Niobium oxide

Toxicity to microorganisms

Link to relevant study record(s)

Reference

Endpoint:

activated sludge respiration inhibition testing

Type of information:

experimental study

Adequacy of study:

key study

Study period:

2003-02-17 to 2003-04-15

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 209 (Activated Sludge, Respiration Inhibition Test

Version / remarks:

adpoted April 04, 1984

Deviations:

yes

Remarks:

reference substance: copper (II) sulphate pentahydrate

GLP compliance:

yes (incl. QA statement)

Specific details on test material used for the study:

SOURCE OF TEST MATERIAL
- Source and lot/batch No.of test material: SNB100G200277M
- Expiration date of the lot/batch: 2003-12-31
- Purity test date: 02.12.2002
- Purity: > 99 %

STABILITY AND STORAGE CONDITIONS OF TEST MATERIAL
- Storage condition of test material: Room temperature, protected from moisture and light
- Stability under test conditions: not specified

OTHER SPECIFICS:
- Appearance: black powder
- Water solubility: Hardly soluble, < 10 mg/L (OECD 105)

Analytical monitoring:

no

Vehicle:

no

Details on test solutions:

PREPARATION AND APPLICATION OF TEST SOLUTION (especially for difficult test substances)
- Method: no stock solution, direct weighing into test vessels
- Differential loading: The test item was weighed out directly into Erlenmeyer flasks, filled with 250 ml autoclaved tap water and stirred for 24 h.
- Controls: 2 control samples without test item were included in every test series at the beginning and at the end of the test.
- Chemical name of vehicle (organic solvent, emulsifier or dispersant): no vehicle
- Evidence of undissolved material (e.g. precipitate, surface film, etc.): At the concentrations 100 and 320 mg/L the test item was completely dispersed.
At the concentrations 1000 to 1000 mg/L the test item was partly dispersed. The test item partly laid on the ground.

Test organisms (species):

activated sludge of a predominantly domestic sewage

Details on inoculum:

- Name and location of sewage treatment plant where inoculum was collected: Municipal sewage treatment plant of D-31157 Sarstedt
- Pretreatment: The sludge was washed with autoclaved tap water and diluted corresponding to a dry weight of 4.0 g/L ± 10 %.
- Initial biomass concentration: not reported. Dry sludge concentration was determined as 4.40 g/L.
- Nutrient solution: Synthetic waste water according to OECD 209.

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

3 h

Test temperature:

20.5 °C

pH:

7.00

Dissolved oxygen:

determined at the start of the 3 minute measurement
Test item: 6.34 - 4.51 mg O2/L
control: 4.11 - 6.48 mg O2/L
Reference item: 8.00 - 6.68 mg O2/L

Nominal and measured concentrations:

Nominal test item concentrations: 0, 100, 320, 1000, 3200, 10000 mg/L
At the concentrations 100 and 320 mg/L the test item was completely dispersed.
At the concentrations 1000 to 10000 mg/L the test item was partly dispersed. The test item partly laid on the ground. No analytical determination of the concentration conducted.

Details on test conditions:

TEST SYSTEM
- Test vessel: 500 mL Erlenmeyer flasks, DIN 12440
- Material, fill volume: glass, 500 mL
- Aeration: Permanent ventilation
- No. of vessels per concentration (replicates): 1
- No. of vessels per control (replicates): 2
- Sludge concentration (weight of dry solids per volume): 4.40 g/L
- Nutrients provided for bacteria: Nutrient solution is synthetic waste water according to OECD 209
- Biomass loading rate: 200 mL inoculum

TEST MEDIUM / WATER PARAMETERS
- Source/preparation of dilution water: 16 ml synthetic waste water, 284 ml autoclaved tap water

OTHER TEST CONDITIONS
- Adjustment of pH: no; pH-value of activated sludge: 7.00
- Details on termination of incubation: after 3h

EFFECT PARAMETERS MEASURED (with observation intervals if applicable): The oxygen depletion of the control, reference and test item was measured after 3 h incubation by means of oximeter and recorded for at least 3 minutes on a flatbed recorder.
TEST CONCENTRATIONS
- Spacing factor for test concentrations: 3.2
- Range finding study: Yes. A range-finding test (NON-GLP-state) was carried out with three concentrations: 10 - 100 - 1000 mg/L.
- Test concentrations in the final test: 100, 320, 1000, 3200, 10000 mg/L
- Results used to determine the conditions for the definitive study: yes

Reference substance (positive control):

yes

Remarks:

copper(II)-sulphate-pentahydrate

Duration:

3 h

Dose descriptor:

EC50

Effect conc.:

> 1 000 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

inhibition of total respiration

Remarks on result:

other: At the concentrations 1000 to 10000 mg/L the test item was partly dispersed. The test item partly laid on the ground.

Key result

Duration:

3 h

Dose descriptor:

NOEC

Effect conc.:

1 000 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

inhibition of total respiration

Remarks on result:

other: At the concentrations 1000 to 10000 mg/L the test item was partly dispersed. The test item partly laid on the ground.

Details on results:

- Any observations (e.g. precipitation) that might cause a difference between measured and nominal values: At the concentrations 1000 to 10000 mg/L the test item was partly dispersed. The test item partly laid on the ground.
- Effect concentrations exceeding solubility of substance in test medium: yes, see above
- Adsorption (e.g. of test material to the walls of the test container): no
- Blank controls oxygen uptake rate: no blank control
- Respiration rate in control: 24.0 mgO2/L*h,22.4 mgO2/L*h
- Coefficient of variation of oxygen uptake rate in control replicates: The two control respiration rates is 7% (see Table 1). No coeffcient of variation determined.
- The effects were not concentration related. EC-values were not calculated. The EC50-value is > 1000 mg/L.

Results with reference substance (positive control):

- Results with reference substance valid? Yes
- Relevant effect levels: EC50 (3 hours) = 118 mg/L.
- Other: The EC50 (3 hours) of copper(ll)sulphate pentahydrate is in the accepted range of 54 - 146 mg/L.

Reported statistics and error estimates:

Statistical analysis was only performed for the reference item: The EC50-value was calculated with probit analysis using the software SIGMAPLOT (Windows) rel. 6.00, 2000, SPSS CORPORATION only for the reference item. Probit values were taken from WEBER (1986). Confidence intervals were calculated according to a standard procedure (BREITIG & TOMPLING 1982). In the reference test the EC50 -value was determined by probit analysis. The EC50 -value of the reference item is: EC50 = 118 mg/L The EC50-value of the reference item copper(ll)-sulphate-pentahydrate is in the confidence range of 54 - 146 mg/L.

In the first main study five concentrations within the range 1000 to 10000 mg/L were tested with a dilution factor of 1.8. No concentration effect relationship was found. The inhibition ranged from 10 to 78 % and was not concentration related.

The study was repeated. In the second study five concentrations within the range 100 - 10000 mg/L in a series with a dilution factor of 3.2 were tested. 2 controls without test item were included (see Table 1).

Table 1: Respitation Rates and Inhibition of Respiration of Test and Reference Item Concentrations

	concentration [mg/L]	respiration rate [mgO2/L*h]	Inhibition [%]
test item	10000	20.8	10
	3200	14.8	36
	1000	23.2	0
	320	22.8	2
	100	26.0	-12
control 1	/	24.0	/
control 2	/	22.4	/
reference item	180	7.2	69
	100	13.6	41
	58	18.0	22

Difference of the control respiration rates: 7 %

Table 2: EC-Values with Confidence Interval of Niobium(II)-Oxide

	EC- values[mg/L]	Confidence interval p=95[%] [mg/L]
EC20	>1000	-
EC50	>1000	-
EC50	>1000	-

The test item Niobium (II)- Oxide is not toxic at concentrations ≤ 1000 mg/L to activated sludge of a municipal sewage treatment plant.

Validity criteria fulfilled:

yes

Conclusions:

A Respiration Inhibition Test with activated sludge (acc. to OECD Guideline No. 209) was performed for 3 h with the test item Niobium(II)-Oxide. The test item is not toxic at concentrations ≤ 1000 mg/L to activated sludge of a municipal sewage treatment plant.

Executive summary:

To investigate potential harmful effects of Niobium(II)-Oxide on aquatic microorganisms, an activated sludge respiration inhibition limit test (OECD 209) was performed at nominal loadings of 0 (control), 100, 320, 1000, 3200 and 1000 mg/L according to OECD 209 and under GLP. At the concentrations 100 and 320 mg/L the test item was completely dispersed. At the concentrations 1000 to 1000 mg/L the test item was partly dispersed. The test item partly laid on the ground.

The effects were not concentration related. EC values were not calculated. The test item is not toxic at concentrations ≤1000 mg/L to activated sludge of a municipal sewage treatment plant.

Results Synopsis

Test Type: Static, activated sewage sludge from municipal STP

 

3-hr EC50: > 1000 mg/L       

3-hr NOEC = 1000 mg/L

Endpoint(s) Effected:  respiration rate

Description of key information

A Respiration Inhibition Test with activated sludge (acc. to OECD Guideline No. 209) was performed for 3 h with the test item Niobium(II)-Oxide in the concentration range of 100 to 10,000 mg/L

The observed effects were not concentration related and hence, EC values were not calculated. However, no toxic effects were noted at concentrations ≤1000 mg/L.

Key value for chemical safety assessment

EC10 or NOEC for microorganisms:

1 000 mg/L