Niobium oxide

Toxicity to aquatic algae and cyanobacteria

Link to relevant study record(s)

Reference

Endpoint:

toxicity to aquatic algae and cyanobacteria

Type of information:

experimental study

Adequacy of study:

key study

Study period:

14 Feb. - 11 March 2003

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

EU Method C.3 (Algal Inhibition test)

Version / remarks:

December 1992

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Specific details on test material used for the study:

SOURCE OF TEST MATERIAL
- Source and batch No.of test material: SNB10OG200277M
- Expiration date of the batch: 2003-12-31
- Purity test date: >99%

STABILITY AND STORAGE CONDITIONS OF TEST MATERIAL
- Storage condition of test material: protected from moisture
- Stability under test conditions: stable

TREATMENT OF TEST MATERIAL PRIOR TO TESTING
- Treatment of test material prior to testing: The test solution (1 L) was shaken for 24 h at 20 rpm in a 1 L glass bottle. Undissolved particles of the test item were removed by filtration (pore size 0.45 µm). A three day-old preculture incubated at study conditions was used for the main study. At test start fluorescence was measured prior to application of the test item. Application was carried out by adding appropriate volumes of stock solution to the test replicates.

OTHER SPECIFICS:
- black powder
- Water solubility: Hardly soluble, <10 mg/L (OECD 105)
- Concentration: saturated solution with 100 mg/L
- Storage at test facility: Room temperature, protected from moisture and light
- The test item and the information concerning the test item were provided by the sponsor

Analytical monitoring:

yes

Details on sampling:

Concentration control analysis was carried out and reported by the sponsor under NON-GLP conditions. 100 mL each of the saturated concentration and control were sampled at the beginning and end of the test.The samples were stored in PE bottles at 4 - 8 °C until shipping.

Vehicle:

no

Details on test solutions:

PREPARATION AND APPLICATION OF TEST SOLUTION (especially for difficult test substances)
- Method: A saturated solution was prepared with 100 mg/L and dilution water. The test solution (1 L) was shaken for 24 h at 20 rpm in a 1 L glass bottle. undissolved particles of the test item were removed by filtration (pore size 0.45 µm).
- Controls: yes

Test organisms (species):

Desmodesmus subspicatus (previous name: Scenedesmus subspicatus)

Details on test organisms:

TEST ORGANISM
- Common name: Desmodesmus subspicatus CHODAT SAG 86.81 (formerly known as Scenedesmus subspicatus CHODAT)
- Strain: 86.81 SAG
- Source (laboratory, culture collection): Sammlung von Algenkulturen (SAG), Pflanzenphysiologisches Institut der Universität Göttingen, Nikolausberger Weg 18, D-37073 Göttingen
- Age of inoculum (at test initiation): A three day-old preculture incubated at study conditions was used for the main study, incubation was performed in 500 mL Erlenmeyer flasks with test medium. For the start of the test the preculture was diluted with test medium to receive an initial cell concentration of approximately 1 x 10^4 cells/mL in the replicates.
- Method of cultivation: Fresh stocks were prepares every month on Z-Agar. Light intensity amounted 35-70 µE/m^2*s for 24 h per day.

ACCLIMATION
- Culturing media and conditions (same as test or not): same as test

Test type:

static

Water media type:

freshwater

Limit test:

yes

Total exposure duration:

72 h

Hardness:

nominal hardness of 0.48 mmol Ca+Mg/L

Test temperature:

23 ± 2 °C

pH:

8.2 ± 0.2

Dissolved oxygen:

n.a.

Salinity:

n.a.

Conductivity:

n.a.

Nominal and measured concentrations:

A saturated solution was prepared at a nominal loading level of 100 mg/L.
Measured concentrations were below 1 mg/L.

Details on test conditions:

TEST SYSTEM
- Test vessel: Erlenmeyer flasks 250 mL
- Material, fill volume: glass, 100 ml
- Aeration: no
- Control initial cells density: 8,815 cells/mL
- Control end cells density: 418,858 cells/mL
- No. of vessels per concentration (replicates): 3
- No. of vessels per control (replicates): 6

GROWTH MEDIUM
- Standard medium used: yes

OTHER TEST CONDITIONS
- Sterile test conditions: no
- Adjustment of pH: no
- Photoperiod: 24 h/d light
- Light intensity and quality: Nominally 60 - 120 μE/m2 • s

EFFECT PARAMETERS MEASURED (with observation intervals if applicable) :
- Determination of cell concentrations: Cell density was measured via Chlorophyll-a-fluorescence (excitation at 435 nm, emission at 685 nm). Each replicate was measured 6-fold. The cell density was measured at the beginning of the test and every 24 h. Filtrated culture medium was used as ground signal.
- Chlorophyll measurement: excitation at 435 nm, emission at 685 nm
- Other: Microscopic evaluation of the cells was determined at the start and end of the incubation. Alga cells were checked for any unusual cell shapes, color differences, differences in chloroplast morphology, flocculations, adherence of algae to test containers or aggregation of alga cells.

TEST CONCENTRATIONS
- Spacing factor for test concentrations: saturated solution
- Justification for using less concentrations than requested by guideline: pretest showed no different results for diluted saturated solutions
- Range finding study: yes
- Test concentrations in preliminary test: 1:2, 1:10, control
- Results used to determine the conditions for the definitive study: yes

- Concentration control analysis was carried out and reported by the sponsor under NON-GLP conditions. 100 mL each of the saturated concentration and control were sampled at the beginning and end of the test. The samples were stored in PE bottles at 4-8 °C until shipping.

Reference substance (positive control):

yes

Remarks:

Potassium dichromate p.a. (MERCK)

Key result

Duration:

72 h

Dose descriptor:

EC0

Effect conc.:

100 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

growth rate

Remarks on result:

other: No adverse effect on the algal growth rate was observed in the saturated solution.

Details on results:

- Exponential growth in the control (for algal test): yes
- Observation of abnormalities (for algal test): no
- Unusual cell shape: no
- Colour differences: not reported
- Flocculation: not reported
- Adherence to test vessels: not reported
- Aggregation of algal cells: not reported
- Other: /
- Any stimulation of growth found in any treatment: no
- Any observations (e.g. precipitation) that might cause a difference between measured and nominal values: no
- Effect concentrations exceeding solubility of substance in test medium: only saturated solution tested, no precipitations

Results with reference substance (positive control):

- Results with reference substance valid? Yes
- EC50: 0.62-0.77 (Inhibiton of biomass growth), 0.73-1.09 (Rate-related inhibition)

Reported statistics and error estimates:

NOEC and LOEC were determined by calculation of statistical significance of biomass integrals and growth rates.

Table 1: NOEC and LOEC (0 -72 h) of Biomass Inhibition and Rate-Related Inhibition based on saturated solution NOEC and LOEC values were calculated using One Way Analysis of Variance and Dunnett`s Method ( α=0.05)

	Inhibition of biomass growth
LOEC	not applicable*
NOEC	saturated solution
	Rate-related inhibition
LOEC	not applicable*
NOEC	saturated solution

* No effects found at the saturated solution level, containing <1 mg/L Niobium

Table 2: Preliminary Test Results: Cell Density Values (2 replicates each, control: 4 replicates)

Dilution level	Replicate No.	Cell density [cells/mL]
		0 h	72 h
Saturated Solution	1	8328	357648
	2	8820	366668
1:2	1	8984	303118
	2	8615	312548
1:10	1	9558	383888
	2	8943	365028
Control	1	8943	385118
	2	8984	378968
	3	9066	353958
	4	8779	378558

No self fluorescence was found up to the saturated solution

Table 3: Cell densities

Test group	RE. No.	Cell density [cell/mL]
		0 h	24 h	48 h	72 h
Saturated solution	1	8861	26235	153017	483211
	2	8759	26870	133419	435343
	3	9261	28213	139077	451128
	Mean	8960	27106	141838	456561
Control	1	8800	23990	122001	418533
	2	8297	24369	122431	435856
	3	8994	23765	111382	423863
	4	8748	24103	112776	412076
	5	9199	23724	107589	418738
	6	8851	23795	107794	404081
	Mean	8815	23958	113996	418858

RE. = Replicate

Validity criteria fulfilled:

yes

Conclusions:

Niobium(II)-Oxide was found to be non-inhibitory to the biomass growth and rate related growth of the freshwater green alga Desmodesmus subspicatus at the saturated solution level.

Executive summary:

In a 72 hour acute toxicity study according to EU method C.3., the cultures of Desmodesmus subspicatus CHODAT (Strain No. 86.81) were exposed to Niobium(II)-Oxide. The test substance was applied at a nominal loading level of 100 mg/L. After shaking for 24 h and filtration the saturated solution was used in the test. The measured Nb concentrations were found to be below 1 mg/L. No effect on the alga were observed. Hence, Niobium(II)-Oxide was found to be non-inhibitory to the biomass growth and rate related growth of the freshwater green alga D. subspicatus at the saturated solution level.

No abnormalities were noted.

 

This toxicity study is classified as acceptable and satisfies the guideline requirements for the Alga, Growth Inhibition Test with D. subspicatus toxicity study according to the EC Directive 92/69/EC Method C3.

Results Synopsis

 

Test Organism: Desmodesmus subspicatus

Test Type: Static, Limit test with saturated solution

 

72hr NOEC: saturated solution (measured < 1 mg a.i./L)             

Endpoint(s) Effected:  biomass, growth rate

Description of key information

No adverse effects could be demonstrated on the growth of Desmodesmus subspicatus after exposure to a saturated NbO solution for up to 72 h. The test was conducted according to EC Directive 92/69/EC method C.3. The saturated solution was prepared at a nominal loading level of 100 mg/L and used in the test after shaking for 24 h and subsequent filtration. The actual concentration of Nb in the test solution was verified to be below 1 mg/L.