Synthetic amorphous magnesium silicate, with molar ratio (SiO2:MgO) range of 1.4-4

Skin irritation / corrosion

Administrative data

Endpoint:

skin irritation: in vivo

Type of information:

experimental study

Adequacy of study:

key study

Study period:

12 July 1989 to 21 July 1989

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

comparable to guideline study with acceptable restrictions

Justification for type of information:

The study has been performed using a sample from Dallas Group of America. The particle size analysis performed on the Dallas and PQ Corporation material show that they are sufficiently similar. The only difference between the materials are the molar ratios. The molar ratio of the tested Dallas material is within the range of the PQ Corporation registered substance. No additional testing is therefore required.

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

1989

Report date:

1989

Materials and methods

Test guideline

Qualifier:

equivalent or similar to guideline

Guideline:

EU Method B.4 (Acute Toxicity: Dermal Irritation / Corrosion)

Principles of method if other than guideline:

The study design complied with the requirements of the Federal Hazardous Substances Act (16 CFR 1500)

GLP compliance:

yes

Test material

Test material information

Constituent 1

Reference substance name:

Silicic acid, magnesium salt

EC Number:

215-681-1

EC Name:

Silicic acid, magnesium salt

Cas Number:

1343-88-0

Molecular formula:

MgO.xSiO2, the molar ratio SiO2:MgO typically ranges from 1.4-4

IUPAC Name:

Synthetic amorphous magnesium silicate, with molar ratio (SiO2:MgO) range of 1.4-4

Details on test material:

The grade of Dallas material is not stated in the report. The only difference between the Dallas and PQ Corporation grades is the particle size distribution and the composition (molar ratios of 2.6 for the Dallas grade and 1.5-4.0 for the PQ Corporation grades, MgO.nSiO2 ). No irritation/corrosion data is available for the PQ Corporation range of synthetic magnesium silicate. However, the particle size distribution and the molar ratios will not affect the outcome of a dermal irritation study.

Magnesium silicate SRR#: 281-60-3 MgO:2.6 SiO2

Specific details on test material used for the study:

The grade of Dallas material is not stated in the report. The only difference between the Dallas and PQ Corporation grades is the particle size distribution and the composition (molar ratios of 2.6 for the Dallas grade and 1.4-4.0 for the PQ Corporation grades, MgO.nSiO2 ). No irritation/corrosion data is available for the PQ Corporation range of synthetic magnesium silicate. However, the particle size distribution and the molar ratios will not affect the outcome of a dermal irritation study.

Magnesium silicate SRR#: 281-60-3 MgO:2.6 SiO2

Test animals

Species:

rabbit

Strain:

New Zealand White

Details on test animals or test system and environmental conditions:

TEST ANIMALS
-Sex: 3 females and 3 males
- Housing: Animals were acclimated to the laboratory for at least one day before being used. Animals were housed singly in suspension cages with wire mesh floors.
- Diet : Purina Laboratory Rabbit Chow
- Water : tap water ad libitum

ENVIRONMENTAL CONDITIONS
- Photoperiod (hrs dark / hrs light): 12 hour light/12 hour dark cycle

Test system

Type of coverage:

occlusive

Preparation of test site:

other: to an intact skin area and to an abraded skin area

Vehicle:

physiological saline

Controls:

no

Amount / concentration applied:

0.5 g of the test article was applied to each intact and abraded site which was moistened with physiological saline. The test material was applied either to or under a surgical gauze patch (circa 2.5 x 2.5 cm), two layers thick on each of the six test rabbits.

Duration of treatment / exposure:

24 hours

Observation period:

The application site was scored prior to and following the removal of the residual test material and again two days later according to the Draize scale.

Number of animals:

6 rabbits were used.

Details on study design:

Young adult, New Zealand White rabbits (three males and three females) were used in this study. Each animal received 0.5 g of test material, moistened with 1.2 mL of physiological saline under a 2.5 x 2.5 cm gauze square. The test material was applied to one intact and one abraded skin site. The application site was scored prior to and following the removal of the residual test material and again two days later according to the Draize scale.

The values for each rabbit were totalled and averaged for each of the following categories:
1. Erythema and eschar formation, intact skin, 24 hours
2. Erythema and eschar formation, abraded skin, 24 hours
3. Erythema and eschar formation, intact skin, 72 hours
4. Erythema and eschar formation, abraded skin, 72 hours
5. Edema, intact skin, 24 hours
6. Edema, abraded skin, 24 hours
7. Edema, intact skin, 72 hours
8. Edema, abraded skin, 72 hours

The eight average scores from above were added together and the results divided by four to obtain the Primary Irritation Index (PII). A corrosive test material is one which causes destruction or irreversible damage to the tissue, while a primary irritant is one which gives a PII of five or more on a scale of 0-8.

Results and discussion

In vivo

Results

Irritation parameter:

primary dermal irritation index (PDII)

Score:

0.8

Irritant / corrosive response data:

The intact site is the area of interest when evaluating the response according to EU criteria. Although no scores were recorded for the 48 hour post application period, the general response can be estimated by taking an average group result for erythema and oedema for the intact site only. On this basis the slight transient erythema observed for two rabbits is not indicative of a significant irritant response,. The mean erythema score was 0.25 and the mean oedema score was 0.00.

Reactions at the abraded site were not markedly more severe but were slightly more persistent and erythema was more closely associated with the mechanical damage caused at the point of abrasion and so does not indicate any greater irritant effect.

Other effects:

No other effects noted.

Any other information on results incl. tables

Skin condition	Observation Time (hours)	Score for each rabbit						Total score	Average score
		1	2	3	4	5	6
Erythema formation
	Site	A	B	C	D	A	B
Intact	24	0	0	0H	2	1	0H	3	0.5
	72	0	0H	0H	0	0	0H	0	0.0
	Site	B	C	D	A	B	C
Abraded	24	1	1	1H	2	1	1HR	7	1.17
	72	1R	1R	1HR	1	1	1HR	6	1.00
Edema formation
	Site	A	B	C	D	A	B
Intact	24	0	0	0	0	0	0	0	0.00
	72	0	0	0	0	0	0	0	0.00
	Site	B	C	D	A	B	C
Abraded	24	0	1	0	1	0	0	2	0.33
	72	0	0	0	0	0	0	0	0.00

Primary irritation index (PII) 0.8

H= Hair on site

R= Erythema on abrasions only.

Applicant's summary and conclusion

Interpretation of results:

GHS criteria not met

Conclusions:

The test material is not classified as a primary irritant or as a corrosive by dermal application.

Executive summary:

The primary skin irritancy of magnesium silicate was evaluated. The Primary Irritation Index (PII) was found to be 0.8 based on erythema and edema. No changes in the coloration or texture of the skin were noted. No evidence of corrosion (necrosis) was found.

The test material is not classified as a primary irritant or as a corrosive by dermal application.