Silicic acid, calcium salt

Endpoint summary

Key value for chemical safety assessment

Genetic toxicity in vitro

Description of key information

Three key studies are available that were all performed according to GLP and the corresponding OECD Guideline for the in vitro tests. The results of the Ames test, the chromosome aberration test and the HPRT test all showed that silicid acid, calcium salt (xonotlite/tobermorite) does not have mutagenic properties.

Four publications are available in which the effects of xonotlite on DNA damage and repair was studied in an UDS test (method deviating from OECD Guidelines and not GLP). The studies have been disregarded as the documentation is not sufficient for assessment and not convincing for an expert judgment. However, the results indicate that xonotlite does not induce UDS.

Short description of key information:
In vitro:
Gene mutations in bacteria (Ames): not mutagenic (OECD 471)
Cytogenicity (Chomosome aberration): not cytogenic (OECD 473)
Gene mutation in mammalian cells (HPRT): not mutagenic (OECD 476)

Endpoint Conclusion:No adverse effect observed (negative)

Link to relevant study records

Reference

Reference 1

Endpoint:

in vitro gene mutation study in bacteria

Remarks:

Type of genotoxicity: gene mutation

Type of information:

experimental study

Adequacy of study:

key study

Study period:

08 Sep. 2010 - 24 Sep. 2010

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Remarks:

Performed under GLP

Qualifier:

according to guideline

Guideline:

OECD Guideline 471 (Bacterial Reverse Mutation Assay)

Deviations:

no

Qualifier:

according to guideline

Guideline:

EU Method B.13/14 (Mutagenicity - Reverse Mutation Test Using Bacteria)

Deviations:

no

Principles of method if other than guideline:

Not applicable

GLP compliance:

yes (incl. QA statement)

Type of assay:

bacterial reverse mutation assay

Target gene:

His-gene: Amino acid histidine

Species / strain / cell type:

other: S. typhimurium TA1535, TA97a, TA98, TA100 and TA102

Details on mammalian cell type (if applicable):

Not applicable

Metabolic activation:

with and without

Metabolic activation system:

Male Sprague-Dawley rat liver S9 induced by Aroclor

Test concentrations with justification for top dose:

Experiment I (plate incorporation test): 50, 148, 497, 1508, and 5007 ug/plate
Experiment II (pre-incubation test): 309, 652, 1262, 2540, and 5008 ug/plate

Vehicle / solvent:

- Vehicle(s)/solvent(s) used: Deionised water
- Justification for choice of solvent/vehicle: The test item was not sufficiently soluble in the accepted solvents for the Ames-test. Therefore, suspensions were prepared. The test item was autoclaved and suspended in deionised water. Water was chosen, because the test item could be suspended completely, and this solvent doesn't have any effects on the viability of the bacteria or the number of spontaneous revertants. The suspensions were stirred during the test.

Untreated negative controls:

no

Negative solvent / vehicle controls:

yes

True negative controls:

no

Positive controls:

yes

Positive control substance:

other: Without metabolic activation: strains TA100 and TA1535: Sodium azide; Strains TA97a, TA98, and TA102: 4-Nitro-1,2-phenylene-diamine. With metabolic activation: strains TA97a, TA100, TA102, and TA1535: 2-Aminoanthracene; strain TA98: Benzo-a-pyrene.

Details on test system and experimental conditions:

METHOD OF APPLICATION: in agar (plate incorporation); preincubation

DURATION
- Preincubation period: 20 minutes
- Selection time (if incubation with a selection agent): 48 hours

SELECTION AGENT (mutation assays): agar containing Histidine

NUMBER OF REPLICATIONS: Per strain and dose, 4 plates with and 4 plates without S9 mix were used.

NUMBER OF CELLS EVALUATED: 10*9

DETERMINATION OF CYTOTOXICITY
- Method: A reduction of the bacterial background lawn or a reduction of the revertant colonies.

Evaluation criteria:

A test item is considered to have mutagenic potential, if a significant, reproducible increase of revertant colonies per plate (increase factor ≥ 2) in at least one strain can be observed. A concentration-related increase over the range tested can also be taken as a sign of mutagenic activity.

Statistics:

Mean and Standard Deviation

Key result

Species / strain:

other: S. typhimurium TA1535, TA97a, TA98, TA100 and TA102

Metabolic activation:

with and without

Genotoxicity:

negative

Cytotoxicity / choice of top concentrations:

no cytotoxicity

Vehicle controls validity:

valid

Untreated negative controls validity:

not applicable

Positive controls validity:

valid

Additional information on results:

TEST-SPECIFIC CONFOUNDING FACTORS
- Water solubility: The test item was autoclaved and suspended in deionised water.

COMPARISON WITH HISTORICAL CONTROL DATA: The determined values for the spontaneous revertants of the negative controls were in the normal range of the test laboratory (historical data of the laboratory).

ADDITIONAL INFORMATION ON CYTOTOXICITY: In both experiments no signs of toxicity towards the tested strains could be observed. The background lawn was visible and the number of revertant colonies was not reduced.

Remarks on result:

other: all strains/cell types tested

Remarks:

Migrated from field 'Test system'.

Conclusions:

Interpretation of results (migrated information):
negative with metabolic activation
negative without metabolic activation

The test item did not show mutagenic effects in both experiments. The number of revertant colonies was not increased in comparison with the spontaneous revertants (solvent only). Cytotoxicity of the test item was not detected. The background lawn was visible and the number of revertants was not significantly decreased. Therefore it can be stated, that under the test conditions, the test item crystalline calcium silicate hydrates (xonotlite - tobermorite) is not mutagenic in the Bacterial Reverse Mutation Test using Salmonella typhimurium strains TA97a, TA98, TA100, TA102 and TA1535.

Executive summary:

The mutagenic potential of crystalline calcium silicate hydrates (xonotlite - tobermorite) was determined in the Bacterial Reverse Mutation Test following OECD 471 and EU B.13/14. Two valid experiments were performed. In the first experiment 5 concentrations of the test item, suspended in deionised water were used (50, 148, 497, 1508, and 5007 ug/plate). Five genetically manipulated strains of Salmonella typhimurium (TA97a, TA98, TA100, TA102 and TA1535) were exposed to the test item both in the presence and in the absence of a metabolic activation system (S9) for 48 hours, using the plate incorporation method. None of the concentrations caused a significant increase in the number of revertant colonies in the tested strains. The test item didn't show any mutagenic effects in the first experiment. No signs of toxicity towards the bacteria could be observed. The determined values for the spontaneous revertants of the negative controls were in the normal range. All positive controls showed mutagenic effects with and without metabolic activation.

To verify the results of the first experiment a second experiment was performed, using 5 concentrations of the test item (309, 652, 1262, 2540, and 5008 ug/plate) and a modification in study performance (pre-incubation method). The test item didn't show mutagenic effects in the second experiment, either. No signs of toxicity towards the bacteria could be observed. The determined values for the spontaneous revertants of the negative controls were in the normal range. All positive controls showed mutagenic effects with and without metabolic activation.

Under the conditions of the test, the test item didn't show mutagenic effects towards Salmonella typhimurium strains TA97a, TA98, TA100, TA102 and TA1535. Therefore, no concentration-effect relationship could be determined. The test item crystalline calcium silicate hydrates (xonotlite - tobermorite) is considered as not mutagenic under the conditions of the test.

Reference 2

Endpoint:

in vitro cytogenicity / chromosome aberration study in mammalian cells

Remarks:

Type of genotoxicity: chromosome aberration

Type of information:

experimental study

Adequacy of study:

key study

Study period:

27 Sep. 2010 - 28 Sep. 2010

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Remarks:

Performed under GLP

Qualifier:

according to guideline

Guideline:

OECD Guideline 473 (In Vitro Mammalian Chromosome Aberration Test)

Deviations:

yes

Remarks:

The chosen concentrations for cytogenetic damage were selected with factors partially smaller than factor 2.

Qualifier:

according to guideline

Guideline:

EU Method B.10 (Mutagenicity - In Vitro Mammalian Chromosome Aberration Test)

Deviations:

yes

Remarks:

The chosen concentrations for cytogenetic damage were selected with factors partially smaller than factor 2.

Principles of method if other than guideline:

Not applicable

GLP compliance:

yes (incl. QA statement)

Type of assay:

in vitro mammalian chromosome aberration test

Target gene:

Not relevant

Species / strain / cell type:

lymphocytes: human

Details on mammalian cell type (if applicable):

- Type and identity of media: Culture base medium RPMI 1640
- Properly maintained: yes

Additional strain / cell type characteristics:

not applicable

Metabolic activation:

with and without

Metabolic activation system:

Male Wistar rat liver S9 induced by Phenobarbital/ß-Naphthoflavone

Test concentrations with justification for top dose:

In the preliminary cytotoxicity test (with and without S9 mix): 10, 50, 100, 200, 300, 400, and 500 ug/mL nominal.
In the cytogenetic experiments (with and without S9 mix): 100, 300, and 500 ug/mL nominal.

Vehicle / solvent:

An eluate of the test item was prepared because the test item is not soluble in water or DMSO. The solvent for the eluate was water, because a small volume water does not have any effects on the viability of the blood cells.

Untreated negative controls:

no

Negative solvent / vehicle controls:

yes

Remarks:

sterile water

True negative controls:

no

Positive controls:

yes

Positive control substance:

other: Without S9 mix: ethylmethane sulphonate; with S9 mix: cyclophosphamide monohydrate

Details on test system and experimental conditions:

METHOD OF APPLICATION: in medium

DURATION
- Exposure duration:
Experiment I: (± S9-mix): 4 hours
Experiment II: + S9-mix: 4 hours; - S9-mix: 22 h continuous exposure
- Fixation time (start of exposure up to fixation or harvest of cells): 22 hours

SPINDLE INHIBITOR (cytogenetic assays): Colcemid, 0.1 μg/mL medium, last 3 hours of incubation
STAIN (for cytogenetic assays): Giemsa (10% solution)

NUMBER OF REPLICATIONS: duplicate cultures for each treatment

NUMBER OF CELLS EVALUATED: 100 metaphase chromosome spreads from each culture

DETERMINATION OF CYTOTOXICITY
- Method: mitotic index

OTHER EXAMINATIONS:
- Determination of polyploidy: yes
- Determination of endoreplication: yes


OTHER: Dose Selection: Due to the preparation procedure of the test item, the exact composition and concentration of the eluate was unknown. To analysis cytogenetic damage in the highest concentration of test item possible, the chosen concentrations for cytogenetic damage were selected with factors partially smaller than factor 2.

Evaluation criteria:

A test item is classified as non-mutagenic if:
- the number of induced structural chromosome aberrations in all evaluated dose groups is below 5.0 % aberrant cells, excluding gaps.
- no significant increase of the number of structural chromosome aberrations is observed.
A test item is classified as mutagenic if:
- the number of induced structural chromosome aberrations is above 5.0 % aberrant cells, excluding gaps.
- and either a concentration-related or a significant increase in the number of cells with structural chromosome aberrations is observed.

Statistics:

Statistical significance was confirmed by means of the Fisher´s exact test (p < 0.05).

Key result

Species / strain:

lymphocytes: human

Metabolic activation:

with and without

Genotoxicity:

negative

Cytotoxicity / choice of top concentrations:

no cytotoxicity

Vehicle controls validity:

valid

Untreated negative controls validity:

not applicable

Positive controls validity:

valid

Additional information on results:

TEST-SPECIFIC CONFOUNDING FACTORS
- Water solubility: crystalline calcium silicate hydrates was examined as eluate, because the test item was not soluble in water or DMSO.
- Precipitation: In all experiments, no precipitation was observed. This was expected, as eluates (corresponding to saturated solutions) were used.

RANGE-FINDING/SCREENING STUDIES: In the preliminary cytotoxicity test (with and without S9 mix) in all chosen concentrations: (10, 50, 100, 200, 300, 400, and 500 ug/mL nominal), no precipitation of the test item occurred and, measured on the data of the mitotic index, no cytotoxicity was detected. The following concentrations were selected for structural evaluation: 100, 300, and 500 ug/mL nominal.

COMPARISON WITH HISTORICAL CONTROL DATA: The range of aberrant cells after treatment with the test item (0.0 – 3.0% aberrant cells, excluding gaps) was similar to the range of the solvent control values (0.5 – 2.5% aberrant cells, excluding gaps). No evidence of an increase in polyploid metaphases was noticed after treatment with the eluate of the test item as compared to the control cultures. The determined values of the solvent controls were in the normal range of the test laboratory (historical data of the laboratory).

ADDITIONAL INFORMATION ON CYTOTOXICITY: There were no cytotoxic effects in all experimental parts of this study.

Remarks on result:

other: all strains/cell types tested

Remarks:

Migrated from field 'Test system'.

Conclusions:

Interpretation of results (migrated information):
negative with metabolic activation
negative without metabolic activation

In both independent experiments, no toxicity was detected and neither a statistically significant nor a biologically relevant increase of structural chromosomal aberrations was observed at the evaluated concentrations. Furthermore, no increase in the frequencies of polyploid metaphases was found after treatment with the eluate of the test item as compared to the frequencies of the controls. All positive control compounds caused large, statistically significant increases in the proportion of aberrant cells, demonstrating the sensitivity of the test system. In conclusion, under the experimental conditions reported, the eluate of Crystalline calcium silicate hydrates does not induce structural chromosomal aberrations in human lymphocytes in vitro.

Executive summary:

This study was performed to assess the mutagenic potential of an eluate of Crystalline calcium silicate hydrates (examined as eluate, because the test item was not soluble in water or DMSO) to induce structural chromosomal aberrations in human lymphocytes cultured in vitro in absence and presence of an exogenous metabolic activation system (liver S9 mix from male rats, treated with phenobarbital/B-naphthoflavone). The study was performed in accordance with OECD Guideline 473. Human lymphocytes, in whole blood culture, were stimulated to divide by addition of phytohaemagglutinin and exposed to the test item.

Two independent experiments were performed. In each experimental group, all cell cultures were set up in duplicates. In order to asses the toxicity of the test solution to cultured human lymphocytes, the mitotic index was calculated for all cultures treated with test item, positive controls and solvent control. On the basis of this data, the following concentrations were selected for metaphase analysis (with and without S9 mix): 100, 300, and 500 ug/mL nominal. Exposure duration was as follows: Experiment I: (± S9-mix): 4 hours; Experiment II: + S9-mix: 4 hours; - S9-mix: 22 h continuous exposure. Solvent (sterile water) and positive control cultures (without S9 mix: ethylmethane sulphonate; with S9 mix: cyclophosphamide monohydrate) were also prepared. Three hours after the end of cultivation, cell division was arrested using Colcemid, the cells were harvested and slides were prepared. Then, the metaphase cells were examined for chromosomal damage. 100 well spread metaphases per evaluated culture were scored.

In this study, in both independent experiments in the absence and presence of S9 mix, no toxicity was detected and neither a statistically significant nor a biologically relevant increase of structural chromosomal aberrations was observed at the evaluated concentrations. The range of aberrant cells after treatment with the test item (0.0 – 3.0% aberrant cells, excluding gaps) was similar to the range of the solvent control values (0.5 – 2.5% aberrant cells, excluding gaps). No evidence of an increase in polyploid metaphases was noticed after treatment with the eluate of the test item as compared to the control cultures. In both experiments, EMS (600 ug/ml and 350 ug/mL, resp.) and CPA (35 ug/mL), used as positive controls, showed distinct increases in cells with structural chromosome aberrations, demonstrating the sensitivity of the test system.

In conclusion, under the experimental conditions reported, the eluate of Crystalline calcium silicate hydrates does not induce structural chromosomal aberrations in human lymphocytes in vitro.

Reference 3

Endpoint:

in vitro gene mutation study in mammalian cells

Remarks:

Type of genotoxicity: gene mutation

Type of information:

experimental study

Adequacy of study:

key study

Study period:

July 27, 2010 - October 5, 2010

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Remarks:

Performed under GLP

Qualifier:

according to guideline

Guideline:

OECD Guideline 476 (In Vitro Mammalian Cell Gene Mutation Test)

Deviations:

no

Qualifier:

according to guideline

Guideline:

EU Method B.17 (Mutagenicity - In Vitro Mammalian Cell Gene Mutation Test)

Deviations:

no

Principles of method if other than guideline:

Not applicable

GLP compliance:

yes (incl. QA statement)

Type of assay:

mammalian cell gene mutation assay

Target gene:

HPRT (hypoxanthine-guanine phosphoribosyl transferase) gene

Species / strain / cell type:

Chinese hamster lung fibroblasts (V79)

Details on mammalian cell type (if applicable):

- Type and identity of media: MEM (minimal essential medium)
- Properly maintained: yes
- Periodically checked for Mycoplasma contamination: yes
- Periodically checked for karyotype stability: yes
- Periodically "cleansed" against high spontaneous background: yes

Additional strain / cell type characteristics:

not applicable

Metabolic activation:

with and without

Metabolic activation system:

Phenobarbital/B-naphthoflavone induced rat liver S9

Test concentrations with justification for top dose:

Experiment I: Exposure period: 4 hours, with and without S9 mix: 18.8, 37.5, 75, 150, and 700 µg/mL.
Experiment II: Exposure period: 24 hours, without S9 mix: 18.8, 37.5, 75, 150, and 700 µg/mL; Exposure period: 4 hours, with S9 mix: 37.5, 75, 150, 300 and 700 µg/mL.

Vehicle / solvent:

- Vehicle(s)/solvent(s) used: DMSO
- Justification for choice of solvent/vehicle: The solvent was chosen according to its solubility properties and its non-toxicity to the cells.

Untreated negative controls:

no

Negative solvent / vehicle controls:

yes

Remarks:

DMSO

True negative controls:

no

Positive controls:

yes

Positive control substance:

other: Without S9: Ethylmethane sulfonate (EMS - 150 µg/mL). With S9: 7,12-dimethylbenz(a)anthracene (DMBA - 1.1 µg/mL)

Details on test system and experimental conditions:

METHOD OF APPLICATION: in medium

DURATION
- Exposure duration:
Short-term treatment: With and without S9-mix: 4 hours;
Prolonged treatment period: Without S9-mix: 24 hours.
- Expression time (cells in growth medium): 7 days
- Selection time (if incubation with a selection agent): about 8 days

SELECTION AGENT (mutation assays): 6-TG (6-thioguanine)

NUMBER OF REPLICATIONS: Duplicate cultures

NUMBER OF CELLS EVALUATED: 10E6 cells

DETERMINATION OF CYTOTOXICITY
- Method: cloning efficiency

OTHER: In the first range finding pre-experiment test item concentrations between 5.4 and 694.5 µg/mL were used to evaluate toxicity in the presence (4 h treatment) and absence (4 h and 24 h treatment) of metabolic activation. Due to technical reasons the experimental part in the absence of metabolic activation and 4 hours treatment was repeated with concentrations between 5.5 and 700.0 µg/mL.

Evaluation criteria:

A test item is classified as positive if it induces either a concentration-related increase of the mutant frequency or a reproducible and positive response at one of the test points. A test item producing neither a concentration- related increase of the mutant frequency nor a reproducible positive response at any of the test points is considered non-mutagenic in this system. A positive response is described as follows: A test item is classified as mutagenic if it reproducibly induces a mutation frequency that is three times above the spontaneous mutation frequency at least at one of the concentrations in the experiment. The test item is classified as mutagenic if there is a reproducible concentration-related increase of the mutation frequency. Such evaluation may be considered also in the case that a threefold increase of the mutant frequency is not observed. However, in a case by case evaluation this decision depends on the level of the corresponding solvent control data. If there is by chance a low spontaneous mutation rate within the laboratory’s historical control data range, a concentration-related increase of the mutations within this range has to be discussed. The variability of the mutation rates of solvent controls within all experiments of this study was also taken into consideration.

Statistics:

A linear regression (least squares) was performed to assess a possible dose dependent increase of mutant frequencies statistics software. The number of mutant colonies obtained for the groups treated with the test item were compared to the solvent control groups. A trend is judged as significant whenever the p-value (probability value) is below 0.05.

Key result

Species / strain:

Chinese hamster lung fibroblasts (V79)

Metabolic activation:

with and without

Genotoxicity:

negative

Cytotoxicity / choice of top concentrations:

cytotoxicity

Vehicle controls validity:

valid

Untreated negative controls validity:

not applicable

Positive controls validity:

valid

Additional information on results:

TEST-SPECIFIC CONFOUNDING FACTORS
- Precipitation: In all experimental parts test item precipitation occurred in the highest treatment concentrations evaluated for mutagenicity. Precipitation was observed in the absence and presence of metabolic activation at 75.0 µg/mL and above in experiment I and at 150.0 µg/mL and above in experiment II.

RANGE-FINDING/SCREENING STUDIES: In the first range finding pre-experiment cytotoxic effects were observed at 87.5 µg/mL and above in the absence of metabolic activation following 4 hours treatment. The test medium was checked for precipitation or phase separation at the end of each treatment period (4 or 24 hours) prior to removal to the test item. Precipitation occurred at 175.0 µg/mL and above in the absence of metabolic activation and at 86.8 µg/mL in the presence of S9 mix (4 hours treatment). Following continuous treatment (24 hours) without metabolic activation precipitation was observed at 86.8 µg/mL and above.

COMPARISON WITH HISTORICAL CONTROL DATA:
- Several mutant frequencies (31.6 – 53.5 mutant colonies/10E6 cells) exceeded the historical range of solvent controls. As these increases were not observed in the respective parallel culture this effect is judged as being biologically not relevant. The induction factor exceeded the threshold of three times the corresponding solvent control in the second culture of the experiment II with metabolic activation at 300.0 µg/mL. This effect however, was judged to be based upon the rather low solvent controls of 8.5 mutant colonies/10E6 cells.
- The highest solvent controls in the absence of S9 mix in experiment I and II, culture II (37.4 and 37.1 colonies per 10E6 cells) slightly exceeded the historical range of solvent control slightly (0.6 – 40.2 colonies per 10E6 cells). However, this effect was judged as irrelevant since it is very minor and the corresponding solvent control of the respective parallel culture remained well within the range of historical controls.

ADDITIONAL INFORMATION ON CYTOTOXICITY: Relevant cytotoxic effects were observed in the first experiment in the absence of S9 mix following 4 hours treatment. At the highest applied dose group (700.0 µg/mL) the cloning efficiency was reduced to 4.2 and 9.5 % of control cultures.

Conclusions:

Interpretation of results (migrated information):
negative with metabolic activation
negative without metabolic activation

No substantial and reproducible dose dependent increase of the mutation frequency was observed in both main experiments. In conclusion it can be stated that under the experimental conditions reported the test item did not induce gene mutations at the HPRT locus in V79 cells. Therefore, crystalline calcium silicate hydrates (xonotlite - tobermorite) is considered to be non-mutagenic in this HPRT assay.

Executive summary:

This study was performed to investigate the potential of crystalline calcium silicate hydrates (xonotlite - tobermorite) to induce gene mutations at the HPRT locus in V79 cells of the Chinese hamster. The assay was performed in accordance with OECD Guideline 476, in two independent experiments, using two parallel cultures each.

The first main experiment was performed with and without liver microsomal activation and a treatment period of 4 hours. The second experiment was performed with a treatment time of 4 hours with and 24 hours without metabolic activation. The highest applied concentration in the first and second pre-test on cytotoxicity (694.5 or 700.0 µg/ml) was chosen with regard to the solubility properties of the test item in an appropriate solvent (DMSO) with respect to the current OECD Guideline 476. As well, the dose range of the main experiments was limited by solubility properties of the test item. The applied concentrations are: Experiment I: Exposure period: 4 hours, with and without S9 mix: 18.8, 37.5, 75, 150, and 700 µg/mL; Experiment II: Exposure period: 24 hours, without S9 mix:18.8, 37.5, 75,150, and 700 µg/mL; Exposure period: 4 hours, with S9 mix: 37.5, 75, 150, 300, and 700 µg/mL.

In all experimental parts test item precipitation occurred in the highest treatment concentrations evaluated for mutagenicity. Precipitation was observed in the absence and presence of metabolic activation at 75.0 µg/mL and above in experiment I and at 150.0 µg/mL and above in experiment II. Relevant cytotoxic effects were observed in the first experiment in the absence of S9 mix following 4 hours treatment. At the highest applied dose group (700.0 µg/mL) the cloning efficiency was reduced to 4.2 and 9.5 % of control cultures. No substantial and reproducible dose dependent increase of the mutation frequency was observed in both main experiments. Appropriate reference mutagens, used as positive controls (EMS (150 µg/mL) and DMBA (1.1 µg/mL)), induced a distinct increase in mutant colonies and thus, showed the sensitivity of the test item and the activity of the metabolic activation system.

In conclusion it can be stated that under the experimental conditions reported the test item did not induce gene mutations at the HPRT locus in V79 cells. Therefore, crystalline calcium silicate hydrates (xonotlite - tobermorite) is considered to be non-mutagenic in this HPRT assay.

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed (negative)

Justification for classification or non-classification

Based on the results of the in vitro genotoxicity study, the test substance does not need to be classified for mutagenicity based on the criteria outlined in Annex I of 1272/2008/EC