Silicic acid, aluminum magnesium sodium salt

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

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 201 (Alga, Growth Inhibition Test)

Qualifier:

according to guideline

Guideline:

EU Method C.3 (Algal Inhibition test)

GLP compliance:

yes (incl. QA statement)

Remarks:

(Landesamt für Umwelt-, Wasserwirtschaft und Gewerbeaufsicht, Rheinland-Pfalz)

Analytical monitoring:

yes

Details on test solutions:

Due to the poor solubility of the test item, the water-accommodated fraction was prepared for the test. This was done by weighing the nominal load of 101.3 mg/L adding the corresponding amount of demineralised water and shaking vigorously for 24 hours. The resulting solution was filtrated through 0.45 μm filters. Then, 10 mL/L of stock solution I and 1 mL/L of each of stock solutions II, III and IV were added.
A blank control will be prepared likewise but without addition of test item and without membrane filtration.

Test organisms (species):

Desmodesmus subspicatus (previous name: Scenedesmus subspicatus)

Details on test organisms:

Unicellular freshwater green alga.
Genus: Desmodesmus
Species: subspicatus
SAG Strain Number: 86.81
Taxonomic position: Chlorophyta - Chlorophyceae

Origin and Culture
The culture of Desmodesmus subspicatus was obtained in February 2014 by MBM Sciencebridge GmbH (Institut für Pflanzenphysiologie of Universität Göttingen). The algae are kept as stock culture on solid agar at 7 °C. From the stock culture, a permanent culture was prepared. From an aliquot of the permanent culture, the pre-culture was prepared.

Test type:

static

Water media type:

freshwater

Test temperature:

21 – 22 °C

pH:

7.6 after 0 h
7.7 after 72 h

Nominal and measured concentrations:

100 mg/L nominal

Details on test conditions:

Number of replicates: six replicates for the control six replicates for the treatment
Vessels: glass flasks total volume 65 mL
Lighting: 5300 Lux
Control: deionised water with nutrient medium and alga
Treatments: test solution and alga

Reference substance (positive control):

yes

Remarks:

Potassium dichromate K2Cr2O7 (CAS No. 7778-50-9) was used as positive control in a separate reference test (GLP study no. 14070902R301).

Key result

Duration:

72 h

Dose descriptor:

NOEC

Effect conc.:

>= 100 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

growth rate

Key result

Duration:

72 h

Dose descriptor:

NOEC

Effect conc.:

>= 100 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

other: yield

Key result

Duration:

72 h

Dose descriptor:

LOEC

Effect conc.:

> 100 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

growth rate

Key result

Duration:

72 h

Dose descriptor:

LOEC

Effect conc.:

> 100 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

other: yield

Key result

Duration:

72 h

Dose descriptor:

EC10

Effect conc.:

> 100 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

growth rate

Key result

Duration:

72 h

Dose descriptor:

EC10

Effect conc.:

> 100 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

other: yield

Key result

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

> 100 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

growth rate

Key result

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

> 100 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

other: yield

Details on results:

At the beginning and at the end of the test, the concentration of aluminium as component of the test item in the test solutions was determined using ICP-OES measurement. Neither in the treatment nor in the control aluminium was detectable.

Results with reference substance (positive control):

The EC50s of potassium dichromate (K2Cr2O7, CAS No. 7778-50-9) were determined in a separate reference test. The values lay within the normal range of the laboratory.

Validity criteria fulfilled:

yes

Conclusions:

Silicic acid Aluminium Magnesium Sodium Salt showed no significant inhibition of algal growth.

Executive summary:

The study was performed using a nominal loading of 100 mg/L. Test period (test system Desmodesmus subspicatus) was 72 hours. The cell concentration of each replicate was determined by measuring the absorption of the solutions at 440 nm every 24 hours with a spectral photometer. The cell density of the cultures was calculated based on the correlation curve between the adsorption and the cell density of the cultures determined by a cell counter. Growth rate μ and the yield1 were determined from the cell densities at the respective observation times.

The treatment showed no significant inhibition of algal growth.

Description of key information

Silicic acid Aluminium Magnesium Sodium Salt showed no significant inhibition of algal growth up to concentrations of 100 mg/L (nominal).

In general the substance has no significant potential for bioconcentration. As explained in the chapter about 'partition coefficient' the substance is inorganic and not expected to be soluble in an organic medium therefore. Additionally its water solubility is very low.

Key value for chemical safety assessment

EC50 for freshwater algae:

100 mg/L

EC10 or NOEC for freshwater algae:

100 mg/L