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Description of key information

Single oral administration of >5000 mg synthetic amorphous aluminum sodium silicate (NAS)/kg bw  failed to produce remarkable signs of toxicity or deaths in treated animals. The acute inhalation of NAS silicate dust may cause discomfort and dyspnea as well as transient signs of local irritation to nasal, bronchiolar and ocular mucous membranes. 

Key value for chemical safety assessment

Additional information

  • Oral uptake

Based on experimental results from synthetic amorphous silicate aluminum sodium (NAS) and the structure-analogous silica (SAS), there is ample evidence that high oral doses of NAS do not exert any significant toxicity in experimental animals.

  • Inhalation

Failing valid corresponding studies with NAS, experimental data about structure-analogous silicas (SAS) is summarised for the purpose of readacross:

Summary of results obtained with SAS :

All acute inhalation studies performed with dry dust of SAS were hampered by the technical problem to achieve the

recommended highest test concentration of 5 mg/l, apparently attributable to the high adhesive forces which caused rapid precipitation onto equipment walls. Therefore, the maximum attainable chamber concentrations were distinctly lower than envisaged.  

In one study, all ten rats (5 m, 5 f) survived when exposed to an average concentration of 2.08 mg/L of pyrogenic SAS, Cab-O-Sil M5, (MMAD = 0.76 µm) for 4 hours. Clinical symptoms were nasal discharge during exposure, in a few animals crusty eyes and nose as well as alopecia at days post-exposure. No macroscopic organ lesions were noted but in one animal discoloration of the lungs was observed [Cabot 1981].

In a further study, an average dust concentration of 0.691 mg/L (range 0.650 – 0.725 mg/L) for the precipitated SAS, Sipernat 22,

was obtained, with a respirable mass fraction of some 45 to 47 % accounting for particles with a mass median aerodynamic diameter (MMAD) of less than 5 µm [Degussa 1983]. No clinically and pathologically meaningful effects were observed after 4-h exposure

of rats (5 m, 5 f, each). The animals showed signs of some discomfort and stress, and body weight of females was retarded for two days post-exposure.

Justification for classification or non-classification

Synthetic amorphous aluminum sodium silicate and silica (SAS) are practically non-toxic by all routes of exposure. Aerosol levels that were technically achievable for SAS under experimental conditions are acutely non-toxic and clearly sub-lethal (=< 2 mg/L). Under comparable testing conditions, we expect that synthetic amorphous aluminum sodium silicate shows the same behaviour.

No classification for acute human health hazards shall be required.