter:

SI

Remarks:

10%

Value:

2

Parameter:

SI

Remarks:

25%

Value:

3.6

Parameter:

SI

Remarks:

50%

Value:

5.9

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

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.

Reference 3

Endpoint:

skin sensitisation: in vivo (non-LLNA)

Type of information:

experimental study

Adequacy of study:

weight of evidence

Study period:

2010-01-25 to 2010-02-25

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 406 (Skin Sensitisation)

Deviations:

no

Qualifier:

according to guideline

Guideline:

EPA OPPTS 870.2600 (Skin Sensitisation)

Deviations:

no

Qualifier:

according to guideline

Guideline:

other: EC No. 440/2008, L 142

Deviations:

no

GLP compliance:

yes

Type of study:

guinea pig maximisation test

Justification for non-LLNA method:

This study was added to the dossier because the results of the LLNA study with magnesium dihydroxide were interpreted as false positive. The same approach was followed in the dossier for magnesium dihydroxide.

Species:

guinea pig

Strain:

Hartley

Sex:

female

Details on test animals and environmental conditions:

TEST ANIMALS
- Strain: Crl:HA
- Source: Charles River, 97633 Sulzfeld, Germany
- Age at study initiation: Approximately 5 weeks old
- Weight at study initiation: 354-408 g
- Housing: The animals were kept in groups in Terluran-cages on Altromin saw fibre bedding in an air-conditioned room.
- Diet: Free access to autoclaved hay and to Altromin 3122 maintenance diet for guinea pigs.
- Water: Free access to tap water.
- Acclimation period: At least five days.

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 22 ± 3°C
- Humidity (%): 55 ± 10%
- Air changes (per hr): At least 10x/ hour

IN-LIFE DATES: From: 25 January 2010 To: 25 February 2010

Route:

intradermal and epicutaneous

Vehicle:

other: physiological saline 0.9% NaCl and vaseline

Concentration / amount:

In the preliminary test one animal was treated intradermally with concentrations of 5% and 2.5% of the test item. Two animals were treated topically with concentrations of 100% and 50% of the test item for 24 as well as 48 hours.
Based on the results of this preliminary test, a concentration of 5% was chosen for the intradermal induction in the main test and a concentration of 50% was selected for the dermal induction.
A concentration of 50% was found to be the highest dose suspended in vehicle which did not cause any signs of irritation after topical treatment over 24 hours and therefore was chosen for the challenge application in the main test.

Route:

epicutaneous, occlusive

Vehicle:

other: physiological saline 0.9% NaCl and vaseline

Concentration / amount:

In the preliminary test one animal was treated intradermally with concentrations of 5% and 2.5% of the test item. Two animals were treated topically with concentrations of 100% and 50% of the test item for 24 as well as 48 hours.
Based on the results of this preliminary test, a concentration of 5% was chosen for the intradermal application of the main test and a concentration of 50% was selected for the dermal induction.
A concentration of 50% was found to be the highest dose suspended in vehicle which did not cause any signs of irritation after topical treatment over 24 hours and therefore was chosen for the challenge application in the main test.

No. of animals per dose:

Number of animals in the test group: 10
Number of animals in the negative control group: 5
Number of animals in the dose range finding study: 3

Details on study design:

INDUCTION - First stage - intradermal injection:
Three pairs of intradermal injections of 0.1 mL volume were given in the shoulder region which was cleared of hair by clipping so that one of each pair lies on each side of the midline.
Day 0:
Injection 1: a 1:1 mixture (v/v) FCA/physiological saline 0.9% NaCl
Injection 2: a 5% concentration of the test item in physiological saline 0.9% NaCl
Injection 3: a 5% concentration of the test item formulated in a 1:1 mixture (v/v) FCA/physiological saline 0.9% NaCl

Injections 1 and 2 were given close to each other and nearest to the head, while injection 3 is given towards the caudal part of the test area.

INDUCTION - Second stage - topical application
Day 6:
Approximately 24 hours before the topical application the test area was painted with 0.5 mL of 10% sodium lauryl sulphate in vaseline after close clipping, in order to create a local irritation.
Day 7:
The test item was suspended in vaseline at a concentration of 50%. A patch was fully loaded with 0.5 g of the prepared test item, applied to the test area and held in contact by an occlusive dressing for 48 hours.

CHALLENGE - Topical application
The flanks of treated animals were cleared of hair by close-clipping.
Day 20:
The test item was suspended in vaseline at a concentration of 50%. A patch, loaded with 0.5 g of the prepared test item was applied to the left flank of the animals. The patches were held in contact by an occlusive dressing for 24 hours. The application area was not rinsed with water.

OBSERVATION PERIOD
Approximately 21 hours after removing the patch, the challenge area was cleared of hair by the use of a depilatory cream. Approximately 24 and 48 hours after removing the patch the skin reaction was observed and recorded according to the grades shown below. Additionally all animals were observed for signs of toxicity at least once daily during the test period.

Patch test reaction
Grade
0 No visible change
1 Discrete or patchy erythema
2 Moderate and confluent erythema
3 Intense erythema and swelling

Challenge controls:

INDUCTION - First stage - intradermal injection:
Day 0:
Injection 1: a 1:1 mixture (v/v) FCA/physiological saline 0.9% NaCl
Injection 2: 100% physiological saline 0.9% NaCl
Injection 3: a 50% (v/v) formulation of NaCl 0.9% in a 1:1 (v/v) mixture FCA/physiological saline 0.9% NaCl.

Injections 1 and 2 were given close to each other and nearest to the head, while injection 3 is given towards the caudal part of the test area.

INDUCTION - Second stage - topical application
Day 6:
Approximately 24 hours before the topical application the test area was painted with 0.5 mL of 10% sodium lauryl sulphate in vaseline after close clipping, in order to create a local irritation.
Day 7:
A patch was fully loaded with 0.5 g of vaseline, applied to the test area and held in contact by an occlusive dressing for 48 hours.

CHALLENGE - Topical application
The flanks of control animals were cleared of hair by close-clipping.
Day 20:
A patch, loaded with 0.5 g of the vehicle was applied to the right flank of the animals. The patches were held in contact by an occlusive dressing for 24 hours. The application area was not rinsed with water.

Positive control substance(s):

yes

Remarks:

mercaptobenzothiazole (15% in vaseline)

Positive control results:

Sensitisation rate was 100%, confirming the reliability of the test system.

Reading:

1st reading

Hours after challenge:

24

Group:

test chemical

Dose level:

50%

No. with + reactions:

0

Total no. in group:

10

Clinical observations:

No effect

Reading:

1st reading

Hours after challenge:

48

Group:

test chemical

Dose level:

50%

No. with + reactions:

0

Total no. in group:

10

Clinical observations:

No effect

Reading:

1st reading

Hours after challenge:

24

Group:

negative control

Dose level:

50%

No. with + reactions:

1

Total no. in group:

5

Clinical observations:

Erythema grade 1 was observed after 24 hours in one animal.

Reading:

1st reading

Hours after challenge:

48

Group:

negative control

Dose level:

50%

No. with + reactions:

0

Total no. in group:

5

Clinical observations:

No effect

Group:

positive control

Remarks on result:

not measured/tested

The animals of the test group showed no reduced weight gain compared to historical data.

All animals of both groups survived throughout the test period.

There are signs of irritation during the induction

Intradermal Induction I (24 hours reading):

- Injection site 1: erythema grade 2 in 5/5 control and 10/10 test animals, oedema grade 2 in 4/5 control and 10/10 test animals, oedema grade 1 in 1/5 control animals

- Injection site 2: erythema grade 1 in 9/10 test animal, eschar in 8/10 test animals

- Injection site 3: erythema grade 2 in 1/5 control and 1/10 test animals, erythema grade 1 in 1/5 control and 9/10 test animals, oedema grade 2 in 1/5 control and 1/10 test animals, oedema grade 1 in 1/5 control and 2/10 test animals eschar in 1/5 control and 6/10 test animals

Intradermal Induction I (48 hours reading):

- Injection site 1: erythema grade 2 in 1/5 control and 3/10 test animals, erythema grade 1 in 4/5 control and 7/10 test animals, oedema grade 2 in 1/5 control and 3/10 test animals, oedema grade 1 in 4/5 control and 7/10 test animals, necrosis (Ø 0.4 cm) in 1/10 test animals eschar in 1/5 control and 1/10 test animals

- Injection site 2: erythema grade 1 in 4/5 test animals

- Injection site 3: erythema grade 1 in 2/5 control and 9/10 test animals, oedema grade 1 in 1/5 control and 1/10 test animals

Dermal Induction II (48 hours exposure, occlusive):

- Immediately after removing the patch: Desquamation in 1/5 control animals, erythema grade 1 in 2/10 test animals

24 hours after removing the patch: Eschar in 5/5 control and 10/10 test animals, erythema grade 1 in 1/10 test animals, desquamation in 1/10 test animals

Interpretation of results:

GHS criteria not met

Conclusions:

Under the conditions of this study, there was no evidence of sensitisation in the test item group at the challenge and the percentage of animals sensitised was 0%.

Executive summary:

The test for sensitisation is performed on the guinea pig according OECD Guidelines No. 406. The following concentrations were determined by a preliminary test:

- intradermal induction: 5% of the test item, vehicle: physiological saline 0.9% NaCl

- dermal induction: 50% of the test item, vehicle: vaseline

- challenge exposure (the highest non-irritating dose): 50% of the test item, vehicle: vaseline.

During the induction slight signs of irritation were observed. These findings confirmed the validity of the study.

After the challenge exposure no erythema was observed in any of the test animals at any time. Erythema grade 1 was observed after 24 hours in one animal of the control group. No oedema was observed in any animal at any time. There was no evidence of sensitisation at the challenge and the percentage of animals sensitised was 0%.

Reference 4

Endpoint:

skin sensitisation, other

Remarks:

LLNA and GPMT

Type of information:

read-across from supporting substance (structural analogue or surrogate)

Adequacy of study:

weight of evidence

Justification for type of information:

Read across based on the study from the Chemicals Inspection and Testing Institute (1999) with yttrium zirconium dioxide (GPMT), a study from van Otterdijk (2010c) with magnesium hydroxide (LLNA) and a study from Ahuja (2010) with magnesium dichloride (GPMT). The read across justification document is attached in IUCLID Section 13.

Reason / purpose for cross-reference:

read-across source

Reason / purpose for cross-reference:

read-across source

Reason / purpose for cross-reference:

read-across source

Key result

Reading:

other: read across conclusion

Remarks on result:

other: Magnesium zirconium oxide is not expected to cause sensitising effects in skin.

Remarks:

Conclusion based on the GPMT studies from Ahuja (2010) and the Chemicals Inspection and Testing Institute (1999) performed with the read across substances magnesium dichloride and yttrium zirconium oxide, respectively. The GPMT study from Ahuja (2010) was considered to overrule the (false positive) results of the LLNA study with magnesium hydroxide (van Otterdijk, 2010c).

Reference 5

Endpoint:

skin sensitisation: in vivo (non-LLNA)

Type of information:

experimental study

Adequacy of study:

weight of evidence

Study period:

1999-03-08 to 1999-05-24

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

guideline study with acceptable restrictions

Remarks:

Non-GLP study.

Qualifier:

according to guideline

Guideline:

other: Maximization Test of the Guideline for Toxicity Studies of Drugs (Notification No. 1-24 of Pharmaceuticals and Cosmetics Division dated September 11, 1989)

Qualifier:

equivalent or similar to guideline

Guideline:

OECD Guideline 406 (Skin Sensitisation)

GLP compliance:

not specified

Type of study:

guinea pig maximisation test

Justification for non-LLNA method:

Study was performed before the LLNA method became the preferred method for skin sensitisation testing.

Species:

guinea pig

Strain:

Hartley

Sex:

female

Details on test animals and environmental conditions:

TEST ANIMALS
- Source: Charles River Laboratories Japan, Inc.
- Age at study initiation: 4 weeks old
- Weight at study initiation: 272 g - 302 g
- Housing: Five guinea pigs were kept together in each aluminum bracket cage (360 W x 520 D x 330 H mm, Bottom: 320 W x 480 D mm) until the elicitation treatment, then were kept individually in aluminum bracket cages (220 W x 380 D x 250 H mm) after the elicitation treatment. The cages were changed once a week.
- Diet: Solid feed (RC4, Oriental Yeast Col, Ltd)
- Water: Hita municipal water supply was used for water, which was provided freely by automatic water-supply equipments.
- Acclimation period: no data

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 23+/- 2 degrees C
- Humidity (%): 55 +/- 15%
- Air changes (per hr): 10 ~ 15 ventilation per hour
- Photoperiod (hrs dark / hrs light): 12 hour light and dark period (light on at 7 am - off at 7 pm)

IN-LIFE DATES: From: 1999-02-23 To: 1999-05-24

Route:

intradermal

Vehicle:

physiological saline

Concentration / amount:

2.5% w/v in physiological saline
Amount applied: 0.1 mL per injection

Day(s)/duration:

Day 1

Adequacy of induction:

not specified

Route:

epicutaneous, occlusive

Vehicle:

other: distilled injection water

Concentration / amount:

25% w/v in distilled injection water
Amount applied: 0.2 mL

Day(s)/duration:

Day 8, 48 h of exposure

Adequacy of induction:

non-irritant substance, but skin pre-treated with 10% SDS

No.:

#1

Route:

epicutaneous, occlusive

Vehicle:

other: distilled injection water

Concentration / amount:

25% and 2.5% w/v in distilled injection water
Amount applied: 0.1 mL

Day(s)/duration:

Day 22, 24 h of exposure

Adequacy of challenge:

not specified

No. of animals per dose:

Control group: 5 animals
Test agent group: 10 animals
Positive conrol group: 5 animals

Details on study design:

Intradermal sensitisation:
Suprascapular fur was shaved by an electric clipper in order to establish 2x4 cm sensitisation regions, and with the midline as the axis of symmetry, 0.1 mL of below preparations were injected per region of each left-right pair.
1) Test agent group
E-FCA
2.5% test agent
2.5% test agent/FCA emulsion
2) Control group
E-FCA (2 pairs in total)
3) Positive control group
E-FCA
0.1% DNCB/olive oil
0.1% DNCB/FCA emulsion

Patch sensitisation:
Six days after the intradermal sensitisation, the fur in the sensitisation regions of the animals in the control groups and the test agent group were shaved by an electric clipper and an electric shaver, then sodium lauryl sulfate (contains 10% petrolatum) was applied. Seven days after the intradermal sensitisation, the control group was applied with distilled injection water, the test agent group with 25% test agent, and the positive control group with 0.5% DNCB, by placing 2x4 cm lints (Nankai Sangyou Co.) moistened with 0.2 mL each of the preparation on the shaved sensitisation regions and by covering them with rubber dam sheets (Nihon Rikagaku Industry Co., Ltd.), then the trunks were wrapped with Dermicel (Johnson & Johnson K.K.) for 48 hours for occlusive dressing.

Elicitation treatment (challenge):
Fourteen days after the start of the patch sensitisation, the flank fur of the animals was shaved by an electric clipper and an electric shaver, and for the control group and the test agent group, the areas were applied with 25% test agent and 2.5% test agent to each group, respectively, by placing 2x2 cm lints moistened with 0.1 mL of the preparation, and by covering them with oil paper and rubber dam sheets, then the trunks were wrapped with Dermicel (Johnson & Johnson K.K.) for 24 hours for occlusive dressing. For the positive control group, 0.1% DNCB was applied by placing 2x2 cm lints moistened with 0.1 mL of the preparation and by covering them with rubber dam sheets, then the trunks were wrapped with Dermicel (Johnson & Johnson K.K.) for 24 hours for occlusive dressing.

Challenge controls:

25% test agent
- 2.5 g of the test agent was suspended in distilled injection water to make 10 mL.
2.5% test agent
- 0.25 g of the test agent was suspended in distilled injection water to make 10 mL.
0.1% DNCB (2,4-dinitrochlorobenzene, positive control substance)
- 0.01 g of DNCB was dissolved in ethanol to make 10 mL.

Positive control substance(s):

yes

Remarks:

DNCB (2,4-dinitrochlorobenzene)

Positive control results:

0.1% DNCB elicited region: Diffuse moderate erythema or severe erythema and oedema were acknowledged in every sample 24 and 48 hours after the elicitation patch removal. Furthermore, scab formations were acknowledged in 4/5 cases after both 24 and 48 hours, and desquamation was acknowledged in all cases after 48 hours. The average scores 24 and 48 hours after the elicitation patch removal were 3.0 and 2.8, respectively.

Reading:

1st reading

Hours after challenge:

24

Group:

test chemical

Dose level:

25% w/v in distilled injection water

No. with + reactions:

0

Total no. in group:

10

Clinical observations:

none

Remarks on result:

no indication of skin sensitisation

Reading:

2nd reading

Hours after challenge:

48

Group:

test chemical

Dose level:

25% w/v in distilled injection water

No. with + reactions:

0

Total no. in group:

10

Clinical observations:

none

Remarks on result:

no indication of skin sensitisation

Reading:

1st reading

Hours after challenge:

24

Group:

test chemical

Dose level:

2.5% w/v in distilled injection water

No. with + reactions:

0

Total no. in group:

10

Clinical observations:

none

Remarks on result:

no indication of skin sensitisation

Reading:

2nd reading

Hours after challenge:

48

Group:

test chemical

Dose level:

2.5% w/v in distilled injection water

No. with + reactions:

0

Total no. in group:

10

Clinical observations:

none

Remarks on result:

no indication of skin sensitisation

Reading:

1st reading

Hours after challenge:

24

Group:

negative control

Dose level:

25% w/v in distilled injection water

No. with + reactions:

0

Total no. in group:

5

Clinical observations:

none

Remarks on result:

no indication of skin sensitisation

Reading:

2nd reading

Hours after challenge:

48

Group:

negative control

Dose level:

25% w/v in distilled injection water

No. with + reactions:

0

Total no. in group:

5

Clinical observations:

none

Remarks on result:

no indication of skin sensitisation

Reading:

1st reading

Hours after challenge:

24

Group:

negative control

Dose level:

2.5% w/v in distilled injection water

No. with + reactions:

0

Total no. in group:

5

Clinical observations:

none

Remarks on result:

no indication of skin sensitisation

Reading:

2nd reading

Hours after challenge:

48

Group:

negative control

Dose level:

2.5% w/v in distilled injection water

No. with + reactions:

0

Total no. in group:

5

Clinical observations:

none

Remarks on result:

no indication of skin sensitisation

Reading:

1st reading

Hours after challenge:

24

Group:

positive control

Dose level:

0.1% w/v DNCB in ethanol

No. with + reactions:

5

Total no. in group:

5

Clinical observations:

Diffuse moderate erythema or severe erythema and oedema were acknowledged in every animal. Furthermore, scab formations were acknowledged in 4 out of 5 animals.

Remarks on result:

positive indication of skin sensitisation

Reading:

2nd reading

Hours after challenge:

48

Group:

positive control

Dose level:

0.1% w/v DNCB in ethanol

No. with + reactions:

5

Total no. in group:

5

Clinical observations:

Diffuse moderate erythema or severe erythema and oedema were acknowledged in every animal. Furthermore, scab formations were acknowledged in 4 out of 5 animals, and desquamation was acknowledged in all cases.

Remarks on result:

positive indication of skin sensitisation

Skin Reaction

2.1 Test Agent Group

1) 25% test agent elicited region

No skin reaction was acknowledged 24 and 48 hours after the elicitation patch removal.

The average scores 24 and 48 hours after the elicitation patch removal were both 0.

2) 2.5% test agent elicited region

No skin reaction was acknowledged 24 and 48 hours after the elicitation patch removal.

The average scores 24 and 48 hours after the elicitation patch removal were both 0.

2.2 Control Group

1) 25% test agent elicited region

No skin reaction was acknowledged 24 and 48 hours after the elicitation patch removal.

The average scores 24 and 48 hours after the elicitation patch removal were both 0.

2) 2.5% test agent elicited region

No skin reaction was acknowledged 24 and 48 hours after the elicitation patch removal.

The average scores 24 and 48 hours after the elicitation patch removal were both 0.

Interpretation of results:

GHS criteria not met

Conclusions:

Since no skin reaction was acknowledged in the elicited region of either the test agent group or the control group, it was concluded that the test substance does not have skin sensitising potential under the conditions of this test. On the other hand, it was confirmed that 2,4-dinitrochlorobenzene, the positive control agent, has an extreme skin sensitising potential.

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed (not sensitising)

Additional information:

1. Information on zirconium dioxide

One reliable (Klimisch 2) study was available for the skin sensitisation endpoint (Chemicals Inspection and Testing Institute, 1999). The test was performed according to OECD guideline 406 and the Maximization Test of the Guideline for Toxicity Studies of Drugs (Notification No. 1-24 of Pharmaceuticals and Cosmetics Division dated September 11, 1989). This study was performed with yttrium zirconium oxide, i.e. zirconia stabilised with a small amount of yttrium, and was considered relevant for zirconium dioxide as yttrium was demonstrated not to affect the non-hazardous toxicological profile of zirconium dioxide. The test substance was not found to be sensitising to the skin, and consequently, pure zirconium dioxide was also concluded not to be sensitising to skin.

2. Information on magnesium oxide

The results for magnesium oxide were based on data for the read across substances magnesium chloride and magnesium hydroxide. A first study (van Otterdijk, 2010c) was performed with magnesium hydroxide according to OECD Guideline 429 (LLNA). 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. This indicates that the substance could be regarded as a skin sensitiser. These results are however interpreted as false positive (see further) and therefore a second study was added to the dossier (same approach followed in the magnesium hydroxide dossier), performed with magnesium chloride according to OECD Guideline 406 (Guinea Pig Maximisation Test) (Ahuja, 2010). Under the conditions of the present study the test item did not elicit a reaction identified as sensitisation at the tested concentration. According to the EC criteria for classification and labelling requirements for dangerous substances and preparations (Guidelines in Commission Directive 2001/59/EC) as well as the Annex I of Regulation (EC) 1272/2008 classification and labelling is not necessary as the sensitisation rate is less than 30%.

Although the results of the local lymph node assay (LLNA) with magnesium hydroxide were apparently positive it is proposed that the positive result should be interpreted as a false positive and that magnesium hydroxide should not be classified as a skin sensitiser.

There are a number of reasons to suggest that it is highly unlikely that magnesium hydroxide is a skin sensitiser. An expert opinion has been provided from the Informationsverbund Dermatologischer Kliniken (IVDK; Schnuch, 2010). The IVDK is a network of over 50 dermatological hospitals, and was formed to monitor and survey the development of contact allergies. Despite 20 years of observations in 192,421 patients they have yet to observe a case of a contact allergy with magnesium hydroxide. Furthermore, no case of contact allergy to magnesium hydroxide has been reported in the world literature, despite extensive exposure of the general population to the substance. Some reports on flame retardants address magnesium hydroxide toxicity, and no sensitising effects are reported (DFE (EPA), 2008; NAP, 2000).

Furthermore, the results of a guinea pig maximisation test (GPMT) performed with magnesium chloride show that magnesium chloride was negative in the GPMT (Ahuja, 2010). As any possible skin sensitising potential of magnesium hydroxide is likely to stem from the cation rather than the hydroxide anion, the outcome of this test provides additional evidence that magnesium ions should not be regarded as a skin sensitiser. Regarding the hydroxide portion of the compound, there is ample evidence in the literature that hydroxides of other metals are not skin sensitisers (NICNAS, 2003; Banerjee et al., 2003; DFE (EPA), 2008).

False positives in the LLNA assay are not uncommon, and indeed the LLNA was judged to be no more than 90% accurate during its validation (Basketter et. al., 2010). On this basis, certain substances have not been classified as contact sensitisers despite giving positive responses in the LLNA test. These include copper chloride (Basketter and Scholes, 1992), sodium lauryl sulphate (Loveless et al., 1996; Montelius et al., 1994), benzalkonium chloride (Basketter et al., 2004) and ethanol (Basketter et al., 2010).

 

Given the combination of the epidemiological data, the negative magnesium chloride guinea pig maximisation test, and the history of false positives using the LLNA test, the weight of evidence suggests that the positive results obtained in the LLNA test are inaccurate and, thus, a skin sensitising effect of magnesium hydroxide is unlikely. Therefore, magnesium hydroxide should not be classified as a skin sensitiser. This conclusion is considered representative for magnesium oxide too.

References:

- Banerjee G, Iyer VJ, Cherian KM, 2003. A rapid in vitro method for identifying contact allergens and irritants. Toxicol Mech Methods 13(2), 103-109.

- Basketter DA, Kimber I, 2010. Skin sensitisation, false positives and false negatives: experience with guinea pig assays. J Appl Toxicology 30(5), 381-386.

- Basketter DA, Scholes EW, 1992. Comparison of the local lymph node assay with the guinea-pig maximization test for the detection of a range of contact allergens. Food Chem Toxicol 30(1), 65-69.

- Basketter DA, Marriott M, Gilmour NJ, White IR, 2004. Strong irritants masquerading as skin allergens: the case of benzalkonium chloride. Contact Dermatitis 50(4), 213-217.

- Loveless SE, Ladics GS, Gerberick GF, Ryan CA, Basketter DA, Scholes EW, House RV, Hilton J, Dearman RJ, Kimber I, 1996. Further evaluation of the local lymph node assay in the final phase of an international collaborative trial. Toxicology 108(1-2), 141-152.

- Montelius J, Wahlkvist H, Boman A, Fernström P, Gråbergs L, Wahlberg JE, 1994. Experience with the murine local lymph node assay: inability to discriminate between allergens and irritants. Acta Derm Venereol 74(1), 22-27.

- Schnuch A, 2010. Expert opinion with regard to the sensitising properties of magnesium hydroxide.

- NAP, 2000. http://www.nap.edu/catalog.php?record_id=9841

- DFE (EPA), 2008. http://www.epa.gov/dfe/pubs/projects/pcb/full_report_pcb_flame_retardants_report_draft_11_10_08_to_e.pdf

- NICNAS, 2003. http://www.nicnas.gov.au/publications/information_sheets/existing_chemical_information_sheets/ecis_naoh_pdf.pdf

3. Conclusion on magnesium zirconium oxide

Based on the available data for the individual substances zirconium dioxide (read across from yttrium zirconium oxide) and magnesium oxide (read across from magnesium hydroxide and magnesium chloride), magnesium zirconium oxide is concluded not to be sensitising to skin. The read across justification is included in IUCLID Section 13.

Respiratory sensitisation

Endpoint conclusion

Endpoint conclusion:

no study available

Justification for classification or non-classification

1. Information on zirconium dioxide

Based on the test results for the read across substance yttrium zirconium oxide and according to the criteria of the CLP Regulation,

zirconium dioxide should not be classified as a skin sensitiser.

No reliable data are available for respiratory sensitisation, therefore no conclusion can be made on the classification of this endpoint.

2. Information on magnesium oxide

Based on the test results for the read across substances magnesium chloride and magnesium hydroxide and according to the criteria of the CLP Regulation, magnesium oxide should not be classified as a skin sensitiser.

No reliable data are available for respiratory sensitisation, therefore no conclusion can be made on the classification of this endpoint.

3. Conclusion on magnesium zirconium oxide

Based on the available information for zirconium dioxide (read across from yttrium zirconium oxide) and magnesium oxide (read across from magnesium chloride and magnesium hydroxide), it is concluded that magnesium zirconium oxide does not have to be classified as a skin sensitiser either.

In the absence of experimental data that would allow to conclude on repiratory sensitisation, no conclusion can be drawn on the

classification for this endpoint.