Synthetic amorphous magnesium silicate, with molar ratio (SiO2:MgO) range of 1.4-4

Toxicity to aquatic algae and cyanobacteria

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

toxicity to aquatic algae and cyanobacteria

Type of information:

read-across from supporting substance (structural analogue or surrogate)

Adequacy of study:

key study

Justification for type of information:

It is considered appropriate to address the data requirements for synthetic amorphous magnesium silicate by read-across to the available studies on structurally similar substances.
An algal toxicity study is available on sodium aluminium silicate, which due to sharing similar structural, physical and chemical properties to synthetic amorphous magnesium silicate, is considered appropriate for read-across purposes.

Reason / purpose for cross-reference:

read-across source

Specific details on test material used for the study:

Sodium aluminium silicate is being used as a read-across for synthetic amorphous magnesium silicate.

Duration:

72 h

Dose descriptor:

NOELR

Effect conc.:

10 000 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

other: biomass and growth rate

Remarks on result:

other: NOELR = No-observed effective loading rate

Remarks:

Data from Lebertz (1998) key study on sodium aluminium silicate

Duration:

72 h

Dose descriptor:

EL50

Effect conc.:

> 10 000 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

other: biomass and growth rate

Remarks on result:

other: Data from Lebertz (1998) key study on sodium aluminium silicate

Details on results:

Data from a key algal toxicity study on sodium aluminium silicate is used for read-across to synthetic amorphous magnesium silicate.

Conclusions:

The toxicity of the target substance, synthetic amorphous magnesium silicate, to the algae Desmodesmus subspicatus was estimated to show no acute and chronic toxic effects, based on read-across from a study testing sodium aluminium silicate.

Executive summary:

An algal toxicity study is available for sodium aluminium silicate, according to OECD Guideline 201 (Alga, growth inhibition test). Due to sharing similar structural, physical and chemical properties to synthetic amorphous magnesium silicate, sodium aluminium silicate is considered appropriate for read-across purposes.  

Under the test conditions, sodium aluminium silicate exhibited no acute and chronic toxic effects towards the algae Desmodesmus subspicatus, showing a 72 h EL50 of >10,000 mg/L and a 72 h NOELR of 10,000 mg/L. The toxicity of the target substance, synthetic amorphous magnesium silicate, to the algae D. subspicatus was estimated to show no acute and chronic toxic effects, based on read-across from a study testing sodium aluminium silicate.

Reference 2

Endpoint:

toxicity to aquatic algae and cyanobacteria

Type of information:

experimental study

Adequacy of study:

key study

Study period:

26 Oct. 1998 - 30 Oct. 1998

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Reason / purpose for cross-reference:

read-across source

Qualifier:

according to guideline

Guideline:

OECD Guideline 201 (Alga, Growth Inhibition Test)

Version / remarks:

version 07 June 1984

Deviations:

yes

Remarks:

The initial cell concentration was about 8x higher than recommended.

GLP compliance:

yes

Specific details on test material used for the study:

Details on properties of test surrogate or analogue material (migrated information):
PHYSICO-CHEMICAL PROPERTIES
- Melting point: ca. 1700 °C
- Boiling point: not relevant
- Vapour pressure: practically 0 Pa
- Water solubility (under test conditions): 48 mg/L (Sum of SiO2, Al, Na)
- Henry's law constant: not applicable
- log Pow: not applicable
- pKa: no data
- Stability in water: stable
- Stability in light: stable
- pH dependence on stability:


OTHER PROPERTIES (if relevant for this endpoint)
- Results of test for ready biodegradability: not applicable
- Other: --

Analytical monitoring:

no

Vehicle:

no

Details on test solutions:

PREPARATION AND APPLICATION OF TEST SOLUTION (especially for difficult test substances)
- Method: stirring the suspensions for 24 h in 0.5 l ultrapure water, followed by  filtration through paper filter.
- Eluate: Water extracts from 6250, 630, and 60 mg silicate/0.5 L, diluted to the target concentration
by additions of stock solutions needed for testing.
- Differential loading: yes
- Controls: without or with respective filtrates, but without algae
- Chemical name of vehicle (organic solvent, emulsifier or dispersant): none
- Evidence of undissolved material (e.g. precipitate, surface film, etc): not specified

Test organisms (species):

Desmodesmus subspicatus (previous name: Scenedesmus subspicatus)

Details on test organisms:

TEST ORGANISM
- Common name: green alga
- Strain: CHODAT
- Source (laboratory, culture collection): Pflanzenphysiol. Inst. University of Göttingen/Germany
- Age of inoculum (at test initiation): see below
- Method of cultivation: preculture 3 days prepared before test from a stock culture

Test type:

static

Water media type:

freshwater

Limit test:

yes

Total exposure duration:

72 h

Post exposure observation period:

none

Hardness:

not specified

Test temperature:

24.9 +-0.3°C

pH:

Initial pH: 8.00 (control); between 8.12 and 8.58 (tests)
final pH: 10.74 - 10.76

Dissolved oxygen:

--

Salinity:

not applicable

Nominal and measured concentrations:

96, 1008, and 10,000 mg/L nominal

Details on test conditions:

TEST SYSTEM
- Test vessel:
- Type: open
- Material, size, headspace, fill volume: 50 ml glass cylinders
- Aeration:
- Renewal rate of test solution (frequency/flow rate): none
- Initial cells density: approx. 8 x10^4/ml
- Control end cells density: 2.83 x10^6/ml
- No. of vessels per concentration (replicates): 5
- No. of vessels per control (replicates): 7 (algal growth control), 3 (TS controls without algae)


GROWTH MEDIUM
- Standard medium used: yes


TEST MEDIUM / WATER PARAMETERS
- Source/preparation of dilution water: synthetic medium from ultrapure water
- Total organic carbon: no data
- Alkalinity: not specified
- Ca/Mg ratio: not specified
- Conductivity: not specified



OTHER TEST CONDITIONS
- Sterile test conditions: yes
- Adjustment of pH: no
- Photoperiod: continuous
- Light intensity and quality: approx. 8000 lux [>= 120 µE/(m2*sec)]


EFFECT PARAMETERS MEASURED (with observation intervals if applicable) :
- Determination of cell concentrations: spectrophotometer at 578 nm after 24, 48, and 72 h

TEST CONCENTRATIONS
- Spacing factor for test concentrations: 10

Duration:

72 h

Dose descriptor:

NOELR

Effect conc.:

10 000 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

other: biomass and growth rate

Remarks on result:

other: NOELR = No-observed effective loading rate

Duration:

72 h

Dose descriptor:

EL50

Effect conc.:

> 10 000 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

other: biomass and growth rate

Details on results:

- Exponential growth in the control (for algal test): yes,
After 72 h, an increase in biomass (cell numbers) at a factor of >30 was achieved at any concentration.

- Observation of abnormalities (for algal test): no particular findings specified

- Any stimulation of growth found in any treatment: slight stimulation rather than inhibition observed

Results with reference substance (positive control):

not applicable

Reported statistics and error estimates:

not applicable

Validity criteria fulfilled:

yes

Conclusions:

Under the test conditions, the test substance exhibited no acute and chronic toxic effect towards the test system (Scenedesmus subspicatus CHODAT).

Description of key information

A structure-analogous silicate failed to produce any aquatic toxicity, EL50 >10,000 mg/L. Based on the high tolerance and ubiquitous natural occurrence of this substance class, the need for generation of data for this specific compound is waived in line with REACH Regulation 1907/2006, Annex IX, Section 9.1.

Key value for chemical safety assessment

EC50 for freshwater algae:

10 000 mg/L

EC10 or NOEC for freshwater algae:

10 000 mg/L

Additional information

No acute and chronic aquatic toxicity - including the marine environment - expected from exposure to magnesium silicate.