Single Wall Carbon Nanotubes (SWCNT)

Short-term toxicity to aquatic invertebrates

Link to relevant study record(s)

Reference

Endpoint:

short-term toxicity to aquatic invertebrates

Type of information:

experimental study

Adequacy of study:

key study

Study period:

27 June 2016 - 22 July 2016

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:

OECD Guidelines for Testing of Chemicals (April 2004) No 202, "Daphnia sp., Acute Immobilisation Test" referenced as Method C.2 of Commission Regulation (EC) No. 440/2008.

Deviations:

no

GLP compliance:

yes

Analytical monitoring:

yes

Details on sampling:

Samples of the control and each test concentration from the range finding and definitive tests were taken for analysis at 0 (fresh media) and 48 hours (old media).
All samples were stored frozen prior to analysis.
Duplicate samples were taken and stored frozen for further analysis if necessary.

Vehicle:

no

Details on test solutions:

Saturated solution at an initial loading rate of 10 mg/L.
A nominal amount of test item (110 mg) was dispersed in 11 liters of test water with the aid of propeller stirring at approximately 1500 rpm for 24 hours. After 24 hours the stirring was stopped and any undissolved test item was removed by filtration through a 0.2 μm Sartorius Sartopore filter (first approximate 1 liter discarded in order to pre-condition the filter). The filtered solution was then centrifuged at 40000 g to give a 100% v/v saturated solution. A series of dilutions was made from this saturated solution to give further test concentrations of 10, 18, 32 and 56% v/v saturated solution.

Test organisms (species):

Daphnia magna

Details on test organisms:

The test was carried out using 1st instar Daphnia magna derived from in-house laboratory cultures.
Adult daphnia were maintained in 150 mL glass beakers containing Elendt M7 medium (see Annex 2) in a temperature controlled room maintaining the water temperature at 18 to 22 °C. The lighting cycle was controlled to give a 16 hours light and 8 hours darkness cycle with 20 minute dawn and dusk transition periods. Each culture was fed daily with a mixture of algal suspension (Desmodesmus subspicatus) and Tetramin® flake food suspension. Culture conditions ensured that reproduction was by parthenogenesis. Gravid adults were isolated the day before initiation of the test, such that the young daphnids produced overnight were less than 24 hours old. These young were removed from the cultures and used for testing. The diet and diluent water are considered not to contain any contaminant that would affect the integrity or outcome of the study.

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

48 h

Hardness:

approximate theoretical total hardness of 250 mg/L as CaCO3

Test temperature:

20 - 22 °C

pH:

7.6 - 8

Dissolved oxygen:

8.1 - 9 mg mg O2/L

Nominal and measured concentrations:

Based on the results of a range-finding test the following test nominal concentrations were assigned to the definitive test: 10, 18, 32, 56 and 100% v/v saturated solution.
All these concentrations were not measured because under the LOQ of the instrument (determined to be around 1 mg/L).

Details on test conditions:

150 mL glass jars containing approximately 100 mL of test preparation were used. At the start of the test 5 daphnids were placed in each test and control vessel at random, in the test preparations. Four replicate test and control vessels were prepared. The test vessels were then covered to reduce evaporation and maintained in a temperature controlled room maintaining the water temperature at 18 to 22 °C with a maximum deviation of ±1 °C with a photoperiod of 16 hours light (between 200 and 1200 Lux) and 8 hours darkness with 20 minute dawn and dusk transition periods. The daphnids were not individually identified, received no food during exposure and the test vessels were not aerated.
The control group was maintained under identical conditions but not exposed to the test item.
The test preparations were not renewed during the exposure period.
Any immobilization or adverse reactions to exposure were recorded at 24 and 48 hours after the start of exposure. The criterion of effect used was that daphnia were considered to be immobilized if they were unable to swim within 15 seconds after gentle agitation.

Reference substance (positive control):

yes

Remarks:

Potassium dichromate

Key result

Duration:

48 h

Dose descriptor:

EC50

Effect conc.:

> 100 other: % v/v saturation

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

mobility

Details on results:

Total Organic Carbon analysis of the test preparations at 0 and 48 hours showed measured test concentrations of less than the limit of quantification (LOQ) of the analytical method employed were obtained which was determined to be 1.0 mg/L. This does not infer that no test item was in solution, just that any dissolved test item was at a concentration of less than the LOQ.
Exposure of Daphnia magna to the test item gave EC50 values based on nominal test concentrations of greater than 100% v/v saturated solution. The No Observed Effect Concentration was 100% v/v saturated solution.

Results with reference substance (positive control):

A positive control used potassium dichromate as the reference item at concentrations of 0.32, 0.56, 1.0, 1.8 and 3.2 mg/L.
Exposure conditions for the positive control were similar to those of test item.
EC 50 after 48 hours was found to be 0.83. The results from the positive control with potassium dichromate were within the normal range for this reference item.
Positive control substance showed clear toxic effects.

Validity criteria fulfilled:

yes

Remarks:

The test was considered to be valid because none of the control daphnids showed immobilization or other signs of disease or stress and that the oxygen concentration at the end of the test was not less than 3 mg/L in the control and test vessels.

Conclusions:

This study showed that there were no toxic effects at saturation. EC50 is greater than 100% v/v saturation. Analytical measurement of this concentration was not possible necause under the LOQ (1 mg/L ca.).

Executive summary:

A study was performed to assess the acute toxicity of the test item to Daphnia magna. The method followed was designed to be compatible with the OECD Guidelines for Testing of Chemicals (April 2004) No 202, "Daphnia sp., Acute Immobilisation Test" referenced as Method C.2 of Commission Regulation (EC) No. 440/2008.

Due to the pure and poorly water soluble nature of the test item, the test media was prepared as a saturated solution at an initial loading rate of 10 mg/L. Following a preliminary range-finding test, twenty daphnids (4 replicates of 5 animals) were exposed to an aqueous solution of the test item at nominal concentrations of 10, 18, 32, 56 and 100% v/v saturated solution for 48 hours at a temperature of 20 to 22 °C under static test conditions. The test item solutions were prepared by stirring an excess (10 mg/L) of test item in test water using a propeller stirrer at approximately 1500 rpm for 24 hours. After the stirring period any undissolved test item was removed by filtration (0.2 μm Sartorius Sartopore filter, first approximate 1 liter discarded in order to pre-condition the filter). The filtered solution was then centrifuged at 40000 g for 30 minutes to produce a 100% v/v saturated solution of the test item. This saturated solution was then further diluted as necessary, to provide the remaining test concentrations. Immobilization and any adverse reactions to exposure were recorded after 24 and 48 hours.

Total Organic Carbon analysis of the test preparations at 0 and 48 hours showed measured test concentrations of less than the limit of quantification (LOQ) of the analytical method employed were obtained which was determined to be 1.0 mg/L. This does not infer that no test item was in solution, just that any dissolved test item was at a concentration of less than the LOQ. Exposure of Daphnia magna to the test item gave EC50 values based on nominal test concentrations of greater than 100% v/v saturated solution. The No Observed Effect Concentration was 100% v/v saturated solution. This study showed that there were no toxic effects at saturation.

Description of key information

Exposure of Daphnia magna to the test item, in a study according to OECD TG 202, gave EC50 values based on nominal test concentrations of greater than 100% v/v saturated solution. The No Observed Effect Concentration was 100% v/v saturated solution.

The study showed that there were no toxic effects at saturation.

Additional information

The concentration of substance in the 100% v/v saturated solution was not possible because it was under the LOQ (1 mg/L ca.).