Cerium terbium magnesium undecaaluminum nonadecaoxide (hexagonal) ((Ce, Tb)MgAl11O19) and aluminium oxide (Al2O3) from calcination of Al2O3, CeO2, MgO and Tb4O7

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:

28 November 2011 - 01 december 2011

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Reason / purpose for cross-reference:

reference to other study

Qualifier:

according to guideline

Guideline:

OECD Guideline 201 (Alga, Growth Inhibition Test)

Deviations:

no

Qualifier:

according to guideline

Guideline:

EU Method C.3 (Algal Inhibition test)

Deviations:

no

Qualifier:

according to guideline

Guideline:

ISO 8692 (Water Quality - Fresh Water Algal Growth Inhibition Test with Scenedesmus subspicatus and Selenastrum capricornutum)

Deviations:

no

Qualifier:

according to guideline

Guideline:

other: Guidance document on aquatic toxicity testing of difficult substances and mixtures, OECD series on testing and assessment number 23, December 14, 2000

Deviations:

no

GLP compliance:

yes

Analytical monitoring:

yes

Details on sampling:

Samples for possible analysis were taken from all test concentrations and the control:
Frequency: at t=0 h, t=24 h and t=72 h
Volume: 4.8 ml
Storage: Samples were stored in a freezer until analysis.

Compliance with the Quality criteria regarding maintenance of actual concentrations was demonstrated by running a test vessel at the highest substance concentration but without algae and samples for analysis were taken at the start, after 24 hours of exposure and at the end of the test period.
Additionally, reserve samples of 4.8 ml were taken from all test solutions for possible analysis.

Vehicle:

no

Details on test solutions:

Preparation of test solutions started with aquatic mixtures prepared individually at loading rates of 1.0, 10 and 100 mg/l. The mixtures were treated with ultrasonic waves for 8 minutes and then magnetically stirred for two days. The resulting dispersions were filtered through a 0.45 μm membrane filter (Whatman; RC55) to remove the remaining undissolved material. The resulting filtrates were all clear and colourless.
After preparation, volumes of 50 ml were added to each replicate of the respective test concentration. Subsequently, 1 ml of an algal suspension was added to each replicate providing a cell density of 10^4 cells/ml.

Test organisms (species):

Raphidocelis subcapitata (previous names: Pseudokirchneriella subcapitata, Selenastrum capricornutum)

Details on test organisms:

TEST ORGANISM
- Common name: Pseudokirchneriella subcapitata
- Strain: NIVA CHL 1
- Source (laboratory, culture collection): In-house laboratory culture
- Method of cultivation: Algae stock cultures were started by inoculating growth medium with algal cells from a pure culture on agar. The suspensions were continuously aerated and exposed to light in a climate room at a temperature of 21-24°C. 3 days before the start of the test, cells from the algal stock culture were inoculated in culture medium at a cell density of 1 x 10^4 cells/ml. The pre-culture was maintained under the same conditions as used in the test. The cell density was measured immediately before use.

ACCLIMATION
- Culturing media and conditions (same as test or not): stock culture medium = M1; Pre-culture medium = M2

Test type:

static

Water media type:

freshwater

Limit test:

yes

Total exposure duration:

72 h

Post exposure observation period:

None

Hardness:

24 mg CaCO3/l

Test temperature:

21.2 - 22.9 ºC

pH:

7.9 - 8.0

Dissolved oxygen:

No information

Salinity:

Not applicable.

Nominal and measured concentrations:

No detectable concentrations of either Al, Ce and Tb were present during the 72-hour exposure period. To demonstrate proper preparation of the test solutions an aliquot of the filter residue was analysed. The elements Al, Ce and Tb were observed in the filter residue solution. It demonstrated that the test substance was used for the preparation of the test solutions.
Similar results were obtained for the highest concentration incubated without algae.

Details on test conditions:

TEST SYSTEM
- Type (delete if not applicable): open
- Material, size, headspace, fill volume: 100 ml, all-glass, containing 50 ml of test solution
- Initial cells density: 1 x 10^4 cells/ml
- Control end cells density: 134.4 x 10^4 cells/ml
- No. of vessels per concentration (replicates): 6 for highest concentration, 3 for each lower concentration
- No. of vessels per control (replicates): 6


GROWTH MEDIUM
- Standard medium used: yes

TEST MEDIUM / WATER PARAMETERS
- Source/preparation of dilution water: M2 medium

OTHER TEST CONDITIONS
- Photoperiod: Continuously using TLD-lamps of the type „Cool-white‟ of 30 Watt, with a light intensity within the range of 77 to 88 µE.m-2.s-1.

EFFECT PARAMETERS MEASURED (with observation intervals if applicable) :
- Determination of cell concentrations: counting chamber at beginning of test, spectrophotometer used thereafter.

TEST CONCENTRATIONS
- Spacing factor for test concentrations: 10
- Combined Limit- Range finding study
- Test concentrations: Filtered solutions prepared at loading rates of 1.0, 10 and 100 mg/l

Reference substance (positive control):

yes

Remarks:

potassium dichromate

Key result

Remarks on result:

other: The 72h-EC50 exceeds and the 72h-NOEC equals the maximum soluble concentration of test substance in test medium.

Details on results:

The EC50 exceeds and the NOEC equals the maximum soluble concentration of test substance in test medium.
No significant differences were recorded between the values for growth rate at any of the test concentrations when compared to the control group.
Microscopic observations at the end of the test revealed a normal and healthy appearance of the exposed cells when compared to the control.

Results with reference substance (positive control):

Potassium dichromate reduced growth rate of this fresh water algae species at nominal concentrations of 0.56 mg/l and higher.
The EC50 for growth rate reduction (ERC50: 0-72h) was 1.5 mg/l with a 95% confidence interval ranging from 1.1 to 2.1 mg/l. The historical ranges for growth rate reduction lie between 0.82 and 2.3 mg/l.
Hence, the ERC50: 0-72h for the algal culture tested corresponds with this range.

Validity criteria fulfilled:

yes

Conclusions:

Under the conditions of the present study with Pseudokirchneriella subcapitata, no reduction of growth rate was recorded in a filtered solution prepared at a loading rate of 100 mg/l after 72 hours of exposure. The EC50 for growth rate reduction exceeded the concentration present in a filtered solution prepared at a loading rate of 100 mg/l, which was considered the maximum soluble concentration in test medium. Due to the very low solubility of CAT in test medium, concentration levels that could affect algal growth could not be reached.

Description of key information

CAT was tested in a fresh water algal growth inhibition test (OECD 201). No reduction of growth rate was recorded at a 0.45 μm filtered solution prepared at a loading rate of 100 mg/l after 72 hours of exposure.

Additional information

CAT was tested in a fresh water algal growth inhibition test (OECD 201). Under the conditions of the study with Pseudokirchneriella subcapitata, no reduction of growth rate was recorded at a 0.45 μm filtered solution prepared at a loading rate of 100 mg/l after 72 hours of exposure. The 72h-EC50 for growth rate reduction exceeded the concentration present in a 0.45 μm filtered solution prepared at a loading rate of 100 mg/l, which was considered the maximum soluble concentration in test medium. The 72h-NOEC equaled the maximum soluble concentration in test medium.