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Short-term toxicity to aquatic invertebrates

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Reference
Endpoint:
short-term toxicity to aquatic invertebrates
Type of information:
experimental study
Adequacy of study:
key study
Study period:
2016-03-24 to 2016-07-08
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:
13. Apr. 2004
Deviations:
yes
Remarks:
Variation of the temperature was greater than 2 °C (range 18.8 to 21.2 °C). As no immobility occurred during the test, this deviation was stated as uncritical. On request of the sponsor, no analytical determination of the test item was performed.
GLP compliance:
yes (incl. QA statement)
Specific details on test material used for the study:
Name: Silicon carbide (SiC)
Batch no.: SiC Lab sample
Appearance: grey granules/grains
Composition: 98 % SiC, 1 % sand, 1 % carbon
CAS No.: 409-21-2
ElNECS-No.: 206-991-8
Molecular formula: SiC
Molecular weight: 40.0965 g/mol
Purity: 98 %
Homogeneity: homogeneous
Solubility H20: <0.1g/L
Expiry date 31. Dezember 2017
Storage Room Temperature (20 ± 5°C); keep in dry condition
Analytical monitoring:
no
Vehicle:
no
Details on test solutions:
PREPARATION AND APPLICATION OF TEST SOLUTION (especially for difficult test substances)
- Method: The water-accommodated fractions (WAFs) were prepared for the test. This was done by weighing the nominal load 1 / 10 / 100 mg/L (real loads 1.0 / 10.2 and 100.7 mg/L) adding the corresponding amount of dilution water and shaking vigorously for 23 hours. The resulting solutions were filtrated through 0.45 pm nylon filters.
- Differential loading: nominal load 1 / 10 / 100 mg/L (real loads 1.0 / 10.2 and 100.7 mg/L)
- Controls:
Positive Control: Potassium dichromate K2Cr207 (CAS No. 7778-50-9) was used as positive control in a current reference study (15102901R201).
Negative control: Dilution water
- Chemical name of vehicle (organic solvent, emulsifier or dispersant): no vehicle used
- Concentration of vehicle in test medium (stock solution and final test solution(s) or suspension(s) including control(s)): n/a
- Evidence of undissolved material (e.g. precipitate, surface film, etc.): not reported
Test organisms (species):
Daphnia magna
Details on test organisms:
Species: Daphnia magna
Variety: STRAUS
Strain: Berlin
Sex: female
Age: between 0 and 24 hours
Origin: Umweltbundesamt Berlin; ln-house breeding since 27. September 2007
Selection of the test system was made following the proposal of the guidelines.

Animal Husbandry
Daphnia magna is bred in the LAUS GmbH throughout the year. The animals are kept for the use in toxicity tests. They multiply by parthenogenesis, thus being genetically identical. The husbandry is performed similar to the method described in EN ISO 6341, following SOP 115 002 01 (,,Zucht und Halterung von Daphnia magna STRAus“), Version 12 from 02. Feb. 2015.
Vessels: preserving glasses, nominal volume 2 L
Medium: M4-Medium (recipe of ELENDT)
Food: unicellular green algae (Desmodesmus subspicatus)
Medium: renewal twice a week
Photo period: 16/8 hours, using neon tubes
Temperature: 20 ± 2 °C
Test type:
static
Water media type:
freshwater
Limit test:
no
Total exposure duration:
48 h
Post exposure observation period:
no
Hardness:
2.502 mmol/L (i.e. 250 mg CaCO3/L)
Test temperature:
20 ± 2 °C
pH:
7.6 to 7.9
Dissolved oxygen:
8.3 to 8.8 mg/L
Nominal and measured concentrations:
1, 10 and 100 mg/L
Details on test conditions:
TEST SYSTEM
CONDUCT OF THE STUDY
Selection of Daphnia
24 hours before the start of the test, the adult animals were separated from the young. 0.5 hours before test start, the adults were caught with the help of a glass tube, and the new-born Daphnia, aged between 0 and 23 hours, were sieved from the medium and immediately placed into a 250 mL-beaker containing dilution water. After a settling-in period of 30 minutes, animals which showed no apparent damage were used for the test. Switching from M4-medium (husbandry) to Dilution water (test) has been shown not to cause any detrimental effects for test Daphnia.
Study Performance
Using a glass tube, the Daphnia were caught and lifted from the beaker. They were put on a small sieve, and the medium surrounding the animals was sucked off using absorbent paper. Immediately after that, the animals were put into the respective test solution. The test vessels were left to stand for 48 hours. After 24 and 48 hours, the immobilised Daphnia were counted. Daphnia are considered immobilised if they perform no movements or are only able to move their antennae when the beaker is gently agitated. Daphnia which are trapped at the surface of the test solution are also considered immobilised. The pH and the concentration of dissolved oxygen in the test vessels were measured at the beginning and at the end of the test.

Experimental Conditions
Date of performance: 05. — 07. April 2016
Treatments: 1 / 10/ 100 mg/L nominal concentration
Temperature: 18.8 — 21.2 °C
Duration: 48 hours
Observation times: 24 and 48 hours
Feeding: none
Lighting: diffuse lighting
Test vessels: glass beakers, nominal volume 50 mL, tall shape
Treatments: 4 vessels, each containing 20 mL test solution and 5 Daphnia
Blank control: 4 vessels, each containing 20 mL dilution water and 5 Daphnia
Reference substance (positive control):
yes
Key result
Duration:
48 h
Dose descriptor:
NOEC
Effect conc.:
100 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
mortality
Remarks on result:
other: no analytical confimation of actual concentration
Results with reference substance (positive control):
Potassium dichromate K2Cr207 (CAS No. 7778-50-9) was used as positive control in a current reference study (15102901R201). The 24h-EC50 value was determined as 1.6 mg/L, lying within the demanded range of 0.6 — 1.7 mg/L stated in the guidelines.
Reported statistics and error estimates:
As in no effect was observed in any concentration applied no statistical evaluation was conducted.

One valid experiment was performed:

 

Criteria of validity:

-       Immobilisation in the controls may not exceed 10 %.

-       Immobilisation in the controls was 0 %.

-       The concentration of dissolved oxygen at the end of the test must be at least 3 mg/L.

-       The lowest concentration of dissolved oxygen at the end of the test was 8.6 mg/L.

-       The pH-value in the test solutions should not vary by more than 1.5 units during the test.

-       The highest variation was 0.3 units.

20 Daphnia were exposed to the test item for 48 hours in a static test system. The concentrations showed no toxicity. None of the animals were immobilised in the blank control and in the treatments.

Validity criteria fulfilled:
yes
Conclusions:
In a 48-h acute toxicity test with Daphnia magna no toxic effect was observed up to a nominal concentration of 100 mg silicon carbide/L:
48h NOEC ≥ 100 mg/L (nominal)
48h LOEC > 100 mg/L (nominal)
On request of the sponsor, no analytical determination of the test item was performed.
Executive summary:

The 48-hr-acute toxicity of silicon carbide to Daphnia magna was studied under static conditions. Test specieswere exposed to control, and test chemical at nominal concentration of 1, 10 and 100 mg a.i./L for 48 hr.  Mortality/immobilisation were observed daily.  The 48-hour LC50/EC50is above 100 mg a.i./L.  The 48-hrNOELbased on mortality/immobilization equals or is above 100 mg a.i./L.  On request of the sponsor, no analytical determination of the test item was performed.

 

Based on the results of this study, silicon carbide would be classified as not toxic to Daphnia magna.  

This study is classified as acceptable and satisfies the guideline requirements for an acute toxicity study with freshwater invertebrates.

 

Results Synopsis

 

Test Organism Age (e.g. 1stinstar): < 24 h

Test Type (Flowthrough, Static, Static Renewal): Static

 

48h NOEC ≥ 100 mg/L

48h LOEC > 100 mg/L

 

Endpoint(s) Effected: mortality/immobility

Description of key information

In a 48-h acute toxicity test with Daphnia magna according to OECD guideline 202 no toxic effect was observed up to a nominal concentration of 100 mg silicon carbide/L:

48h NOEC ≥ 100 mg/L (nominal)

48h LOEC > 100 mg/L (nominal)

48h EC50 > 100 mg/L (nominal)

On request of the sponsor, no analytical determination of the test item was performed.

Key value for chemical safety assessment

Additional information