Calcium wolframate

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:

2004-03-29 to 2004-05-05

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Remarks:

Well document study according to OECD guideline 471 and GLP.

Justification for type of information:

The dissociation of calcium wolframate is reversible and the ratio of the salt /dissociated ions is dependent on the metal-ligand complexation constant of the salt, the composition of the solution and its pH.

Therefore, in the assessment of the ecotoxicity of calcium wolframate, a read-across to data for sodium wolframate/wolfram metal and soluble calcium substances is applied since only the ions of calcium and wolframate are available in the environment and determine the ecotoxicological potential. Due to its electronegativity E0(Ca/Ca2+) = -2,84V calcium is present in the environment only in the divalent cationic form. At high solution pH, i.e. above 12, calcium hydroxide complexes are formed.
Other calcium species, potentially relevant for the environmental of human health hazard assessment, are not present at environmentally or physiologically relevant redox conditions and solution pH.
According to the Hägg-graph and the Pourbaix- diagram wolframate is the dominant species under ENV conditions (Seiler et al., 2005). Anthropogenic use of W utilizes W metal or WC, which are thermodynamically unstable and when introduced into environmental systems begins to alter to a more stable form (WO42-) (Andersson and Bergstrom 2000).
Wolfram metal is (due to its negative potential (-0.09 to -1.074, pH0 -> pH14)) transformed to wolframate which represents the most stable oxidation state of Wolfram. Hence, under physiological conditions wolframic acid, hydrogen wolframate and wolframate co-exist in a pH-dependent manner, irrespective of their origin.

Data source

Reference

Reference 1

Reference Type:

study report

Title:

Unnamed

Year:

2004

Report date:

2004

Reference 2

Reference Type:

publication

Title:

Genotoxicity Evaluation of Sodium Tungstate Dihydrate and Tungsten Powder.

Author:

Reddy G, McCain WC, Leach GJ.

Year:

2007

Bibliographic source:

The Toxicologist, Vol.96, No. 1, March 2007

Materials and methods

Test guideline

Qualifier:

according to guideline

Guideline:

OECD Guideline 471 (Bacterial Reverse Mutation Assay)

Deviations:

no

GLP compliance:

yes

Type of assay:

bacterial reverse mutation assay

Test material

Test material information

Constituent 1

Reference substance name:

Tungsten

EC Number:

231-143-9

EC Name:

Tungsten

Cas Number:

7440-33-7

Molecular formula:

W

IUPAC Name:

tungsten

Constituent 2

Reference substance name:

Tungsten metal

IUPAC Name:

Tungsten metal

Details on test material:

- Name of test material (as cited in study report): Tungsten powder, APS 1-5 micron
- Substance type: Active
- Physical state: Dark-grey powder
- Analytical purity: 99.9 % (metal basis)
- Storage condition of test material: room temperature

Method

Target gene:

Salmonella tyhimurium: Histidine locus and E.coli: tryptophan locus

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: See below in additional information on materials and methods.

Species / strain 2

Species / strain / cell type:

E. coli WP2 uvr A

Additional strain / cell type characteristics:

other: See below in additional information on materials and methods.

Metabolic activation:

with and without

Metabolic activation system:

Aroclor 1254 induced rat liver S9

Test concentrations with justification for top dose:

33.3, 100, 333, 1000, 3330 and 5000 ug/plate

Vehicle / solvent:

- Vehicle(s)/solvent(s) used: Saline (0.9 % NaCl)

Controls

Controls 1

Untreated negative controls:

no

Negative solvent / vehicle controls:

yes

True negative controls:

no

Positive controls:

yes

Positive control substance:

benzo(a)pyrene

Remarks:

Migrated to IUCLID6: Used in the presence of S9 for strain TA98 at 2.5 ug/plate

Controls 2

Untreated negative controls:

no

Negative solvent / vehicle controls:

yes

True negative controls:

no

Positive controls:

yes

Positive control substance:

2-nitrofluorene

Remarks:

Migrated to IUCLID6: Used in the absence of S9 for strain TA98 at 1.0 ug/plate

Controls 3

Untreated negative controls:

no

Negative solvent / vehicle controls:

yes

True negative controls:

no

Positive controls:

yes

Positive control substance:

other: 2-aminoanthracene used in the presence of S9 for strains TA100, TA1535, TA1537 and WP2uvrA at 2.5, 2.5, 2.5 and 25.0 ug/plate, respectively.

Controls 4

Untreated negative controls:

no

Negative solvent / vehicle controls:

yes

True negative controls:

no

Positive controls:

yes

Positive control substance:

sodium azide

Remarks:

Migrated to IUCLID6: Used in the absence of S9 for strains TA100 and TA1535 at 2.0 ug/plate

Controls 5

Untreated negative controls:

no

Negative solvent / vehicle controls:

yes

True negative controls:

no

Positive controls:

yes

Positive control substance:

other: ICR-191-used in the absence of S9 for strain TA1537 at 2.0 ug/plate

Controls 6

Untreated negative controls:

no

Negative solvent / vehicle controls:

yes

True negative controls:

no

Positive controls:

yes

Positive control substance:

4-nitroquinoline-N-oxide

Remarks:

Migrated to IUCLID6: Used in the absence of S9 for strain WP2uvrA at 1.0 ug/plate

Details on test system and experimental conditions:

METHOD OF APPLICATION: in agar (plate incorporation)

DURATION
- Exposure duration: 52 +/- 4 hours
- Selection time (if incubation with a selection agent): 52 +/- 4 hours (simultaneous with exposure)

SELECTION AGENT (mutation assays): histidine (Salmonella) and tryptophan (E. coli)

NUMBER OF REPLICATIONS: 3

DETERMINATION OF CYTOTOXICITY
- Method: decrease in the number of revertant colonies per plate and/or thinning or disappearance of the bacterial background lawn

CONFIRMATION OF TESTER STRAIN GENOTYPE-Tester strain cultures were checked for the following genetic markers on the day of their use in the mutagenicity assay:
1. rfa Wall Mutation - exhibited by crystal violet sensitivity
2. pKM101 Plasmid - exhibited by resistance to ampicillin
3. Characteristic Number of Spontaneous Revertants: TA98 (8-60), TA100 (60-240), TA1535 (4-45), TA1537 (2-25), WP2uvrA (5-40)

OTHER: The most concentrated test substance dilution and the S9 mix were checked for sterility.

Evaluation criteria:

Tester Strains TA98, TA100 and WP2uvrA- The test substance was considered positive, if it produce at least a 2-fold increase in the mean revertants per plate in at least one of the tester strains over the mean revertants per plate of the appropriate vehicle control. This increase in the mean number of revertants per plate had to be accompanied by a dose response to increasing concentrations of the test substance.
Tester Strains TA1535 and tA1537- The test substance was considered positive, if it produce at least a 3-fold increase in the mean revertant per plate in at least one of the tester strains over the mean revertants per plate of the appropriate vehicle control. This increase in the mean number of revertants per plate had to be accompanied by a dose response to increasing concentrations of the test substance.

Statistics:

no data

Results and discussion

Test results

Test results 1

Key result

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, but tested up to precipitating concentrations

Vehicle controls validity:

valid

Untreated negative controls validity:

not applicable

Positive controls validity:

valid

Test results 2

Key result

Species / strain:

E. coli WP2 uvr A

Metabolic activation:

with and without

Genotoxicity:

negative

Cytotoxicity / choice of top concentrations:

no cytotoxicity, but tested up to precipitating concentrations

Vehicle controls validity:

valid

Untreated negative controls validity:

not applicable

Positive controls validity:

valid

Additional information on results:

TEST-SPECIFIC CONFOUNDING FACTORS
- Precipitation: Range-finding and Mutagenicity assay- Test substance precipitate was observed on the plates at >/=3330 ug/plate.
- Other confounding effects: The test substance was observed to form an opaque, dark-grey, non-viscous suspension at 50 mg/mL, which was the most concentrated stock dilution prepared for the mutagenicity assay. The test substance was observed to dilute to a solution at 3.33 mg/mL and all succeeding lower dilutions prepared.


RANGE-FINDING/SCREENING STUDIES: The test substance was evaluated for toxicity in a range-finding assay using tester strains TA100 and UP2uvrA in the presence and absence of S9 activation at concentrations ranging from 6.67-5000 ug/plate.
No toxicity was observed in either strain at any concentration level in the presence and absence of S9 as evidenced by non dose-related decreases in the number of revertants per plate and normal bacterial background lawns. Therefore, 5000 ug/plate was selected as the maximum dose level for the mutagenicity test.


COMPARISON WITH HISTORICAL CONTROL DATA: The vehicle and positive control values for revertants/plate fell in historical control data range.

Applicant's summary and conclusion

Conclusions:

The test substance was evaluated for mutagenic potential in Bacterial Reverse Mutation Assay. Under the conditions of the study, the test substance did not cause a positive increase in the mean number of revertants per plate with any of the tester strains in the presence or absence of S9 activation.