12-wolframosilicic acid

Toxicity to aquatic algae and cyanobacteria

Administrative data

Endpoint:

toxicity to aquatic algae and cyanobacteria

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2015

Materials and methods

Test guideline

Qualifier:

according to guideline

Guideline:

EU Method C.3 (Algal Inhibition test)

GLP compliance:

yes (incl. QA statement)

Test material

Test material information

Constituent 1

Reference substance name:

12-wolframosilicic acid

EC Number:

234-719-8

EC Name:

12-wolframosilicic acid

Cas Number:

12027-38-2

Molecular formula:

H.1/4O40SiW12

IUPAC Name:

tetrakis(hexaoxocyclotritungstoxane); silicic acid

Test material form:

solid

Specific details on test material used for the study:

dentification: Tungstosilicic-acid
Physical state/Appearance: White Crystalline Solid
Batch: MKBR8664V
Purity: 65.0% w/w
Expiry Date: 26 August 2016
Storage Conditions: Room temperature in the dark over silica gel

Sampling and analysis

Analytical monitoring:

yes

Details on sampling:

Analysis carried out at 0 and 72 hours.

Test solutions

Vehicle:

no

Details on test solutions:

1000mg of test item was dissolved in culture medium and the volume adjusted to 1 liter to give a 1000 mg/L stock solution. For the standard test a series of dilutions was made from this stock solution to give further stock solutions of 100, 10, 1.0 and 0.10 mg/L. An aliquot (450 mL) of each of the stock solutions was separately inoculated with algal suspension (2.4 mL) to give the required test concentrations of 0.10, 1.0, 10, 100 and 1000 mg/L. For the pH adjusted test an aliquot (500 mL) of the 1000 mg/L stock solution prepared for use in the standard test was taken and the pH adjusted from 3.0 to 7.5.

Test organisms

Test organisms (species):

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

Details on test organisms:

TEST ORGANISM
- Strain: CCAP 278/4.
- Source (laboratory, culture collection): SAMS Research Services Ltd, Scottish Marine Institute, Oban, Argyll, Scotland.
- Age of inoculum (at test initiation):
- Method of cultivation: periodic replenishment of culture medium under constant aeration and illumination.

Study design

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

72 h

Test conditions

Test temperature:

24 ± 1 ºC

pH:

The pH value of the control cultures increased from pH 7.5 at 0 hours to pH 8.1 at 72 hours.
All test systems pH range was 7.2-8.1, except for the 100mg/L which was 6.9 initially and dropped to 6.1 at the end of the study.

Nominal and measured concentrations:

nominal: 1.0, 3.2, 10, 32 and 100 mg/L.
Measure concentrations at time 0: 0.067, 0.81, 5.9, 26, 82mg/L
Measured concentrations at 72hrs: 0.083, 0.29, 3.4, 24, 81mg/L
Calculated geometric mean concentrations: 0.074, 0.49, 4.5, 35, 81mg/L

Details on test conditions:

TEST SYSTEM
- Test vessel: 250ml glass conical flask
- Type (delete if not applicable): closed
- Material, size, headspace, fill volume: 100ml fill
- Aeration: no
- Initial cells density: 5.7E3 cells/mL.
- Control end cells density: 8.4E5 cells/mL.
- No. of vessels per concentration (replicates): 6

GROWTH MEDIUM
- Standard medium used: yes

TEST MEDIUM / WATER PARAMETERS
- standard culture medium

OTHER TEST CONDITIONS
- Sterile test conditions: no
- Adjustment of pH: no
- Photoperiod: continuous light.
- Light intensity and quality: 7000 lux -warm white lighting (380 – 730 nm)

EFFECT PARAMETERS MEASURED (with observation intervals if applicable) :
- Determination of cell concentrations: Samples were taken at 0, 24, 48 and 72 hours and the cell densities determined using a Coulter® Multisizer Particle Counter.

TEST CONCENTRATIONS
- Spacing factor for test concentrations:
- Justification for using less concentrations than requested by guideline:
- Range finding study
- Test concentrations:
- Results used to determine the conditions for the definitive study:

Reference substance (positive control):

yes

Remarks:

potassium dichromate

Results and discussion

Effect concentrations

Effect concentrations 1

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

14 mg/L

Nominal / measured:

meas. (geom. mean)

Conc. based on:

test mat.

Basis for effect:

growth rate

Effect concentrations 2

Duration:

72 h

Dose descriptor:

EC10

Effect conc.:

1.1 mg/L

Nominal / measured:

meas. (geom. mean)

Conc. based on:

test mat.

Basis for effect:

growth rate

Details on results:

- Exponential growth in the control (for algal test): yes
- Observation of abnormalities (for algal test): After 72 hours there were no abnormalities detected in the control or test cultures at 1.0, 3.2 and 10 mg/L, however no intact cells were observed to be present in the test cultures at 32 and 100 mg/L.

Results with reference substance (positive control):

- Results with reference substance valid?
- EC50: ErC50 (0 – 72 h) : 1.0 mg/L; 95% confidence limits 0.90 – 1.2 mg/L.
- Other: The results from the positive control with potassium dichromate were within the normal ranges for this reference item.

Reported statistics and error estimates:

It was not possible to calculate 95% confidence limits for the ErC50 value as the data generated did not fit the models available for the calculation of confidence limits.

Applicant's summary and conclusion

Validity criteria fulfilled:

yes

Executive summary:

In a guideline algal growth inhibition study, the substance tungstosilicic acid was found to have a 72hr EC50 value of 14mg/L based on growth rate. Results were based on the geometric mean of the measured concentrations at the beginning and end of the study due to apparent and early loss of material potentially due to complexation with the salts of the test medium. At concentrations above 35mg/L, no intact cells were seen at the end of the study.