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EC number: 908-343-6
CAS number: -
A reliable key study is available that assesses the short-term toxicity
of the reaction mass of
calcium carbonate and calcium dihydroxide and calcium peroxide to
aquatic invertebrates. The resulting 48h-EC50 is 6.8 mg/L.
From a supporting studies on hydrogen peroxide it can be concluded that
the ecotoxicological effects observed for the reaction mass can be
attributed to the adverse effects exerted by the hydrogen peroxide that
is formed upon hydrolysis of the reaction mass.
The short-term toxicity of the reaction
mass of calcium carbonate and calcium dihydroxide and calcium peroxide
to aquatic invertebrates has been assessed in a recent GLP study
according to OECD guideline 202 (Migchielsen, 2012).
In this key study, the daphnia were
exposed to nominal concentrations of 1.0, 3.2, 10, 32 and 100 mg/L. The
concentrations could not be verified by analyses based on calcium due to
the high Ca background concentration of the test medium. Analyses based
on hydrogen peroxide at the start of the test showed measured
concentrations of 0.36, 1.1, 3.6, 11 and 22 mg/L. Nevertheless, the
measured concentrations of hydrogen peroxide cannot be used for the
derivation of the dose descriptors; this due to its instable nature. As
a consequence, the nominal initial loading rates were used to calculate
the NOEC and EC50.
An 48h EC50 of 6.8 mg/L and
a NOEC of 3.2 mg/L was calculated.
Furthermore, supporting information is
available on hydrogen peroxide (H2O2) and calcium
dihydroxide (Ca(OH)2), the primary hydrolytic degradation
products of the reaction mass of calcium carbonate and calcium
dihydroxide and calcium peroxide.
For calcium dihydroxide, the
short-term toxicity test with Daphnia magna (Egeler et al., 2007) was
carried out according to the OECD 202 guideline taking into account GLP
and thus resulting in a Klimish 1 score. The biological findings for
Daphnia magna (immobility) were closely related to the initial pH of the
test solutions, which ranged from 7.7 in the controls to 9.5, 9.7, 10.1,
10.7 and 11.1 at 14.8, 22.2, 33.3, 50 and 75 mg Ca(OH)2/L,
respectively. Therefore the initial pH is considered to be the main
reason for the effects of calcium dihydroxide on Daphnia magna (Egeler
et al., 2007). The 48h-EC50 was found to be 49.1 mg/L under
the conditions of this test.
The acute toxicity of hydrogen
peroxide to invertebrates was tested in a 48h experiment with Daphnia
pulex (Shurtleff, 1989). The test was performed in 1989 according to US
EPA TSCA guidelines. The 48h-LC50value determined from this
study was 2.4 mg/L. As the 48h-LC50 value for hydrogen
peroxide is lower than the value found for calcium
dihydroxide, the former was selected for the assessment of the reaction
From this 48h-LC50value a
corresponding 48h-LC50value can be calculated for the
reaction mass, by taking into account the applicable chemical reaction
(i.e. the amount of hydrogen peroxide formed is equimolar to
the amount of calcium peroxide present in the reaction mass)
and the composition of the reaction mass (i.e. the reaction mass
contains ca. 75% calcium peroxide). Thus: 100 mg of the reaction mass
contains 75 mg of calcium peroxide, which corresponds to 1.04 mmol of
calcium peroxide. Therefore, 1.04 mmol (= 35.36 mg) of hydrogen peroxide
is formed upon dissolution of 100 mg of calcium peroxide.
As a consequence, the 48h-LC50 for
the reaction mass, when calculated based on the 48h-LC50 for
hydrogen peroxide (2.4 mg/L) is:
100 mg reaction
mass yields 35.36 mg hydrogen peroxide
mass yields 2.4 mg hydrogen peroxide
48h-LC50 (reaction mass)
= 6.8 mg/L
calculated 48h-LC50 value
is the same as the value derived experimentally for the reaction
mass, which demonstrates that the EC50 value for the reaction
mass can be predicted based on the toxicity of hydrogen peroxide.
thus be concluded that the ecotoxicological effects observed for the reaction
mass can be attributed to the adverse effects exerted by the hydrogen
peroxide that is formed upon hydrolysis of calcium peroxide.
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