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EC number: 274-324-8
CAS number: 70131-50-9
Short description of key information on bioaccumulation potential result: A toxicokinetic assessment of bentonite acid leached has been written based on the available data
TEST MATERIAL: Bentonite acid leached
The test material
bentonite acid leached (EC no 274-324-8) is a UVCB substance which
consists of the following mineralogy: smectite
(montmorillonite), amorphous silica, feldspar, sepiolite, kaolinite, and
quartz. It is an off white solid which can compose of fine, medium and
In a water solubility
study with bentonite acid leached the nominal loading rate of 1.0 g/l
confirmed that bentonite acid leached was essentially insoluble in
water, with less than 1.0 mg/l of each element being detected in
solution with the exception of calcium (1.6 mg/l) (O’Connor & Woolley
bentonite acid leached was also assessed in artificial gastric fluid and
simulated alveolar fluid. Analytical verification of the following
elements sodium, magnesium, aluminium, silicon, potassium and calcium)
equated to a total solubility of ~ 1% (O’Connor & Woolley 2010b).
Particle size analysis
of a typical sample of medium grade sample showed that 75.5% of
particles were smaller than 100µm only 0.14% of particles were smaller
than 10 µm (O’Connor & Woolley 2010c).
In the acute
inhalation study the 4 hr LC50of bentonite acid leached was
calculated to be 50 mg/L (Nitka 1988). As such although bentonite acid
leached has the potential to be inhaled due to its particle size
distribution it doesn’t exhibit inhalation toxicity at a high dose in
the test material has a low solubility in artificial alveolar fluid it
is considered the inhaled test material will not be absorbed.
The acute oral median
lethal dose (LD50) of the test material was estimated to be > 5000 mg/kg
bw (Nitka 1985). As such, the test material has a very low potential for
toxicity by oral absorption. The LD50 in the dermal toxicity study was >
2000 mg/kg (Bradshaw 2010). In conclusion, the test material has a low
potential for any absorption by oral ingestion and dermal absorption.
Since the test
material has a low potential for absorption by any route it means that
the test material will not be readily bioavailable. The majority of any
test material that is ingested orally is likely to pass through the
gastrointestinal (GI) tract unchanged and be excreted in the faeces. Any
small amount of constituents from the test material that are absorbed by
the gut will enter the essential elemental pool along with those that
are absorbed from the daily nutritional requirement of elements and
therefore are not considered to be of any toxicological significance.
conclusion is taken from the UNEP (2004) report for synthetic and
amorphous silicas regarding absorption, disposition and elimination
which may be considered relevant for the test material which also
contains amorphous silica and quartz:
Analytical data on the
kinetics of silica deposition in the lung of experimental animals during
and after prolonged exposure to silica are largely consistent. The
initial uptake phase is characterized by relatively high deposition
followed by a phase of low increase. Synthetic amorphous silicas are
rapidly eliminated from the lung tissue, whereas crystalline silica
exhibits a marked tendency to accumulate. No disproportionate deposition
of synthetic amorphous silica occurs in the lymph nodes.
After oral ingestion,
there is no accumulation of synthetic amorphous silica in body tissues.
Upon cessation of exposure rapid elimination occurs. Intestinal
resorption appears to be insignificant in animals and humans the human
test, the small apparent increases in the urine output of human
volunteers were remarkably low as compared with the high dose of 2500 mg
SiO2applied subcutaneously are subjected to rapid dissolution
O’Connor & Woolley
2010a Bentonite acid-leached: Determination of general physico-chemical
properties Harlan Laboratories Ltd, Project no 2881/0001
O’Connor & Woolley
2010b Bentonite acid leached: Determination of solubility in simulated
gastric fluid and simulated alveolar lung fluid Harlan Laboratories Ltd,
Project no 2881/0015
O’Connor & Woolley
acid-leached: Determination of general physico-chemical properties
Harlan Laboratories Ltd, Project no 2881/0001
Nitka S (1988) Acute
inhalation toxicity in rats, Consumer Product Testing, Report no 88047-2.
Nitka S (1985) Acute
oral toxicity in rats, Consumer Product Testing, Report no 85365-4.
Bentonite acid-leached: Acute dermal toxicity (limit test) in the rat,
Harlan Laboratories Ltd, Project no 2881/0003
amorphous silica and silicates - SIDS Initial Assessment Report for 19.
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