Benzofuran-2-yl methyl ketone

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:

07 Feb - 30 Mar 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:

May 2008

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Remarks:

Swiss Federal Office of Public Health, Consumer protection directorate, Notification authority for chemicals, Bern, Switzerland (16 Dec 2015)

Analytical monitoring:

yes

Remarks:

HPLC/UV

Details on sampling:

- Concentrations: Control, 10, 22, 46, and 100 mg/L. The samples of the lowest test concentration (4.6 mg/L) were not analyzed since this concentration was below the 48-h NOEC determined in this test and was therefore not relevant for the interpretation of the biological results.
- Sampling method: Duplicate samples were taken from each test concentration and the control at the start (0 h) and at the end of test (48 h). For the 48-h stability samples, the contents of the respective replicates were combined prior to sampling.
- Sample storage conditions before analysis: Immediately after sampling, all samples were frozen at about -20 °C. Based on the pre-experiments for investigation of the storage stability (non-GLP study), the test item was found to be stable in the test water under these storage conditions.

Vehicle:

no

Details on test solutions:

PREPARATION AND APPLICATION OF TEST SOLUTION
- Method: The test medium of the highest concentration of 100 mg/L was prepared by completely dissolving 100.02 mg of test item in 1000 mL of test water using ultrasonic treatment for 30 min and intense stirring for 30 min at room temperature. After the dissolving procedure the highest test concentration was a clear solution. This highest test concentration was diluted with test water to prepare the test media of the lower test concentrations. The test media were prepared just before the introduction of the daphnia (i.e. the start of the exposure).
- Controls: Test water without test item was tested in parallel.
- Evidence of undissolved material: No remarkable observations were made concerning the appearance of the test media. All test media were clear solutions throughout the entire test duration.

Test organisms (species):

Daphnia magna

Details on test organisms:

TEST ORGANISM
- Common name: Water flea
- Age of parental stock: The strain bred in the testing facility was obtained in 2015.
- Age of daphnia at test start: The test organisms were 6 - 24 h old and were not first brood progeny.
- Feeding during test: No feeding during the test.
- Breeding conditions: The cultivation of the parental daphnia is performed in reconstituted water of the same quality as the water quality used in the tests (pH, ions, total hardness).
- Food type during breeding: Algal suspension of the green alga Desmodesmus subspicatus (cultivated at the testing facility under standard conditions) or a mixture of this algal suspension and a commercial fish diet (TetraMin Hauptfutter, Tetra-Werke, Melle, Germany).
- Frequency of feeding during breeding: Three times per week.

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

48 h

Hardness:

2.5 mmol/L (250 mg/L as CaCO3)

Test temperature:

20 °C

pH:

7.8 (0 h)
7.9 - 8.0 (48 h)

Dissolved oxygen:

8.4 - 8.6 mg/L (0 h)
8.5 - 8.7 mg/L (48 h)

Nominal and measured concentrations:

Control, 4.6, 10, 22, 46, and 100 mg/L (nominal)
< LOQ, - , 9.77, 21.7, 45.4, and 97.3 (measured at 0 h)
< LOQ, - , 9.14, 20.5, 42.5, and 91.2 mg/L (measured at 48 h)

Details on test conditions:

TEST SYSTEM
- Test vessel: Beakers
- Type: Covered with glass plates to reduce the loss of water by evaporation and to avoid the entry of dust into the solutions.
- Material, size, headspace, fill volume: Material: glass; Size: 100 mL; Fill volume: 50 mL
- Aeration: The test water was aerated prior to the start of the study until oxygen saturation was reached.
- No. of organisms per vessel: 5
- No. of vessels per concentration (replicates): 4
- No. of vessels per control (replicates): 4
- Biomass loading rate: 1 daphnid/2 mL test medium

TEST MEDIUM / WATER PARAMETERS
- Source/preparation of dilution water: Purified water/ISO Test water according to OECD Guideline No. 202
- Ca/Mg ratio: 4:1
- Na/K ratio: 10:1
- Culture medium different from test medium: Culture medium same as test medium.
- Intervals of water quality measurement: At the start and end of the test, the pH values, dissolved oxygen concentrations and water temperature were determined in each treatment. In addition, the appearance of the test media was visually controlled and documented at the same time.

OTHER TEST CONDITIONS
- Photoperiod: 16 h light/ 8 h dark
- Light intensity: 15 - 17 µmol m^-2 s^-1

EFFECT PARAMETERS MEASURED:
- Immobility of the daphnia: at 24 and 48 h
- Observation of non-lethal effects (behavior and appearance): at 24 and 48 h

RANGE-FINDING STUDY
- Test concentrations: Control, 2.0, 20, and 200 mg/L
- Results used to determine the conditions for the definitive study:Yes: 0% immobilization at 2.0 mg/L, 20% at 20 mg/L, and 100% at 100 mg/L

Reference substance (positive control):

yes

Remarks:

potassium dichromate

Key result

Duration:

48 h

Dose descriptor:

EC50

Effect conc.:

32 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

mobility

Remarks on result:

other: geom. mean of EC0/EC100

Remarks:

95% confidence interval: 22 - 46 mg/L

Details on results:

- Behavioural abnormalities: After 48 h exposure, no effects were observed in the control and up to and including the test concentration of 10 mg/L. Sub-lethal effects were observed in 8 of 20 daphnia at a concentration of 22 mg/L (slower swimming, sticky antennae). At the next higher concentration (46 mg/L) and above, 100% immobility was recorded.
- Mortality of control: 0%
- Any observations (e.g. precipitation) that might cause a difference between measured and nominal values: No remarkable observations were made concerning the appearance of the test media. All test media were clear solutions throughout the entire test duration.
- Effect concentrations exceeding solubility of substance in test medium: No

Results with reference substance (positive control):

- Results with reference substance valid? Yes, the sensitivity of the test organisms was within the range given by the guideline (0.60 - 2.1 mg/L).
- EC50 (24 h) = 1.0 mg/L (Oct 2016)
- Other: For evaluation of the quality of the daphnia and the experimental conditions, potassium dichromate is tested as a positve control twice a year.

Reported statistics and error estimates:

Statistical analysis was performed using ToxRat Professional.
The 24-h EC50 and 95% confidence limits were calculated by the Trimmed Spearman-Karber procedure.
The 48-h EC50 was determined as the geometric mean value of the two consecutive test concentrations with 0 and 100% immobility (EC0 and EC100), and with confidence limits for the EC50 corresponding to the EC0 and EC100 values, due to the steep concentration-effect relationship.
The 24-h and 48-h NOEC, EC0 and EC100 were determined directly from the raw data.

ANALYTICAL RESULTS

The measured concentrations of the test item in the test media of the treatments from 10 - 100 mg/L were between 97 - 99% of the nominal values at the start of the test and between 91 - 93% at the end of the test.

Thus, the correct dosage of the test item was confirmed and the results indicate, that the test item was stable in the test media over the test period of 48 h. Therefore, the endpoint values were related to the nominal concentrations of the test item.

BIOLOGICAL RESULTS

Table 1. Effect of test item on the mobility of Daphnia magna.

Nominal test item concentration [mg/L]	N° of daphnia tested	Immobilized daphnia after 24 h		Immobilized daphnia after 48 h
		N°	[%]	N°	[%]
Control	20	0	0	0	0
4.6	20	0	0	0	0
10	20	0	0	0	0
22	20	0	0	0 (5F; 3C)	0
46	20	2 (15F; 4C)	10	20	100
100	20	20	100	20	100

Values in parenthesis: number of mobile test animals with adverse effects:

                                                        A: daphnia trapped at the water surface

                                                        B: daphnia sticking together

                                                        C: antennae sticking together

                                                        D: daphnia discolored/pale

                                                        E: spina stuck

                                                        F: slower swimming activity

Validity criteria fulfilled:

yes

Conclusions:

This study resulted in an EC50 (48 h) of 32 mg/L (nominal) based on the mobility of D. magna (OECD 202, GLP).

Description of key information

EC50 (48 h) = 32 mg/L (nominal, OECD 202, D. magna)

Key value for chemical safety assessment

Fresh water invertebrates

Fresh water invertebrates

Effect concentration:

32 mg/L

Additional information

There is one GLP study available, in which the acute toxicity of the substance to aquatic invertebrates was assessed according to OECD 202.

In a static test, Daphnia magna was exposed to the nominal test concentrations 4.6, 10, 22, 46, and 100 mg/L for 48 h. A control was run in parallel and test item concentrations in the test media were analytically verified by HPLC/UV at the beginning (0 h) and at the end of the test (48 h).

The measured concentrations in the test media were between 97 and 99% of the nominal values at the start of the test and between 91 and 93% at the end of the test. The analytical results confirmed the correct dosage of the test item and showed that it was stable in the test media over the test period of 48 h. Therefore, effect concentrations are stated in terms of nominal concentrations.

After 48 h acute toxic effects were observed at concentrations higher 10 mg/L. The obtained EC50 (48 h) is 32 mg/L, which was determined as the geometric mean value of the EC0 and EC100, due to the steep dose-response curve.