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Ecotoxicological information

Short-term toxicity to fish

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Description of key information

No experimental data are available that assess the short-term toxicity of the reaction mass of calcium carbonate and calcium dihydroxide and calcium peroxide to fish. Nevertheless, a 96h-LC50 value can be derived from reliable information that is available for hydrogen peroxide.
The 96h-NOEC for the reaction mass is 14,14 mg/L.
The 96h-LC50 for the reaction mass is 46.38 mg/L

Key value for chemical safety assessment

LC50 for freshwater fish:
46 mg/L

Additional information

No experimental data are available that assess the short-term toxicity of the reaction mass of calcium carbonate and calcium dihydroxide and calcium peroxide to fish. Nevertheless, for this endpoint reliable information is available for hydrogen peroxide (H2O2) and calcium hydroxide (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 Oncorhynchus mykiss (rainbow trout) (Egeler et al., 2007) was carried out according to the OECD 203 guidance taking into account GLP and thus resulting in a Klimish 1 score. The biological findings for Oncorhynchus mykiss were closely related to the initial pH of the test solutions, which ranged from 7.8 in the controls to 9.6, 9.9, 10.4, 10.8 and 11.1 at nominal concentrations of 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 the fish. The 96h-LC50 was found to be 50.6 mg/L under the conditions of this test.

The key study assessing the acute toxicity of hydrogen peroxide to fish as identified in the REACH registration dossier for hydrogen peroxide dates from 1989 and is performed according to US EPA guidelines (Shurtleff, 1989). In this semi-static experiment, Pimephales promelas (fathead minnow) were exposed for 96 hours to nominal hydrogen peroxide concentrations of 0.5, 5, 25, 50 and 250 ppm. The test solutions were replaced every day. The 96h-LC50 was found to be 16.4 mg/L (95% confidence interval: 13.1 -20.5 mg/L), and the 96h-NOEC value was 5 mg/L. As the 96h-LC50 value for hydrogen peroxide is lower than the value found for calcium dihydroxide, the former was selected for the assessment of the reaction mass.

 

From this 96h-LC50 value a corresponding 96h-LC50 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 96h-LC50 for the reaction mass can be calculated from the 96h-LC50 for hydrogen peroxide (16.4 mg/L):

           100 mg reaction mass                       yields             35.36 mg hydrogen peroxide

           46.38 mg reaction mass                    yields             16.4 mg hydrogen peroxide

           ==>      the 96h-LC50 (reaction mass) = 46 mg/L