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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:
The study was conducted between 20 July 2013 and 3 October 2013
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to
Guideline:
OECD Guideline 202 (Daphnia sp. Acute Immobilisation Test)
Deviations:
no
GLP compliance:
yes (incl. certificate)
Specific details on test material used for the study:

Description: Clear, colourless liquid
Batch: 20130510
Purity: N/A (complex mixture)
Expiry date: 10 May 2018
Storage conditions: Room temperature in the dark
Analytical monitoring:
yes
Details on sampling:
Water samples were taken from the control and the 32 and 100 mg/L loading rate WAF test group (replicates R1 - R4 pooled) at 0 (fresh media), 24 (old and fresh media) and 48 hours (old media) for quantitative analysis. 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:
Due to the low aqueous solubility and complex nature of the test item, for the purposes of the study the test medium was prepared as a Water Accomodated Fraction (WAF) of the test item.

The loading rate to be used in the initial experiment was determined by a preliminary range-finding test. In the range-finding test Daphnia magna were exposed to a series of nominal loading rates of 1.0, 10 and 100 mg/L.

No immobilization was observed at 1.0, 10 and 100 mg/L loading rate WAF. Based on this information, a single loading rate of four replicates of 100 mg/L was selected for the initial experiement.

During the initial experiments, some significant immobilization and trapping of the daphnids at the surface of the media was observed at 100 mg/L loading rate WAF. This was considered to be due to contamination. However, as a precautionary measure, loading rates of 1.0, 3.2, 10, 32 and 100 mg/L loading rate WAF were selected for the definitive test.
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 150mL glass beakers containing Elendt M7 medium in a temperature controlled room at approximately 20 ºC. 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. Daphnids were not less than 26 hours old as stated in the study plan, however this was not considered to have had an effect on the outcome or integrity of the study. these young were removed from the cultures and used for testing. The diet and diluent water are considered not to contain and contaminant that would affect the integrity or outcome of the study.
Test type:
semi-static
Water media type:
freshwater
Limit test:
no
Total exposure duration:
48 h
Post exposure observation period:
None
Hardness:
Not measured
Test temperature:
20 - 22ºC
pH:
7.6 - 7.8
Dissolved oxygen:
8.4 - 8.9 mg O2/L
Salinity:
Not measured
Conductivity:
Not measured
Nominal and measured concentrations:
Nominal rates of 32 and 100 mg/L loading rates
Reference substance (positive control):
yes
Remarks:
Potassium dichromate
Key result
Duration:
24 h
Dose descriptor:
EL50
Effect conc.:
> 100 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
mobility
Key result
Duration:
48 h
Dose descriptor:
EL50
Effect conc.:
> 100 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
mobility
Key result
Duration:
48 h
Dose descriptor:
LOELR
Effect conc.:
100 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
mobility
Details on results:
There was no immobilization in 20 daphnids exposed to concentrations of 32 and 100 mg/L loading rate WAF for a period of 48 hours.

Observations on Test Item Solubility:

Observations on the test media were carried out during the mixing and testing of the WAFs.

At the start of the mixing period the 32 and 100 mg/L loading rates were observed to be clear, colourless water columns with oily globules of test item floating on the surface. After 71 hours stirring and a 1 -hour standing period the 32 and 100 mg/L loading rates were observed to remain as at the start of stirring. Microscopic inspection of the WAFs showed no micro-dispersions or undissolved test item to be present. After siphoning and for the duration of the test, the loading rates were observed to be clear, colourless solutions.

Validity criteria fulfilled:
yes
Conclusions:
The acute toxicity of the test item to the freshwater invertebrate Daphnia magna has been investigated and gave a 48-hour EL50 value of > 100 mg/L loading rate WAF. The No Observed Effect Loading rate was 100 mg/L loading rate WAF.
Executive summary:

Introduction

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.

Methods

Due to the low aqueous solubility and complex nature of the test item, for the purposes of the test, the test medium was prepared as a Water Accommodated Fraction (WAF).

Following a preliminary range-finding test and initial experiments, twenty daphnids (4 replicates of 5 animals) were exposed to a WAF of the test item at nominal loading rates of 32 and 100 mg/L for 48 hours at a temperature of approximately 21 ºC under semi-static test conditions. The number of immobilized Daphnia and any adverse reactions to exposure were recorded after 24 and 48 hours.

Results

Chemical analysis of the 100 mg/L loading rate WAF at 0 and 24 hours (fresh media) showed that measured concentrations of 0.068 and 0.047 mg/L were obtained respectively, and at 24 and 48 hours (old media) showed that measured concentrations of 0.079 and 0.053 mg/L were obtained respectively.

Given that the toxicity cannot be attributed to a single component or a mixture of components, but to the test item as a whole, the results were based on nominal loading rates only.

Exposure of Daphnia magna to the test item gave EL50 values of greater than 100 mg/L loading rate WAF. The No Observed Effect Loading Rate was 100 mg/L loading rate WAF.

Description of key information

The acute toxicity of the test item to the freshwater invertebrate Daphnia magna has been investigated and gave a 48-hour EL50 value of > 100 mg/L loading rate WAF. The No Observed Effect Loading rate was 100 mg/L loading rate WAF.

Key value for chemical safety assessment

EC50/LC50 for freshwater invertebrates:
100 mg/L

Additional information