Magnesium hydroxide

Skin irritation / corrosion

Administrative data

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

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2010

Report date:

2010

Materials and methods

Test guideline

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

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

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

In vitro test system

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

Results and discussion

In vitro

Results

Results 1

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

Results 2

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".

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

Applicant's summary and conclusion

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”.