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

Short-term toxicity to aquatic invertebrates

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

short-term toxicity to aquatic invertebrates

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.
Short-term toxicity studies on Daphnia are available on silicon dioxide, 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

Reason / purpose for cross-reference:

read-across source

Reason / purpose for cross-reference:

read-across source

Specific details on test material used for the study:

Silicon dioxide is being used as a read-across for synthetic amorphous magnesium silicate.

Duration:

24 h

Dose descriptor:

EL50

Effect conc.:

> 1 000 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

mobility

Remarks:

1/40 animals were immobile

Remarks on result:

other: Data from Hooftman (1992a) key study on silicon dioxide

Key result

Duration:

24 h

Dose descriptor:

EL50

Effect conc.:

> 10 000 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

mobility

Remarks:

19/80 animals were immobile = 24% (average of the 2 tests)

Remarks on result:

other: Data from Hooftman (1992b) supporting study on silicon dioxide

Duration:

24 h

Dose descriptor:

EL50

Effect conc.:

> 10 000 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

mobility

Remarks:

1/40 animals were immobile = 2.5%

Remarks on result:

other: Data from Hooftmann (1992) supporting study on silicon dioxide

Details on results:

Key data from short-term Daphnia toxicity studies on silicon dioxide are used for read-across to synthetic amorphous magnesium silicate.

Conclusions:

The acute toxicity of the target substance, synthetic amorphous magnesium silicate, to Daphnia was estimated to be low (24 h EL50 = >10000 mg/L), based on read-across studies testing silicon dioxide.

Executive summary:

Acute toxicity studies on Daphnia magna are available for the read-across substance silicon dioxide. Due to sharing similar structural, physical and chemical properties to synthetic amorphous magnesium silicate, silicon dioxide is considered appropriate for read-across purposes.  

The acute toxicity of silicon dioxide toD. mangawas shown to be low in all three studies used for read-across. The acute toxicity of the target substance, synthetic amorphous magnesium silicate, to Daphnia was therefore estimated to be low (24 h EL50 = > 10000 mg/L), based on read-across studies testing silicon dioxide.

Reference 2

Endpoint:

short-term toxicity to aquatic invertebrates

Type of information:

experimental study

Adequacy of study:

supporting study

Study period:

12 Dec. 1991 - 13 Dec. 1991

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

guideline study with acceptable restrictions

Remarks:

24 h instead of 48 h study

Reason / purpose for cross-reference:

reference to other study

Reason / purpose for cross-reference:

read-across source

Qualifier:

according to guideline

Guideline:

OECD Guideline 202 (Daphnia sp. Acute Immobilisation Test)

Deviations:

yes

Remarks:

Test duration 24 h (acc. to the valid guideline of 04 April 1984) instead of 48 h (today) / In one test, the oxygen content was 4.2 mg/L after 24 h, i.e. less than 60 % of saturation (not assumed to have affected the outcome).

GLP compliance:

yes

Analytical monitoring:

no

Vehicle:

no

Details on test solutions:

PREPARATION AND APPLICATION OF TEST SOLUTION (especially for difficult test substances)
- Method: stirring for 20 h at 20 °C, and standing for 4 h before use
- Eluate: no, suspensions used after settling
- Differential loading: yes, limit tests with 1000 and 10,000 mg/L
-Evidence of undissolved material: The test media remained turbid throughout the test, and starchy particles
were observed on the bottom of the test vessels
Controls: Synthetic medium from groundwater

Test organisms (species):

Daphnia magna

Details on test organisms:

TEST ORGANISM
- Common name: see above
- Strain: --
- Source: laboratory culture
- Age at study initiation (mean and range, SD): <24 h
- Method of breeding: Standard conditions according to principles of NPR 6503 (Nederlandse practijkrichtlijn of 1980)
Every week, new cultures started with approx. 125 daphniae of the same age (1 day old), fed on Chlorella (about 4 x10^9 cells and about 0.13 g yeast per 4 L
- Feeding during test: no

Test type:

static

Water media type:

freshwater

Limit test:

yes

Total exposure duration:

24 h

Post exposure observation period:

none

Hardness:

204 mg/L as CaCO3

Test temperature:

20 +-1 °C

pH:

7.4 - 8.1

Dissolved oxygen:

4.2 - 8.4 mg/L

Salinity:

not applicable

Nominal and measured concentrations:

1000 and 10,000 mg SiO2/L (nominal, loading)

Details on test conditions:

TEST SYSTEM
- Test vessel: 150-mL beaker
- Type: open
- Material, size, headspace, fill volume: glass beaker, 50 mL headspace, 100 mL test volume
- Aeration: none
- Renewal rate of test solution (frequency/flow rate): none
- No. of organisms per vessel: 5
- No. of vessels per concentration (replicates): 8
- No. of vessels per pure control (replicates): 8 (with synthetic medium)
- Biomass loading rate: 5 animals/ 100 mL


TEST MEDIUM / WATER PARAMETERS
- Source/preparation of dilution water: groundwater with mineral salts supplemented (synthetic medium)
- Total organic carbon: 1.7 mg/L
- Alkalinity: no data
- Ca/Mg ratio: 1.83
- Conductivity: no data


OTHER TEST CONDITIONS
- Adjustment of pH: no
- Photoperiod: 16 h light, 8 h dark
- Light intensity: no data

Reference substance (positive control):

no

Duration:

24 h

Dose descriptor:

EL50

Effect conc.:

> 10 000 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

mobility

Remarks:

: 1/40 animals were immobile = 2.5 %

Details on results:

- Mortality/immobility of control: 0/40
- Other adverse effects control: none
- Abnormal responses: Immobilisation effects can be attributed to physical hampering of the daphnias.

- Detailed results (see also Table under "Remarks on results..." below):
3/40 (15 %) and 1/40 (2.5 %) of the daphniae were immobile/dead at a loading of 1000 and 10000 mg/L, respectively
(non-filtered suspension after settling).

Results with reference substance (positive control):

not applicable

Reported statistics and error estimates:

not applicable

Overview of results - Number of mobile animals at given loadings of Ultrasil VN 3

(from Report, Table C1)

Test
Time [h]	Loading [mg/L]
	0	1000^*)	10,000^*)
0	40	40	40
24	40	37	39

  ^*) Supernatant of the suspensions used after 4-h settling

Conclusions:

The observed effects were not dose related, and it is likely that they are caused by physical hampering of the test animals.

Reference 3

Endpoint:

short-term toxicity to aquatic invertebrates

Type of information:

experimental study

Adequacy of study:

supporting study

Study period:

29 Aug. 1991 - 30 Aug. 1991 / 04 Sep. 1991 - 05 Sep. 1991

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

guideline study with acceptable restrictions

Remarks:

24 h instead of 48 h study

Reason / purpose for cross-reference:

reference to same study

Reason / purpose for cross-reference:

reference to other study

Reason / purpose for cross-reference:

read-across source

Qualifier:

according to guideline

Guideline:

OECD Guideline 202 (Daphnia sp. Acute Immobilisation Test)

Deviations:

yes

Remarks:

Test duration 24 h (acc. to the valid guideline of 04 April 1984) instead of 48 h (today)

GLP compliance:

yes

Analytical monitoring:

no

Vehicle:

no

Details on test solutions:

PREPARATION AND APPLICATION OF TEST SOLUTION (especially for difficult test substances)
- Method: stirring for 20 h at 20 °C
- Eluate: no, suspensions used:
1st test non-filtered, settling of 4 h before use (Report, p. 10)
2nd test grossly filtered through a wad of perlon wool (still suspension).
- Differential loading: yes, limit tests with 1000 and 10,000 mg/L
- Controls: Synthetic medium from groundwater
- Evidence of undissolved material (e.g. precipitate, surface film, etc): suspended test material,
part of it accumulated at the surface, more pronounced in the suspension of 1000 mg/L than of 10,000 mg/L (Report, p. 13).

Test organisms (species):

Daphnia magna

Details on test organisms:

TEST ORGANISM
- Common name: see above
- Strain: --
- Source: laboratory culture
- Age at study initiation (mean and range, SD): <24 h
- Method of breeding: standard conditions according to principles of NPR 6503 (Nederlandse practijkrichtlijn of 1980)
- Feeding during test: no

Test type:

static

Water media type:

freshwater

Limit test:

yes

Total exposure duration:

24 h

Post exposure observation period:

none

Hardness:

204 mg/L as CaCO3

Test temperature:

20 +-1°C

pH:

Test 1: 7.2 - 8.1
Test 2: 7.3 - 8.2

Dissolved oxygen:

Test 1: 6.2 - 8.8 mg/L
Test 2: 6.6 - 8.6 mg/L

Salinity:

not applicable

Nominal and measured concentrations:

1st test: 1000 and 10,000 mg SiO2/L (nominal, loading, non-filtered)
2nd test: 1000 and 10,000 mg SiO2/L (nominal, loading, filtered through perlon wool)

Details on test conditions:

TEST SYSTEM
- Test vessel: 150-mL beaker
- Type: open
- Material, size, headspace, fill volume: glass, 50 mL headspace, 100 mL test volume
- Aeration: none
- No. of organisms per vessel: 5
- No. of vessels per concentration (replicates):16 (2 tests à 8 vessels)
- No. of vessels per pure control (replicates): 16 (2 tests à 8 with synthetic medium)
- Biomass loading rate: 5 animals / 100 mL


TEST MEDIUM / WATER PARAMETERS
- Source/preparation of dilution water: groundwater with mineral salts supplemented (synthetic medium)
- Total organic carbon: 1.5 mg/L
- Alkalinity: no data
- Ca/Mg ratio: 1.76
- Conductivity: no data


OTHER TEST CONDITIONS
- Adjustment of pH: no
- Photoperiod: 16 h light, 8 h dark
- Light intensity: no data

Reference substance (positive control):

no

Duration:

24 h

Dose descriptor:

EL50

Effect conc.:

> 10 000 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

mobility

Remarks:

: 19/80 animals were immobile = 24 % (average of the 2 tests)

Details on results:

- Mortality/Immobility of control: none 0/80 (Test 1 and 2)
- Abnormal responses: Based on these pre-tests with suspensions, it is suspected  that the immobility observed, 
particularly with the 10,000 mg/l suspensions, could be attributed to physical effects
(Report, Tables B1 - B4: First and second test).

- Detailed results (see also Table under "Remarks on results..." below)

Sample 1 (Test 1):
2/40 (5%)  and 10/40 (25%) of the daphnias were immobile at loadings of 1000  mg/l  and 10,000 mg/l, respectively, non-filtered.

Sample 2 (Test 2): 
4/40 (10%) and 9/40 (22.5%) of the daphnias were immobile (or dead in one case) at loadings of 1000 mg/l and 10,000 mg/l, respectively,
filtered through perlon wool.

Overall, in the presence of SiO2 suspensions of 1000 and 10,000 mg/L, 6/80 (7.5 %) and 19/80 (~24 %) of the animals were found immobile
after 24 h of exposure [Report, Table B1 - B4 (first + second test)].

Results with reference substance (positive control):

not applicable

Reported statistics and error estimates:

not applicable

Overview of the results - Number of mobile animals at given loadings of Aerosil 200

(from Report, Tables B1 and B3)

Test 1	Loading [mg/L]
Time [h]
	0	--	1000^*)	10,000^*)
0	40	--	40	40
24	40	--	38	30
Test 2	Loading [mg/L]
Time [h]
	0	0^**)	1000^**)	10,000^**)
0	40	40	40	40
24	40	40	36	31

^{*) non-filtered suspension}

^**)previously filtered through perlon wool

Validity criteria fulfilled:

yes

Reference 4

Endpoint:

short-term toxicity to aquatic invertebrates

Type of information:

experimental study

Adequacy of study:

key study

Study period:

26 Sep. 1991 - 27 Sep. 1991

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

guideline study with acceptable restrictions

Remarks:

24 h instead of 48 h study

Reason / purpose for cross-reference:

reference to same study

Reason / purpose for cross-reference:

reference to other study

Reason / purpose for cross-reference:

read-across source

Qualifier:

according to guideline

Guideline:

OECD Guideline 202 (Daphnia sp. Acute Immobilisation Test)

Deviations:

yes

Remarks:

Test duration 24 h (acc. to the valid guideline of 04 April 1984) instead of 48 h (today) / In one test, the oxygen content was 4.4 mg/L at time 0, i.e. less than 60 % of saturation (not assumed to have affected the outcome).

GLP compliance:

yes

Analytical monitoring:

no

Vehicle:

no

Details on test solutions:

PREPARATION AND APPLICATION OF TEST SOLUTION (especially for difficult test substances)
- Method: stirring for 20 h at 20 °C, followed by gross filtration (perlon wool) and microfiltration (1.7 µm and/or 1.2 µm)
- Eluate: no, filtrate
Filtration: through perlon wool, then through glass-fibre filter
A filtrate through 1.7 microfilter (still milky/cloudy)
B. filtrate through 1.7 and 1.2 µm microfilter (visibly clear)
- Differential loading: no, limit test with 1000 mg/L
- Controls: Synthetic medium from groundwater

Note: In two pre-tests, suspensions with 1000 and 10,000 mg/L SiO2 were used.
(see following entry: 02_Degussa AG 92-0139-DGO_pre-test, short-term toxicity to aquatic invertebrates)

Test organisms (species):

Daphnia magna

Details on test organisms:

TEST ORGANISM
- Common name: see above
- Strain: --
- Source: laboratory culture
- Age at study initiation (mean and range, SD): <24 h
- Method of breeding: standard conditions according to principles of NPR 6503 (Nederlandse practijkrichtlijn of 1980)
- Feeding during test: no

Test type:

static

Water media type:

freshwater

Limit test:

yes

Total exposure duration:

24 h

Post exposure observation period:

none

Hardness:

204 mg/L as CaCO3

Test temperature:

20 +-1°C

pH:

7.9 - 8.2

Dissolved oxygen:

4.4 - 8.3 mg/L

Salinity:

not applicable

Nominal and measured concentrations:

1000 mg/L SiO2 nominal

Details on test conditions:

TEST SYSTEM
- Test vessel: 150-ml beaker
- Type: open
- Material, size, headspace, fill volume: glass, 50 mL headspace, 100 mL test volume
- Aeration: none
- Renewal rate of test solution (frequency/flow rate): none
- No. of organisms per vessel: 5
- No. of vessels per concentration (replicates): 8
- No. of vessels per pure control (replicates): 8 (synthetic medium)
- No. of vessels per filtration control (replicates): 8 (test in synthetic medium passed through perlon filter)
- Biomass loading rate: 5 animals/100 mL


TEST MEDIUM / WATER PARAMETERS
- Source/preparation of dilution water: groundwater with mineral salts supplemented (synthetic medium)
- Total organic carbon: 1.5 mg/L
- Alkalinity: no data
- Ca/mg ratio: 1.76
- Conductivity: no data


OTHER TEST CONDITIONS
- Adjustment of pH: no
- Photoperiod: 16 h light, 8 h dark
- Light intensity: no data

Reference substance (positive control):

no

Duration:

24 h

Dose descriptor:

EL50

Effect conc.:

> 1 000 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

mobility

Remarks:

: 1/40 animals were immobile

Duration:

24 h

Dose descriptor:

EL0

Effect conc.:

1 000 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

mobility

Remarks:

: 1/40 animals were immobile

Details on results:

- Mortality/immobility of control: none [0/40 animals]
- Mortality/immobility of treated animals: 1/40
Overall, 1/40 animals treated with the WAFs was found immobile after 24 h of exposure (2.5 %) (Report, Table B5 and B6 [Third (main) test]:
This consisted of two parallel series using clear or slightly milky solutions of the water-soluble fractions (WSF):
0/15 immobile animals (0 %)  (assumed to relate to test medium microfiltrated 1.7 µm #)
1/25 immobile animals (4 %) (in the clear solution, assumed to relate to test medium microfiltrated 1.7 µm and 1.2 µm #)

- Abnormal responses: Based on pre-tests with suspensions, it is suspected  that the immobility observed, 
particularly with the 10,000 mg/l suspensions, could be attributed to physical effects.
(see following entry 02_Degussa 92-0139-DGO_pre-test.)
-----------------------------------

# Note: The wording under 3.5 (p. 14) says that "....there was one immobile animal (out of 25) in the clear solution prepared by filtration of the 1000 mg/L solution". This statement would correlate with the test medium microfiltrated at 1.7 and 1.2 µm, according to Report 3.4.3 (p. 14). However, the allocation of the results to the filtration conditions is inconsistent due to contradictory indexing in the Tables B5 and B6 of the Report (p.24/25).

Results with reference substance (positive control):

not applicable

Reported statistics and error estimates:

not applicable

Number of mobile animals at given loadings of Aerosil 200

(from Report, Table B5):

Test 3	Loading [mg/L]
Time [h]
	0	0^*)	1000^*)	1000^**)
0	40	40	25	15
24	40	40	24	15

^*) filtered through perlon wool, followed by microfiltration of 1.7- and 1.2-µm pore size

^**) filtered through perlon wool, followed by microfiltration of 1.7-µm pore size

Validity criteria fulfilled:

yes

Conclusions:

Aerosil 200 is not acutely toxic at a loading of >=1 000 mg/l.

Description of key information

No acute toxicity data on daphnia for magnesium silicate available, however, based on read-across from silicon dioxide it is expected to shows no acute toxicity with an EL50 >10,000 mg/L (effective loading).  

Key value for chemical safety assessment

Fresh water invertebrates

Fresh water invertebrates

Effect concentration:

10 000 mg/L

Additional information

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.

There was no adverse effect on daphniae in the presence of water-accommodated fractions ofstructure-analogous synthetic amorphous silica (SAS). Therefore, it is concluded that magnesium silicate will

also not be toxic to daphnia.

It is assumed that the freshwater results are also applicable to marine life, i.e. no acute aquatic toxicity expected from exposure to magnesium silicate.