Niobium

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:

2009-08-10 to 2009-08-27

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2009

Report date:

2009

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:

Niobium

EC Number:

231-113-5

EC Name:

Niobium

Cas Number:

7440-03-1

Molecular formula:

Nb

IUPAC Name:

Niobium

Test material form:

solid: compact

Method

Target gene:

S. typhimurim histidine reversion system
E. coli tryptophan reversion system

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:

cofactor supplemented post-mitochondrial fraction (S9 mix), prepared from the livers of rats treated with phenobarbital and beta-naphthoflavone.

Test concentrations with justification for top dose:

10, 20, 40, 60, 80, 100% of test item extracts

Vehicle / solvent:

- Vehicles used:
polar extraction medium: physiolog. saline
non-polar extraction medium: DMSO

Controls

Untreated negative controls:

yes

Negative solvent / vehicle controls:

yes

True negative controls:

no

Positive controls:

yes

Positive control substance:

sodium azide

methylmethanesulfonate

other: 4-nitro-o-phenylene-diamine (4-NOPD; 10 µg/plate for TA98 and 40 µg/plate for TA1537, in DMSO, without S9); 2-aminoanthracene (2-AA; 2.5 µg/plate for TA98, TA100, TA1535, TA1537 and 10 µg/plate for E.coli WP2 uvrA, in DMSO, with S9)

Details on test system and experimental conditions:

METHOD OF APPLICATION: in agar (plate incorporation); preincubation;

DURATION
- Preincubation period: 60 minutes
- Exposure duration: at least 48 h

NUMBER OF REPLICATIONS: 3

DETERMINATION OF CYTOTOXICITY
- Method: relative total growth

Evaluation criteria:

The mutation factor is calculated by dividing the mean value of the revertant counts through the mean values of the extract vehicle control. A test item is considered as mutagenic if:
- a clear and dose-related increase in the number of revertants occurs and/or - a biologically relevant positive response for at least one of the dose group occurs in at least one tester strain with or without metabolic activation.
A biologically relevant increase is described as follows:
- if in tester strain TA 100 and E. coli WP2 uvrA the number of reversions is at least twice as high
- if in tester strain TA 98, TA 1535, TA 1537 the number of reversions is at least three times higher as high than the reversion rate of the extract vehicle control

Statistics:

not necessary

Results and discussion

Test results

Test results 1

Key result

Species / strain:

S. typhimurium TA 1535

Metabolic activation:

with and without

Genotoxicity:

negative

Cytotoxicity / choice of top concentrations:

cytotoxicity

Remarks:

at an extract concentration of 100% without metabolic activation

Vehicle controls validity:

valid

Untreated negative controls validity:

valid

Positive controls validity:

valid

Test results 2

Key result

Species / strain:

S. typhimurium TA 1537

Metabolic activation:

with and without

Genotoxicity:

negative

Cytotoxicity / choice of top concentrations:

no cytotoxicity

Vehicle controls validity:

valid

Untreated negative controls validity:

valid

Positive controls validity:

valid

Test results 3

Key result

Species / strain:

S. typhimurium TA 98

Metabolic activation:

with and without

Genotoxicity:

negative

Cytotoxicity / choice of top concentrations:

no cytotoxicity

Vehicle controls validity:

valid

Untreated negative controls validity:

valid

Positive controls validity:

valid

Test results 4

Key result

Species / strain:

S. typhimurium TA 100

Metabolic activation:

with and without

Genotoxicity:

negative

Cytotoxicity / choice of top concentrations:

no cytotoxicity

Vehicle controls validity:

valid

Untreated negative controls validity:

valid

Positive controls validity:

valid

Test results 5

Key result

Species / strain:

E. coli WP2 uvr A

Metabolic activation:

with and without

Genotoxicity:

negative

Cytotoxicity / choice of top concentrations:

no cytotoxicity

Vehicle controls validity:

valid

Untreated negative controls validity:

valid

Positive controls validity:

valid

Any other information on results incl. tables

Table 1: Experiment 1 - Without Metabolic Activation

S9 Mix	Test substance concentration (% / plate)	Number of revertants (mean number of colonies per plate)
		Base-pair substitution type			Frameshift type
		TA100	TA1535	Wp2uvrA	TA98	TA1537
–	0*	108	7	59	22	6
–	0**	98	7	60	30	4
–	10	111	10	47	22	9
–	20	96	8	42	16	7
–	40	108	9	59	23	6
–	60	105	8	56	26	5
–	80	106	12	72	22	7
–	100	112	9	59	23	6
Pos controls ‑S9	Name	NaN3	NaN3	MMS	4-NOPD	4-NOPD
	Conc. (µg/plate)	10	10	1 µL	10	40
	No. of revertants per plate	771	1278	389	530	124

* = aqua dest; ** = 0.9% NaCl

NaN₃       Sodium azide

4-NOPD 4-nitro-o-phenylene-diamine

MMS     Methyl methane sulfonate

 

 

Table 2: Experiment 1 - With Metabolic Activation

S9 Mix	Test substance concentration (% / plate)	Number of revertants (mean number of colonies per plate)
		Base-pair substitution type			Frameshift type
		TA100	TA1535	WP2 uvrA	TA98	TA1537
+	0*	115	10	72	28	6
+	0**	100	5	62	29	6
+	10	98	5	66	27	7
+	20	105	11	58	30	6
+	40	100	9	60	25	5
+	60	100	11	52	37	7
+	80	111	9	57	27	6
+	100	105	10	55	30	7
Pos controls +S9	Name	2-AA	2-AA	2-AA	2-AA	2-AA
	Conc. (µg/plate)	2.5	2.5	10	2.5	2.5
	No. of revertants per plate	618	76	135	491	96

* = aqua dest; ** = 0.9% NaCl

2AA       2-Aminoanthracene

 

Table 3: Experiment 2 - Without Metabolic Activation

S9 Mix	Test substance concentration (% / plate)	Number of revertants (mean number of colonies per plate)
		Base-pair substitution type			Frameshift type
		TA100	TA1535	WP2 uvrA	TA98	TA1537
–	0*	111	9	68	26	7
-	0*	88	12	51	22	5
–	10	100	9	44	20	7
–	20	97	9	55	24	7
–	40	83	8	57	20	7
–	60	83	6	44	24	8
–	80	71	7	51	20	5
–	100	93	6	55	23	6
Pos controls ‑S9	Name	NaN3	NaN3	MMS	4-NOPD	4-NOPD
	Conc. (µg/plate)	10	10	1 µL	10	40
	Avg. no. of revertants per plate	844	1179	480	406	126

* = aqua dest; ** = 0.9% NaCl

NaN₃       Sodium azide

4-NOPD 4-nitro-o-phenylene-diamine

MMS     Methyl methane sulfonate

 

Table 4: Experiment 2 - With Metabolic Activation

S9 Mix	Test substance concentration (%/ plate)	Number of revertants (mean number of colonies per plate)
		Base-pair substitution type			Frameshift type
		TA100	TA1535	WP2 uvrA	TA98	TA1537
+	0*	114	10	76	32	5
+	0**	88	6	63	37	6
+	10	95	9	65	37	11
+	20	91	6	53	31	8
+	40	83	6	69	31	7
+	60	88	6	68	37	3
+	80	77	10	60	35	9
+	100	95	7	57	38	8
Pos controls +S9	Name	2-AA	2-AA	2-AA	2-AA	2-AA
	Conc. (µg/plate)	2.5	2.5	10	2.5	2.5
	No. of revertants per plate	1723	120	135	1590	123

* = aqua dest; ** = 0.9% NaCl

2AA       2-Aminoanthracene

 

Applicant's summary and conclusion

Conclusions:

Based on the results of this study, the test substance extracts did not cause gene mutations by base pair changes or frameshifts in the genome of the tester strains used.
Polar and non-polar extracts of niobium are considered to be non-mutagenic in the bacterial reverse mutation assay with and without metabolic activation.