Calcium carbonate

Genetic toxicity: in vitro

Administrative data

Endpoint:

in vitro gene mutation study in bacteria

Type of information:

experimental study

Adequacy of study:

key study

Study period:

21 December 2009 - 19 January 2010

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2010

Report date:

2010

Materials and methods

Test guideline

Test guideline 1

Qualifier:

according to guideline

Guideline:

OECD Guideline 471 (Bacterial Reverse Mutation Assay)

Deviations:

no

Test guideline 2

Qualifier:

according to guideline

Guideline:

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

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Type of assay:

bacterial reverse mutation assay

Test material

Test material information

Constituent 1

Reference substance name:

Calcium carbonate

EC Number:

207-439-9

EC Name:

Calcium carbonate

Cas Number:

471-34-1

Molecular formula:

CH2O3.Ca

IUPAC Name:

calcium carbonate

Test material form:

solid: nanoform

Details on test material:

- Name of test material (as cited in study report): Calcium carbonate (nano)
- Description: White powder
- Purity: 98.5%
- Batch No.: GICM014427
- Storage condition of test material: Room temperature in the dark

The nano form of calcium carbonate was tested because this form was anticipated to represent the worst case as it is likely to be more soluble than the bulk form due to the smaller particle size and hence greater surface area. Furthermore, the smaller particle size will be more likely to penetrate the cells.

Method

Species / strain

Species / strain 1

Species / strain / cell type:

S. typhimurium TA 1535, TA 1537, TA 98 and TA 100

Species / strain 2

Species / strain / cell type:

E. coli WP2 uvr A

Metabolic activation:

with and without

Metabolic activation system:

S9-mix (rat liver homogenate metabolising system (10% liver S9 in standard co-factors))

Test concentrations with justification for top dose:

Preliminary toxicity test: 0, 0.15, 0.5, 1.5, 5, 15, 50, 150, 500, 1500 and 5000 μg/plate

Mutation test - Experiments 1 and 2: 50, 150, 500, 1500 and 5000 μg/plate

Vehicle / solvent:

- Vehicle: Dimethyl sulphoxide (DMSO)

- Justification for choice of vehicle: The test material was insoluble in sterile distilled water and acetone at 50 mg/mL and tetrahydrofuran at 200 mg/mL but was fully soluble in dimethyl sulphoxide and dimethyl formamide at 50 mg/mL in solubility checks performed in-house. Dimethyl sulphoxide was therefore selected as the vehicle.

Controls

Controls 1

Untreated negative controls:

yes

Remarks:

Concurrent untreated controls (spontaneous mutation rates)

Negative solvent / vehicle controls:

yes

Positive controls:

yes

Positive control substance:

N-ethyl-N-nitro-N-nitrosoguanidine

Remarks:

Migrated to IUCLID6: 2 μg/plate for WP2uvrA-, 3 μg/plate for TA100, 5 μg/plate for TA1535 - without S9-mix

Controls 2

Positive controls:

yes

Positive control substance:

9-aminoacridine

Remarks:

Migrated to IUCLID6: 80 μg/plate for TA1537 - without S9-mix

Controls 3

Positive controls:

yes

Positive control substance:

4-nitroquinoline-N-oxide

Remarks:

Migrated to IUCLID6: 0.2 μg/plate for TA98 - without S9-mix

Controls 4

Positive controls:

yes

Positive control substance:

other: 2-Aminoanthracene (2AA) with S9-mix: 1 μg/plate for TA100; 2 μg/plate for TA1535 and TA1537; 10 μg/plate for WP2uvrA-

Controls 5

Positive controls:

yes

Positive control substance:

benzo(a)pyrene

Remarks:

Migrated to IUCLID6: 5 μg/plate for TA98 - with S9-mix

Details on test system and experimental conditions:

METHOD OF APPLICATION: in agar (plate incorporation) for Experiment 1 and preincubation for Experiment 2:

Preliminary Toxicity Test: In order to select appropriate dose levels for use in the main test, a preliminary test was carried out to determine the toxicity of the test material. The concentrations tested were 0, 0.15, 0.5, 1.5, 5, 15, 50, 150, 500, 1500 and 5000 μg/plate. The test was performed by mixing 0.1 mL of bacterial culture (TA100 or WP2uvrA-), 2 mL of molten, trace histidine or tryptophan supplemented, top agar, 0.1 mL of test material formulation and 0.5 mL of S9-mix or phosphate buffer and overlaying onto sterile plates of Vogel-Bonner Minimal agar (30 mL/plate). After approximately 48 hours incubation at 37 °C the plates were assessed for numbers of revertant colonies using a Domino colony counter and examined for effects on the growth of the bacterial background lawn.

Mutation Test - Experiment 1: Five concentrations of the test material (50, 150, 500, 1500 and 5000 μg/plate) were assayed in triplicate against each tester strain, using the direct plate incorporation method.
Measured aliquots (0.1 mL) of one of the bacterial cultures were dispensed into sets of test tubes followed by 2.0 mL of molten, trace histidine or tryptophan supplemented, top agar, 0.1 mL of the test material formulation, vehicle or positive control and either 0.5 mL of S9-mix or phosphate buffer. The contents of each test tube were mixed and equally distributed onto the surface of Vogel-Bonner Minimal agar plates (one tube per plate). This procedure was repeated, in triplicate, for each bacterial strain and for each concentration of test material both with and without S9-mix.
All of the plates were incubated at 37 °C for approximately 48 hours and the frequency of revertant colonies assessed using a Domino colony counte
r.

Mutation Test - Experiment 2: The second experiment was performed using fresh bacterial cultures, test material and control solutions. The test material dose range was the same as Experiment 1 (50 to 5000 μg/plate).
The test material formulations and vehicle control were dosed using the pre-incubation method as follows:
Measured aliquots (0.1 mL) of one of the bacterial cultures were dispensed into sets of test tubes followed by 0.5 mL of S9-mix or phosphate buffer and 0.1 mL of the vehicle or test material formulation and incubated for 20 minutes at 37 °C with shaking at approximately 130 rpm prior to the addition of 2 mL of molten, trace histidine or tryptophan supplemented, top agar. The contents of the tube were then mixed and equally distributed on the surface of Vogel-Bonner Minimal agar plates (one tube per plate). This procedure was repeated, in triplicate, for each bacterial strain and for each concentration of test material both with and without S9-mix. Manual counts were required after employing the pre-incubation method at 5000 μg/plate (absence of S9-mix only) because of a particulate test material precipitation.


DURATION
- Preincubation period: 20 minutes (Experiment 2)
- Exposure duration: 48 h (Experiment 1)


NUMBER OF REPLICATIONS: Plates were prepared in triplicate


NUMBER OF CELLS EVALUATED: All tester strain cultures should be in the range of 1 to 9.9 x 10^09 bacteria per mL.

Evaluation criteria:

There were several criteria for determining a positive result, such as a dose-related increase in revertant frequency over the dose range tested and/or a reproducible increase at one or more concentrations in at least one bacterial strain with or without metabolic activation. Biological relevance of the results were considered first, statistical methods, as recommended by the UKEMS were also used as an aid to evaluation, however, statistical significance was not the only determining factor for a positive response.

Results and discussion

Test results

Test results 1

Species / strain:

S. typhimurium TA 1535, TA 1537, TA 98 and TA 100

Metabolic activation:

with and without

Genotoxicity:

negative

Vehicle controls validity:

valid

Untreated negative controls validity:

valid

Positive controls validity:

valid

Test results 2

Species / strain:

E. coli WP2 uvr A

Metabolic activation:

with and without

Genotoxicity:

negative

Vehicle controls validity:

valid

Untreated negative controls validity:

valid

Positive controls validity:

valid

Additional information on results:

TEST-SPECIFIC CONFOUNDING FACTORS
- Precipitation: No test material precipitate was observed on the plates at any of the doses tested in either the presence or absence of S9-mix after employing the plate incorporation method of dosing (preliminary toxicity test and Experiment 1). However, after employing the pre-incubation method (Experiment 2) a particulate test material precipitate was noted from 1500 and at 5000 μg/plate, in the absence and presence of S9-mix, respectively.


RANGE-FINDING/SCREENING STUDIES: The test material was non-toxic to the strains of bacteria used (TA100 and WP2uvrA-). The test material formulation and S9-mix used in this experiment were both shown to be sterile.


COMPARISON WITH HISTORICAL CONTROL DATA: A history profile of vehicle and positive control values for 2007 and 2008 is presented in Appendix I.

Results for the negative controls (spontaneous mutation rates) are presented in Table 1 and were considered to be acceptable. These data are for concurrent untreated control plates performed on the same day as the Mutation Test.

The individual plate counts, the mean number of revertant colonies and the standard deviations, for the test material, positive and vehicle controls, both with and without metabolic activation, are presented in Table 2 and Table 3 for Experiment 1 and Table 4 and Table 5 for Experiment 2.

The vehicle (dimethyl sulphoxide) control plates gave counts of revertant colonies within the normal range. All of the positive control chemicals used in the test induced marked increases in the frequency of revertant colonies, both with or without metabolic activation. Thus, the sensitivity of the assay and the efficacy of the S9-mix were validated.

The test material caused no visible reduction in the growth of the bacterial background lawn at any dose level and was, therefore, tested up to the maximum recommended dose level of 5000 μg/plate.

No significant increases in the frequency of revertant colonies were recorded for any of the bacterial strains, with any dose of the test material, either with or without metabolic activation or exposure method.

Remarks on result:

other: all strains/cell types tested

Remarks:

Migrated from field 'Test system'.

Any other information on results incl. tables

Results for the negative controls (spontaneous mutation rates) are presented in Table 1 and were considered to be acceptable. These data are for concurrent untreated control plates performed on the same day as the Mutation Test.

The individual plate counts, the mean number of revertant colonies and the standard deviations, for the test material, positive and vehicle controls, both with and without metabolic activation, are presented in Table 2 and Table 3 for Experiment 1 and Table 4 and Table 5 for Experiment 2.

The vehicle (dimethyl sulphoxide) control plates gave counts of revertant colonies within the normal range. All of the positive control chemicals used in the test induced marked increases in the frequency of revertant colonies, both with or without metabolic activation. Thus, the sensitivity of the assay and the efficacy of the S9-mix were validated.

The test material caused no visible reduction in the growth of the bacterial background lawn at any dose level and was, therefore, tested up to the maximum recommended dose level of 5000 μg/plate.

No significant increases in the frequency of revertant colonies were recorded for any of the bacterial strains, with any dose of the test material, either with or without metabolic activation or exposure method.

Applicant's summary and conclusion

Conclusions:

Interpretation of results (migrated information):
negative

The test material was considered to be non-mutagenic under the conditions of this test.