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EC number: 701-065-4
CAS number: -
The dusts of synthetic amorphous silicas are considered as acutely
non-toxic by all routes of exposure.
The acute inhalation of dust may cause discomfort and stress as well as
signs of local irritation to nasal, bronchiolar and ocular mucous
The innocuous nature of synthetic amorphous magnesium silicate is
established based on study results and by read across to data for the
structurally related synthetic amorphous silica.
The median lethal doses by oral dermal or inhalation routes all exceed
the regulatory threshold or limit dose levels.
The acute oral and dermal toxicity studies completed with synthetic
amorphous magnesium silicate in rats and rabbits respectively showed no
signs of adverse reaction to exposure at the limit dose levels in each
case. Magnesium silicate was shown to be innocuous or toxicologically
inert in acute investigations. Acute oral administration of Magnesol
(trade name for a synthetic amorphous magnesium silicate) to rats,
resulted in no adverse toxic effects at 5000 mg/kg bw.
Magnesium silicate was administered in a second oral toxicity study as a
25% suspension in water and elicited no toxic effects at 5000 mg/kg bw.
Results are presented for read across to three studies with forms of
silicon dioxide. In all three studies using silicon dioxide, the median
lethal dose was calculated to be greater than 5000 mg/kg bw in rats.
Acute dermal toxicity of magnesium silicate was investigated in rabbits
dosed at 2000 mg/kg bw. No clinical signs of reaction to dermal
application were observed.
The dermal toxicity of 4 products containing silicon dioxide were
investigated and results are presented for read across purposes. Local
irritation was evident in some cases but there was no evidence of
systemic toxicity at the limit dose of 5000 mg/kg bw. The dermal median
lethal dose for silicon dioxide was also confirmed to exceed 2000 mg/kg
acute inhalation studies performed with dry dust were hampered by the
technical problem that the high adhesive forces caused rapid
precipitation onto equipment walls. This resulted in failure to achieve
the highest test concentration of 5 mg/L as recommended in the OECD and
EC-Guideline. Therefore, the maximum attainable chamber concentrations
were distinctly lower than envisaged for forms of synthetic amorphous
Studies with Magnesol, a synthetic amorphous
magnesium silicate, are presented in the dossier. Inhalation of Magnesol
at a nominal concentration of at least 20 mg/L of air in the test
atmosphere produced no mortality in any of the ten test subjects
indicating that the LC50 of the test article is greater than a minimum
nominal concentration of 20 mg/L of air for a one hour period.
five grades of Magnesol (a synthetic amorphous magnesium silicate). Four
of the samples had circa 10% of the particles within the respirable
range. The respirable range is generally <10 micron. For the PQ grades
of magnesium silicate, the respirable range is approximately 10% of the
particles and therefore is comparable with the Magnesol. It can
therefore be concluded that the PQ grades of magnesium silicates
included in Grades 1, 2a, 2b and 3 are also not toxic by inhalation.
Read across information is also presented for synthetic
amorphous silicon dioxide due to the similarity in . Rats exposed by
whole body exposure to a nominal concentration of 58.8 mg/L, analytical
concentration of 2.08 mg/L air, the maximum practical atmosphere
concentration, resulted in no deaths and no evidence of systemic
toxicity. In a second study, synthetic amorphous
silicon dioxide was administered by nose only exposure at
the maximum achievable test concentration of 0.69 mg/L. (Due to substance-inherent properties resulting
in sedimentation and adsorption to the equipment, the technical
maximum attainable aerosol concentration in the chamber ranged
from 650 to 725 mg/m3, while the nominal concentration was 36.7 g/m3).
About 65 % of the aerosol comprised particles with an
aerodynamic diameter of <6 µm (part of respirable fraction).
None of the available data for synthetic amorphous
magnesium silicate or read-across analogues, such as synthetic amorphous
silica, gave any indications of adverse toxic responses following acute
exposure via oral, dermal or inhalation routes.
Justification for read-across is therefore warranted given the
similarities in toxicity profile and physico-chemical properties for the
synthetic amorphous forms of silicon dioxide and magnesium silicate.
No classification for acute human
health hazards is required: synthetic amorphous magnesium
silicate or read-across analogues, such as synthetic amorphous silicon
dioxide are non-toxic
by all routes of exposure. Aerosol levels that are technically
achievable under experimental conditions are acutely non-toxic and
Information on Registered Substances comes from registration dossiers which have been assigned a registration number. The assignment of a registration number does however not guarantee that the information in the dossier is correct or that the dossier is compliant with Regulation (EC) No 1907/2006 (the REACH Regulation). This information has not been reviewed or verified by the Agency or any other authority. The content is subject to change without prior notice.Reproduction or further distribution of this information may be subject to copyright protection. Use of the information without obtaining the permission from the owner(s) of the respective information might violate the rights of the owner.
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