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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:
from 2009-04-14 to 2009-07-06
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Reason / purpose:
reference to other study
Qualifier:
according to
Guideline:
OECD Guideline 202 (Daphnia sp. Acute Immobilisation Test)
Deviations:
yes
Remarks:
see below
Qualifier:
according to
Guideline:
EU Method C.2 (Acute Toxicity for Daphnia)
Deviations:
yes
Remarks:
see below
Principles of method if other than guideline:
• The temperature for the main study lay in a range of 23.2 to 24.8 °C and therefore higher than stated in the guidelines. As no significant immobility in the control occurred during the test, this deviation was stated as uncritical.
• The temperature in the positive control lay in a range of 24.3 to 24.7 °C and therefore higher than stated in the guidelines. As no immobility occurred during the test, this deviation was stated as uncritical.
GLP compliance:
yes (incl. certificate)
Specific details on test material used for the study:
Details on properties of test surrogate or analogue material:
not indicated
Analytical monitoring:
yes
Details on sampling:
Standard solutions containing 10 and 100 mg/L of the test item in dilution water were measured twice each after 0, 24 and 48 hours. The recovery rates after 48 hours storage at room temperature was determined as 101.0 % and 96.4 %.
Vehicle:
no
Details on test solutions:
The solubility in dilution water was tested before the start of the test. As solubility surpasses 100 mg/L, a stock solution of an appropriate concentration in dilution water was prepared. The stock solution then was used to prepare solutions of the concentrations to be tested.
Test organisms (species):
Daphnia magna
Details on test organisms:
Specification
Species Daphnia magna
Variety STRAUS
Strain Berlin
Sex female
Age between 0 and 24 hours
Origin Umweltbundesamt Berlin
Arrival of Strain 27. Sep. 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 holding is performed similar to the method described in EN ISO 6341, following SOP 115 002 01 („Zucht und Hälterung von Daphnia magna STRAUS“), edition 9, adopted 27. Apr. 2007.
Vessels glass beakers, nominal volume 2 l
Medium M4-Medium (recipe of ELENDT), composition see annex
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 post exposure period.
Hardness:
250 mg CaCO3/L
Test temperature:
23.2-24.8 °C
pH:
6.9 - 7.7
Dissolved oxygen:
The concentration of dissolved oxygen stayed above 7.7 mg/L throughout the test.
Salinity:
freshwater was used.
Nominal and measured concentrations:
nominal: 0, 1, 2.2, 4.6, 10, 22, 46, 100 mg/L
measured (geometric mean): 0, 1.44, 2.7, 4.86, 9.61, 21.29, 43.53, 97.89 mg/L
Details on test conditions:
no further details.
Reference substance (positive control):
yes
Remarks:
K2Cr2O7
Key result
Duration:
48 h
Dose descriptor:
NOEC
Effect conc.:
1.44 mg/L
Nominal / measured:
meas. (geom. mean)
Conc. based on:
test mat.
Basis for effect:
mortality
Key result
Duration:
48 h
Dose descriptor:
EC50
Effect conc.:
4.7 mg/L
Nominal / measured:
meas. (geom. mean)
Conc. based on:
test mat.
Basis for effect:
mortality
Key result
Duration:
48 h
Dose descriptor:
EC100
Effect conc.:
21 mg/L
Nominal / measured:
meas. (geom. mean)
Conc. based on:
test mat.
Basis for effect:
mortality
Details on results:
In the control, 10% (2 daphnia) died. The others showed no signs of abnormal behaviour throughout the test.
Each concentration was measured threefold. The mean of the measured concentrations after 48 hours was in a range of 109 % and 138 % of the start concentration. The mean of the measured concentrations at the beginning was in a range of 83 % – 134 % and at the end 106 % - 155 % of the nominal concentration. Therefore, the determination of the bio-logical results was based on the mean of the measured concentrations.
All validity criteria were met. For the estimation of the EC50s of test item and positive control, the fits showed good statistical correspondence of the data with the dose-response-equation. The 24h-EC50i of potassium dichromate was determined as 1.6 mg/L, lying within the demanded range of 0.6 – 1.7 mg/L.
The analytical determinations of the test item showed medium correlation between nominal and measured concentrations and good recovery rates. Therefore, the test item sodium cyanate can be stated as stable under the test conditions. The measured concentrations at the end of the test were more than 100 % of the start concentration. This might be caused by evaporation of dilution water and therefore higher measured concentrations at the end of the test. As the measured concentrations were in a range of 83% and 155 % of the nominal concentrations, the determination of the results was based on the mean of the measured concentrations.
The result of the test is considered valid.
Results with reference substance (positive control):
All validity criteria were met. For the estimation of the EC50s of test item and positive con-trol, the fits showed good statistical correspondence of the data with the dose-response-equation. The 24h-EC50 of potassium dichromate was determined as 1.6 mg/L, lying within the demanded range of 0.6 – 1.7 mg/L.
The pH values in the test media and the control ranged from 7.5 to 7.6. The concentration of dissolved oxygen stayed above 8.2 mg/L throughout the test. Temperature range was 24.3 – 24.7 °C.
Reported statistics and error estimates:
The estimation of the EC50 was accomplished using the software OriginTM. The calculated values for p resp. χ2 are given in the graph.
The data were evaluated using sigmoidal fit on a linear-logarithmic scale.
If a sigmoidal fit is used, no confidence interval can be calculated. Since there were not enough values between 0 % and 100 % immobility at 48 hours, a linear fit with a probability-y-axis could not be performed.
Validity criteria fulfilled:
yes
Conclusions:
The following results were determined for the test item sodium cyanate (species: Daphnia magna).
48h-NOEC = 1.44 mg/L
48h-EC50 = 4.7 mg/L
Executive summary:

The 48 –hr-acute toxicity of sodium cyanate to Daphnia magna was studied under static conditions. Daphnids were exposed to control and test chemical at measured concentrations of 0, 1.44, 2.7, 4.86, 9.61, 21.29, 43.53, 97.89 mg/L for 48 hr. Mortality/immobilization and sublethal effects were observed daily Only 10 % of the animals were immobilised in the control.

The 24h-EC50 of potassium dichromate was tested in a current reference test. The value was determined as 1.6 mg/L, lying within the demanded range of 0.6 – 1.7 mg/L.

At the beginning and at the end of the test, the content of the test item in the test solutions was determined using a spectral photometer. The recovery after 48 hours ranged from 109 % to 138 % of the start concentration. The correlation between nominal and measured concentration ranged from 83 % to 155%. Therefore, the determination of the biological results was based on the geometric mean of the measured concentration.

The following results were determined for the test item sodium cyanate (species: Daphnia magna).

24h-NOEC = 1.44 mg/L

48h-NOEC = 1.44 mg/L

24h-EC50 = 16 mg/L

48h-EC50 = 4.7 mg/L

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

Results Synopsis

Test Organism Age: between 0 and 24 h

Test Type: Static

48h NOEC: 1.44.mg/L

48h EC50: 4.7mg/L

Description of key information

In an acute toxicity test to Daphnia an EC50 value of 4.7 mg/L was determined for sodium cyanate.

Key value for chemical safety assessment

EC50/LC50 for freshwater invertebrates:
4.7 mg/L

Additional information

Key study:

The 48 hr-acute toxicity of sodium cyanate to Daphnia magna (Muckle, 2009) was studied under static conditions. Daphnids were exposed to control and test chemical at measured concentrations of 0, 1.44, 2.7, 4.86, 9.61, 21.29, 43.53, 97.89 mg/L for 48 hr. Mortality/immobilization and sublethal effects were observed daily Only 10 % of the animals were immobilised in the control.

The 24 h-EC50 of potassium dichromate was tested in a current reference test. The value was determined as 1.6 mg/L, lying within the demanded range of 0.6 – 1.7 mg/L.

At the beginning and at the end of the test, the content of the test item in the test solutions was determined using a spectral photometer. The recovery after 48 hours ranged from 109 % to 138 % of the start concentration. The correlation between nominal and measured concentration ranged from 83 % to 155%. Therefore, the determination of the biological results was based on the geometric mean of the measured concentration.

The following results were determined for the test item sodium cyanate (species: Daphnia magna).

24 h-NOEC = 1.44 mg/L

48 h-NOEC = 1.44 mg/L

24 h-EC50 = 16 mg/L

48 h-EC50 = 4.7 mg/L

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