Hydrothermal synthesis product of calcium oxide, quartz and water

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:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

study well documented, meets generally accepted scientific principles, acceptable for assessment

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

1999

Report date:

1999

Materials and methods

Test guideline

Qualifier:

according to guideline

Guideline:

OECD Guideline 201 (Alga, Growth Inhibition Test)

Deviations:

yes

Remarks:

The initial cell density of ~ 70000/mL was distinctly above the recommended one of 10000/mL.

GLP compliance:

no

Test material

Test material information

Constituent 1

Reference substance name:

Silicic acid, calcium salt

EC Number:

215-710-8

EC Name:

Silicic acid, calcium salt

Cas Number:

1344-95-2

IUPAC Name:

Silicic acid, Calcium salt

Test material form:

solid

Specific details on test material used for the study:

Name of test material (as cited in study report) = Shieldex AC 3

Sampling and analysis

Analytical monitoring:

no

Test solutions

Vehicle:

no

Details on test solutions:

PREPARATION AND APPLICATION OF TEST SOLUTION (especially for difficult test substances)
- Method: Aqueous extracts of loadings (water-accommodated fraction, WAF)
after 24-h shaking of the suspensions in deionised water at approx. 130 revolutions/min;.
fitration through folded paperfilter;
addition of necessary salts from stock solutions before test
- Differential loading: yes
- Controls: yes, without respective filtrates, but with algae
- Evidence of undissolved material (e.g. precipitate, surface film, etc): Filtrates (WAFs) were clear.

Test organisms

Test organisms (species):

Desmodesmus subspicatus (previous name: Scenedesmus subspicatus)

Details on test organisms:

TEST ORGANISM
- Common name: green alga
- Strain: Scenedesmus subspicatus CHODAT
- Source (laboratory, culture collection): Institute of Plant Physiology, University Göttingen
- Age of inoculum (at test initiation): 3 d, actively growing cell culture
- Method of culture: preculture 3 days prepared before test from a stock culture

Study design

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

72 h

Test conditions

Hardness:

no data

Test temperature:

25 ± 1 °C

pH:

control: 8.29 (initial); 9.97 (final)
tests: 8.35 --> 9.43 (100 mg/L)
8.66 --> 8,44 (200 mg/L)
9.04 --> 8.39 (400 mg/L)
9.16 --> 8.49 (800 mg/L)
9.19 --> 8.73 (1000 mg/L)

Dissolved oxygen:

not applicable

Salinity:

no data

Nominal and measured concentrations:

100, 200, 400, 800, and 1000 mg/L (nominal, WAFs of loadings)

Details on test conditions:

TEST SYSTEM
- Test vessel:
- Type (delete if not applicable): open
- Material, size, headspace, fill volume: no data
- Initial cells density: ~ 72000/mL
- No. of vessels per concentration (replicates): 5
- No. of vessels per control (replicates): 7


GROWTH MEDIUM
- Standard medium used: yes



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


OTHER TEST CONDITIONS
- Sterile test conditions: no
- Adjustment of pH: no
- Photoperiod: continuous
- Light intensity and quality: > 120 µE/m2s; ~ 8000 Lux (400 - 700 nm)


EFFECT PARAMETERS MEASURED
- Determination of cell concentrations: spectrophotometer at 578 nm (cell density, extinction)
- Chlorophyll measurement: no


TEST CONCENTRATIONS
- Spacing factor for test concentrations: 2
- Range finding study
- Test concentrations: 100; 1000; and 10000 mg/L (loadings)

Reference substance (positive control):

no

Results and discussion

Effect concentrations

Effect concentrations 1

Key result

Duration:

72 h

Dose descriptor:

EL10

Effect conc.:

41 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

growth rate

Effect concentrations 2

Key result

Duration:

72 h

Dose descriptor:

EL50

Effect conc.:

> 1 000 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

growth rate

Effect concentrations 3

Duration:

72 h

Dose descriptor:

EL10

Effect conc.:

33 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

biomass

Effect concentrations 4

Duration:

72 h

Dose descriptor:

EL50

Effect conc.:

410 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

biomass

Details on results:

- Exponential growth in the control (for algal test): yes
- Observation of abnormalities (for algal test): no data
- 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: no, WAFs were used

Reported statistics and error estimates:

No standard deviations of mean cell concentrations reported. 95%-Confidence limits graphically given in the growth curve plot.
No statistical evaluation available.

Any other information on results incl. tables

Average cell densities and inhibition values over time  (from Report, Sections 7.1 and 7.2)

Concentration [mg/L]	Cell density^*) after time of incubation			% inhibition after 72 h
	24 h	48 h	72 h	Biomass	Growth rate
Control (0)	2.92 x10^5	1.14 x10^6	3.32 x10^6	0	0
100	2.38 x10^5	7.72 x10^5	1.98 x10^6	37.4	14.5
200	4.37 x10^5	8.55 x10^5	2.00 x10^6	27.4	30.2
400	3.92 x10^5	6.70 x10^5	1.48 x10^6	44.3	34.6
800	2.85 x10^5	4.97 x10^5	9.37 x10^5	63.2	36.9
1000	2.64 x10^5	4.25 x10^5	8.38 x10^5	68.1	39.8

^*) Initial cell density = ~ 7.2 x10⁴ cells/mL

Results of pre-testing not provided.

The EC10 value was extrapolated, but procedure not explicitely documented. However, the value is plausible.

The inhibitory effect showed a relatively weak dose-response relationship, with no unequivocal dose response

discernible from 100 to 400 mg/L.

Applicant's summary and conclusion

Validity criteria fulfilled:

not specified

Remarks:

Cell proliferation valid (~50-fold increase of initial over 72 h); statistical criteria for the validation parameters appear to be met.