Silicon dioxide

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:

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

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 oxgen 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

Key result

Duration:

24 h

Dose descriptor:

EL50

Effect conc.:

> 10 000 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat. (total fraction)

Basis for effect:

mobility

Remarks:

: 1/40 animals were immobile = 2.5 %

Remarks on result:

other: suspension

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.

Executive summary:

A GLP study was performed in accordance with OECD 202 to assess the acute toxicity of the test item to Daphnia Magna. Test solutions were prepared by stirring an excess amount (1,000 and 10,000 mg/L nominal loading) for 20 h and then were allowed to stand for 4 h before testing. The resulting suspension was used for testing. 7.5% and 2.5% of the animals were immobile in the suspensions (without filtration) of 1,000 mg/L and 10,000 mg/L respectively. The immobile animals had some particles on their appendages and the condition of the mobile animals was equal to that of the controls. The observed effects on mobility were not does related and it is likely that they are caused by physical hampering of the test animals. The actual concentrations in the test solutions were not determined by chemical analysis.

Reference 2

Endpoint:

short-term toxicity to aquatic invertebrates

Type of information:

experimental study

Adequacy of study:

key study

Study period:

29 August 1991 to 28 September 1991

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

guideline study with acceptable restrictions

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 oxgen content was 4.4 mg/L at time 0, i.e. less than 60 % of saturation (not assumed to have affected the outcome).

Principles of method if other than guideline:

Three tests were carried out - the 1st with a suspension of the test item, the 2nd with the WAF filtered through a wad of perlon wool, and the 3rd with the WAF filtered through microfibre glass filters

GLP compliance:

yes

Analytical monitoring:

no

Vehicle:

no

Details on test solutions:

PREPARATION AND APPLICATION OF TEST SOLUTION
First test: 1.0 and 10.0 g of the test substance were accurately weighed out and each portion was added to 1.0 litre of dilution water, giving test suspensons containing 1000 and 10,000 mg/L.. These suspensions were stirred for about 20 hours on a magnetic stirrer at 20 °C. The test suspensions were allowed to stand for four hours after placing in the test vessels and before introducing the test animals.

2nd test: 1.5 and 15.0 g of Aerosil 200 were accurately weighed out and each portion was added to 1.5 litre of dilution water, giving test suspensions containing 1000 and 10,000 mg/L. These suspensions were stirred for about 20 hours on a magnetic stirrer at 20 °C and then filtered through a wad of perlon wool. The filtrates, which were only slightly less turbid than the original suspensions,were used as test suspensions.

3rd test: 1.0 and 10.0 g of Aerosil 200 were accurately weighed out and each portion was added to 1.0 litre of dilution water, giving test suspensons containing 1000 and 10,000 mg/L.. These suspensions were stirred for about 20 hours on a magnetic stirrer at 20 °C and then filtered through a wad of perlon wool; subsequently an attempt was made to filter the suspension obtained through micro-fibre glass filters; initially a 1.7 micrometre filter and then a 1.2 micrometer filter. The filters became completely blocked and only a limited volume of 1000 mg/L could be filtered. Therefore, a suspension of 10,000 mg/L (15,000 mg weighed out and suspended in 1.5 litre of dilution water) was centrifuged at 2000 rpm (=about 984 gmax). However, the test suspension became not clear and was therefore not tested.

Test organisms (species):

Daphnia magna

Details on test organisms:

TEST ORGANISM
- Common name: water flea
- 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 and 10,000 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

Key result

Duration:

24 h

Dose descriptor:

EL50

Effect conc.:

> 10 000 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat. (total fraction)

Basis for effect:

mobility

Remarks:

10/40 daphnia were immobile (25%) (test 1)

Remarks on result:

other: suspension

Key result

Duration:

24 h

Dose descriptor:

LOELR

Effect conc.:

1 000 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat. (total fraction)

Basis for effect:

mobility

Remarks:

2/40 daphnia were immobile (5%) (test 1)

Remarks on result:

other: suspension

Key result

Duration:

24 h

Dose descriptor:

EL50

Effect conc.:

> 10 000 mg/L

Nominal / measured:

nominal

Conc. based on:

other: initial loading rate

Remarks:

filtered through perlon wool; precipitation observed on the bottom of the test vessel at the end of the exposure period

Basis for effect:

mobility

Remarks:

9/40 daphnia were immobile (22.5%) (test 2)

Remarks on result:

not determinable because of methodological limitations

Remarks:

filtered suspension

Key result

Duration:

24 h

Dose descriptor:

LOELR

Effect conc.:

1 000 mg/L

Nominal / measured:

nominal

Conc. based on:

other: initial loading rate

Remarks:

filtered through perlon wool; precipitation observed on the bottom of the test vessel at the end of the exposure period

Basis for effect:

mobility

Remarks:

4/40 animals immobile (10%) (test 2)

Remarks on result:

not determinable because of methodological limitations

Remarks:

filtered suspension

Key result

Duration:

24 h

Dose descriptor:

LOELR

Effect conc.:

1 000 mg/L

Nominal / measured:

nominal

Conc. based on:

other: initial loading rate

Remarks:

filtered through glass filter (1.7 and 1.2 micrometre)

Basis for effect:

mobility

Remarks:

One immobile animal (out of 25)(test 3)

Remarks on result:

not determinable because of methodological limitations

Remarks:

filtered suspension

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

Validity criteria fulfilled:

yes

Conclusions:

The filtered suspension of substance is not acutely toxic at a loading of >=1 000 mg/L.

Executive summary:

A GLP study was performed in accordance with OECD 202 to assess the acute toxicity of the test item to Daphnia Magna. Three tests were conducted by using the test item either in a suspension or in a filtered suspension. Test solutions were prepared by stirring an excess amount (1000 and 10,000 mg/L nominal loading) for 20 h and the resulting suspension was tested. In the first test, 5% and 25% of the animals were immobile in the suspensions (without filtration) of 1,000 mg/L and 10,000 mg/L respectively. In the second test there were 10 % and 22.5 % dead or immobile animals at these concentrations (after filtration through a wad of perlon wool). The filtrates, which were only slightly less turbid than the original suspensions, were used as test suspensions for the second test. When treated with a water accomodated fraction (WAF, microfiltrated through 1.7 µm and 1.2 µm filters) one out of 40 daphnids (2.5%) was found immobile after 24 h of exposure to 1000 mg/L.

Reference 3

Endpoint:

short-term toxicity to aquatic invertebrates

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

guideline study without detailed documentation

Qualifier:

equivalent or similar to guideline

Guideline:

OECD Guideline 202 (Daphnia sp. Acute Immobilisation Test)

GLP compliance:

no

Analytical monitoring:

no

Vehicle:

no

Details on test solutions:

no details reported

Test organisms (species):

Daphnia magna

Test type:

static

Water media type:

freshwater

Total exposure duration:

48 h

pH:

Values for two replicate test chambers:
0 mg/L: 7.3, 7.3 (t0), 7.5. 7.5 (t48h)
0.5 mg/L: 7.3, 7.3 (t0), 7.5, 7.5 (t48h)
1.0 mg/L: 7.3, 7.3 (t0), 7.5, 7.5 (t48h)
50 mg/L: 7.4, 7.4 (t0), 7.5, 7.5 (t48h)
500 mg/L: 7.6, 7.6 (t0), 7.6, 7.6 (t48h)
5000 mg/L: 8.8, 8.8 (t0), 8.4, 8.4 (t48h)

Dissolved oxygen:

Values [mg/L] for two replicate test chambers:
0 mg/L: 8.7, 8.7 (t0), 8.5. 8.5 (t48h)
0.5 mg/L: 8.7, 8.7 (t0), 8.5, 8.5 (t48h)
1.0 mg/L: 8.7, 8.7 (t0), 8.6, 8.5 (t48h)
50 mg/L: 8.7, 8.7 (t0), 8.5, 8.5 (t48h)
500 mg/L: 8.7, 8.7 (t0), 8.5, 8.5 (t48h)
5000 mg/L: 8.7, 8.7 (t0), 8.5, 8.5 (t48h)

Key result

Duration:

48 h

Dose descriptor:

EC50

Effect conc.:

> 5 000 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

mobility

Key result

Duration:

48 h

Dose descriptor:

NOEC

Effect conc.:

5 000 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

mobility

Details on results:

Based on visual observations, the water control solution and the 0.5, 1.0, 50, 500 and 5000 mg/L test solutions were clear with no color throughout the test. Immobilities were 0, 0, 0, 0, 0 and 0% in the 0, 05, 1.0, 50, 500 and 5000 mg/L test concentrations, respectively.

Validity criteria fulfilled:

not applicable

Conclusions:

Collodidal silica (40% SiO2 in water) exhibited no toxicity in a 48-hour, unaerated, static acute test using Daphnia magna at the highest tested concentration (5000 mg/L).

Executive summary:

A range-finding study was conducted to provide an estimate of aquatic toxicity using fixed test concentraitons. Based on visual observations, the water control solution and the 0.5, 1.0, 50, 500 and 5000 mg/L test solutions were clear with no color throughout the test. Immobilities were 0, 0, 0, 0, 0 and 0% in the 0, 05, 1.0, 50, 500 and 5000 mg/L test concentrations, respectively.

Description of key information

For the assessment of the aquatic toxicity of synthetic amorphous silica (SAS) to aquatic invertebrates, the database compiles 3 studies from 1992 and 1998. All these studies were conducted according to OECD TG 202 under GLP. All 24h- and 48h- EL50s (Daphnia magna) were higher than 5,000 mg/L (suspensions or colloidal dispersions); physical effects on daphnid mobility were only noted with unfiltered test medium at loading rates of 1000 mg/L or higher. The No Observed Effect Concentration determined with colloidal dispersions was 5,000 mg/L (48 hours, nominal).

Additional information

Physical effects impairing mobility or survival of the daphnids were observed in tests using unfiltered test medium containing 1000 and 10,000 mg/L. There was no significant mortality/immobilisation when a filtered extract from 1000 mg/L was used.