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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:
01-08 June 2012
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Remarks:
Well conducted and well described study in accordance with GLP and OECD Guideline 201 without any major deviation
Reason / purpose:
reference to same study
Reason / purpose:
reference to other study
Qualifier:
according to
Guideline:
OECD Guideline 202 (Daphnia sp. Acute Immobilisation Test)
Deviations:
no
Principles of method if other than guideline:
Not applicable
GLP compliance:
yes (incl. certificate)
Analytical monitoring:
yes
Details on sampling:
- Concentrations: Samples for analysis were taken from the control, the highest and lowest test concentrations.
- Sampling method: Samples were taken at the start (t = 0 h) and the end of the test (t = 48 h). Approximately 1 mL were taken for each sample and analysed by UHPLC-MS/MS.
- Sample storage conditions before analysis: Samples were stored in a freezer until analysis or analysed directly after sampling.
Vehicle:
yes
Details on test solutions:
PREPARATION AND APPLICATION OF TEST SOLUTION (especially for difficult test substances)
- Method: A weighed amount of the test item (100.1 mg) was carefully added to 1 L of test water in a sealed glass vessel of 1 L capacity containing a magnetic stirring bar. The mixing was performed during 24 h in the dark. Following mixing the contents of the vessel was allowed to stand undisturbed for 1 h. Then, the stock solution was diluted with test water to obtain the required test concentrations and filled into the test tubes. Each prepared concentration was inverted several times before filling of test tubes to ensure adequate mixing and homogeneity. The final test solutions were all clear and colourless, and remained unchanged during the 48 h of incubation.
- Controls: Test water without test substance but treated in the same way as the test substance solutions
Test organisms (species):
Daphnia magna
Details on test organisms:
TEST ORGANISM
- Common name: Water Flea (Daphnia)
- Strain: Daphnia magna (Straus), clone 5
- Source: In-house laboratory cultures
- Age at study initiation: < 24 h
- Method of breeding: Parthenogenesis
- Feeding during test: No

ACCLIMATION
- Acclimation period: 48 h
- Acclimation conditions (same as test or not): Same as test
- Type and amount of food: Suspension of freshwater algae (mix of 3 algae strains)
- Feeding frequency: Daily
- Health during acclimation (any mortality observed): Daphnids originated from a healthy stock, showing no signs of stress such as mortality, presence of males, ephippia or discoloured animals.
Test type:
static
Water media type:
freshwater
Limit test:
no
Total exposure duration:
48 h
Post exposure observation period:
No
Hardness:
250 mg/L as CaCO3
Test temperature:
19.5-20.0 °C
pH:
7.11-7.82
Dissolved oxygen:
7.28-8.50 mg O2/L
Salinity:
Not applicable
Nominal and measured concentrations:
- Nominal concentrations: 10, 14.6, 21.4, 31.5, 46.3, 68 and 100 mg/L
Details on test conditions:
TEST SYSTEM
- Test vessel: Glass test tubes (approximately 20 mL)
- Aeration: No
- No. of organisms per vessel: Five
- No. of vessels per concentration (replicates): Four
- No. of vessels per blank control (replicates): Four

TEST MEDIUM / WATER PARAMETERS
- Source/preparation of dilution water: Reconstituted water, as prescribed by the OECD Guideline 202
- Conductivity: < 10 µS/cm
- Culture medium different from test medium: No
- Intervals of water quality measurement: Water temperature was recorded continuously throughout the test. Dissolved oxygen concentrations and pH were recorded at the beginning and at the end of the test, for the highest concentration and the control.

OTHER TEST CONDITIONS
- Photoperiod: 16 h light: 8 h dark

EFFECT PARAMETERS MEASURED (with observation intervals if applicable): Immobility and abnormal behaviour were determined by visual observation after 24 and 48 h. The daphnids were considered to be immobile if they were not able to swim within 15 seconds after gentle agitation of the test vessels.

TEST CONCENTRATIONS
- Spacing factor for test concentrations: 1.47
- Range finding study
- Test concentrations: 0.10, 1.0, 10 and 100 mg/L (nominal)
- Results used to determine the conditions for the definitive study: In the range-finding test, immobilisations after 24 h of exposure were 0, 0, 0, 0 and 100 % at 0, 0.10, 1.0, 10 and 100 mg/L (nominal), respectively. The chemical analyses revealed that test item concentrations were not stable during the test period. Based on these results, test concentrations of 10, 14.6, 21.4, 31.5, 46.3, 68 and 100 mg/L (nominal) were selected for the main test.
Reference substance (positive control):
yes
Remarks:
potassium dichromate (non-concurrent)
Key result
Duration:
48 h
Dose descriptor:
EC50
Effect conc.:
32.4 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
other: mobility and behaviour
Remarks on result:
other: 95 % CL = 21.4-46.3
Details on results:
- Mortality of control: No
- After 24 and 48 h of exposure, immobilizations were 0, 0, 0, 0, 35, 100, 100 and 100 % at 0, 10, 14.6, 21.4, 31.5, 46.3, 68 and 100 mg/L, respectively.
- EC50 value at 24 and 48 h was 32.4 (21.4-46.3) mg/L.
Results with reference substance (positive control):
- Results with reference substance valid: Yes
- Historical data (dated: February 2012): EC50 (24 h): 1.14 mg/L
Reported statistics and error estimates:
- Effective concentrations were determined using the software ToxRat® Professional.

None

Validity criteria fulfilled:
yes
Remarks:
mortality in control < 10 % (no immobilisation observed); dissolved oxygen concentration at the end of test was ≥ 7.28 mg/L in control and test vessels
Conclusions:
The 48 h EC50 for Nerol to Daphnia magna was estimated to be 32.4 (21.4-46.3) mg/L (nominal).
Executive summary:

An acute aquatic toxicity study was performed on Daphnia magna in accordance with GLP and OECD Guideline 202. Following a preliminary range-finding test, twenty daphnids (four replicates, five daphnids/replicate) were exposed to an aqueous solution of nerol, at the required nominal test concentrations of 10, 14.6, 21.4, 31.5, 46.3, 68 and 100 mg/L. The immobility of the daphnids was determined in a static 48-h test by visual observation after 24 and 48 h.

The concentrations of the test item were determined by chemical analyses at start and at the 48-h incubation period. The test item levels were found to be relatively stable throughout the test and the evaluation of the effects on daphnids was based on the nominal concentrations.

After 24 and 48 h of exposure, immobilizations were 0, 0, 0, 0, 35, 100, 100 and 100 % at 0, 10, 14.6, 21.4, 31.5, 46.3, 68 and 100 mg/L, respectively. The EC50 value at 24 and 48 h was 32.4 (21.4-46.3) mg/L.

Therefore, the 48 h EC50 for Nerol to Daphnia magna was estimated to be 32.4 (21.4-46.3) mg/L (nominal).

Description of key information

The substance exhibits a LC50 for freshwater invertebrates of 32.4 mg/L.

Key value for chemical safety assessment

EC50/LC50 for freshwater invertebrates:
32.4 mg/L

Additional information

One reliable study is available for the registered substance. The toxicity to freshwater invertebrates was studied according to OECD TG No. 202 and GLP. Daphnids (Daphnia magna) were exposed to substance at nominal test concentrations of 10, 14.6, 21.4, 31.5, 46.3, 68 and 100 mg/L over a test period of 48 hours (static test). Concentrations were analytically verified at the start and at the end of the test. Measured concentrations did not deviate from 20% of the initial concentrations. Thus the endpoints were based on nominal concentration.

The 48h-EC50 was determined to 32.4 mg/L, the EC0 and EC100 to 21.4 mg/l and 46.3 mg/L, respectively.