Calcium hydride

Endpoint summary

Key value for chemical safety assessment

Genetic toxicity in vitro

Description of key information

CaH2 reacts violently or is ignited by air; reacts exothermically with water or moisture producing hydrogen and calcium hydroxide. Due to these physico-chemical properties, CaH2 was not tested for mutagenicity.

Due to the fact that the substance hydrolyses rapidly within less than one second under formation of Hydrogen (volatilises) and calciumhydroxide, studies with the metabolite staying in the system are relevant for the substance itself. In fact if Calcium dihydride would be used as test substance, calcium hydroxide would be tested as well. Therefore  the data from calciumdihydroxide are directly relevant for calcium diydride.

Calcium dihydroxide was negative in a valid mes test with S. typhimurium TA 1535, 1537, 98 and 100 and E. coli WP2 uvrA, both with and without metabolic activation. The test was performed accordign to OECD TG 471 and GLP.

In a publication a chromosomal aberration test in human dental pulp cells (D824 cells) was reported. The study was performed with Calcium dihydroxide with and without metabolic activation and included postive and negative control substances. Two different incubation times, 3 h and 30 h were also applied to detect effects oafter prolonged exposure.

Under the conditions of this test Calcium di hydroxide did not induce chromosomal aberrations in human dental pulp cells with and without metabolic activation. Negative results were obtained after 3 h of incubation and after prolonged incubation for 30 hours. Due to the rapid hydrolysis if calciumhydride in aqueous systems (t1/2 < 1 s) under formation of calcium dihydroxide this result is directly relevant for the target substance.

Link to relevant study records

Reference

Reference 1

Endpoint:

in vitro gene mutation study in bacteria

Type of information:

read-across from supporting substance (structural analogue or surrogate)

Remarks:

read across to hydrolysis product

Adequacy of study:

key study

Study period:

2007-03-29 to 2007-07-19

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Justification for type of information:

REPORTING FORMAT FOR THE ANALOGUE APPROACH
1. HYPOTHESIS FOR THE ANALOGUE APPROACH
Due to the fact that the substance hydrolyses rapidly within less than one second under formation of Hydrogen (volatilises) and calciumhydroxide, studies with the metabolite staying in the system are relevant for the substance itself. In fact if Calcium dihydride would be used as test substance, calcium hydroxide would be tested as well. Therefore the data from calciumdihydroxide are directly relevant for calcium diydride.
3. ANALOGUE APPROACH JUSTIFICATION
See above. As the substance hydrolyses instantly under formation of calcium di hydroxide in an aqueaous test system, such as the Ames assay, the data on genotxicity of the metabonate are ditrectly relevant for calcium dihydride.
(for the hydrolytical stability see section 5.1.2).

Reason / purpose for cross-reference:

read-across source

Reason / purpose for cross-reference:

read-across: supporting information

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

Specific details on test material used for the study:

- Name of test material (as cited in study report): PRECAL 50S (Calcium hydroxide (hydrated lime))
- Physical state: solid
- Storage condition of test material: at room temperature, moisture protected

Species / strain / cell type:

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

Details on mammalian cell type (if applicable):

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 / cell type:

E. coli WP2 uvr A

Additional strain / cell type characteristics:

other: trp-; uvrA

Metabolic activation:

with and without

Metabolic activation system:

rat liver S9 mix

Test concentrations with justification for top dose:

In the pre-experiment/experiment I the concentration range of the test item was 0.3; 1.0; 3.0; 10; 33; 100; 300; 600; 1875 and 3750
Mg/plate.
The following concentrations were tested in experiment II: 117.2; 234.4; 468.75; 937.5; 1875 and 3750 Mg/plate

Vehicle / solvent:

- Vehicle(s)/solvent(s) used: On the day of the experiment, the test item was suspended in 1 M 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.

Untreated negative controls:

yes

Remarks:

untreated control

Negative solvent / vehicle controls:

yes

Remarks:

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

Positive controls:

yes

Positive control substance:

sodium azide

Remarks:

10 micro-g/plate dissolved in deionised water

Untreated negative controls:

yes

Remarks:

untreated controls

Negative solvent / vehicle controls:

yes

Remarks:

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

Positive controls:

yes

Positive control substance:

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

Remarks:

(10 or 50 Mg/plate), dissolved in DMSO

Untreated negative controls:

yes

Remarks:

untreated control

Negative solvent / vehicle controls:

yes

Remarks:

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

Positive controls:

yes

Positive control substance:

ethylmethanesulphonate

Remarks:

(3.0 ML/plate), dissolved in deionised water

Untreated negative controls:

yes

Remarks:

untreated controls

Negative solvent / vehicle controls:

yes

Remarks:

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

Positive controls:

yes

Positive control substance:

other: 2-aminoanthracene, 2-AA

Remarks:

(2.5 Mg/plate or 10 Mg/plate), dissolved in DMSO

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 resulted 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 precipitation of the test item and widespread 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 TA 98, TA 100, and WP2 uvrA) or thrice (strains TA 1535 and TA 1537) 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 a statistical analysis of the data is not mandatory.

Key result

Species / strain:

S. typhimurium TA 1535

Metabolic activation:

with and without

Genotoxicity:

negative

Cytotoxicity / choice of top concentrations:

no cytotoxicity nor precipitates, but tested up to recommended limit concentrations

Vehicle controls validity:

valid

Untreated negative controls validity:

valid

Positive controls validity:

valid

Key result

Species / strain:

S. typhimurium TA 1537

Metabolic activation:

with and without

Genotoxicity:

negative

Cytotoxicity / choice of top concentrations:

no cytotoxicity nor precipitates, but tested up to recommended limit concentrations

Vehicle controls validity:

valid

Untreated negative controls validity:

valid

Positive controls validity:

valid

Key result

Species / strain:

S. typhimurium TA 98

Metabolic activation:

with and without

Genotoxicity:

negative

Cytotoxicity / choice of top concentrations:

no cytotoxicity nor precipitates, but tested up to recommended limit concentrations

Vehicle controls validity:

valid

Untreated negative controls validity:

valid

Positive controls validity:

valid

Key result

Species / strain:

S. typhimurium TA 100

Metabolic activation:

with and without

Genotoxicity:

negative

Cytotoxicity / choice of top concentrations:

no cytotoxicity nor precipitates, but tested up to recommended limit concentrations

Vehicle controls validity:

valid

Untreated negative controls validity:

valid

Positive controls validity:

valid

Key result

Species / strain:

E. coli WP2 uvr A

Metabolic activation:

with and without

Genotoxicity:

negative

Cytotoxicity / choice of top concentrations:

no cytotoxicity nor precipitates, but tested up to recommended limit concentrations

Vehicle controls validity:

valid

Untreated negative controls validity:

valid

Positive controls validity:

valid

Additional information on results:

No substantial increase in revertant colony numbers of any of the five tester strains was observed following treatment with PRECAL
50S 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 pre-tests (reported as
Experiment I), an additional plate incorporation assay was performed with the maximum dose level suitable for the reverse
mutation assay of 3750 Mg/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.

Conclusions:

An Ames test was conducted with calcium hydroxide according to OECG TG 471. Species S. typhimurium TA 1535, TA 1537, TA 98 and TA 100 and E. coli WP2 uvr A (met. act.: with and without) were used with the following concentrations: 0.3; 1.0; 3.0; 10; 33; 100; 300; 600; 1875 and 3750 µg/plate in the experiment I and 117.2; 234.4; 468.75; 937.5; 1875 and 3750 µg/plate in the experiment II. The results regarding genotoxicity of Ca(OH)2 were negative under the testing conditions. In conclusion, during the described mutagenicity test and under the experimental conditions reported, the test item 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, PRECAL 50S is considered to be non-mutagenic in this in this Salmonella typhimurium and Escherichia coli reverse
mutation assay. Due to the rapid hydrolysis if calciumhydride in aqueous systems (t1/2 < 1 s) under formation of calcium dihydroxide this result is directly relevant for the target substance.

Executive summary:

An Ames test was conducted with calcium hydroxide according to OECG TG 471. Species S. typhimurium TA 1535, TA 1537, TA 98 and TA 100 and E. coli WP2 uvr A (met. act.: with and without) were used with the following concentrations: 0.3; 1.0; 3.0; 10; 33; 100; 300; 600; 1875 and 3750 µg/plate in the experiment I and 117.2; 234.4; 468.75; 937.5; 1875 and 3750 µg/plate in the experiment II. The results regarding genotoxicity of Ca(OH)2 were negative under the testing conditions. In conclusion, during the described mutagenicity test and under the experimental conditions reported, the test item 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, PRECAL 50S is considered to be non-mutagenic in this in this Salmonella typhimurium and Escherichia coli reverse

mutation assay. Due to the rapid hydrolysis if calciumhydride in aqueous systems (t1/2 < 1 s) under formation of calcium dihydroxide this result is directly relevant for the target substance.

Reference 2

Endpoint:

in vitro cytogenicity / chromosome aberration study in mammalian cells

Type of information:

read-across from supporting substance (structural analogue or surrogate)

Adequacy of study:

key study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

study well documented, meets generally accepted scientific principles, acceptable for assessment

Justification for type of information:

REPORTING FORMAT FOR THE ANALOGUE APPROACH
1. HYPOTHESIS FOR THE ANALOGUE APPROACH
Due to the fact that the substance hydrolyses rapidly within less than one second under formation of Hydrogen (volatilises) and calciumhydroxide, studies with the metabolite staying in the system are relevant for the substance itself. In fact if Calcium dihydride would be used as test substance, calcium hydroxide would be tested as well. Therefore the data from calciumdihydroxide are directly relevant for calcium diydride.
3. ANALOGUE APPROACH JUSTIFICATION
See above. As the substance hydrolyses instantly under formation of calcium di hydroxide in an aqueaous test system, such as the Ames assay, the data on genotxicity of the metabonate are ditrectly relevant for calcium dihydride.
(for the hydrolytical stability see section 5.1.2).

Reason / purpose for cross-reference:

read-across source

Reason / purpose for cross-reference:

read-across: supporting information

Qualifier:

no guideline followed

Principles of method if other than guideline:

Examination of the ability to induce chromosome aberrations in human dental pulp cells.

GLP compliance:

no

Type of assay:

other: chromosomal aberration in mammalian cells

Specific details on test material used for the study:

- Name of test material (as cited in study report): Calcium hydroxide
- Physical state: solid
- Purity: 99,9 % (Wako Pure Chemical)

Species / strain / cell type:

other: human dental pulp cells D824 cells

Details on mammalian cell type (if applicable):

The enzymazically released cells were suspended in alpha-minimum essential medium (alpha-MEM)
supplemented with 20 % fetal bovine serum, 100 MM L-ascorbic acid phosphate magnesium salt n-hydrate, 2mM
L-glutamine, 0.22 % NaHCO3, 100 units/mL penicilline and 100 Mg/mL streptomycin and passed through a 70
Mm nylon cell strainer to remove cell aggregates. After counting the number of cells, 1.5x10^5 cells were plated
into 75cm² flasks. When confluent, cells were harvested with a solution containing 0.25 % trypsin and 0.1 %
EDTA and replated into new flasks.

Additional strain / cell type characteristics:

not specified

Metabolic activation:

with and without

Metabolic activation system:

S9 mix

Test concentrations with justification for top dose:

30; 100 and 300 micro-M

Vehicle / solvent:

Test substance was dissolved at 30 mM in glycerol at 65 °C.

Untreated negative controls:

not specified

Negative solvent / vehicle controls:

yes

Positive controls:

yes

Positive control substance:

cyclophosphamide

Remarks:

Cells were treated for 2 hours in the presence of 5% PMS

Untreated negative controls:

not specified

Negative solvent / vehicle controls:

yes

Positive controls:

yes

Positive control substance:

other: Formalin

Remarks:

CA in D824 cells induced by treatment for 30 hours.

Details on test system and experimental conditions:

METHOD OF APPLICATION: in medium
DURATION
- Exposure duration: 3 hours
- Expression time (cells in growth medium): After treatment, cells were washed twice with fresh medium and subsequently
Substance: Ca(OH)2 / calcium dihydroxide / calcium dihydroxide / cal... file:///C:/Users/Sonia/Desktop/lime_sonia/Ca(OH)2/index.html
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incubated for a further 27-hour period, or cells were treated continuously for 30 hours.
- Fixation time (start of exposure up to fixation or harvest of cells): 3 hours before the end of the incubation, colcemid was
administered at 0.02 Mg/mL, and metaphase chromosomes were prepared for analysis.
NUMBER OF METAPHASES EVALUATED: 100 to 200
DETERMINATION OF CYTOTOXICITY
- Method: Mitotic index; cloning efficiency; relative total growth; other: Cytotoxicity was measured to select concentrations for
analysis of chromosome aberrations. Cytotoxicity was determined as the number of cells treated with calcium hydroxide, relative to
the number of cells in the control cultures x 100.
D824 cells after 6 to 8 passages were plated in triplicate onto 60-mm dishes at 8x10³ cells/cm², equivalent to 1.6x10^5 cells/dish,
and incubated overnight. The cells were treated with calcium hydroxide (in absence or presence of metabolic activation) at varying
concentrations for 3 hours. After two washings with 2 mL of fresh medium, cells were incubated for a further 24 hours and the
number of cells was counted after harvesting cells with 0.25% trypsin.
EXAMINATIONS:
The aberrations scored were gaps, breaks, exchanges, dicentric chromosomes, ring chromosomes and fragmentations.

Evaluation criteria:

not reported

Statistics:

Statistical analysis was performed by qui-square test to assess the significance of the difference in the incidences of chromosome
aberrations between control cultures and cultures treated with calcium hydroxide. The level of significance in the statistical analysis
was determined at p<0.05.

Key result

Species / strain:

mammalian cell line, other: D824 cells human dental pulp

Metabolic activation:

with and without

Genotoxicity:

negative

Remarks:

No increases in the levels of chromosome aberrations were observed in cells treated with calcium hydroxide

Cytotoxicity / choice of top concentrations:

no cytotoxicity

Vehicle controls validity:

valid

Untreated negative controls validity:

not examined

Positive controls validity:

valid

Additional information on results:

Calcium hydroxide did not induce chromosome aberrations within 3 h. Since it is known that some substances induce
chromosome aberrations only after longer exposure, a protocol with a continuous treatment for 30 hours was employed
additionally. Results show that calcium hydroxide did not enhance the level of chromosome aberrations in D824 cells even after
prolonged exposure.

Conclusions:

Under the conditions of this test Calcium hydroxide did not induce chromosomal aberrations in human dental pulp cells with and without metabolic activation. Negative results were obtained after 3 h of incubation and after prolonged incubation for 30 hours. Due to the rapid hydrolysis if calciumhydride in aqueous systems (t1/2 < 1 s) under formation of calcium dihydroxide this result is directly relevant for the target substance.

Executive summary:

In a publication a chromosomal aberration test in human dental pulp cells (D824 cells) was reported. The study was performed with Calcium dihydroxide with and without metabolic activation and included postive and negative control substances. Two different incubation times, 3 h and 30 h were also applied to detect effects oafter prolonged exposure.

Under the conditions of this test Calcium hydroxide did not induce chromosomal aberrations in human dental pulp cells with and without metabolic activation. Negative results were obtained after 3 h of incubation and after prolonged incubation for 30 hours. Due to the rapid hydrolysis if calciumhydride in aqueous systems (t1/2 < 1 s) under formation of calcium dihydroxide this result is directly relevant for the target substance.

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed (negative)