Silicic acid, aluminum magnesium salt

Endpoint summary

Description of key information

Oral: Silicic acid, aluminium magnesium sodium salt
LD50: > 2000 mg/kg bw for rats (Colas 2009)
In accordance with the OECD guideline 423, the LD50 cut-off of the test item may be considered higher than 5000 mg/kg bw by oral route in the rat.
Inhalation: 
Synthetic amorphous silica: The acute inhalation of dust may cause local irritation to nasal, bronchiolar and ocular mucous membranes. Synthetic amorphous silica dusts are considered as acutely non-toxic.
Dermal: various forms of synthetic amorphous silica
LD50: > 5000 mg/kg bw for rabbit after 14 observation days (Calkins 1978a-e)
LD50: > 2000 mg/kg bw for rabbit after 2 observation days (Calkins 1976)

Additional information

Oral

Only secondary literature is available on Silicic acid, aluminium magnesium salt (MAS) for acute oral toxicity. The original study is not available and documentation of the reviewed data is limited. Therefore data of MAS are insufficient for assessment. However, there are data for the structurally related compound Silicic acid, aluminium magnesium sodium salt.

The acute oral toxicity of Silicic acid, aluminium magnesium sodium salt (SMAS) was tested according to the OECD guideline 423 (Colas 2009). The test substance was administered to female rats at a dose of 2000 mg/kg bw. During the observation period of 14 days, no signs of toxicity or mortality were recorded. In accordance with the OECD guideline 423, the LD50 cut-off of the test item may be considered higher than 5000 mg/kg bw for the oral route in the rat.

The acute oral LD50 value for Silicic acid, aluminium magnesium salt (MAS) was calculated > 50,000 mg/kg bw in mice (Munch 1944).Based on the limited documentation of the reviewed study, available data of MAS are insufficient for assessment and only the LD50 value of Silicic acid, aluminium magnesium sodium salt (SMAS) was taken into account for risk assessment.

Inhalation

No experimental data are available on Silicic acid, aluminium magnesium salt for acute inhalation toxicity, but there is an acute inhalation study performed with dry dust of the structurally related compound Cab-O-Sil M5 (Cabot 1981). However, this study was hampered by the technical problem to achieve the recommended highest test concentration of 5000 mg/m³. In the study of Cabot (1981), rats were exposed to an average concentration of 2080 mg/m³Cab-O-Sil M5 (MMAD = 0.76 µm) for 4 hours. All animals survived. Clinical symptoms were nasal discharge during exposure, crusty eyes, crusty nose and alopecia at 14 days post-exposure. No macroscopic organ lesions were observed, but one animal showed discoloration of the lung. Measuring the particle size distribution of Cab-O-Sil M5, approx. 84% of the particles had a diameter of ≤ 3 µm and approx. 98% ≤ 10 µm.

Under experimental conditions, the particle size distribution of Silicic acid, aluminium magnesium salt (MAS) showed that approx. 28% of the particles had a diameter of ≤ 2 µm and approx. 70% of ≤ 10 µm (Grace 2009). Thus the particle size distribution of MAS is in the same order of magnitude as of Cab-O-Sil M5. During normal handling and use, MAS usually forms agglomerates of high mass median aerodynamic diameter that are not respirable (see chapter 1.3). Taking into account these larger particles, most of the inhaled material will be retained in the upper airways and/or be swallowed. Therefore, it can be assumed that no acute toxic effects due to inhalation of MAS will occur.

Dermal

Only secondary literature is available on Silicic acid, aluminium magnesium salt (MAS) for acute dermal toxicity. The original study is not available and documentation of the reviewed data is limited. Therefore data of MAS are insufficient for assessment. However, there are data for structurally related compounds.

After acute dermal application of 2000 mg/kg bw of Syloid 244 as powder to the intact skin of rabbits for 24 hours under occlusive conditions, no signs of systemic or organ toxicity were recorded. Not even erythemas or edemas were observed 24 and 48 hours after exposition (Calkins 1976).

After acute dermal application of up to 5000 mg/kg bw of aqueous pastes of synthetic amorphous silica to the intact skin of rabbits for 24 hours under occlusive conditions, no signs of systemic or organ toxicity were noted. There were only slight reversible erythemas and partly edemas (Draize score 1; Calkins 1978 a-e).

The acute dermal LD50 value for Silicic acid, aluminium magnesium salt (MAS) was calculated > 3500 mg/kg for rabbits (Hazelton Laboratories, Inc. 1968). Based on the limited documentation of the reviewed study, the available data of MAS are insufficient for assessment and only data of the structurally related compounds were taken into account for risk assessment.

Justification for classification or non-classification

Oral

According to the criteria for classification, packaging and labelling of dangerous substances and preparations in accordance with the E. E. C. Directives 67/548, 2001/59 and 99/45, the test item silicic acid, aluminium magnesium salt (MAS) does not need to be classified. No symbol and risk phrase are required.

In accordance with the Globally Harmonised System (Regulation (EC) No 1272/2008), the test item does not need to be classified. No signal word and hazard statement are required.

 

Inhalation

Taking into account that MAS usually forms larger particles that are not respirable, no acute inhalation toxicity is expected from the exposure to MAS. No need for classification.

 

Dermal

Based on structure analogy, no acute dermal toxicity is expected to occur likewise from the exposure to silicic acid, aluminium magnesium salt for which corresponding studies are not available. The test item does not need to be classified.