Tantalum

Endpoint summary

Key value for chemical safety assessment

Genetic toxicity in vitro

Description of key information

Tantalum metal (target substance) gave a negative response in an in vitro gene mutation assay in bacteria according to OECD 471.

Mutagenic and cytogenic potential in mammalian cells was assesd using data from the structural analogues tantalum pentoxide (OECD 473) and tantalum pentachloride (OECD 476) in a read-across approach.

In a mammalian cell HPRT mutation assay according to OECD 476 and GLP tantalum pentachloride was tested negative. Moreover, tantalum pentachloride did not induce structural and/or numerical chromosomal damage tested by an in vitro micronucleus test in Chinese hamster V79 cells (OECD 487, GLP).

Based on these results the target subtance tantalum metal is non-mutagenic.

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:

weight of evidence

Study period:

8 December 2000 to 21 December 2000

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Remarks:

Study conducted in compliance with agreed protocols, with no or minor deviations from standard test guidelines and/or minor methodological deficiencies, which do not affect the quality of the relevant results. The study report was conclusive, done to valid guidelines and the study was conducted under GLP conditions.

Qualifier:

according to guideline

Guideline:

OECD Guideline 471 (Bacterial Reverse Mutation Assay)

Deviations:

not specified

Qualifier:

according to guideline

Guideline:

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

Deviations:

not specified

Qualifier:

according to guideline

Guideline:

EPA OPPTS 870.5100 - Bacterial Reverse Mutation Test (August 1998)

Deviations:

not specified

Qualifier:

according to guideline

Guideline:

other: Japan Ministry of Agriculture, Forestry and Fisheries. (1985) Notification of Director General, Agricultural Production Bureau. NohSan No. 4200.

Deviations:

not specified

Qualifier:

according to guideline

Guideline:

other: Joint Directives of J EPA, J MHW and J MITI. (31 October 1997) Kanpoan No. 287, Eisei No. 127 and Kikyoku No. 2 (31 October 1997).

Deviations:

not specified

Principles of method if other than guideline:

In addition, the study was also designed to comply with the following guidelines:
-JMHW Genotoxicity Testing Guideline, PAB Notification No. 1604 (1 November 1999)
-Official Notice of J MOL. (8 February 1999)
-ICH (1995 & 1997)
-followed the recommendations of the United Kingdom Environmental Mutagen Society (Gatehouse et al 1990).

GLP compliance:

yes

Type of assay:

bacterial reverse mutation assay

Target gene:

S. typhimurium: histidine locus
E. coli: tryptophan locus

Species / strain / cell type:

S. typhimurium TA 1535, TA 1537, TA 98, TA 100 and E. coli WP2

Details on mammalian cell type (if applicable):

Batches of the strains were obtained from master stocks held in liquid nitrogen. The test batches were aliquots of nutrient broth cultures and were stored at -80 °C. Dimethyl sulphoxide (DMSO) was added to the cultures at 8 % v/v as a cryopreservative. Each batch of frozen strain was tested, where applicable, for cell membrane permeability (rfa mutation), sensitivity to UV light and the pKM101 plasmid, which confers resistance to ampicillin. The responses of the strains to a series of diagnostic mutagens were also assessed.

Additional strain / cell type characteristics:

not applicable

Metabolic activation:

with and without

Metabolic activation system:

S9-mix

Test concentrations with justification for top dose:

50, 150, 500, 1500 and 5000 µg/plate

Vehicle / solvent:

- Vehicle(s)/solvent(s) used: the test material was suspended in purified water (obtained by reverse-osmosis) containing 0.15 % agar.
- Justification for choice of solvent/vehicle: the test material was found to be insufficiently soluble in all compatible solvents.

Untreated negative controls:

no

Negative solvent / vehicle controls:

yes

Remarks:

purified water contining 0.15 % agar

True negative controls:

no

Positive controls:

yes

Positive control substance:

9-aminoacridine

2-nitrofluorene

sodium azide

benzo(a)pyrene

furylfuramide

other: 2-aminoanthracene

Details on test system and experimental conditions:

PREPARATION OF S9 METABOLIC ACTIVATION SYSTEM: S9 fraction was prepared from a group of ca. 10 male Sprague-Dawley rats. Mixed function oxidase systems in the rat livers were stimulated by Aroclor 1254, administered as a single intra-peritoneal injection in corn oil at a dosage of 500 mg/kg bw. On the fifth day after injection, following overnight fasting, the rats were killed by cervical dislocation and their livers aseptically removed. Under aseptic conditions, at 0 - 4 ºC, the livers were placed in 0.15 M KCl (3 mL KCl:1 g liver) before being transferred to a homogeniser. Following preparation, the homogenate was centrifuged at 9000 x gravity for 10 minutes. The supernatant fraction (S9 fraction) was stored at -80 ºC until required. Each batch of S9 mix was tested for sterility and efficacy.
PREPARATION OF S9 MIX: S9 fraction (10 % v/v), MgCl2 (8 mM), KCl (33 mM), sodium phosphate buffer pH 7.4 (100 mM), glucose-6 -phosphate (5 mM), NADPH (4 mM), NADH (4 mM). All the cofactors were filter-sterilised before use.

METHOD OF APPLICATION: in medium; the range finding test was a standard plate incorporation assay; the definitive test included a preincubation step.

DURATION
- Preincubation period: 30 minutes at 37 °C
- Exposure duration: 72 hours

NUMBER OF REPLICATIONS: test concentrations were performed in triplicate

EVALUATION PROCEDURE: following the total incubation period the plates were examined for the lack of microbial contamination and evidence that the test was valid, i.e. there was a background lawn on the solvent control plates and on the plates for (at least) the lower concentrations of test material, and that the positive controls had responded as expected. All plates were counted using a Domino automated colony counter.

Evaluation criteria:

For a test to be considered valid, the mean of the solvent/vehicle control revertant colony numbers for each strain should lie within the 99 % confidence limits of the historical control range of the laboratory (previous 2 - 5 years). Also, positive control compounds must cause at least a doubling of mean revertant colony numbers over the negative control.

The mean number of revertant colonies for each treatment group was compared with those obtained for the solvent/vehicle control groups. The mutagenic activity of the test material was assessed by applying the following criteria:

- If treatment with a test material produces an increase in revertant colony numbers of at least twice the concurrent solvent/vehicle controls, with some evidence of a positive dose-response relationship, in two separate experiments, with any bacterial strain either in the presence or absence of S9-mix, the material will be considered to show evidence of mutagenic activity in the test system.

- If treatment with a test material does not produce reproducible increases of at least 1.5 times the concurrent solvent/vehicle controls in either mutation test, the test material will be considered to show no evidence of mutagenic activity in the test system.

- If the results obtained fail to satisfy a clear positive or negative response, even after additional testing, the test data may be subjected to analysis to determine the statistical significance of any increases in revertant colony numbers.

Statistics:

If required, the procedure used to determine the statistical significance of any increases in revertant colony numbers was analysis of variance followed by Dunnett's test.

Species / strain:

S. typhimurium TA 98

Metabolic activation:

with and without

Genotoxicity:

negative

Cytotoxicity / choice of top concentrations:

no cytotoxicity

Remarks:

tested up to recommended limit concentrations

Vehicle controls validity:

valid

Untreated negative controls validity:

not applicable

True negative controls validity:

not applicable

Positive controls validity:

valid

Species / strain:

S. typhimurium TA 100

Metabolic activation:

with and without

Genotoxicity:

negative

Cytotoxicity / choice of top concentrations:

no cytotoxicity

Remarks:

tested up to recommended limit concentrations

Vehicle controls validity:

valid

Untreated negative controls validity:

not applicable

True negative controls validity:

not applicable

Positive controls validity:

valid

Species / strain:

S. typhimurium TA 1535

Metabolic activation:

with and without

Genotoxicity:

negative

Cytotoxicity / choice of top concentrations:

no cytotoxicity

Remarks:

tested up to recommended limit concentrations

Vehicle controls validity:

valid

Untreated negative controls validity:

not applicable

True negative controls validity:

not applicable

Positive controls validity:

valid

Species / strain:

S. typhimurium TA 1537

Metabolic activation:

with and without

Genotoxicity:

negative

Cytotoxicity / choice of top concentrations:

no cytotoxicity

Remarks:

tested up to recommended limit concentrations

Vehicle controls validity:

valid

Untreated negative controls validity:

not applicable

True negative controls validity:

not applicable

Positive controls validity:

valid

Species / strain:

E. coli WP2 uvr A

Metabolic activation:

with and without

Genotoxicity:

negative

Cytotoxicity / choice of top concentrations:

no cytotoxicity

Remarks:

tested up to recommended limit concentrations

Vehicle controls validity:

valid

Untreated negative controls validity:

not applicable

True negative controls validity:

not applicable

Positive controls validity:

valid

Additional information on results:

-The absence of colonies on sterility check plates confirmed that no microbial contamination took place.
-The total colony counts on nutrient agar plates confirmed the viability and high cell density of the cultures of the individual organisms.
-The mean revertant colony counts for the solvent controls were within the 99 % confidence limits of the current historical control range of the laboratory (except strain TA 98, definitive test, where counts were slightly higher; this was not considered to affect the integrity of the study). Appropriate positive control chemicals (with S9 mix where required) induced substantial increases in revertant colony numbers with all strains, confirming sensitivity of the cultures and activity of the S9 mix.

RANGE FINDING TEST
-No substantial increases in revertant colony numbers over control counts were obtained with any of the tester strains following exposure to the test material at any concentration in either the presence or absence of S9 mix.
-No visible thinning of the background lawn of the non-revertant cells was obtained following exposure to the test material. A maximum exposure concentration of 5000 µg/plate was therefore selected for use in the definitive study.

DEFINITIVE TEST
-No substantial increases in revertant colony numbers over control counts were obtained with any of the tester strains following exposure to the test material at any concentration in either the presence of absence of S9 mix.
-No visible thinning of the background lawn of non-revertant cells was obtained following exposure to test material.

Remarks on result:

other: all strains/cell types tested

Remarks:

Migrated from field 'Test system'.

Table 1 Summary of Second Test

+/- S9 Mix	Concentration (µg/plate)	Mean number of revertant colony counts
		TA100	TA1535	WP2uvrA	TA98	TA1537
- - - - - -	Solvent Control 50 150 500 1500 5000	124 121 122 135 134 128	17 17 14 20 25 21	130 138 124 93 109 109	42 43 39 36 43 45	14 14 14 14 13 11
+ + + + + +	Solvent Control 50 150 500 1500 5000	152 134 138 143 147 126	19 12 16 11 12 12	159 150 139 147 161 155	50 51 54 48 47 50	21 16 19 17 18 13
Positive Controls
-	Name	SA	SA	AF2	2NF	9AA
	Concentration (µg/plate)	0.5	0.5	0.05	1	30
	Mean no. colonies	534	362	483	227	423
+	Name	BP	2AA	2AA	BP	BP
	Concentration (µg/plate)	5	2	10	5	5
	Mean no. colonies	743	196	395	496	115

SA = sodium azide 2-NF = 2-nitrofluorene BP = benzo[a]pyrene 2AA = 2-aminoanthracene AF-2 = furylfuramide 9AA = 9-aminoacridine

Conclusions:

Under the conditions of the assay according to OECD 471, the test material gave a negative response (i.e. non-mutagenic), in Salmonella typhimurium strains TA98, TA100, TA1535, TA1537 and E. coli strain WP2uvrA/pKM101. The study is considered to be reliable, relevant and adequate for risk assessment and classification and labelling purposes.

Executive summary:

The potential of the test material tantalum metal (purity: 99.9 %) to cause gene mutation in bacterial strains was determined in accordance with standardised guidelines OECD 471, EU Method B.13/14 and EPA OPPTS 870.5100. Four strains of Salmonella typhimurium (TA98, TA100, TA1535, 1537) and E.coli strain WP2uvrA/pKM101 were treated in the presence and absence of a rat liver derived metabolic activation system (S9 mix).

Under the conditions of the test, the test material did not induce any significant, reproducible increases in the observed number of revertant colony numbers in any of the tester strains used. The concurrent positive controls demonstrated the sensitivity of the assay and the metabolising activity of the liver preparations. It was therefore concluded that, under the test conditions employed, the test material showed no evidence of mutagenic activity in this bacterial system.

Reference 2

Endpoint:

in vitro cytogenicity / chromosome aberration study in mammalian cells

Remarks:

Type of genotoxicity: chromosome aberration

Type of information:

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

Adequacy of study:

weight of evidence

Justification for type of information:

For justification of read-across please refer to the read-across report attached to IUCLID section 13.

Reason / purpose for cross-reference:

read-across source

Species / strain:

Chinese hamster lung fibroblasts (V79)

Metabolic activation:

with and without

Genotoxicity:

negative

Cytotoxicity / choice of top concentrations:

cytotoxicity

Remarks:

observed at concentrations of 500 µg/mL or greater

Vehicle controls validity:

valid

Untreated negative controls validity:

not examined

Positive controls validity:

valid

Additional information on results:

CHROMOSOME ABERRATION ASSAYS
None of the treatment concentrations caused a biologically significant increase in the number of cells with structural chromosome aberrations in either assay with or without metabolic activation. At 2000 µg/mL with metabolic activation in Assay 1, a marginal statistically significant increase was recorded, compared with the corresponding negative control which had no aberrant cells in either replicate. However, both replicates at 2000 µg/mL were observed to have 3 aberrant cells, which is well within the negative historical control range of 0-5.

TEST-SPECIFIC CONFOUNDING FACTORS
- Effects of pH: No large changes were observed.
- Effects of osmolality: No large changes were observed.
- Water solubility:
> In Assay 1, insolubility was detected at the end of the treatment period in the final treatment medium in the 2000-125 µg/mL concentration range (experiment without metabolic activation) or 4000-125 µg/mL concentration range (experiment with metabolic activation).
> In Assay 2, similarly to the first experiment, insolubility was detected at the end of the treatment period in the final treatment medium in the 2000-250 µg/mL concentration range (experiment without metabolic activation) or 4000-125 µg/mL concentration range (experiment with metabolic activation).

COMPARISON WITH HISTORICAL CONTROL DATA: The spontaneous aberration frequencies of the negative (vehicle) controls in the performed experiments were within the historical control range of the testing laboratory.

ADDITIONAL INFORMATION ON CYTOTOXICITY:
> In Assay 1, marked cytotoxicity was observed at 2000, 1000 and 500 µg/mL without metabolic activation (relative survival values were 21, 28 and 50%, respectively) and at 4000 and 2000 µg/mL with metabolic activation (relative survival values were 49 and 49%, respectively).
> In Assay 2, cytotoxicity was also observed at 2000, 1000 and 500 µg/mL without metabolic activation (relative survival values were 25, 25 and 49%, respectively) and at 4000, 2000 and 1000 µg/mL with metabolic activation (relative survival values were 35, 42 and 43%, respectively).

ADDITIONAL INFORMATION ON POLYPLOID ABD ENDOREDUPLICATED METAPHASES:
Polyploid metaphases (1 - 2) were found in some cases in the negative (vehicle) control or test item treated samples in the performed experiments. Endoreduplicated metaphases (1 - 2) were found in some cases in the positive control or test item treated samples in the performed experiments.

Remarks on result:

other: all strains/cell types tested

Table 1: Summary of Results Main Assay 1

Concentration (µg/mL)	Time of Treatment/Sampling	Relative Survival (%)#	Insolubility##	Mean % Aberrant Cells###
Without metabolic activation (-S9)
Negative control	3 h/20 h	100	-	0.5
2000	3 h/20 h	21	+	NE
1000	3 h/20 h	28	+	NE
500	3 h/20 h	50	+	0.0
250	3 h/20 h	64	+a	0.5
125	3 h/20 h	90	+a	0.0
62.5	3 h/20 h	90	-b	NE
31.25	3 h/20 h	96	-	NE
Positive Control	3 h/20 h	72	-	16.9***
With metabolic activation (+S9)
Negative control	3 h/20 h	100	-	0.0
4000	3 h/20 h	49	+	NE
2000	3 h/20 h	49	+	3.0*
1000	3 h/20 h	67	+	2.5
500	3 h/20 h	82	+	2.0
250	3 h/20 h	79	+a	NE
125	3 h/20 h	83	+a	NE
62.5	3 h/20 h	91	-b	NE
31.25	3 h/20 h	88	-	NE
Positive Control	3 h/20 h	57	-	93.8***

 

Table 2: Summary of Results Main Assay 2

Concentration (µg/mL)	Time of Treatment/Sampling	Relative Survival (%)#	Insolubility##	Mean % Aberrant Cells###
Without metabolic activation (-S9)
Negative control	20 h/28 h	100	-	2.0
2000	20 h/28 h	25	+	NE
1000	20 h/28 h	25	+	NE
500	20 h/28 h	49	+	4.0
250	20 h/28 h	78	+a	3.0
125	20 h/28 h	81	-b	1.0
62.5	20 h/28 h	91	-b	NE
31.25	20 h/28 h	87	-	NE
Positive Control	20 h/28 h	56	-	21.0***
With metabolic activation (+S9)
Negative control	3 h/28 h	100	-	3.5
4000	3 h/28 h	35	+	NE
2000	3 h/28 h	42	+	NE
1000	3 h/28 h	43	+	2.0
500	3 h/28 h	64	+	4.0
250	3 h/28 h	75	+a	5.5
125	3 h/28 h	100	+a	1.5
62.5	3 h/28 h	98	-b	NE
31.25	3 h/28 h	84	-	NE
Positive Control	3 h/28 h	67	-	36.1***

 

Negative (vehicle) control: 1% (v/v) DMSO

Positive control (-S9): Ethyl methanesulfonate, 1 µL/mL

Positive control (+S9): Cyclophosphamide, 6 µg/mL

NE: not evaluated

#: compared to the negative (vehicle) control

##: in the final treatment medium at the end of the treatment

###: excluding gaps

a: Minimal amount of precipitate/opalescence was observed

b: Discoloured medium

 

*: p<0.05 comparing numbers of aberrant cells excluding gaps with corresponding negative control

***: p<0.001 comparing numbers of aberrant cells excluding gaps with corresponding negative control

Conclusions:

Under the conditions of the test according to OECD 473, the test material ditantalum pentoxide did not induce chromosome aberrations in the performed experiments with or without metabolic activation. The test material is therefore considered not to be clastogenic in this test system.

Executive summary:

The clastogenic potential of the test material ditantalum pentoxide with and without metabolic activation was determined in an in vitro mammalian chromosome aberration test. The study was conducted under GLP conditions and in line with the standardised guidelines OECD 473, EU Method B. 10 and EPA OPPTS 870.5375. Two chromosome aberration assays were performed using Chinese hamster lung fibroblasts (V79) cells. In Assay 1, cells were exposed to the test material for 3 hours with and without metabolic activation and given a 20 hour fixation time. In assay 2, cells were exposed to the test material for 3 hours with and 20 hours without metabolic activation, both were given a fixation time of 28 hours.

Under the conditions of the test, exposure to the test material with or without metabolic activation did not result in a statistically and biologically significant, repeatable, dose-dependent increase in the frequency of the cells with structural chromosome aberrations. Cytotoxicity was observed with and without metabolic activation at concentrations of ≥ 1000 µg/mL and 500 µg/mL, respectively. Therefore, the test material is not considered to be clastogenic in this test system.

This information is used in a read-across approach in the assessment of the target substance tantalum.

For justification of read-across please refer to the attached read-across report (see IUCLID section 13).

Reference 3

Endpoint:

in vitro gene mutation study in mammalian cells

Remarks:

Type of genotoxicity: gene mutation

Type of information:

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

Adequacy of study:

weight of evidence

Justification for type of information:

For justification of read-across please refer to the read-across report attached to IUCLID section 13.

Reason / purpose for cross-reference:

read-across source

Species / strain:

Chinese hamster lung fibroblasts (V79)

Metabolic activation:

with and without

Genotoxicity:

negative

Cytotoxicity / choice of top concentrations:

cytotoxicity

Remarks:

A biologically relevant growth inhibition (reduction of relative growth below 70%) was observed after the treatment with the test item in experiment I and II without metabolic activation

Vehicle controls validity:

valid

Untreated negative controls validity:

valid

Positive controls validity:

valid

Additional information on results:

TEST-SPECIFIC CONFOUNDING FACTORS
- Effects of pH: The pH-value detected with the test item was within the physiological range (pH 7.0 ± 0.4).
- Effects of osmolality: not examined
- Precipitation: Precipitation of the test item was noted in experiment I without and with metabolic activation at concentrations of 0.25 mM and higher. At experiment II precipitation of the test item was observed at concentrations of 0.2 mM and higher with metabolic activation

RANGE-FINDING/SCREENING STUDIES:
A solubility test was performed with different solvents and vehicles. Based on the results of the solubility test EtOH was used as solvent. After pre-dissolving the test item in EtOH (100 mM) a dilution series was prepared in EtOH. First a 9fold volume of phosphate buffer was used adding it to each concentration. After noticing that in the pre-experiment without metabolic activation the buffer reacts with the cells the phosphate buffer was replaced for the main experiments by Aqua ad injectabilia. So the 9fold volume of Aqua ad injectabilia was added to each concentration. After an initial reaction of approx. 10 minutes, this test item solution was added to cell culture medium (MEM without serum) at a ratio of 1 :10, resulting in 1% EtOH and 9% Aqua ad injectabilia in the final treatment medium. The pH-value detected with the test item was within the physiological range (pH 7.0 ± 0.4). The solvent used is a composition of well-established solvents and is compatible with the survival of the cells and the activity of the S9 mix.

Table 4
Experiment I - Mutagenicity, without metabolic activation
Dose Group	Concentration [mM]	Number of mutant colonies per flask^a					Mean	SD	Mutant SD colonies per 10^6 cells^b	Mutation factor
		I	II	III	IV	V
NC1	0	7	8	10	11	11	9.4	1.62	30.82
NC2		4	5	6	8	9	6.4	1.85	21.33
S1	0	7	8	11	11	15	10.4	2.80	32.60
S2		4	6	11	11	12	8.8	3.19	27.50
2	0.025	17	13	13	7	8	11.6	3.67	33.62	1.12
3	0.05	5	6	7	8	7	6.6	1.02	20.75	0.69
4	0.10	4	5	7	7	11	6.8	2.40	22.01	0.73
5	0.25	6	5	6	5	14	7.2	3.43	24.24	0.81
6	0.50	4	6	6	8	8	6.4	1.50	20.51	0.68
7	0.75	7	10	9	4	18	9.6	4.67	32.32	1.08
8	1.0	7	7	7	10	15	9.2	3.12	31.72	1.06
9	1.5	10	13	13	18	25	15.8	5.27	44.38	1.48
10	2.0	6	8	8	8	11	8.2	1.60	26.20	0.87
EMS	300µg/mL	80	74	72	77	86	77.8	4.92	261.95	8.72
NC:	negative control/ medium control
S:	solvent control
a:	number of mutant colonies in flask I to V
b:	mean mutant colonies x 10^6/ (400000 x Cloning Efficiency/100)
EMS:	Ethylmethanesulfonate [300 µg/mL]

Table 6
Experiment I - Mutagenicity, with metabolic activation
Dose Group	Concentration [mM]	Number of mutant colonies per flask^a					Mean	SD	Mutant SD colonies per 10^6 cells^b	Mutation factor
		I	II	III	IV	V
NC1	0	6	7	10	10	11	8.8	1.94	22.00
NC2		4	6	6	6	7	5.8	0.98	16.16
S1	0	5	7	7	7	10	7.2	1.60	18.32
S2		3	7	9	9	12	8.0	2.97	21.51
2	0.025	2	9	9	10	13	8.6	3.61	24.02	1.21
3	0.05	7	10	11	12	16	11.2	2.93	28.43	1.43
4	0.10	8	8	9	10	11	9.2	1.17	24.47	1.23
5	0.25	6	8	9	9	13	9.0	2.28	24.73	1.24
6	0.50	6	8	10	10	12	9.2	2.04	24.73	1.24
7	0.75	5	6	9	13	13	9.2	3.37	23.29	1.17
8	1.0	3	8	9	9	9	7.6	2.33	19.69	0.99
9	1.5	5	6	10	11	11	8.6	2.58	25.07	1.26
10	2.0	8	9	14	15	15	12.2	3.06	31.94	1.60
DMBA	1µg/mL	118	119	126	104	109	115.2	7.78	331.03	16.62
NC:	negative control/ medium control
S:	solvent control
a:	number of mutant colonies in flask I to V
b:	mean mutant colonies x 10^6/ (400000 x Cloning Efficiency/100)
DMBA:	7, 12-Dimethylbenz(a)anthracene [1 µg/mL]

Table 8
Experiment II - Mutagenicity, without metabolic activation
Dose Group	Concentration [mM]	Number of mutant colonies per flask^a					Mean	SD	Mutant SD colonies per 10^6 cells^b	Mutation factor
		I	II	III	IV	V
NC1	0	10	13	11	16	10	12.0	2.28	34.09
NC2		5	6	6	4	5	5.2	0.75	15.07
S1	0	18	17	12	12	12	14.2	2.71	42.14
S2		12	12	15	11	7	11.4	2.58	30.32
2	0.025	16	12	12	13	20	14.6	3.07	39.57	1.09
3	0.010	18	13	12	9	10	12.4	3.14	33.70	0.93
4	0.025	10	17	6	12	10	11.0	3.58	32.26	0.89
5	0.050	13	5	9	13	16	11.2	3.82	27.12	0.75
6	0.10	13	8	13	5	5	8.8	3.60	24.11	0.67
7	0.25	9	8	16	16	15	12.8	3.54	33.16	0.92
8	0.50	10	6	12	8	4	8.0	2.83	21.56	0.60
9	0.75	11	10	7	6	4	7.6	2.58	23.03	0.64
10	1.0	7	10	6	16	11	10.0	3.52	28.17	0.78
EMS	300µg/mL	154	133	135	140	144	141.2	7.47	534.85	14.76
NC:	negative control/ medium control
S:	solvent control
a:	number of mutant colonies in flask I to V
b:	mean mutant colonies x 10^6/ (400000 x Cloning Efficiency/100)
EMS:	Ethylmethanesulfonate [300 µg/mL]

Table 10
Experiment II - Mutagenicity, with metabolic activation
Dose Group	Concentration [mM]	Number of mutant colonies per flask^a					Mean	SD	Mutant SD colonies per 10^6 cells^b	Mutation factor
		I	II	III	IV	V
NC1	0	8	5	7	6	13	7.8	2.79	20.86
NC2		13	7	9	11	6	9.2	2.56	25.34
S1	0	9	7	12	2	5	7.0	3.41	20.06
S2		12	11	14	10	7	10.8	2.32	32.53
2	0.004	9	15	6	11	8	9.8	3.06	28.91	1.10
3	0.007	15	11	13	11	23	14.6	4.45	39.46	1.50
4	0.02	9	9	13	15	12	11.6	2.33	34.73	1.32
5	0.04	10	10	9	13	9	10.2	1.47	28.49	1.08
6	0.07	6	10	11	15	15	11.4	3.38	32.76	1.25
7	0.2	6	6	6	5	10	6.6	1.74	18.44	0.70
8	0.4	9	10	5	11	9	8.8	2.04	23.78	0.90
9	0.7	12	11	14	6	17	12	3.63	36.59	1.39
10	1.0	13	9	11	14	10	11.4	1.85	35.08	1.33
DMBA	1.0µg/mL	116	135	127	123	124	125.0	6.16	376.51	14.32
NC:	negative control/ medium control
S:	solvent control
a:	number of mutant colonies in flask I to V
b:	mean mutant colonies x 10^6/ (400000 x Cloning Efficiency/100)

Conclusions:

Under the experimental conditions reported, the test item Tantalum pentachloride (decomposed) is considered to be non-mutagenic in the in vitro mammalian cell HPRT gene mutation assay using V79 cells of the Chinese Hamster.

Executive summary:

In a mammalian cell HPRT gene mutation assay accoridng to OECD 476, V79 cells cultured in vitro were exposed to Tantalum pentachloride (decomposed) (99.9 %) in 1% ethanol/9% Aqua ad injectabilia at concentrations of 0.025, 0.05, 0.10, 0.25, 0.50, 0.75, 1.0, 1.5 and 2.0 mM in the presence and absence of mammalian metabolic activation (experiment I) and for experiment II at concentrations of 0.005, 0.010, 0.025, 0.050, 0.10, 0.25, 0.50, 0.75 and 1.0 mM without metabolic activation and 0.004, 0.007, 0.02, 0.04, 0.07, 0.2, 0.4, 0.7 and 1.0 mM with metabolic activation.

Tantalum pentachloride (decomposed) was tested in experiment I up to 2.0 mM (without and with metabolic activation) and in experiment II up to 1.0 mM (without and with metabolic activation) based on data from the solubility test and the pre-experiments according to the OECD guideline 476. For all tested treatment groups no dose-response relationship could be observed. The positive controls did induce the appropriate response. There was no evidence of induced mutant colonies over background. 

This study is classified as acceptable. This study satisfies the requirement for Test Guideline OECD 476 for in vitro mutagenicity (mammalian forward gene mutation) data. 

Based on these results tantalum pentachloride does not warrant for classification as mutagenic according to CLP criteria.

This information is used in a read-across approach in the assessment of the target substance tantalum metal.

For justification of read-across please refer to the attached read-across report (see IUCLID section 13).

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed (negative)

Genetic toxicity in vivo

Description of key information

One supporting study was available with implanted tantalum metal showing no genetic toxicity in vivo. As only few information on the methodology was given in the publication, the study was used as supporting infomation only.

Link to relevant study records

Reference

Endpoint:

genetic toxicity in vivo

Type of information:

experimental study

Adequacy of study:

supporting study

Study period:

Not reported

Reliability:

4 (not assignable)

Rationale for reliability incl. deficiencies:

documentation insufficient for assessment

Qualifier:

no guideline followed

Principles of method if other than guideline:

Studies with depleted uranium embedded animals were reviewed to help assess the risk for carcinogenesis and mutagenesis from depleted uranium embedded fragments. Animals with tantalum embedded fragments served as a control.

GLP compliance:

not specified

Studies with depleted uranium embedded animals demonstrated that increased tissue uranium content was associated with aberrant activation of several of the oncogenes and tumour suppressor genes associated with preneoplastic lesions and human carcinogenesis. Specific point mutations in these genes have also been identified. In contrast, tissues from animals with tantalum implants did not show this aberrant oncogene pattern. Oncoproteins and tumour suppressor proteins were also found in the serum of animals with depleted uranium pellets. These proteins were not detected in serum from animals implanted with tantalum.

Conclusions:

Tissues from animals with tantalum implants did not show an aberrant oncogene pattern. Oncoproteins and tumour suppressor proteins were not detected in serum from animals implanted with tantalum.

Executive summary:

Studies to help assess the risk for carcinogenesis and mutagenesis from depleted uranium embedded fragments were conducted, with tantalum serving as a control. The studies with depleted uranium embedded animals demonstrated that increased tissue uranium content was associated with aberrant activation of several of the oncogenes and tumour suppressor genes associated with preneoplastic lesions and human carcinogenesis. Specific point mutations in these genes were also identified. In contrast, tissues from animals with tantalum implants did not show this aberrant oncogene pattern. Oncoproteins and tumour suppressor proteins were also found in the serum of animals with depleted uranium pellets. These proteins were not detected in serum from animals implanted with tantalum.

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed (negative)

Additional information

Bacterial reverse mutation

The potential of tantalum to cause gene mutation in bacterial strains was determined in accordance with standardised guidelines OECD 471, EU Method B.13/14 and EPA OPPTS 870.5100. Four strains of Salmonella typhimurium (TA98, TA100, TA1535, TA1537) and E.coli strain WP2uvrA/pKM101 were treated in the presence and absence of a rat liver derived metabolic activation system (S9 mix). Under the conditions of the test, tantalum did not induce any significant, reproducible increases in the observed number of revertant colony numbers in any of the tester strains used. The concurrent positive controls demonstrated the sensitivity of the assay and the metabolising activity of the liver preparations. It was therefore concluded that, under the test conditions employed, tantalum showed no evidence of mutagenic activity in this bacterial system.

 

Chromosome aberration test in vitro

This information is used in a read-across approach in the assessment of tantalum metal.

The clastogenic potential of tantalum pentoxide with and without metabolic activation was determined in an in vitro mammalian chromosome aberration test. The study was conducted under GLP conditions and in line with the standardised guidelines OECD 473, EU Method B. 10 and EPA OPPTS 870.5375. Two chromosome aberration assays were performed using Chinese hamster lung fibroblasts (V79) cells. In Assay 1, cells were exposed to the test material for 3 hours with and without metabolic activation and given a 20 hour fixation time. In assay 2, cells were exposed to the test material for 3 hours with and 20 hours without metabolic activation, both were given a fixation time of 28 hours. Under the conditions of the test, exposure to tantalum pentoxide with or without metabolic activation did not result in a statistically and biologically significant, repeatable, dose-dependent increase in the frequency of the cells with structural chromosome aberrations. Cytotoxicity was observed with and without metabolic activation at concentrations of ≥ 1000 µg/mL and 500 µg/mL, respectively. Therefore, tantalum pentoxide is not considered to be clastogenic in this test system.

Gene mutation in mammalian cells

This information is used in a read-across approach in the assessment of tantalum metal.

In a mammalian cell HPRT gene mutation assay, V79 cells cultured in vitro were exposed to Tantalum pentachloride (decomposed) (99.9 %) in 1% ethanol/9% Aqua ad injectabilia at concentrations of 0.025, 0.05, 0.10, 0.25, 0.50, 0.75, 1.0, 1.5 and 2.0 mM in the presence and absence of mammalian metabolic activation (experiment I) and for experiment II at concentrations of 0.005, 0.010, 0.025, 0.050, 0.10, 0.25, 0.50, 0.75 and 1.0 mM without metabolic activation and 0.004, 0.007, 0.02, 0.04, 0.07, 0.2, 0.4, 0.7 and 1.0 mM with metabolic activation.

Tantalum pentachloride (decomposed) was tested in experiment I up to 2.0 mM (without and with metabolic activation) and in experiment II up to 1.0 mM (without and with metabolic activation) based on data from the solubility test and the pre-experiments according to the OECD guideline 476. For all tested treatment groups no dose-response relationship could be observed. The positive controls did induce the appropriate response. There was no evidence of induced mutant colonies over background. This study is classified as acceptable. This study satisfies the requirement for Test Guideline OECD 476 for in vitro mutagenicity (mammalian forward gene mutation) data. 

Summary 

The three key studies presented to assess the mutagenicity of tantalum were performed in line with GLP and accepted standardised guidelines with a high standard of reporting. The reverse mutation test in bacterial cells was assigned a reliability score of 1 since it was performed with the substance specifically under consideration, tantalum, while the gene mutation and chromosome aberration tests were performed with tantalum pentachloride respectively tantalum pentoxide and were assigned a reliability score of 2. Since both substances used in the read-across approach, tantalum pentoxide and tantalum pentachloride, showed negative results in the chromosome aberration study respetively the gene mutation study, the tantalum ion as auch can be considered to show the same results.

For justification of read-across please refer to the attached read-across report (see IUCLID section 13).

Supporting Information

Supporting information is available, in the form of a literature paper by Miller. The paper substantiates the conclusion that tantalum is non-mutagenic. Tantalum fragments served as a control in a study investigating the risk for carcinogenesis and mutagenesis from depleted uranium embedded fragments. The studies with depleted uranium embedded animals demonstrated that increased tissue uranium content was associated with aberrant activation of several of the oncogenes and tumour suppressor genes associated with preneoplastic lesions and human carcinogenesis. Specific point mutations in these genes were also identified. In contrast, tissues from animals with tantalum implants did not show this aberrant oncogene pattern. Oncoproteins and tumour suppressor proteins were also found in the serum of animals with depleted uranium pellets. These proteins were not detected in serum from animals implanted with tantalum. The literature papers did not contain a sufficient level of detail to enable a proper assessment on the reliability of the findings presented. Moreover, both papers detailed studies conducted to non-standard methods. They were assigned reliability scores of 4. 

Justification for classification or non-classification

In accordance with criteria for classification as defined in Annex I, Regulation 1272/2008, the test material, tantalum, does not require classification for genetic toxicity based on the overall negative response noted in available genetic toxicity studies conducted both with tantalum and its analogues tantalum pentachloride and tantalum pentoxide. Tantalum pentachloride and tantalum pentoxide are considered to be a suitable substances to use for read across as judstified in the read across report attached to chapter 13 of this dossier.