2-hydroxy-1-[4-[4-(2-hydroxy-2-methylpropanoyl)phenoxy]phenyl]-2-methylpropan-1-one

Toxicity to aquatic algae and cyanobacteria

Link to relevant study record(s)

Reference

Endpoint:

toxicity to aquatic algae and cyanobacteria

Type of information:

experimental study

Adequacy of study:

key study

Study period:

2019-10-14 - 2019-10-18 (experimental phase)

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 201 (Freshwater Alga and Cyanobacteria, Growth Inhibition Test)

Version / remarks:

OECD Guideline for the Testing of Chemicals No. 201, adopted 23. Mar. 2006, Annex 5 corrected: 28 July 2011 “Freshwater Alga and Cyanobacteria, Growth Inhibition Test”

Deviations:

yes

Remarks:

but not affecting the validity or integrity of the study

Qualifier:

according to guideline

Guideline:

EU Method C.3 (Algal Inhibition test)

Version / remarks:

Commission Regulation (EU) No. 2016/266 amending Regulation (EC) No. 440/2008, Annex IV, Method C.3: “FRESHWATER ALGAE AND CYANOBACTERIA, GROWTH INHIBITION TEST,” adopted 07. December 2015

Deviations:

yes

Remarks:

but not affecting the validity or integrity of the study

GLP compliance:

yes (incl. QA statement)

Specific details on test material used for the study:

The test item was stored in the test facility in a closed vessel in a fridge at 2.5 – 8.3 °C, away from light and humidity.

Analytical monitoring:

yes

Details on sampling:

- Concentrations: 0 / 1 / 3.2 / 10 / 32 / 100 mg/L (nominal)
- Miscellaneous: On each sampling day, validity of calibration was controlled by measuring QC samples (1 mg/L). Before the first measurement at the start of the test, a new calibration was performed.

Vehicle:

no

Remarks:

test medium was used

Details on test solutions:

PREPARATION AND APPLICATION OF TEST SOLUTION (especially for difficult test substances)
A saturated solution was prepared for the test. This was done by weighing the real load of 100.0 mg/L, adding the corresponding amount of algal medium (demineralised water enriched with minerals but without algae) and shaking vigorously for 24 hours. The resulting solution was filtrated through 0.45 µm PTFE filters and the filtrate was used as test medium of the highest test concentration of nominal 100 mg/L. The lower treatments (1.0 / 3.2 / 10 / 32 mg/L nominal) were prepared by dilution of this filtrate with algal medium.
- Controls: algal medium / potassium dichromate
- Evidence of undissolved material (e.g. precipitate, surface film, etc.): none

Test organisms (species):

Desmodesmus subspicatus (previous name: Scenedesmus subspicatus)

Details on test organisms:

TEST ORGANISM
- Common name: Unicellular freshwater green alga
- Strain: Desmodesmus subspicatus, SAG Strain Number 86.81
- Source (laboratory, culture collection): The culture of Desmodesmus subspicatus was obtained in January 2016 by MBM Sci-encebridge GmbH (Institut für Pflanzenphysiologie of Universität Göttingen). The algae are kept as stock culture on solid agar at 2 - 8 °C. From the stock culture, a permanent culture was prepared. From an aliquot of the permanent culture, the pre-culture was prepared.
- Age of inoculum (at test initiation): For the pre-culture an aliquot of the permanent culture was brought into nutrient medium and incubated under continuous lighting for 96 hours under test conditions. The resulting culture grew exponentially.
Before usage, the 5 days old pre-culture was checked for the absence of cell aggregates and the cell number of the culture was determined.

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

72 h

Post exposure observation period:

none

Test temperature:

20.4 – 22.8 °C

pH:

7.4 - 8.4

Nominal and measured concentrations:

Nominal: 0 / 1.0 / 3.2 / 10 / 32 / 100 mg/L
Measured, t=0h: n.d. / 0.32 / 0.83 / 2.62 / 7.55 / 25.02 mg/L
Measured, t=72h: n.d. / 0.21 / 0.52 / 1.33 / 4.05 / 12.53 mg/L

Details on test conditions:

TEST SYSTEM
- Test vessel: glass flasks
- Type (delete if not applicable): open, covered with perforated plastic foil acting as a stopper
- Material, size, headspace, fill volume: glass flasks total volume 65 mL, filled with 45 ±1 mL
- Renewal rate of test solution (frequency/flow rate): none
- Initial cells density: 2300 cells/mL
- Control end cells density: 425073 cells/mL
- No. of vessels per concentration (replicates): 3 replicates for each treatment
- No. of vessels per control (replicates): 6 replicates for the blank control
- No. of vessels per vehicle control (replicates): n/a

GROWTH MEDIUM
- Standard medium used: Yes, the algal medium corresponds to the OECD TG 201 medium.

OTHER TEST CONDITIONS
- Sterile test conditions: yes
- Adjustment of pH: no
- Photoperiod: continuous
- Light intensity and quality: 4440 - 8880 lux

EFFECT PARAMETERS MEASURED (with observation intervals if applicable) :
- Determination of cell concentrations: electronic particle counter
- Other: pH; appearance of the algae

TEST CONCENTRATIONS
The concentrations to be tested are based on non GLP pre-tests.

Reference substance (positive control):

yes

Remarks:

Potassium dichromate K2Cr2O7 (CAS No. 7778-50-9) was used as positive control in a separate reference test.

Duration:

72 h

Dose descriptor:

NOEC

Effect conc.:

0.26 mg/L

Nominal / measured:

meas. (geom. mean)

Conc. based on:

test mat.

Basis for effect:

growth rate

Duration:

72 h

Dose descriptor:

NOEC

Effect conc.:

< 0.26 mg/L

Nominal / measured:

meas. (geom. mean)

Conc. based on:

test mat.

Basis for effect:

biomass

Remarks:

yield

Duration:

72 h

Dose descriptor:

LOEC

Effect conc.:

0.65 mg/L

Nominal / measured:

meas. (geom. mean)

Conc. based on:

test mat.

Basis for effect:

growth rate

Duration:

72 h

Dose descriptor:

LOEC

Effect conc.:

< 0.26 mg/L

Nominal / measured:

meas. (geom. mean)

Conc. based on:

test mat.

Basis for effect:

biomass

Remarks:

yield

Duration:

72 h

Dose descriptor:

EC10

Effect conc.:

4.25 mg/L

Nominal / measured:

meas. (geom. mean)

Conc. based on:

test mat.

Basis for effect:

growth rate

Duration:

72 h

Dose descriptor:

EC10

Effect conc.:

0.26 mg/L

Nominal / measured:

meas. (geom. mean)

Conc. based on:

test mat.

Basis for effect:

biomass

Remarks:

yield

Key result

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

8.95 mg/L

Nominal / measured:

meas. (geom. mean)

Conc. based on:

test mat.

Basis for effect:

growth rate

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

2.11 mg/L

Nominal / measured:

meas. (geom. mean)

Conc. based on:

test mat.

Basis for effect:

biomass

Remarks:

yield

Details on results:

- Exponential growth in the control (for algal test): yes
- Observation of abnormalities (for algal test): none
- Any observations (e.g. precipitation) that might cause a difference between measured and nominal values: no
- Effect concentrations exceeding solubility of substance in test medium: none

Results with reference substance (positive control):

- Results with reference substance valid? yes, the 72h-EC50 values of potassium dichromate (K2Cr2O7, CAS No. 7778-50-9) laid within the range of the laboratory (growth rate 0.65 - 1.10 mg/L, yield 0.21 – 0.66 mg/L).

Reported statistics and error estimates:

Calculation of results was performed with the help of validated software (Microsoft Excel®). The estimation of the biological data was accomplished using the software ToxRat® Professional, version 3.3.0.

Validity criteria fulfilled:

yes

Conclusions:

- NOEC (Growth Rate) 72 h: 0.26 mg/L
- NOEC (Yield) 72 h: <0.26 mg/L
- LOEC (Growth Rate) 72 h: 0.65mg/L
- LOEC (Yield) 72 h: ≤0.26 mg/L
- 72h ErC10: 4.25 mg/L
- 72h EyC10: 0.26 mg/L
- 72h ErC50: 8.95 mg/L
- 72h EyC50: 2.11 mg/L

Executive summary:

A study was conducted to determine the toxicity of the test substance to green alga (Desmodesmus subspicatus, SAG Strain Number 86.81) according to OECD Guideline 201 and EU Method C.3, in compliance with GLP. One valid experiment was performed using 5 concentrations ranging from 1.0 to 100 mg/L (nominal). Due to the poor water solubility of the substance, a saturated solution was prepared at the highest concentration by direct weighting, prolonged stirring and subsequent filtration according to OECD Guidance Document No. 23. The lower treatments were prepared by dilution of this filtrate with test water. The incubation time was 72 h. The cell concentration of each replicate was determined by measuring cell numbers every 24 h with an electronic particle counter. Growth rate µ and yield were determined from the cell number at the respective observation times. At the beginning and end of the study, test substance concentrations were verified using HPLC-UV.

At all concentrations (except 1.0 mg/L (nominal) for growth rate), significant inhibition of algal growth was observed. Test substance concentrations determined at the start of the study ranged from 24 to 32% of nominal values. At the end of the study, the determined concentrations ranged from 13 to 21 % of nominal values. Therefore, the results were based on geometric mean of the measured concentrations. The 72 h EC50 values of potassium dichromate (K2Cr2O7, CAS No.7778-50-9) were determined in a separate reference test. The values lay within the range of the laboratory (growth rate 0.65 - 1.10 mg/L, yield 0.21 – 0.66 mg/L).

The following results were determined:

Endpoint	NOEC	LOEC	EC10	EC50
Growth Rate	0.26 mg/L	0.65mg/L	4.25 mg/L	8.95 mg/L
Yield	< 0.26 mg/L	≤ 0.26 mg/L	0.26 mg/L	2.11 mg/L

Key value for chemical safety assessment

EC50 for freshwater algae:

8.95 mg/L

EC10 or NOEC for freshwater algae:

0.26 mg/L

Additional information

A study was conducted to determine the toxicity of the test substance to green alga (Desmodesmus subspicatus, SAG Strain Number 86.81) according to OECD Guideline 201 and EU Method C.3, in compliance with GLP. One valid experiment was performed using 5 concentrations ranging from 1.0 to 100 mg/L (nominal). Due to the poor water solubility of the substance, a saturated solution was prepared at the highest concentration by direct weighting, prolonged stirring and subsequent filtration according to OECD Guidance Document No. 23. The lower treatments were prepared by dilution of this filtrate with test water. The incubation time was 72 h. The cell concentration of each replicate was determined by measuring cell numbers every 24 h with an electronic particle counter. Growth rate µ and yield were determined from the cell number at the respective observation times. At the beginning and end of the study, test substance concentrations were verified using HPLC-UV.

At all concentrations (except 1.0 mg/L (nominal) for growth rate), significant inhibition of algal growth was observed. Test substance concentrations determined at the start of the study ranged from 24 to 32% of nominal values. At the end of the study, the determined concentrations ranged from 13 to 21 % of nominal values. Therefore, the results were based on geometric mean of the measured concentrations. The 72 h EC50 values of potassium dichromate (K2Cr2O7, CAS No.7778-50-9) were determined in a separate reference test. The values lay within the range of the laboratory (growth rate 0.65 - 1.10 mg/L, yield 0.21 – 0.66 mg/L).

The following results were determined:

Endpoint	NOEC	LOEC	EC10	EC50
Growth Rate	0.26 mg/L	0.65mg/L	4.25 mg/L	8.95 mg/L
Yield	< 0.26 mg/L	≤ 0.26 mg/L	0.26 mg/L	2.11 mg/L