Reaction mass of calcium carbonate and calcium dihydroxide and silicon dioxide

Endpoint summary

Additional information

Instead of conducting new tests on the reaction mass itself, data on the three main constituents of the reaction mass of calcium carbonate and calcium dihydroxide and silicon dioxide were used to evaluate the genotoxic potential of the substance. Guideline studies or information are availabe demonstrating the absence of genotoxic activity in vitro for each of the constituents. The 30 September 2014, Solvay received a final decision on compliance check from ECHA for the REACH dossier : reaction mass of calcium carbonate and calcium dihydroxide and silicon dioxide, List No 932 -084 -8, registration number : 01 -2119557874 -24 -0000. Decision number : CCH-D0000004065 -$0 -03/F. Since the reaction mass contains 21 impurities which together can constitute up to 30% of the registered substance, ECHA asked Solvay to perform the three in vitro genotoxic tests on the reaction mass itself. Solvay accepted to perform these 3 tests and the laboratory CITOXLab has been contacted. The three followed in vitro gentoxic tests have been started : Bacterial reverse mutation test (OECD guideline n°471), in vitro mammalian cell gene mutation test in L5178Y TK+/- mouse lymphoma cells (OECD guideline n°476) and in vitro micronucleus test in L5178Y TK+/- mouse lymphoma cells (OECD guideline n°487).

Solubility assays were undertaken with the reaction mass for the three in vitro tests and the vehicles were selected among the usually used solvent cited in the guidelines. None of these vehicles allowed obtaining a solution even a homogenous suspension of the reaction mass despite the use of 20 minutes of ultrasounds and 1 hour of magnetic stirring at up to 70°C.

No homogenous suspension and no improvement of the aspect of the formulations were obtained either when using 0.5% aqueous methylcellulose, grinding using mortar and pestle, and then mixing with an ultra turrax. None of the vehicles or tested conditions allowed obtaining a dose-formulation compatible with the realization of suitable treatments. Therefore the laboratory decided to stop the three tests (for more details please see the three endpoints study records corresponding to the threein vitro tests performed on the reaction mass itself).

Since the three in vitro genotoxic tests required by ECHA on the reaction mass itself are technically infeasible a bibliographic research targeted on genotoxic data (in vitroandin vivo tests) was done on the 21 impurities. The genotoxic data on each impurity are reported on the table attached below in the section ‘Attached document(s)’.

As indicated in the table, magnesium oxide, strontium carbonate, barium carbonate, strontium oxide and magnesium hydroxide are not considered to be genotoxic based at least on the three reliablein vitrotests performed on the substance itself and/or on analogues. Diron trioxide, titanium dioxide and calcium oxide are not considered to be genotoxic based on reliablein vitroandin vivostudies on the substance itself and/or analogues. Since the substance is naturally present in cells or is commonly used in food, sodium carbonate and sodium chloride are respectively considered to be non-genotoxic. In a weight of evidence approach based on available data on the substance itself and/or on analogues calcium sulfate, tricalcium bis(othophosphate), potassium carbonate, potassium oxide, disodium oxide, sodium hydroxide, potassium hydroxide, iron hydroxide and magnesium carbonate are not expected to be genotoxic. For two impurities, i.e. aluminium oxide and aluminium hydroxide, literature reports indicated that some genotoxicity was observed when testing pure, synthetic (30 and 40 nm), mono-disperse and stable nanoparticles (Mutation Research 676 (1-2): 41-47). These same litterature reports showed that larger particles (50 to 200 µm) did not show this characteristic, indicating that the observed genotoxicity was primarily driven by the high surface area of the aluminium oxide/hydroxide particles when present in a pure nanosize grade. As such, these data on nanoparticles are not representative for the aluminium oxide/hydroxide impuritiy present in the reaction of calcium carbonate, calcium dihydroxide and silicon dioxide because it is constituted from solid particles (D10 31 µm, D50 570 µm) composed of 3 main constituents (>70%) and 21 impurities. Therefore no genotoxic effects are expected for the two impurities: aluminum oxide and aluminum hydroxide present in the reaction mass of calcium carbonate, calcium dihydroxide and silicon dioxide, nor for the reaction mass as a whole.

 

Taken into account the data on the main constituents and on the 21 impurities, the reaction mass of calcium carbonate, calcium dihydroxide and silicon dioxide is not expected to be genotoxic. Therefore no classification is required for this endpoint.

Short description of key information:
Instead of conducting new tests on the reaction mass itself, data on the constituents and on the 21 impurities of the reaction mass of calcium carbonate and calcium dihydroxide and silicon dioxide were used to evaluate the genotoxic potential of the substance. Guideline studies or information are availabe demonstrating the absence of genotoxic activity in vitro for each main constituent (carbone carbonate and calcium dihydroxide and silicon dioxide). In vitro and in vivo genotoxic data on impurities were also analyzed. Taking into gather, these data showed that genotoxic effect is not expected for the 21 impurities present in the reaction mass of calcium carbonate and calcium dihydroxide and silicon dioxide. Therefore based on the three main constituents and on the 21 impurities, the reaction mass of calcium carbonate and calcium dihydroxide and silicon dioxide is not considered to be genotoxic.

Endpoint Conclusion: No adverse effect observed (negative)

Justification for classification or non-classification

Taken into account the data on the main constituents and on the 21 impurities, the reaction mass of calcium carbonate and calcium dihydroxide and silicon dioxide is not expected to be genotoxic. Therefore no classification is required for this endpoint.