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Bioconcentration refers to the accumulation of a substance dissolved in water by an aquatic organism (definition from section R.7.10.1.1 of ECHA's guidance document on "Information requirements and chemical safety assessment" R7c p. 9). As the reaction mass of calcium carbonate and calcium dihydroxide and calcium peroxide is a solid inorganic multi-constituent substance which undergoes dissociation and hydrolysis in aqueous media, this means that Ca2 +, OH- and hydrogen peroxide are the species to be taken into account when assessing its potential to bioconcentrate.

 

* H2O2: Hydrogen peroxide is reactive and a polar substance with a short half-life, and the log Kow value of hydrogen peroxide is estimated at approximately –1.5. These properties indicate negligible potential of bioconcentration of hydrogen peroxide (cf., European Union Risk Assessment Report: hydrogen peroxide; European Chemicals Bureau, Institute for Health and Consumer Protection, 2nd Priority List Volume 38; EUR 20844 EN; page 35).

Moreover, the enzyme catalase is almost ubiquitously distributed in biotic systems enabling the organisms to convert hydrogen peroxide into water and oxygen.

 

* Ca(OH)2: Exposure to calcium dihydroxide actually comes down to exposure to calcium ions and hydroxyl ions. There will be no intake of calcium dihydroxide as such from an aquatic medium, nor will calcium dihydroxide prevail under its original form in the organisms. Moreover, both the intake of the essential element calcium and the internal pH of an organism are actively regulated (homeostasis). Therefore, this endpoint is considered not to be relevant for calcium dihydroxide, and a bioconcentration test in fish is not deemed required.

In conclusion, the reaction mass of calcium carbonate and calcium dihydroxide and calcium peroxide is an inorganic multi-constituent substance that hydrolyses in water. The constituents and hydrolysis products are not bioaccumulative. Studies to determine the bioaccumulation of the reaction mass of calcium carbonate and calcium dihydroxide and calcium peroxide are therefore not needed.