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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:
no details given
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
comparable to guideline study with acceptable restrictions
Qualifier:
equivalent or similar to guideline
Guideline:
OECD Guideline 202 (Daphnia sp. Acute Immobilisation Test)
Deviations:
yes
Remarks:
Test duration = 72 h instead of 48 h as mandatory in the TGL OECD 202
Principles of method if other than guideline:
Test duration = 72 h instead of 48 h as mandatory in the TGL OECD 202
GLP compliance:
not specified
Remarks:
no information on GLP compliance available in this publication
Specific details on test material used for the study:
GO was prepared by oxidizing graphite powder via the modified Hummers' method and the subsequent sonication. The morphology and size of GO layers were characterized by employing an atomic force microscope with tapping mode. Composition analysis of GO was conducted by X-ray photoelectron spectroscopy (XPS). GO carbon element percentage was measured as 54.44% weight using an elemental analyzer.
Analytical monitoring:
yes
Vehicle:
no
Details on test solutions:
A 50 mL GO aqueous dispersion (1 mg/mL) was prepared by ultrasonic treatment (2h) in ultrapure water. Suspensions of lower concentrations were prepared by diluting the aqueous dispersion with aerated tap water.
In order to evaluate the interference of daphnia activities on GO dispersion, the sedimentation curves were measured for treatments with and without daphnia. All of the above measurements were conducted with triplicates, and the average values were calculated.
Test organisms (species):
Daphnia magna
Details on test organisms:
TEST ORGANISM
- Common name: Daphnia magna
- Source: Nankai University, China
- Age of parental stock (mean and range, SD): 5 days
- Feeding during test: no
- Food type: green algae Scenedesmus obliquus, daily

ACCLIMATION
- Acclimation period: 5h
- Acclimation conditions (same as test or not): clean tap water, 25 ± 2 °C with a natural light - dark cycle
Test type:
static
Water media type:
freshwater
Limit test:
no
Total exposure duration:
72 h
Post exposure observation period:
not applicable
Hardness:
no details given
Test temperature:
25 ± 2 °C
pH:
7.8
Dissolved oxygen:
no details given
Salinity:
no details given
Conductivity:
no details given
Nominal and measured concentrations:
0, 1, 5, 10, 20, and 50 mg/L nominal
Details on test conditions:
For each of the tested GO concentrations (i.e. 0, 1, 5, 10, 20, and 50 mg/L), 10 individuals of D. magna were placed in a 100 mL glass beaker containing 70 mL solution, and the tests were performed in triplicate. The test solution was not renewed and no additional food was added throughout the tests. All the cultures were maintained under the condition of 25 ± 2 °C with a natural light - dark cycle. The immobility and mortality of D. magna were recorded using a Leica microscope equipped with a digital camera (Leica, Germany) at 24, 48, and 72 h. Individuals unable to swim within 15 s under gentle agitation were regarded as immobile, while those without heartbeats were considered as dead. The concentrations of GO causing 50% immobility (EC50)/mortality (LC50) were calculated after 72 h of exposure.
Reference substance (positive control):
no
Key result
Duration:
72 h
Dose descriptor:
EC50
Effect conc.:
44.3 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
mobility
Duration:
72 h
Dose descriptor:
LC50
Effect conc.:
45.4 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
mortality
Details on results:
The immobility and mortality of D. magna progressively worsened as the doses (1 - 50 mg/L) and exposure time (up to 72 h) increased, displaying dose- and time-dependent patterns. There was no mortality and immobility found at concentrations <10 mg/L at 24 h, and severe acute toxicity only occurred at the highest GO concentration (50 mg/L) at the longest exposure time (72 h). The 72-h EC50 and LC50 values of GO were 44.3 mg/L and 45.4 mg/L, respectively, indicating a modest acute toxicity of GO in D. magna.
Results with reference substance (positive control):
not applicable
Reported statistics and error estimates:
Statistical analysis
All experiments were repeated three times, independently, and the average values were used along with standard deviation (SD). The 72 h EC50 (immobility) and LC50 (mortality) values were calculated via a probit method (US EPA Probit Analysis Program, Ver. 1.5). Oneway analysis of variance (ANOVA) with Tukey's multiple comparisons was performed to detect significant differences between groups using the SPSS software (Ver. 15.0). A 5% confidence level was considered as the least significant difference of means for all analyses.
Validity criteria fulfilled:
not applicable
Conclusions:
The 72h EC50 was determined as 44.3 mg/L for immobility and 45.4 mg/L for mortality.
Executive summary:

The acute toxicity of graphene oxide (GO) to Daphnia magna was determined in a 72-hour static test similar to the EU Commission Directive 92/69/EEC, Part C.2 (1992), and the OECD Guideline for Testing of Chemicals, No. 202, Part I (1984).This study is classified as reliable with restrictions (Klimisch 2) and satisfies the guideline requirements for an acute toxicity study with freshwater invertebrates.

The results revealed non severe acute toxicities, including immobility (72 h EC50: 44.3 mg/L) and mortality (72 h LC50: 45.4 mg/L), of GO on D. magna.

Description of key information

The acute toxicity of graphene oxide (GO) to Daphnia magna was determined in a 72-hour static test similar to the EU Commission Directive 92/69/EEC, Part C.2 (1992), and the OECD Guideline for Testing of Chemicals, No. 202, Part I (1984). This study is classified as reliable with restrictions (Klimisch 2) and satisfies the guideline requirements for an acute toxicity study with freshwater invertebrates.

The results revealed non severe acute toxicities, including immobility (72 h EC50: 44.3 mg/L) and mortality (72 h LC50: 45.4 mg/L), of GO on D. magna.

Key value for chemical safety assessment

Fresh water invertebrates

Fresh water invertebrates
Effect concentration:
44.3 mg/L

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