3-ethoxy-4,6-difluoro-7-hexyloxy-dibenzothiophene

Short-term toxicity to aquatic invertebrates

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

short-term toxicity to aquatic invertebrates

Type of information:

experimental study

Adequacy of study:

key study

Study period:

Apr 02 - May 10, 2019

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 202 (Daphnia sp. Acute Immobilisation Test)

Version / remarks:

2004

Deviations:

no

Qualifier:

according to guideline

Guideline:

EU Method C.2 (Acute Toxicity for Daphnia)

Version / remarks:

Council Regulation (EC) No. 440/2008 laying down test methods pursuant to Regulation (EC) No. 1907/2006 of the European Parliament and the council on the Registration, Evaluation, Authorisation and Restriction of Chemicals (REACH).

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Specific details on test material used for the study:

Preparation of the Test Item:
A stock preparation with a test item concentration of 100 mg/L was freshly prepared for each exposure period (exposure periods: 0h – 24h and 24h – 48h). For that purpose, the test item was weighed in a calibrated flask and vehicle was added. The preparation was stirred with a magnetic stirrer for 24 hours. Then the formulation was passed through a filter membrane (pore size: 0.2 µm). The filtrate was used for the study. The pH was not adjusted.

Analytical monitoring:

yes

Details on sampling:

The present study was performed as a semi-static test with a renewal of the test item preparation (test item group) and the vehicle (control group) after 24 hours. Analysis of the test item concentration directly after each preparation (fresh medium) and after 24h (old medium) was performed. The samples were analyzed undiluted due to the very low solubility in water (< 0.025 mg/L). The concentrations of the test item were determined using the calibration curve. One replicate was used for analysis.

Vehicle:

yes

Details on test solutions:

Macro nutrients (mg/L)
CaCI2 •2H20 293.80
MgSO4•7H20 123.30
NaHCO3 64.80
KCI 5.80
Na2SiO3•9H20 10.00
NaNO3 0.27
KH2PO4 0.14
K2HPO4 0.18

Trace elements (mg/L)
B 0.5000
Fe 0.2000
Mn 0.1000
Li, Rb and Sr 0.0500
Mo 0.0250
Br 0.0125
Cu and Zn 0.0063
Co and I 0.0025
Se 0.0010
V 0.0003

Macro nutrients (mg/L)
Na2EDTA • 2H20 2.50

Vitamins (µg/L):
Thiamine 75.00
B12 1.00
Biotin 0.75

- pH: 7.90
- O2: 8.78 mg/L
- Conductivity: 674 µS/cm
- Total hardness: 237 mg CaCO3/L

Preparation of the Test Item:
A stock preparation with a test item concentration of 100 mg/L was freshly prepared. For that purpose, the test item was weighed in a calibrated flask and vehicle was added. The preparation was stirred with a magnetic stirrer for 24 hours. Then the formulation was passed through a filter membrane (pore size: 0.2 µm). The filtrate was used for the study. The pH was not adjusted.

Test organisms (species):

Daphnia magna

Details on test organisms:

Species: Daphnia magna Straus
Culture conditions: The clone is bred in the laboratories .
Parental daphnids are used for reproduction until they are about 6 weeks old. Thereafter, they are replaced by neonates.
Daphnids are kept individually in 100 mL glass vessels containing approximately 60 mL reconstituted water (ELENDT M4 medium) at a water temperature of 20 ± 2°C and a 16 hour light and 8 hour dark regime to ensure similar conditions as in the experiment. Offspring are removed from the vessels at least twice per week.
Feeding: The parental daphnids are fed ad libitum with unicellular green algae Desmodesmus subspicatus three times per week.
Age: Offspring less than 24 hours old were used for the study.
Acclimation period: same as test

Feeding during test: None

Test type:

semi-static

Water media type:

freshwater

Limit test:

yes

Total exposure duration:

48 h

Hardness:

254-257 mg CaCO3/L

Test temperature:

20.9 to 21.7°C

pH:

7.90 to 7.93

Dissolved oxygen:

8.19 - 8.28 mg/L

Conductivity:

673-680 µS/cm

Nominal and measured concentrations:

Nominal 100 mg/L (

Details on test conditions:

TEST SYSTEM
- Test vessel: Glass test tubes
- Type (delete if not applicable): open
- Material, size, headspace, fill volume: 20 mL glass test tubes containing 20 mL medium
- Aeration: no
- No. of organisms per vessel: 5
- No. of vessels per concentration (replicates): 4
- No. of vessels per control (replicates): 4

TEST MEDIUM / WATER PARAMETERS
- Source/preparation of dilution water: reconstituted water (ELENDT M4 medium according OECD 202)
- Total organic carbon: no data
- Particulate matter: no data
- Metals: no data
- Pesticides: no data
- Chlorine: no data
- Alkalinity: no data
- Conductivity: 673-680 µS/cm
- Ca/mg ratio: no data
- Salinity: no data
- Culture medium different from test medium: no
- Intervals of water quality measurement: at start and end of exposure

OTHER TEST CONDITIONS
- Adjustment of pH: no
- Photoperiod: 16h light / 8h dark
- Light intensity: The mean light intensities were 570 Lux and 574 Lux prior to and at the end of the exposure period, respectively.

EFFECT PARAMETERS MEASURED (with observation intervals if applicable) : Immobilisation (daily)

VEHICLE CONTROL PERFORMED: no

RANGE-FINDING STUDY
- Test concentrations: 100 mg/L
- Results used to determine the conditions for the definitive study: no immobilisation observed at 100 mg/L

Reference substance (positive control):

no

Remarks:

No positive control used in this study. The accuracy and reliability of the test method is demonstrated periodically as recommended by guidelines with potassium dichromate.

Duration:

24 h

Dose descriptor:

EC50

Effect conc.:

> 100 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

mobility

Remarks on result:

other: EC50 > 0.001 mg/L

Key result

Duration:

48 h

Dose descriptor:

EC50

Effect conc.:

> 100 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

mobility

Remarks on result:

other: EC50 > 0.001 mg/L

Details on results:

An aqueous solution of nominal 100 mg/L of the test item revealed no aquatic toxicity in the test system.

The 48h EC50 exceeded the LOD of 0.001 mg/L (nominal >100 mg/L) and, thus, could not be determined in this study.

- Behavioural abnormalities: no
- Other biological observations: no
- Mortality of control: no
- Other adverse effects control: no
- Abnormal responses: no
- Any observations (e.g. precipitation) that might cause a difference between measured and nominal values: no

Results with reference substance (positive control):

Objective:
The objective of this study was to determine the effect of the positive control substance
Art. 104864 (Potassium dichromate) on the immobilization of Daphnia magna in order to check the sensitivity of the test system as recommended by guidelines (Council Regulation (EC) No. 440/2008 and OECD Guideline No. 202).

Study design:
Juvenile daphnids were exposed to different concentrations of the test item (0, 0.31, 0.46, 0.69, 1.02 and 1.52 mg/L) in an open static system. 20 daphnids, divided into four replicates, each with five animals were used per concentration and control. The daphnids were observed for immobilization after 24 and 48 hours of exposure.

Results:
No effect on the mobility of the daphnia was observed at the lowest concentration of 0.31 mg/L. A concentration dependent immobilization was observed at concentrations of 0.46 to 1.52 mg/L.
For the test item Art. 104864 (Potassium dichromate) the following nominal EC50 values and 95% confidence intervals were determined:

24h 0.92 mg/L 0.81 – 1.04 mg/L
48h 0.70 mg/L 0.62 – 0.79 mg/L

Conclusion:
Under the conditions of the present study, the test item Potassium dichromate showed a 24h EC50 value of 1.13 mg/L which is within the range of the published data of 0.6 to 1.7 mg/L (Council Regulation (EC) No. 440/2008) and 0.6 to 2.1 mg/L (OECD Guideline No. 202).

Therefore, this study confirms the sensitivity and reliability of the test system used in the test facility.

Validity criteria fulfilled:

yes

Conclusions:

Under the conditions of the present study, an aqueous solution of nominal 100 mg/L of the test item revealed no toxicity to daphnids.
The 48h EC50 was > 0.001 mg/L (nominal >100 mg/L) and, thus, could not be determined in this study.

Executive summary:

Objective

The objective of this study was to determine the effect of the test item on the immobilization of Daphnia magna.

Study Design

Juvenile daphnids were exposed to a nominal test item concentration of 100 mg/L (limit test) in an open static system. 20 daphnids, divided into four replicates, each with five animals were used in the test item group and the control group. The daphnids were observed for immobilization after 24 and 48 hours of exposure.

Concentrations of the test item in the test medium were analyzed via HPLC with UV-detection directly after each preparation (fresh medium), 24h and 48h after each preparation (old medium).

Results

The measured concentrations of the test material were <LOD (LOD = 0.001 mg/L) during the experimental phase. No test item was measured in the control medium. Therefore, it was confirmed that daphnia in the control group were not exposed to the test item.

Due to the absence of any adverse effects at the saturation concentration, the study was performed without analytical concentration verification.

No effect on the mobility of the daphnia was observed at a nominal concentration of 100 mg/L.

For the test item the following EC50values were determined:

EC50 (24h)> 100 mg/L (nominal); >0.001mg/L

EC50 (48h)>100 mg/L (nominal); >0.001mg/L

Conclusion

Under the conditions of the present study, an aqueous solution of nominal 100 mg/L of the test item revealed no toxicity to daphnids.The 48h EC50 was > 0.001 mg/L (nominal > 100 mg/L) and, thus, could not be determined.

Reference 2

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 a one-to-one read across was performed to a chemical similar compound (CAS 1818916 -02 -7) 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. A detailed read across justification is provided in chapter 13 of this dossier.

Reason / purpose for cross-reference:

read-across source

Key result

Duration:

48 h

Dose descriptor:

EC50

Effect conc.:

> 100 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

mobility

Remarks on result:

other: EC50 > 0.001 mg/L (LOD)

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. A saturated solution of the source compound shows no effects on mobility in daphnia magna. A detailed read across justification is provided in chapter 13 of this dossier.

Description of key information

Since no short-term toxicity study to aquatic invetebrates is available for the test item, an analogue Read Across approach was applied to a structural analogue substance. The study performed with the structural analogue substance (CAS 1818916 -02 -7) was perfomred under GLP conditions and according to the OECD TG 202.

No adverse effects on daphnids were observed up to the water solubility when exposed to the structural analogue substance.

EC50 (48h)>100 mg/L (nominal); > 0.001 mg/L (LOD = 0.001 mg/L)