2-[7-(diethylamino)-2-oxo-2H-1-benzopyran-3-yl]benzoxazole-5-sulphonamide

Short-term toxicity to aquatic invertebrates

Link to relevant study record(s)

Reference

Endpoint:

short-term toxicity to aquatic invertebrates

Type of information:

experimental study

Adequacy of study:

key study

Study period:

30 December 2016 to 06 March 2017

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:

2008

Deviations:

no

Qualifier:

according to guideline

Guideline:

other: Guidance document on aquatic toxicity testing of difficult items and mixtures, OECD series on testing and assessment number 23

Version / remarks:

2000

Deviations:

no

GLP compliance:

yes

Analytical monitoring:

yes

Details on sampling:

- Concentrations: Samples for possible analysis were taken from the test concentration and the control. In addition, the filter used to prepare the saturated solution (SS) was retained for possible analysis of the residue.
- Sampling method: At t = 0 and t = 48 h, 3.0 mL was sampled from the approximate centre of the test vessels. At the end of the exposure period, the replicates were pooled at each concentration before sampling.
- Sample storage conditions before analysis: Samples were stored in a freezer (≤ -15 °C) until analysis.

Vehicle:

no

Details on test solutions:

PREPARATION AND APPLICATION OF TEST SOLUTION (especially for difficult test substances)
Preparation of test solutions started with a loading rate of 100 mg/L applying three days of magnetic stirring to reach the maximum dissolution of the test material in medium. The obtained aqueous mixture was filtered through a 0.45 μm membrane filter (RC55, Whatman) and the resulting saturated solution (SS) was used as the highest test concentration. Lower test concentrations for the combined limit/range-finding test were prepared by subsequent dilutions of the SS in test medium. All test solutions were clear and colourless at the end of the preparation procedure.

Test organisms (species):

Daphnia magna

Details on test organisms:

TEST ORGANISM
- Common name: Water flea
- Strain/clone: Straus, 1820, at least third generation
- Source: In-house laboratory culture with a known history; obtained by a cyclical parthenogenesis under specified breeding conditions.
- Age of parental stock (mean and range, SD): Daphnids originated from a healthy stock, 2nd to 5th brood. For the test, young daphnids with an age of < 24 hours, from parental daphnids of more than two weeks old were selected.
- Feeding during test: No

ACCLIMATION
- Acclimation period: Each batch is started with newborn daphnids, i.e. less than 3 days old, by placing about 250 into 5 litres of medium in an all-glass culture vessel. The maximum age of the cultures is 4 weeks. After 7 days of cultivation, half of the medium is renewed twice a week.
- Acclimation conditions (same as test or not): Yes. Daphnids were kept in medium M7 at 18 to 22 °C.
- Type and amount of food: A suspension of fresh water algae
- Feeding frequency: Daily
- Health during acclimation (any mortality observed): Daphnia showed no signs of stress such as mortality >20 %, presence of males, ephippia or discoloured animals and there was no delay in the production of the first brood.

Test type:

static

Water media type:

freshwater

Limit test:

yes

Total exposure duration:

48 h

Hardness:

180 mg/L expressed as CaCO3

Test temperature:

19 to 20 °C

pH:

7.9 to 8.1

Dissolved oxygen:

8.5 to 9.2 mg O2/L

Nominal and measured concentrations:

- Nominal concentration: 100 % of a SS prepared at 100 mg/L
- Measured concentration: 0.012 mg/L

Details on test conditions:

TEST SYSTEM
- Test vessel: 100 mL test vessels
- Material, size, headspace, fill volume: All-glass vessels containing 80 mL of solution
- Aeration: No aeration of the test solutions
- 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: The following chemicals are dissolved in tap water purified by Reverse Osmosis (RO-water):
ISO medium: Macro salts: CaCl2.2H2O 211.5 mg/L, MgSO4.7H2O 88.8 mg/L, NaHCO3 46.7 mg/L and KCl 4.2 mg/L.
Medium M7: trace elements, macronutrients and vitamins are added to freshly prepared ISO medium to reach the following concentrations:
Trace elements: B 0.125 mg/L, Fe 0.05 mg/L, Mn 0.025 mg/L, Li, Rb and Sr 0.0125 mg/L, Mo 0.0063 mg/L, Br 0.0025 mg/L, Cu 0.0016 mg/L, Zn 0.0063 mg/L, Co and I 0.0025 mg/L, Se 0.0010 mg/L, V 0.0003 mg/L and Na2EDTA.2H2O 2.5 mg/L.
Macro nutrients: Na2SiO3.9H2O 10.0 mg/L, NaNO3 0.27 mg/L, KH2PO4 0.14 mg/L and K2HPO4 0.18 mg/L.
Vitamins: Thiamine 75.0 μg/L, B12 1.0 μg/L and Biotin 0.75 μg/L.
- Culture medium different from test medium: Daphnids were cultured in medium M7 and the test carried out in adjusted ISO medium.
- Intervals of water quality measurement: At the beginning and at the end of the test, pH and dissolved oxygen were determined. Temperature of medium was monitored continuously in a temperature control vessel, beginning at the start of the test.

OTHER TEST CONDITIONS
- Adjustment of pH: No
- Photoperiod: 16 hours of light daily

EFFECT PARAMETERS MEASURED (with observation intervals if applicable):
Immobility (including mortality) was determined at 24 hours and at 48 hours.

RANGE-FINDING STUDY
- Test concentrations: 1.0, 10 and 100 % of a SS at 100 mg/L
- Results used to determine the conditions for the definitive study: Yes. The results of the control group were not valid because >10 % immobility was observed after 48 hours of exposure. However, it could be expected from the results of the test concentrations that the test material did not affect the mobility of the exposed daphnids. Therefore, the study was continued with a limit test in which only the highest test concentration (100 % of a SS prepared at 100 mg/L) and a control group were used.

Reference substance (positive control):

yes

Remarks:

potassium dichromate

Key result

Duration:

48 h

Dose descriptor:

EC50

Effect conc.:

> 0.012 mg/L

Nominal / measured:

meas. (initial)

Conc. based on:

test mat.

Basis for effect:

mobility

Details on results:

After 48 hours of exposure no immobility was observed at the limit concentration and the control. The responses recorded in this test allowed for reliable determination of an EC50. Due to the low solubility of the test material in water, concentration levels that might be toxic for daphnids could not be reached.

Samples taken from 100 % of the SS prepared at 100 mg/L were analysed. The measured concentration was just above LOD, i.e. 0.012 mg/L at the start of the test. During the exposure period the measured concentration remained stable and was 98 % of initial at the end of the test. Given this results, the EC50 values were calculated using the measured initial concentration.

Results with reference substance (positive control):

The reference test was carried out to check the sensitivity of the test system as used by the testing facility. Daphnids were exposed for a maximum of 48 hours to K2Cr2O7 concentrations of 0.10, 0.18, 0.32, 0.56, 1.0 and 1.8 mg/L and to a control. Twenty daphnids were exposed per concentration.
The actual responses in this reference test were within the ranges of the expected responses at the different concentrations, i.e. the 48h-EC50 was within the expected range of 0.28 to 0.9 mg/L. Hence, the sensitivity of the daphnia was within the range determined with the historical data collected at the testing facility.
The 24 h EC50 was 0.91 mg/L with a 95 % confidence interval ranging from 0.77 to 1.1 mg/L.
The 48 h EC50 was 0.58 mg/L with a 95 % confidence interval ranging from 0.49 to 0.67 mg/L.

Reported statistics and error estimates:

The 24 and 48 h EC50 could not be determined because the observed effects were below 50 %.

Validity criteria fulfilled:

yes

Conclusions:

Under the conditions of this study, the 48 h EC50 was >0.012 mg/L based on the measured initial concentration.

Executive summary:

The potential for the test material to cause acute toxicity to Daphnia magna was investigated in accordance with the standardised guidelines OECD 202, EU Method C.2 and the OECD series on testing and assessment number 23 under GLP conditions.

A limit test was performed based on the results of a preceding combined limit/range-finding test. The test material was not completely soluble in test medium at the loading rate initially prepared. A saturated solution (SS) was prepared at a loading rate of 100 mg/L and used as the test concentration.

Twenty daphnids per group (four replicates, five daphnids per replicate) were exposed to a control and to 100 % of the SS prepared at 100 mg/L under static conditions. The total exposure period was 48 hours and samples for analytical confirmation of exposure concentrations were taken at the start and at the end of the test.

After 48 hours of exposure no immobility was observed at the limit concentration and the control. The responses recorded in this test allowed for reliable determination of an EC50. Due to the low solubility of the test material in water, concentration levels that might be toxic for daphnids could not be reached.

Samples taken from 100 % of the SS prepared at 100 mg/L were analysed. The measured concentration was 0.012 mg/L at the start of the test. During the exposure period the measured concentration remained stable and was 98 % of initial at the end of the test. Given the result, the EC50 values were calculated using the measured initial concentration.

The study met the acceptability criteria prescribed by the study plan and was considered valid.

Under the conditions of this study, the 48 h EC50 was >0.012 mg/L based on the measured initial concentration.

Description of key information

Under the conditions of this study, the 48 h EC50 was >0.012 mg/L based on the measured initial concentration.

Key value for chemical safety assessment

Fresh water invertebrates

Fresh water invertebrates

Effect concentration:

0.012 mg/L

Additional information

The potential for the test material to cause acute toxicity to Daphnia magna was investigated in accordance with the standardised guidelines OECD 202, EU Method C.2 and the OECD series on testing and assessment number 23 under GLP conditions. The study was awarded a reliability score of 1 in accordance with the criteria set forth by Klimisch et al. (1997).

A limit test was performed based on the results of a preceding combined limit/range-finding test. The test material was not completely soluble in test medium at the loading rate initially prepared. A saturated solution (SS) was prepared at a loading rate of 100 mg/L and used as the test concentration.

Twenty daphnids per group (four replicates, five daphnids per replicate) were exposed to a control and to 100 % of the SS prepared at 100 mg/L under static conditions. The total exposure period was 48 hours and samples for analytical confirmation of exposure concentrations were taken at the start and at the end of the test.

After 48 hours of exposure no immobility was observed at the limit concentration and the control. The responses recorded in this test allowed for reliable determination of an EC50. Due to the low solubility of the test material in water, concentration levels that might be toxic for daphnids could not be reached.

Samples taken from 100 % of the SS prepared at 100 mg/L were analysed. The measured concentration was 0.012 mg/L at the start of the test. During the exposure period the measured concentration remained stable and was 98 % of initial at the end of the test. Given the result, the EC50 values were calculated using the measured initial concentration.

The study met the acceptability criteria prescribed by the study plan and was considered valid.

Under the conditions of this study, the 48 h EC50 was >0.012 mg/L based on the measured initial concentration.

In a supporting study, the acute toxicity of the test material was calculated using ECOSAR v1.1 (2012) 2000 U.S. Environmental Protection Agency. Given that the substance is an organic molecule within the Molecular Weight range and Log Kow range of the training set compounds, the prediction is considered to be acceptable. The study was awarded a reliability score of 2 in accordance with the criteria set forth by Klimisch et al. (1997).

The acute toxicity of the test material to Daphnia magna was calculated to be 85.946 mg/L.