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Short-term toxicity to aquatic invertebrates

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Endpoint:
short-term toxicity to aquatic invertebrates
Type of information:
experimental study
Adequacy of study:
key study
Study period:
Exp. part: Feb 27 – Oct 25, 2018
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)
Analytical monitoring:
yes
Details on sampling:
The samples were taken from the biological phase of the study. Collecting, storage and handing over of the samples were the Study Director’s responsibility. The information concerning the samples was provided by the Study Director.
One sample of the filtrate of the stock solution and duplicate samples from the freshly prepared test media of all test concentrations and the control were taken at the start of the test and at day 1.
For the determination of the stability of the test item under the test conditions and of the maintenance of the test item concentrations during the test period, duplicate samples from the aged test media of all test concentrations and the control were collected at day 1 (after 24 hours of exposure) and at the end of the test by pouring together the contents of the test beakers of each treatment.
All samples were diluted by a factor of two with acetonitrile.
Additional samples of the control and the dilution solvent were taken at each sampling without any sample treatment.
Vehicle:
no
Details on test solutions:
The test item is not well soluble in test medium. To avoid physical effects of undissolved test item on the daphnids, no concentrations above the solubility limit of the test item in test water was tested. Therefore, a supersaturated stock solution of nominal 100 mg test item/L was prepared by suspending 50 and 55.8 mg test item in 500 and 558 mL test water. The stock suspension was stirred for 48h hours at room temperature in the dark to dissolve as much test item as possible. Then, non-dissolved fractions of the test item were separated from the test medium by membrane filtration (0.45 μm cellulose acetate filter). The solution with dissolved test item was used to prepare the desired 1:8, 1:16, 1:32, 1:64 and1:128 dilutions.
The test media were prepared just before introduction of the daphnids (= start of the test) and test medium renewal on Day 1.
Test organisms (species):
Daphnia magna
Details on test organisms:
Strain/Clone: Daphnia magna, clone 5;
Age: 1.5 to 19.25 hours old
Source: The daphnids introduced in the test were taken from in-house laboratory culture.
Test type:
static
Water media type:
freshwater
Limit test:
no
Total exposure duration:
48 h
Hardness:
250 mg/L
Test temperature:
18.3 to 19.7 °C in the freshly prepared media; 18.7 to 19.2°C in the aged test media
pH:
7.9 to 8.1 in the freshly prepared media; 7.8 to 7.9 in the aged test media
Dissolved oxygen:
9.3 to 10.0 mg/L in the freshly prepared media; 8.7 to 9.9 mg/L in the aged test media
Nominal and measured concentrations:
Due to the low limit of water solubility of the test item, a filtrate of nominal 100 mg/L was produced. Afterwards dilutions of this filtrate (1:8/ 1:16 / 1:32/ 1:64 and 1:128) resulting in nominal concentrations of 12.5, 6.3, 3.1 and 1.6 and 0.8 mg test item/L were tested.
Reference substance (positive control):
yes
Remarks:
Potassium dichromate
Key result
Duration:
48 h
Dose descriptor:
EC50
Effect conc.:
11.151 mg/L
Nominal / measured:
estimated
Conc. based on:
test mat.
Basis for effect:
mobility
Remarks on result:
other: based on nominal loading rate
Duration:
48 h
Dose descriptor:
NOEC
Effect conc.:
6.3 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
mobility
Duration:
48 h
Dose descriptor:
LOEC
Effect conc.:
12.5 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
mobility
Key result
Duration:
48 h
Dose descriptor:
EC50
Effect conc.:
3.33 µg/L
Nominal / measured:
estimated
Conc. based on:
test mat.
Basis for effect:
mobility
Remarks on result:
other: based on measured concentration
Details on results:
After 48 hours of exposure no immobilisation of the test animals was observed in the control and up to and including the nominal loading rate of 6.30 mg test item/L. At the loading rate of 12.50 mg test item/L, 12 animals were immobile after 48 h of exposure.
The 48 h EC50 was determined to be 11.151 mg/L based on a nominal loeading rate. This is corresponding to 3.33 µg/L test material concentration.
Results with reference substance (positive control):
EC50 [mg/L]: 1.58 (24h) and 1.01 (48 h)
Validity criteria fulfilled:
yes
Conclusions:
The toxic effect of the test item to Daphnia magna was assessed in a semi-static concentration-response test. The 48 h EC50 was determined to be 11.151 mg/L based on a nominal loeading rate. This is corresponding to 3.33 µg/L test material concentration.
The initial concentrations and the maintenance of the exposure concentrations during the test were determined in the analytical part. All reported results refer to nominal loading rates since the concentrations of the test samples could not be quantified.
Endpoint:
short-term toxicity to aquatic invertebrates
Type of information:
read-across from supporting substance (structural analogue or surrogate)
Adequacy of study:
key study
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Justification for type of information:
For this endpoint information from structural similar compounds is available. The studies for these similar compounds were performed according to GLP and the methods applied are fully compliant with OECD TG 202. See chapter 13 report for a more detailed justification.
Reason / purpose:
read-across source
Duration:
48 h
Dose descriptor:
EC50
Effect conc.:
11.51 mg/L
Nominal / measured:
estimated
Conc. based on:
test mat.
Basis for effect:
mobility
Remarks on result:
other: based on loading rate
Key result
Duration:
48 h
Dose descriptor:
EC50
Effect conc.:
3.33 µg/L
Nominal / measured:
estimated
Conc. based on:
test mat.
Basis for effect:
mobility
Remarks on result:
other: based on measured values
Conclusions:
For this endpoint a one-to-one read across was performed to a chemical similar compound of the same chemical class with a comparable phys. chem. profile and similar response in biological assays. The relevant study was performed according to GLP and the methods applied are fully compliant with OECD TG 202. The read across results shows an EC50 (48 h) of 11.51 mg/L (nominal concentration) which corresponds to 3.33 µg/L (calculated based on measured concentration). A detailed read across justification is provided in chapter 13 of this dossier.

Description of key information

No data for short-term toxicity to aquatic invertebrates are available for the test item, however, a Guideline study under GLP conditions was conducted with a structural analogue substance to cover the endpoint adequately.

In the OECD 202 study, the EC50 (48 h) was calculated to be at 11.115 mg/L based on the nominal loading rate. Using the measured concentration of 30 µg/L for the stock solution (100 mg/L) and considering a dilution factor of 9, the nominal concentration of 11.115 mg/L corresponds to a measured concentration 3.33 µg/L.

Key value for chemical safety assessment

EC50/LC50 for freshwater invertebrates:
3.33 µg/L

Additional information