Magnesium hydroxide

Endpoint summary

Description of key information

The potential of magnesium hydroxide to induce skin and eye corrosion/irritation was tested in suitable in vitro and in vivo methods. Based on the results, magnesium hydroxide is considered to be non-irritant to the skin and eye.

Key value for chemical safety assessment

Skin irritation / corrosion

Link to relevant study records

Reference

Reference 1

Endpoint:

skin corrosion: in vitro / ex vivo

Type of information:

experimental study

Adequacy of study:

weight of evidence

Study period:

2010-03-05 to 2010-03-23

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 431 (In Vitro Skin Corrosion: Human Skin Model Test)

Version / remarks:

adopted 13 April 2004

Deviations:

no

GLP compliance:

yes

Specific details on test material used for the study:

- Name of the test material used in the report: Magnesium hydroxide
- Appearance: white powder
- Batch No.: 20BR0026
- Purity: 99.90%
- Storage: at room temperature in the dark
- Expiry date: 2012-01-31

Test system:

human skin model

Source species:

human

Cell type:

non-transformed keratinocytes

Justification for test system used:

This test uses the EpiDerm™ reconstructed human epidermis model which consists of human-derived epidermal keratinocytes which have been cultured to form a multilayered, highly differentiated model of the human epidermis and therefore represents in vitro the target organ of the species of interest and closely mimics the biochemical and physiological properties of the upper parts of the human.

Vehicle:

water

Details on test system:

RECONSTRUCTED HUMAN EPIDERMIS (RHE) TISSUE
- Model used: EpiDerm Skin Model (EPI-200) from MatTek Corporation, Ashland MA, U.S.A.
- Tissue batch number(s): 12985 kit H

TEMPERATURE USED FOR TEST SYSTEM
- Temperature used during treatment / exposure: 37.0 ± 1.0 °C (actual range: 37.0 – 37.4 °C)

REMOVAL OF TEST MATERIAL AND CONTROLS
- After exposure period, the tissues were washed with phosphate buffered saline to remove residual test substance. Rinsed tissues were kept in 24 well plates in 300 µL DMEM medium until 6 tissues were dosed and rinsed.

MTT DYE USED TO MEASURE TISSUE VIABILITY AFTER TREATMENT / EXPOSURE
- MTT concentration: 1 mg/mL
- Incubation time: 3 hours at 37 °C
- Spectrophotometer: Multiskan Spectrum (Thermo Labsystems)
- Wavelength: 540 nm

NUMBER OF REPLICATE TISSUES: 2

PREDICTION MODEL / DECISION CRITERIA (choose relevant statement)
- The test substance is considered to be corrosive to skin if
a) The relative mean tissue viability obtained after 3-minute treatment compared to the negative control tissues is decreased below 50%.
b) In addition, a test substance considered non-corrosive (viability a 50%) after the 3-minute treatment is considered corrosive if the relative tissue viability after 1-hour treatment with the test substance is decreased below 15%.

- The test substance is considered non-corrosive in the in vitro skin corrosion test if:
a) The relative mean tissue viability obtained after the 3-minute treatment compared to the negative control tissues is not decreased below 50%.
b) In addition, the relative tissue viability after the 1-hour treatment is not decreased below 15%.

Control samples:

yes, concurrent vehicle

yes, concurrent positive control

Amount/concentration applied:

TEST MATERIAL
- Amount(s) applied (volume or weight with unit): 25 mg

VEHICLE
- Amount(s) applied (volume or weight with unit): 25 µL

NEGATIVE CONTROL
- Amount(s) applied (volume or weight): 25 µL

POSITIVE CONTROL
- Amount(s) applied (volume or weight): 50 µL

Duration of treatment / exposure:

3 min and 60 min

Duration of post-treatment incubation (if applicable):

3 hours

Number of replicates:

2 for each incubation time

Irritation / corrosion parameter:

% tissue viability

Run / experiment:

3 minutes / mean of two tissues

Value:

88

Vehicle controls validity:

valid

Negative controls validity:

not applicable

Positive controls validity:

valid

Remarks on result:

no indication of irritation

Irritation / corrosion parameter:

% tissue viability

Run / experiment:

1 hour / mean of two tissues

Value:

95

Vehicle controls validity:

valid

Negative controls validity:

not applicable

Positive controls validity:

valid

Remarks on result:

no indication of irritation

Other effects / acceptance of results:

OTHER EFFECTS:
- Direct-MTT reduction: No color change was observed. Thus, magnesium hydroxide did not interact with MTT

ACCEPTANCE OF RESULTS:
- The absolute mean OD540 (optical density at 540 nm) of the negative control tissues was within the laboratory historical control data range. The mean relative tissue viability following 3-minute exposure to the positive control was 9%. The maximum inter-tissue variability in viability between two tissues treated identically was less than 13% and the maximum difference in percentage between the mean viability of two tissues and one of the two tissues was less than 7%. lt was therefore concluded that the test system functioned properly.

For detailed results see Tables 1 to 3 in box "Any other information on results incl. tables".

Table 1: Mean absorption in the in vitro skin corrosion test with magnesium hydoxide 

	3 minute application			1 hour application
	A	B	Mean ± SD	A	B	Mean ± SD
Negative control	1.683	1.699	1.691 ± 0.011	1.707	1.710	1.708 ± 0.002
Magnesium hydroxide	1.586	1.393	1.490 ± 0.137	1.664	1.578	1.621 ± 0.061
Positive control	0.150	0.143	0.147 ± 0.005	0.148	0.145	0.147 ± 0.002

 

 

Table 2: Mean tissue viability

	3 minute application viability (% of control)	1 hour application viability (% of control)
Negative control	100	100
Magnesium hydroxide	88	95
Positive control	9	9

Table 3: Historical control data for in vitro skin corrosion studies

	Negative control		Positive control
	3-minute treatment (OD540)	1-hour treatment (OD540)	3-minute treatment (OD540)	1-hour treatment (OD540)
Range	1.226 - 2.003	1.419 - 2.007	0.075 - 0.234	0.057 – 0.178
Mean	1.60	1.59	0.12	0.10
SD	0.16	0.13	0.04	0.03
n	44	44	44	44

Interpretation of results:

GHS criteria not met

Conclusions:

In this study under the given conditions, magnesium hydroxide showed no corrosive effects. The relative mean tissue viability after 3 min and 60 min of exposure was > 50%. The test item is therefore not classified for skin corrosion in accordance with UN GHS “No Category”.

Executive summary:

In a primary dermal corrosion study conducted according to OECD guideline 431, the possible corrosive potential of magnesium hydroxide was tested using topical application for either 3 minutes or 1 hour. 25 mg of magnesium hydroxide was added directly on top of the skin tissue which was moistened with water. Water and potassium hydroxide were used as the negative and positive control substances, respectively.

The positive control had a mean relative tissue viability of 9 % after 3 minutes exposure, and the absolute mean optical density of the negative control tissues was within the historical control range, indicating the acceptability of the assay.

The mean relative tissue viabilities for magnesium hydroxide after 3 minute and 1-hour treatments were 88% and 95%, respectively. The mean relative tissue viability for magnesium hydroxide was not below 50% after the 3-minute treatment or 15 % after the 1 hour treatment. The test item is therefore not classified for skin corrosion in accordance with UN GHS “No Category”.

Reference 2

Endpoint:

skin irritation: in vitro / ex vivo

Type of information:

experimental study

Adequacy of study:

weight of evidence

Study period:

2010-05-03 to 2010-12-06

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

other: OECD Guidelines for the testing of chemicals, draft proposal for a new guideline: In vitro skin irritation: reconstructed human epidermis (RhE) test method

Deviations:

no

Qualifier:

according to guideline

Guideline:

EU Method B.46 (In Vitro Skin Irritation: Reconstructed Human Epidermis Model Test)

Version / remarks:

adopted 24 August 2009

Deviations:

no

GLP compliance:

yes

Specific details on test material used for the study:

- Name of the test material used in the report: Magnesium hydroxide
- Appearance: white powder
- Batch No.: 20BR0026
- Purity: 99.90%
- Storage: at room temperature in the dark
- Expiry date: 2012-01-31

Test system:

human skin model

Source species:

human

Cell type:

non-transformed keratinocytes

Justification for test system used:

This test uses the EPISKIN Standard Model™ (EPISKIN-SM™) is a three-dimensional human epidermis model, which consists of adult human-derived epidermal keratinocytes which have been seeded on a dermal substitute consisting of a collagen type I matrix coated with type IV collagen and therefore represents in vitro the target organ of the species of interest and closely mimics the biochemical and physiological properties of the upper parts of the human.

Vehicle:

water

Details on test system:

RECONSTRUCTED HUMAN EPIDERMIS (RHE) TISSUE
- Model used: EPISKIN Standard ModelTM (EPISKIN-SMTM) from SkinEthic Laboratories, Nice, France
- Tissue batch number(s): 10-EKIN-015

TEMPERATURE USED FOR TEST SYSTEM
- Temperature used during treatment / exposure: All incubations, with the exception of the test substance incubation of 15 minutes at room temperature, were carried out in a controlled environment at 37.0 ± 1.0°C (actual range 36.6 - 37.5°C)
- Temperature during post-exposure: 37 °C

REMOVAL OF TEST MATERIAL AND CONTROLS
After exposure, tissues were washed with phosphate buffered saline to remove residual test substance.

MTT DYE USED TO MEASURE TISSUE VIABILITY AFTER TREATMENT / EXPOSURE
- MTT concentration: 0.3 mg/mL final concentration
- Incubation time: 3 hours
- Spectrophotometer: Multiskan Spectrum (Thermo Labsystems)
- Wavelength: 570 nm

NUMBER OF REPLICATE TISSUES: 3

PREDICTION MODEL / DECISION CRITERIA (choose relevant statement)
- A test substance is considered irritant in the skin irritation test if:
The relative mean tissue viability of three individual tissues after 15 minutes of exposure to the test substance and 42 hours of post incubation is 50% of the mean viability of the negative controls.

- A test substance is considered non-irritant in the in vitro skin irritation test if:
The relative mean tissue viability of three individual tissues after 15 minutes of exposure to the test substance and 42 hours of post incubation is > 50% of the mean viability of the negative controls.

Control samples:

yes, concurrent negative control

yes, concurrent positive control

Amount/concentration applied:

TEST MATERIAL
- Amount(s) applied (volume or weight with unit): 10 mg

VEHICLE
- Amount(s) applied (volume or weight with unit): 5 µL

NEGATIVE CONTROL
- Amount(s) applied (volume or weight): 10 µL

POSITIVE CONTROL
- Amount(s) applied (volume or weight): 10 µL

Duration of treatment / exposure:

15 minutes

Duration of post-treatment incubation (if applicable):

42 hours

Number of replicates:

3

Irritation / corrosion parameter:

% tissue viability

Run / experiment:

mean of three tissues

Value:

91

Vehicle controls validity:

not examined

Negative controls validity:

valid

Positive controls validity:

valid

Remarks on result:

no indication of irritation

Other effects / acceptance of results:

See field "Any other information on results incl. tables"

Magnesium hydroxide was checked for possible direct MTT reduction by adding the test substance to MTT medium. Because no colour change was observed it was concluded that magnesium hydroxide did not interact with MTT.

The mean absorption at 570 nm measured after treatment with magnesium hydroxide and controls are presented in Table 1. Table 2 shows the mean tissue viability obtained after 15 minutes of treatment with magnesium hydroxide compared to the negative control tissues. Skin corrosion is expressed as the remaining cell viability after exposure to the test substance.

The in vitro skin irritation test is considered to be acceptable if it meets the following criteria:

- The absolute mean OD₅₇₀ of the three tissues of the negative control should reasonably be within the laboratory historical control data range and the SD of the % viability should be ≤ 1

- The mean relative tissue viability of the positive control should be ≤ 40 % relative to the negative control and the SD of the % viability should be ≤ 1

- The SD calculated from individual % tissue viabilities of the three identically treated replicates should be ≤ 18.

The relative mean tissue viability obtained after 15 minutes of treatment with magnesium hydroxide compared to the negative control tissues was 91%. As the mean relative tissue viability for magnesium hydroxide was above 50%, magnesium hydroxide is considered to be non-irritant. The absolute mean OD540 of the negative control tissues was within the historical control range. The mean relative tissue viability following 3 minutes and 1 hour of exposure to the positive control were 9 %. Therefore, it was concluded that the test system was suitable for this analysis.

Table 1: Mean absorption in the in vitro skin corrosion test with magnesium hydroxide (OD₅₄₀) 

	A	B	C	Mean ± SD
Negative control	1.103	0.839	0.987	0.976 ± 0.133
Magnesium hydroxide	0.832	0.878	0.941	0.884 ± 0.055
Positive control	0.039	0.039	0.028	0.035 ± 0.006

 

 

Table 2: Mean tissue viability

	Mean tissue viability (% of control)
Negative control	100
Magnesium hydroxide	91
Positive control	4

Interpretation of results:

GHS criteria not met

Conclusions:

In an in vitro skin irritation test conducted according to EC method B.46, the relative mean tissue viability after 15 min of exposure and 42 h post-incubation was > 50%. The test item is therefore classified as “non-irritant” in accordance with UN GHS “No Category”.

Executive summary:

The potential of magnesium hydroxide to induce skin irritation was tested using a human three-dimensional epidermal model. The possible skin irritation potential of magnesium hydroxide was tested using topical application for 15 minutes, followed by a 42-hour incubation period. 10 mg of magnesium hydroxide was added directly on top of the skin tissue which was moistened with water. Water and SDS were used as the negative and positive control substances, respectively.

The positive control had a mean relative tissue viability of 4% after 15 minutes exposure, and the absolute mean optical density of the negative control tissues was within the historical control range, indicating the acceptability of the assay.

The mean relative tissue viabilities for magnesium hydroxide after 15 minutes of treatment was 91%. Because the mean relative tissue viability for magnesium hydroxide was not below 50% after the 15-minute treatment, it was concluded that magnesium hydroxide is not a skin irritant under the conditions of this test. Based on this result, magnesium hydroxide is classified as a non-irritant according to the UN GHS.

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed (not irritating)

Eye irritation

Link to relevant study records

Reference

Reference 1

Endpoint:

eye irritation: in vivo

Type of information:

experimental study

Adequacy of study:

weight of evidence

Study period:

2010-04-22 to 2010-09-03

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 405 (Acute Eye Irritation / Corrosion)

Deviations:

no

Qualifier:

according to guideline

Guideline:

EU Method B.5 (Acute Toxicity: Eye Irritation / Corrosion)

Deviations:

no

Qualifier:

according to guideline

Guideline:

EPA OPPTS 870.2400 (Acute Eye Irritation)

Deviations:

no

Qualifier:

according to guideline

Guideline:

other: JMAFF guidelines (2000); including the most recent partial revisions.

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Specific details on test material used for the study:

- Name of the test material used in the report: Magnesium hydroxide
- Appearance: white powder
- Batch No.: 20BR0026
- Purity: 99.90%
- Storage: at room temperature in the dark
- Expiry date: 2012-01-31

Species:

rabbit

Strain:

New Zealand White

Details on test animals or tissues and environmental conditions:

TEST ANIMALS
- Source: Harlan, Belton, Leics, England
- Age at study initiation: Animals used within the study were at least 6 weeks old
- Weight at study initiation: Body weights were at least 1.0 kg
- Housing: Animals were individually housed in labelled cages with perforated floors and shelters.
- Diet: Pelleted diet for rabbits approximately 100 grams per day was provided at least three times a week.
- Water: Free access to tap water
- Acclimation period: Acclimitisation period was at least 5 days before start of treatment under laboratory conditions.
Results of analysis for diet, hay and water were assessed and did not reveal any findings that were considered to have affected the study integrity.
ENVIRONMENTAL CONDITIONS
- Temperature (°C): 21.0±3.0°C
- Humidity (%): 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: 06-04-2010 to: 2-04-2010

Test system:

Amount/ concentration applied:
Animals were treated by instillation of on average, 57.3 mg (range 57.0-57.5 mg) of the test substance (a volume of approximately 0.1mL) in the conjunctival sac of one of the eyes.

Observation period:
Observations were made 1, 24, 48 and 72 hours after instillation.
Mortality/ Viability: Twice daily
Toxicity: At least once daily
Body weight: Day of treatment and after the final observation
Necropsy: No necropsy was performed according to protocol.
Irritation: The eyes of each animal were examined approximately 1, 24, 48 and 72 hours after instillation of the test substance. The irritation scores and a description of all other (local) effects were recorded.

Vehicle:

unchanged (no vehicle)

Controls:

yes, concurrent no treatment

Amount / concentration applied:

TEST MATERIAL
- Amount(s) applied (volume or weight with unit): 57.3 mg (range 57.0 – 57.5 mg)

Duration of treatment / exposure:

24 hours

Observation period (in vivo):

72 hours

Number of animals or in vitro replicates:

3 males were used in the treatment.

Details on study design:

REMOVAL OF TEST SUBSTANCE
- Washing (if done):
no


SCORING SYSTEM:
See box: Any other information on materials ane methods incl. tables.

TOOL USED TO ASSESS SCORE: 2% fluorescein; Where standard lighting was considered inadequate for observing minor effects, eye examinations were performed using an ophthalmic examination lamp.

Irritation parameter:

cornea opacity score

Basis:

mean

Time point:

24/48/72 h

Score:

0

Max. score:

4

Remarks on result:

no indication of irritation

Irritation parameter:

iris score

Basis:

mean

Time point:

24/48/72 h

Score:

0

Max. score:

2

Remarks on result:

no indication of irritation

Irritation parameter:

conjunctivae score

Remarks:

redness

Basis:

mean

Time point:

24/48/72 h

Score:

1

Max. score:

3

Reversibility:

fully reversible within: 72 hours

Irritation parameter:

chemosis score

Basis:

mean

Time point:

24/48/72 h

Score:

0.2

Max. score:

4

Reversibility:

fully reversible within: 72 hours

Irritant / corrosive response data:

Instillation of approximately 57 mg of Magnesium hydroxide into one eye of each of three rabbits resulted in effects on the cornea, iris and conjunctivae. The corneal injury consisted of a slight dulling of the normal lusture and/or epithelial damage (maximum 10% of the corneal area) in two animals. The corneal injury had resolved within 24 or 48 hours. Iridial irritation grade 1 was observed in all animals and had resolved within 24 hours. The irritation of the conjunctivae consisted of redness, chemosis and discharge and completely resolved within 72 hours in all animals.

Coloration/ Remnants
Remnants of the test substance were present in the eye of two animals on Day 1.

Toxicity/ Mortality:
No symptoms of systemic toxicity were observed in the animals during the test period and no mortality occurred.

Table 1: Mean value eye irritation scores 

	Mean 24, 48 and 72 hours.
Animal	Corneal opacity	Iris	Conjunctivae
			Redness	Chemosis
328	0.0	0.0	1.0	0.0
377	0.0	0.0	1.0	0.3
379	0.0	0.0	1.0	0.3

 

 

Table 2: Animal specifications

Animal	Sex	Age at start (weeks)	Body weights( grams)
			Prior to application	At termination
328	Male	10-12	2198	2256
377	Male	7-9	1516	1701
379	Male	7-9	1615	1739

 

Table 3: Individual Eye Irritation Scores

		Cornea			Iris	Conjunctivae
Animal No.	Time after dosing (hours)	Opacity (0-4)	Area (0-4)	Fluor area (%)	(0-2)	Redness (0-3)	Chemosis (0-4)	Discharge (0-3)	Comments
1	1	0	0	-	1	1	1	1	-
	24	0	0	0	0	2	0	0	-
	48	0	0	-	0	1	0	0	-
	72	0	0	-	0	0	0	0	-
2	1	0	1	-	1	1	2	1	b g
	24	0	0	0	0	2	1	0	-
	48	0	0	-	0	1	0	0	-
	72	0	0	-	0	0	0	0	-
3	1	0	1	-	1	2	2	2	b g
	24	0	1	10	0	2	1	1	g
	48	0	0	-	0	1	0	0	-
	72	0	0	0	0	0	0	0	-

Fluor area: Green staining after fluorescein treatment (percentage of total corneal area)

b Remnants of the test substance in the eye.

g Slight dulling of the normal luster of the cornea.

Interpretation of results:

GHS criteria not met

Conclusions:

Based on these results Magnesium hydroxide does not have to be classified and has no obligatory labelling requirement for eye irritation according to the GHS criteria.

Executive summary:

In a primary eye irritation study conducted according to OECD guideline 405, 57 mg of magnesium hydroxide was instilled into the conjunctival sac of one of the eyes of 3 male rabbits without rinsing. Observations were made 1, 24, 48 and 72 hours after instillation. Irritation was scored by the method of Draize.

 

Instillation of the test substance resulted in effects on the cornea, iris and conjunctivae. The corneal injury consisted of slight dulling of the normal lustre and/or epithelial damage (maximum 10% of the corneal area) in two animals. The corneal injury had resolved within 24 or 48 hours. Iridial irritation grade 1 was observed in all animals and had resolved within 24 hours. The irritation of the conjunctivae consisted of redness, chemosis and discharge and completely resolved within 72 hours in all animals.

 

In this study, magnesium hydroxide is not an eye irritant based on GHS criteria.  

Reference 2

Endpoint:

eye irritation: in vitro / ex vivo

Type of information:

experimental study

Adequacy of study:

weight of evidence

Study period:

2010-03-16 to 2010-05-10

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 437 (Bovine Corneal Opacity and Permeability Test Method for Identifying i) Chemicals Inducing Serious Eye Damage and ii) Chemicals Not Requiring Classification for Eye Irritation or Serious Eye Damage)

Version / remarks:

adopted 07 September 2009

Deviations:

no

GLP compliance:

yes

Specific details on test material used for the study:

- Name of the test material used in the report: Magnesium hydroxide
- Appearance: white powder
- Batch No.: 20BR0026
- Purity: 99.90%
- Storage: at room temperature in the dark
- Expiry date: 2012-01-31

Species:

cattle

Strain:

not specified

Details on test animals or tissues and environmental conditions:

Bovine eyes from young cattle were obtained from the slaughterhouse, where the eyes were excised by a slaughterhouse employee as soon as possible after slaughter. The eyes were collected and transported in physiological saline in a suitable container and were used within 30 minutes.

Vehicle:

physiological saline

Controls:

yes, concurrent no treatment

Amount / concentration applied:

TEST MATERIAL
- Concentration (if solution): 20% (w/v)

NEGATIVE CONTROL:
- Amount: 750 µL

POSITIVE CONTROL:
- Concentration (if solution): 20% (w/v)

Duration of treatment / exposure:

topical treatment for 240 ± 10 minutes

Observation period (in vivo):

After incubation with the test substance, the solutions were removed, fresh cMEM was added and an opacitiy determination was performed without any further incubation

Number of animals or in vitro replicates:

Three corneas were used in each treatment group

Details on study design:

REMOVAL OF TEST SUBSTANCE
- Washing: After the incubation with the test substance, corneas were washed at least 3 times with cMEM prior to determination of opacity
- Time after start of exposure: 240 ± 10 minutes

OPACITY:
The opacitometer determined the difference in light transmission between each control and treated cornea and an air filled chamber. The numerical opacity value was displayed and recorded. The change in opacity for each individual cornea was calculated by subtracting the initial opacity reading from the post-treatment reading. The corrected opacity was calculated by subtracting the opacity of the negative control.

PERMEABILITY
Following the final opacity method, permeability of the cornea to Na-fluorescein was evaluated. The medium of both compartments (anterior compartment first) was removed. The posterior compartment was refilled with fresh cMEM. The anterior compartment was filled with 1 mL of Na-fluorescein solution. The corneas were completely covered and were incubated in a horizontal position for 90 ± 5 minutes at 37 ± 1 °C.

After the incubation period, the medium in the posterior compartment of each holder was removed and placed into a sampling tube labelled according to holder number. 360 µL of the medium from each sampling tube was transferred to a 96-well plate. The optical density at 490 nm of each sampling tube was measured in triplicate using a microplate reader.

Irritation parameter:

in vitro irritation score

Run / experiment:

mean

Value:

5.1

Vehicle controls validity:

valid

Negative controls validity:

valid

Positive controls validity:

valid

Irritation parameter:

cornea opacity score

Run / experiment:

mean

Value:

5

Vehicle controls validity:

valid

Negative controls validity:

valid

Positive controls validity:

valid

Irritation parameter:

other: permeability

Run / experiment:

mean

Value:

0.006

Vehicle controls validity:

valid

Negative controls validity:

valid

Positive controls validity:

valid

Table 1: Summary of opacity, permeability and in vitro scores

Treatment	Mean Opactiy	Mean Permeability	Mean In vitroIrritation Score^1,2
Negative control	0	0.000	0.0
Positive control	80	2.490	117
Magnesium hydroxide	5	0.006	5.1

1 Calculated using the negative control mean opacity and mean permeability values.

2 In vitro irritancy score (IVIS) = mean opacity + (15 x mean OD₄₉₀value).

Table 2: Opacity score

 

Eye	Opacity before treatment	Opacity after treatment	Final opacity	Negative control corrected final opacity	Mean opacity
Negative control
1	0	0	0	0	0
2	0	1	1	1
3	0	0	0	0
Positive control
4	0	80	80	80	80
5	0	79	79	79
6	0	81	81	81
Magnesium hydroxide
10	0	6	6	6	5
11	0	3	3	3
12	0	7	7	7

 

 

Table 3: Permeability score (corrected)

 

 

Eye	Dilution factor	Corrected OD4901	Corrected OD4902	Corrected OD4903	Average OD490	Final OD490	Average OD
Negative control
1	1	0.014	0.001	0.004	0.006	0.006	0.000
2	1	0.000	0.000	0.003	0.001	0.001
3	1	-0.001	-0.008	-0.009	-0.006	-0.006
Positive control
4	6	0.369	0.366	0.372	0.369	2.214	2.490
5	6	0.349	0.362	0.354	0.355	2.130
6	6	0.527	0.518	0.519	0.521	3.126
Magnesium hydroxide
10	1	0.008	0.008	0.011	0.009	0.009	0.006
11	1	0.008	0.002	0.000	0.003	0.003
12	1	0.006	0.004	0.005	0.005	0.005

 

 

Table 4: In vitro irritancy score

 

Eye	Negative control corrected final opacity	Negative control corrected final OD490	In vitro irritancy score
Negative control
1	0	0.006	0.1
2	0	0.001	1.0
3	0	-0.006	-0.1
Positive control
4	80	2.214	113.2
5	79	2.130	111.0
6	81	3.126	127.9
Magnesium hydroxide
10	6	0.009	6.1
11	3	0.003	3.0
12	7	0.005	7.1

In vitro irritancy score (IVIS) = mean opacity + (15 x mean OD₄₉₀value).

Interpretation of results:

study cannot be used for classification

Conclusions:

In conclusion, based on the mean in vitro irritation score of 5.1 obtained in the bovine corneal opacity and permeability assay (BCOP, OECD 437), no prediction can be made regarding the classification of the test substance.

Executive summary:

The eye irritation potential of magnesium hydroxide (99.9% purity) was investigated in the bovine corneal opacity and permeability assay (BCOP, OECD 437). The test item was suspended in physiological saline to gain a 20% concentration. A mean in vitro irritation score of 5.1 was determined. The positive and negative controls induced the appropriate responses, indicating the validity of the assay. Based on the results obtained, no prediction can be made regarding the classification of the substance.

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed (not irritating)

Respiratory irritation

Endpoint conclusion

Endpoint conclusion:

no study available

Additional information

The potential of magnesium hydroxide to induce skin irritation (OECD 439 draft/EC method B.46 and OECD 431) and eye irritation (OECD 437, 405) was tested in suitable in vitro and in vivo test methods.

Based on the results from the in vitro skin irritation/corrosion tests, magnesium hydroxide can be considered as non-irritant to the skin.

To assess the eye irritant potential of the magnesium hydroxide, the Bovine Corneal Opacity & Permeability (BCOP) assay was conducted in accordance with OECD 437. The BCOP allows classification as “not classified” and “Eye Dam. 1, H318” based on the In Vitro Irritancy Score (IVIS). Results which are in between both categories are identified as “No prediction can be made”. Based on the results from the BCOP test, no prediction can be made regarding the classification of the target substance.

Subsequently, the test item was tested in an in vivo study conducted according to OECD 405.

In this study, instillation of the test substance resulted in effects on the cornea, iris and conjunctivae. The corneal injury consisted of slight dulling of the normal lustre and/or epithelial damage (maximum 10% of the corneal area) in two animals. The corneal injury had resolved within 24 or 48 hours. Iridial irritation grade 1 was observed in all animals and had resolved within 24 hours. The irritation of the conjunctivae consisted of redness, chemosis and discharge and completely resolved within 72 hours in all animals.

Based on the results of this study, the test item is considered non-irritant to the eye.

Justification for classification or non-classification

Based on the results from suitable in vitro and in vivo tests, no classification for eye and/or skin irritation is warranted according to CLP Regulation 1272/2008.