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Short-term toxicity to aquatic invertebrates

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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.
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.
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.

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.
Basis for effect:
mobility
Remarks on result:
other: 10/40 daphnia were immobile (25%) (test 1)
Key result
Duration:
24 h
Dose descriptor:
LOELR
Effect conc.:
1 000 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
mobility
Remarks on result:
other: 2/40 daphnia were immobile (5%) (test 1)
Key result
Duration:
24 h
Dose descriptor:
EL50
Effect conc.:
> 10 000 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat. (dissolved fraction)
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 on result:
other: 9/40 daphnia were immobile (22.5%) (test 2)
Key result
Duration:
24 h
Dose descriptor:
LOELR
Effect conc.:
1 000 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat. (dissolved fraction)
Basis for effect:
mobility
Remarks on result:
other: 4/40 animals immobile (10%) (test 2)
Key result
Duration:
24 h
Dose descriptor:
LOELR
Effect conc.:
1 000 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat. (dissolved fraction)
Remarks:
filtered through glass filter (1.7 and 1.2 micrometre)
Basis for effect:
mobility
Remarks:
One immobile animal (out of 25)(test 3)
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:
Aerosil 200 is not acutely toxic at a loading of >=1 000 mg/L.
Executive summary:

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.

Endpoint:
short-term toxicity to aquatic invertebrates
Type of information:
experimental study
Adequacy of study:
key study
Study period:
13 March 2000 to 15 June 2000
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:
24-hour exposure instead of 48-hours
Qualifier:
according to guideline
Guideline:
other: DIN 38412-11 (1982)
Version / remarks:
withdrawn
Deviations:
no
GLP compliance:
yes
Analytical monitoring:
no
Vehicle:
no
Details on test solutions:
PREPARATION AND APPLICATION OF TEST SOLUTION
- Method: 10, 100 and 1000 mg of test substance were added to 100 mL dilution water and stirred
for 24 hours at room temperature, followed by filtration through filter paper which had been rinsed thoroughly with ultrapure water;
- Differential loading: 10, 100, 1000 mg
Test organisms (species):
Daphnia magna
Details on test organisms:
TEST ORGANISM
- Common name: water flea
- Strain: Daphnia magna STRAUS
- Source: laboratory bred, derived from Dr. Knie, LWA Düsseldorf;
- Age at study initiation (mean and range, SD): not older than 24 hours
- Method of breeding: according to laboratory in-house SOP
- Feeding during test: no
Test type:
static
Water media type:
freshwater
Limit test:
no
Total exposure duration:
24 h
Post exposure observation period:
none
Test temperature:
20.0 to 20.8 °C
pH:
control: 7.35 (0h), 7.47 (48h)
10,000 mg loading: 8.21 (0h), 7.48 (48h)
1000 mg loading: 7.35 (0h), 7.38 (48h)
100 mg loading: 7.69 (0h), 7.45 (48h)
Dissolved oxygen:
[mg O2/L]
control: 8.5 (0h), 8.0 (48h)
10,000 mg loading: 8.6 (0h), 8.0 (48h)
1000 mg loading: not determined
100 mg loading: not determined
Salinity:
not applicable
Nominal and measured concentrations:
Nominal (loading rates): 100, 1000 and 10000 mg/L
Details on test conditions:
TEST SYSTEM
- Test vessel: not reported
- Type: not reported
- Material, size, headspace, fill volume: not reported
- Aeration: not reported
- Renewal rate of test solution (frequency/flow rate): not reported
- No. of organisms per vessel: 5
- No. of vessels per concentration (replicates): 4 (loading rate 10,000 mg/L), 2 (loading rates of 100 and 1000 mg/L)
- No. of vessels per pure control (replicates): 4
- No. of vessels per filtration control (replicates): not performed
- Biomass loading rate: not reported


TEST MEDIUM / WATER PARAMETERS
- Source/preparation of dilution water: water with mineral salts supplemented (synthetic medium) according to DIN 38412-11 (1982)

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. (dissolved fraction)
Basis for effect:
mobility
Key result
Duration:
24 h
Dose descriptor:
NOELR
Effect conc.:
> 10 000 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat. (dissolved fraction)
Basis for effect:
mobility
Details on results:
- Mortality/immobility of control: none [0/20 animals]
- Mortality/immobility of treated animals: 0/20 (loading rate 10000 mg/L), 0/10 (loading rates of 100 and 1000 mg/L)
Results with reference substance (positive control):
not applicable
Reported statistics and error estimates:
not applicable
Validity criteria fulfilled:
yes
Conclusions:
The dissolved fraction of Aerosil R 504 is not acutely toxic at a loading rate of >=10,000 mg/L.
Executive summary:

No immobilisation was found with the filtered water accomodated fraction (24 hrs, room temperature) at a loading rate of 10,000 mg/L.

Endpoint:
short-term toxicity to aquatic invertebrates
Type of information:
experimental study
Adequacy of study:
key study
Study period:
22 August 1991 to 16 September 1992
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
guideline study with acceptable restrictions
Remarks:
exposure for 24 hours (as recommended in the OECD and national guidelines at the time of testing)
Qualifier:
according to guideline
Guideline:
OECD Guideline 202 (Daphnia sp. Acute Immobilisation Test)
Deviations:
yes
Remarks:
Test duration 24 hours (in accordance with the guideline of 04 April 1984) instead of 48 hours (current guideline)
GLP compliance:
yes
Analytical monitoring:
no
Vehicle:
no
Details on test solutions:
PREPARATION AND APPLICATION OF TEST SOLUTION)
Two tests were carried out.
In the first test, 1.0 and 10.0 g of the test substance were weighed out and each portion was added to 1.0 litre of dilution water, giving test suspensions containing 1000 and 10000 mg/L. These suspensions were stirred for about 20 hours on a magnetic stirrer at 20 °C. The suspensions were added to the test vessels and then allowed to stand for 4 hours before adding the test animals.
For the second test, 15.0 g of the test substance was weighed out and added to 1.5 litre of dilution water, giving a test suspension containing 10000 mg/L. This suspension was also stirred for about 20 hours on a magnetic stirrer at 20 °C, but then filtered through a wad of perlon wool. The filtrate was used for the test.
Test organisms (species):
Daphnia magna
Details on test organisms:
TEST ORGANISM
- Source: laboratory culture
- Age at study initiation (mean and range, SD): <24 hours
- 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:
8.0 to 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 hours light, 8 hours 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.
Basis for effect:
mobility
Remarks on result:
other: no adverse effects (40 animals tested at the limit dose)
Key result
Duration:
24 h
Dose descriptor:
NOELR
Effect conc.:
> 10 000 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Remarks:
suspension and filtrate were tested
Basis for effect:
mobility
Remarks on result:
other: no adverse effects (40 animals tested at the limit dose)
Details on results:
Two tests were carried out: one with a suspension, and one with the filtrate (using a wad of perlon wool for filtration). The second test was carried out because the daphnids were not visible in the 10000 mg/L suspension due to the presence of undissolved test substance.
No adverse effects were observed in the two studies.



Results with reference substance (positive control):
not applicable
Reported statistics and error estimates:
not applicable
Validity criteria fulfilled:
yes
Conclusions:
Aerosil R 974 is not acutely toxic.
Executive summary:

No immobilisation was found at 10,000 mg/L (suspension and filtrate).

Endpoint:
short-term toxicity to aquatic invertebrates
Type of information:
experimental study
Adequacy of study:
key study
Study period:
21 December 1999 to 29 March 2000
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to guideline
Guideline:
OECD Guideline 202 (Daphnia sp. Acute Immobilisation Test)
Version / remarks:
1984
Deviations:
yes
Remarks:
modification to the standard method for the preparation of aqueous media and exposure of organisms to a filtered Water Accommodated Fraction (WAF)
Qualifier:
according to guideline
Guideline:
EU Method C.2 (Acute Toxicity for Daphnia)
Version / remarks:
1992
Deviations:
yes
Remarks:
modification to the standard method for the preparation of aqueous media and exposure of organisms to a filtered Water Accommodated Fraction (WAF)
GLP compliance:
yes (incl. QA statement)
Analytical monitoring:
no
Details on sampling:
There was no analytical monitoring of test item specific exposure concentrations. However, samples of the controls (R1 and R2, pooled) and the 1000 mg/L loading rate filtered WAF test groups (R1 and R2 pooled, and R3 and R4, pooled) were taken for dissolved organic carbon (DOC) and dissolved silica analyses at 0 and 48 hours.
- Sample storage conditions before analysis: frozen (approximately -20 °C)
Vehicle:
no
Details on test solutions:
PREPARATION AND APPLICATION OF TEST SOLUTION
- WAF: the test organisms were exposed to a filtered Water Accommodation Fraction (WAF) of the test material. Aqueous media were prepared by mixing the test item with water for a prolonged period. Preliminary work showed that a stirring period of 143 hours with a 1-hour settlement period was necessary to ensure saturation of the test media by any soluble components. An amount of test item (4.0 g) was added to the vortex created in 4 litres of culture medium to give the required 1000 mg/L loading rate. At the completion of mixing, the test material phase was separated by filtration through 0.2 µm filters and the test organisms exposed to the aqueous phase of filtered WAF which may contain dissolved test item and/or leachates from the test item. Exposures are expressed in terms of the original concentration of test item in water at the start of the mixing period (loading rate) irrespective of the actual concentration of test material in the filtered WAF. It was considered appropriate to filter the WAF as undissolved test item was distributed throughout the water column at the end of the stirring and settlement periods.
- Differential loading: 10, 100 and 1000 mg/L (range-finding test); 1000 mg/L (definitive test)
- Controls: yes , treated identically but without test item
Test organisms (species):
Daphnia magna
Details on test organisms:
TEST ORGANISM
- Common name: Water flea
- Source: 1st instar Daphnia magna derived from in-house laboratory cultures;
- Gravid adults were isolated 24 hours prior to the initiation of the test, the young daphnids produced overnight were then removed for testing;
- Food type: algae (Chlorella spp.)
- Frequency: daily
Test type:
static
Water media type:
freshwater
Limit test:
yes
Total exposure duration:
48 h
Hardness:
250 mg/L as CaCO3
Test temperature:
21 °C
pH:
7.6-7.8;
Dissolved oxygen:
8.2 mg O2/L at the beginning; 8.0-8.1 mg O2/L at termination of study
Salinity:
not applicable
Nominal and measured concentrations:
Water samples were taken from the control and 1000 mg/L loading rate filtered WAF test group (replicates R1, R2 and R3,R4 pooled) at 0 and 48 hours for Dissolved Organic Carbon analysis, analysis of silicon by AAS and for stability analysis by GC/MS.
Details on test conditions:
TEST SYSTEM
- Test vessel: 250 mL test and control vessels containing 200 mL of test media;
- Type. covered;
- Aeration: not during the test
- No. of organisms per vessel: 10
- No. of vessels per concentration (replicates): 4
- No. of vessels per control (replicates): 2
- Renewal of test solutions during exposure period: no

TEST WATER PARAMETERS
- Source/preparation of dilution water: reconstituted water, same as that used to maintain stock animals;
- Culture medium different from test medium: no

OTHER TEST CONDITIONS
- Adjustment of pH: no
- Photoperiod: 16 hours light and 8 hours darknness cycles with 20 minute dawn and dusk transition periods.

EFFECT PARAMETERS MEASURED: after 24 and 48 hours the number of immobilised Daphnia magna were recorded. Daphnia were considered to be immobilised if they were unable to swim for approximately 15 seconds after gentle agitation.

RANGE-FINDING STUDY
- 10 daphnids/vessel
- Test concentrations: 10, 100, 1000 mg/L
- Results used to determine the conditions for the definitive study: yes. Based on the results of the range-finding study a "Limit test" was conducted for the definitive study at a loading rate of 1000 mg/L to confirm that at the maximum test concentration given in the OECD/EEC Test Guidelines, no immobilisation or adverse reactions to exposure were observed.
Reference substance (positive control):
no
Key result
Duration:
48 h
Dose descriptor:
EL50
Effect conc.:
> 1 000 mg/L
Nominal / measured:
nominal
Conc. based on:
other: loading rate filtered water accommodated fraction
Basis for effect:
mobility
Key result
Duration:
48 h
Dose descriptor:
NOELR
Effect conc.:
1 000 mg/L
Nominal / measured:
nominal
Conc. based on:
other: loading rate filtered water accommodated fraction
Basis for effect:
mobility
Details on results:
After 143 hours stirring and 1 hour settlement the 1000 mg/L loading rate was observed to be an opaque white dispersion. After filtration and throughout the range-finding and the definitive studies the WAF was observed to be a clear, colourless solution. No significant changes in Dissolved Organic Carbon were observed between the measured concentrations at 0 and 48 hours. The GC/MS profiles showed no noticeable difference between 0 and 48 hours therefore indicating that the test item was stable over the study duration. In the range-finding study no immobilisation was observed at 10, 100 and 1000 mg/L loading rate filtered WAF.
Definitive study (1000 mg/L loading rate filtered WAF):
- Immobilisation of control Daphnia: 0/20
- Immobilisation of treated Daphnia: 0/40

Results with reference substance (positive control):
not applicable
Reported statistics and error estimates:
not applicable
Validity criteria fulfilled:
not specified
Conclusions:
The No Observed Effect Loading Rate (filtered WAF) was 1000 mg/L.
Executive summary:

A GLP study was performed in accordance with OECD and EC guidelines to assess the acute toxicity of the test item to Daphnia magna. Following a range-finding study, forty daphnids (4 replicates of 10 animals) were exposed to a filtered Water Accommodated Fraction (WAF) of the test item at a single nominal loading rate of 1000 mg/L for a period of 48 hours under static test conditions. Immobilisation and any adverse reactions to exposure were recorded after 24 and 48 horus. There were no mortalities or abnormalities in the behaviour observed and correspondingly the No Observed Effect Loading Rate (filtered WAF) was 1000 mg/L.

Description of key information

In GLP studies with hydrophilic and surface treated (hydrophobic) synthetic amorphous silica (SAS), all 24h- and 48h- EL50s (Daphnia magna) were at 1000 mg/L or higher (water accomodated fractions or colloidal dispersions); physical effects on daphnid mobility were only noted with hydrophilic SAS using unfiltered test medium at loading rates of 1000 mg/L or higher.

No mortality, immobilisation or abnormalities in the behaviour of Daphnia magna were observed in GLP studies with surface-treated SAS performed in accordance with OECD and EC guidelines and using the filtered water accommodated fractions. The No Observed Effect Loading Rates were 1,000 mg/L (48 hours, nominal) or higher (24 hours, nominal).

Key value for chemical safety assessment

Additional information

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