Calcium magnesium oxide

Genetic toxicity: in vitro

Administrative data

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:

2007-03-29 to 2007-07-25

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: GLP Guideline study

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2007

Report date:

2007

Materials and methods

Test guideline

Qualifier:

according to guideline

Guideline:

OECD Guideline 471 (Bacterial Reverse Mutation Assay)

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 magnesium oxide

EC Number:

253-425-0

EC Name:

Calcium magnesium oxide

Cas Number:

37247-91-9

Molecular formula:

CaMgO2

IUPAC Name:

calcium magnesium(2+) dioxidandiide

Details on test material:

- Name of test material (as cited in study report): Neutralac QM (calcium magnesium oxide (burnt dolomitic lime))
- Physical state: solid
- Storage condition of test material: at room temperature, moisture protected

Method

Species / strain

Species / strain 1

Species / strain / cell type:

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

Additional strain / cell type characteristics:

other: TA1537: his C 3076; rfa-; uvrB-; TA98: his D 3052; rfa-; uvrB-;R-factor; TA:1535: his G 46; rfa-; uvrB- and TA100: his G 46; rfa-; uvrB-;R-factor

Species / strain 2

Species / strain / cell type:

E. coli WP2 uvr A

Additional strain / cell type characteristics:

other: trp-; uvrA-

Metabolic activation:

with and without

Metabolic activation system:

S9-mix

Test concentrations with justification for top dose:

In the pre-experiment/experiment I the following concentrations were tested: 0.03; 0.1; 0.3; 1.0; 3.0; 10; 33; 100; 375 and 750 µg/plate
The following concentrations were tested in experiment II: 3.0; 10; 33; 100; 375 and 750 µg/plate

Vehicle / solvent:

- Vehicle(s)/solvent(s) used: On the day of the experiment, the test item was suspended in 1M N-(2-Hydroxyethyl)piperazine-N-2-ethane sulfonic acid (HEPES, SERVA, D-69115 Heidelberg, analytical grade).
- Justification for choice of solvent/vehicle: The solvent has been chosen according to its solubility properties.

Controls

Controls 1

Untreated negative controls:

yes

Remarks:

untreated controls, no test item or solvent added

Negative solvent / vehicle controls:

yes

Remarks:

1 M N-(2-Hydroxyethyl)piperazine-N-2-ethane sulfonic acid (HEPES)

True negative controls:

no

Positive controls:

yes

Positive control substance:

sodium azide

Remarks:

without metabolic activation; strains TA1535 and TA100

Migrated to IUCLID6: (10 µg/plate), dissolved in deionised water

Controls 2

Untreated negative controls:

yes

Remarks:

untreated controls, no test item or solvent control added

Negative solvent / vehicle controls:

yes

Remarks:

1 M N-(2-Hydroxyethyl)piperazine-N-2-ethane sulfonic acid (HEPES)

True negative controls:

no

Positive controls:

yes

Positive control substance:

other: 4-nitro-o-phenylene-diamine, 4-NOPD (10 or 50 µg/plate), dissolved in DMSO

Remarks:

without metabolic activation; strains TA1537 and TA98

Controls 3

Untreated negative controls:

yes

Remarks:

untreated controls, no test item or solvent control added

Negative solvent / vehicle controls:

yes

Remarks:

1 M N-(2-Hydroxyethyl)piperazine-N-2-ethane sulfonic acid (HEPES)

True negative controls:

no

Positive controls:

yes

Positive control substance:

methylmethanesulfonate

Remarks:

without metabolic activation; strain WP2 uvrA

Migrated to IUCLID6: (3.0 µL/plate), dissolved in deionised water

Controls 4

Untreated negative controls:

yes

Remarks:

untreated controls, no test item or solvent control added

Negative solvent / vehicle controls:

yes

Remarks:

1 M N-(2-Hydroxyethyl)piperazine-N-2-ethane sulfonic acid (HEPES)

True negative controls:

no

Positive controls:

yes

Positive control substance:

other: 2-aminoanthracene, 2-AA (2.5 µg/plate or 10 µg/plate), dissolved in DMSO

Remarks:

with metabolic activation; all strains

Details on test system and experimental conditions:

METHOD OF APPLICATION: In agar (plate incorporation) and preincubation

DURATION
- Preincubation period: 60 minutes
- Exposure duration: The plates were incubated upside down for at least 48 hours at 37 °C in the dark.

NUMBER OF REPLICATIONS: For each strain and dose level, including the controls three plates were used.

DETERMINATION OF CYTOTOXICITY
To evaluate the toxicity of the test item a pre-experiment was performed with all strains. 8 concentrations were tested for toxicity and mutation induction with three plates each. The experimental conditions in this pre-experiment were the same as described below for the experiment I (plate incorporation test). Toxicity of the test item results in a reduction in the number of spontaneous revertants or a clearing of the bacterial background lawn.

DATA RECORDING:
The colonies were counted using the Petri Viewer Mk2 (Perceptive Instruments Ltd, Suffolk CB 7BN, UK) with the software program Ames Study Manager. The counter was connected to an IBM AT compatible PC with printer which printed out both, the individual and mean values of the plates for each concentration together with standard deviations and enhancement factors as compared to the spontaneous reversion rates. Due to the precipitation of the test item and wide spread bacteria colony growth some plates were counted manually.

Evaluation criteria:

A test item is considered as a mutagen if a biologically relevant increase in the number of revertants exceeding the threshold of twice (strains TA98, TA100 and WP2 uvrA) or thrice (strains TA1535 and TA1537) the colony count of the corresponding solvent/vehicle control is observed.
A dose dependent increase is considered biologically relevant if the threshold is exceeded at more than one concentration.
An increase exceeding the threshold at only one concentration is judged as biologically relevant if reproduced in an independent second experiment.
A dose-dependent increase in the number of revertant colonies below the threshold is regarded as an indication of a mutagenic potential if reproduced in an independent second experiment. However, whenever the colony counts remain within the historical range of negative and solvent controls such an increase is not considered biologically relevant and the substance hence not regarded to be mutagenic in the bacterial reverse mutation assay.

Statistics:

According to the OECD guideline 471, statistical analysis of the data is not mandatory.

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

Cytotoxicity / choice of top concentrations:

no cytotoxicity

Remarks:

No toxic effects, evident as a reduction in the number of revertants, occurred in the test groups with and without metabolic activation.

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

Cytotoxicity / choice of top concentrations:

no cytotoxicity

Remarks:

No toxic effects, evident as a reduction in the number of revertants, occurred in the test groups with and without metabolic activation.

Vehicle controls validity:

valid

Untreated negative controls validity:

valid

Positive controls validity:

valid

Additional information on results:

No substantial increase in revertant colony numbers was observed in any of the five tester strains following treatment with calcium magnesium oxide at any concentration level, neither in presence nor in absence of metabolic activation (S9 mix). There was also no tendency of higher mutation rates with increasing concentrations in the range below the generally acknowledged border of biological relevance.

RANGE-FINDING/SCREENING STUDIES:
The assay was performed with and without liver microsomal activation. Based on the results of the pretests, an additional plate incorporation assay was performed with the maximum dose level suitable for the reverse mutation assay of 750 µg/plate.

COMPARISON WITH HISTORICAL CONTROL DATA: yes; used data represent the laboratory´s historical control data from May 2005 until June 2006 representing approx. 200 experiments (WP2 uvrA the historical data are based on approx. 100 experiments). The historical control data of the solvent control are pooled from all commonly used solvents like deionized water, DMSO, ethanol, and THF not including control data for HEPES.

In Experiment I, without metabolic activation, the number of colonies did not quite reach the lower limit of the historical control data in strain TA1535 (untreated control). Since this deviation is rather small, this effect is judged to be based upon statistical fluctuations and has no detrimental impact on the outcome of the study.

Remarks on result:

other: all strains/cell types tested

Remarks:

Migrated from field 'Test system'.

Applicant's summary and conclusion

Conclusions:

Interpretation of results (migrated information):
negative

In conclusion, during the described mutagenicity test and under the experimental conditions reported, calcium magnesium oxide did not induce gene mutations by base pair changes or frameshifts in the genome of the strains used up to and including the highest testable concentration.
Therefore, calcium magnesium oxide is considered to be non-mutagenic in this Salmonella typhimurium and Escherichia coli reverse mutation assay.