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EC number: 908-343-6
CAS number: -
No experimental data are available that assess the toxicity of the
reaction mass of calcium carbonate and calcium dihydroxide and calcium
peroxide to aquatic algae and cyanobacteria. Nevertheless, a relevant
dose descriptor can be derived from the most reliable information that
is available for hydrogen peroxide. For hydrogen peroxide the marine
water 72h-EC50 is 1.38 mg/L and the 72h-NOEC is 0.63 mg/L.
These values can be recalculated based on the amount of H2O2
that can be formed from the reaction mass of calcium
carbonate and calcium dihydroxide and calcium peroxide and hence yields
an EC50 of 3.9 mg/L and a NOEC of 1.78 mg/L for the reaction mass.
No experimental data are available that
assess the toxicity of the reaction mass of calcium carbonate and
calcium dihydroxide and calcium peroxide to aquatic algae. Nevertheless,
for this endpoint reliable information is available for 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.
Furthermore, a supporting study is available on the toxicity of calcium
peroxide on cyanobacteria, in which a LOEC is determined based on the
PSII efficiency. However, as PSII efficiency is an indirect parameter
related to the photosynthesis process, this LOEC is not comparable to
the dose descriptors determined in the OECD 201 studies.
For calcium dihydroxide, the algal
growth inhibition test (Egeler, 2007) was carried out according to GLP
and to the OECD 201 guideline. In a 72-h static experiment, the test
species (Pseudokirchnerella subcapitata) was exposed to nominal
concentrations of 0, 48, 80, 138, 235 and 400 mg calcium dihydroxide/L.
The inital pH of the test vessels was 5.8
for the control and 6.4, 6.8, 7.2, 8.1 and 11.4, respectively for the
solutions containing increasing amounts of test material. A clear
concentration-response relationship was observed and a 72h-EC50 of
184.57 mg/L and a 72h-NOEC of 48 mg/L were established.
The pH of the medium at concentrations
resulting in a considerable growth inhibition, was below 8 and the
biological findings are therefore not attributed to the initial pH of
the test solutions. It was however observed that with increasing test
item concentrations precipitates were formed over time to which algae
adhered, leading to their flocculation. This can be explained since the
test item is known to react with CO2 to calcium carbonate,
which is poorly soluble in water leading to the formation of
precipitates. The flocculation of algae is thus considered to be the
predominant biologically relevant effect in this system test.
The key study assessing the toxicity
of hydrogen peroxide to aquatic algae and cyanobacteria as identified in
the REACH registration dossier for hydrogen peroxide is
performed on a salt water species, namely Skeletonema costatum. In this
study (Knight et al, 1997), the test organisms were exposed to nominal
concentrations of 0, 0.625, 1.25, 2.5, 5 and 10 ppm of hydrogen peroxide
for 72 hours. The 72h-EC50 and 72h-NOEC values were
1.38 mg/L and 0.63 mg/L, respectively.
From the 72h-EC50 value for
hydrogen peroxide, a corresponding 72h-EC50 value 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 marine 72h-EC50 for
the reaction mass can be calculated from the 72h-EC50 for
hydrogen peroxide (1.38 mg/L):
100 mg reaction
mass yields 35.36 mg hydrogen peroxide
mg reaction mass
yields 1.38 mg hydrogen peroxide
MW 72h-EC50 (reaction mass)
= 3.9 mg/L
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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