2-methyl-1-(4-methylthiophenyl)-2-morpholinopropan-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:

2005

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 201 (Alga, Growth Inhibition Test)

GLP compliance:

yes (incl. QA statement)

Analytical monitoring:

yes

Details on sampling:

For the analysis of the actual test item concentrations the following samples were taken:
Just before the start of the test:
- one sample from the freshly prepared stock solution
- duplicate samples from each test medium (without algae)
- duplicate samples from the solvent control (without algae)
After 72 hours:
- duplicate samples from each test medium (without algae)
- duplicate samples from the solvent control (without algae)

All samples were deep-frozen (at about -20 °C) immediately after sampling. Based on pre-experiments (without GLP) for investigation of the storage stability the test item is sufficiently stable in the test water under these storage conditions.

Vehicle:

yes

Details on test solutions:

PREPARATION AND APPLICATION OF TEST SOLUTION
- Chemical name of vehicle: N,N-Dimethylformamide (DMF)
- Concentration of vehicle:
A stock solution of nominal 46 mg/mL was prepared by dissolving 460 mg of the test item completely in 10 mL DMF ( p.A.) This stock solution was used as application solution for the preparation of the test medium with the highest test concentration. Adequate volumes of the DMF stock solution were diluted with DMF to prepare the application solutions for the dosage of the test media with lower test concentrations.

A control (test water without addition of the test item) and a solvent control (addition of DMF) was tested in parallel. The DMF concentration in the test media and the solvent control was 100 μL/L.

Test organisms (species):

Desmodesmus subspicatus (previous name: Scenedesmus subspicatus)

Details on test organisms:

TEST ORGANISM
- Strain: No. 86.81 SAG
- Source: Collection of Algal Cultures (SAG, Institute for Plant Physiology, University of Göttingen, D-37073 Göttingen, Germany)
- Age of inoculum (at test initiation): exponentially growing pre-culture, set up three days prior to the test

ACCLIMATION
- Culturing media and conditions: same as test

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

72 h

Hardness:

0.24 mmol/L (= 24 mg/L) as CaCO3

Test temperature:

23 – 24 °C

pH:

start 7.9 - 8.2
end 8.2 - 9.1

Nominal and measured concentrations:

Nominal: 0.0, 0.22, 0.46, 1.0, 2.2, 4.6 mg/L
Mean measured: n.d., n.m., 0.39, 0.86, 1.9, 3.8 mg/L

n.d.: not detected
n.m.: not measured

Details on test conditions:

TEST SYSTEM
- Test vessel: 50 mL Erlenmeyer flasks, covered with glass dishes, continuously stirred by magnetic stirrers
- Initial cells density: 10,000 algal cells per mL of test medium
- Control end cells density: 830000 cells/mL
- No. of vessels per concentration (replicates): 3
- No. of vessels per control (replicates): 3
- No. of vessels per vehicle control (replicates): 6

GROWTH MEDIUM
- Standard medium used: yes

TEST MEDIUM / WATER PARAMETERS
- Source/preparation of dilution water: synthetic test water, prepared according to the test guidelines
- Intervals of water quality measurement:
pH: at the start and at the end of the test
Temperature: daily (in extra flask incubated under test conditions)
Apparence of test media: daily

OTHER TEST CONDITIONS
- Photoperiod: continuous illumination
- Light intensity and quality: 7800 Lux (mean value), by fluorescent tubes installed above the test flasks

EFFECT PARAMETERS MEASURED :
- Determination of cell concentrations: electronic particle counter, after 24, 48 and 72 hours
- Examination of the shpe of the algal cells: after 72h, sample from the control and from a test concentration with reduced algal growth (nominal 2.2 mg/L), no obvious effects on the shape and size

TEST CONCENTRATIONS
The test concentrations were based on the results of a range-finding test and the results of the pre-experiment to determine the solubility of the test item in test water (without GLP).

Reference substance (positive control):

yes

Remarks:

potassium dichromate

Duration:

72 h

Dose descriptor:

EC10

Effect conc.:

0.92 mg/L

Nominal / measured:

meas. (not specified)

Conc. based on:

test mat.

Basis for effect:

growth rate

Remarks on result:

other: 95% CL 0.14 - 1.4 mg/L

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

1.6 mg/L

Nominal / measured:

meas. (not specified)

Conc. based on:

test mat.

Basis for effect:

growth rate

Remarks on result:

other: 95% CL 0.92 - 2.8 mg/L

Duration:

72 h

Dose descriptor:

EC90

Effect conc.:

2.9 mg/L

Nominal / measured:

meas. (not specified)

Conc. based on:

test mat.

Basis for effect:

growth rate

Remarks on result:

other: 95% CL 2.0 - 17 mg/L

Duration:

72 h

Dose descriptor:

NOEC

Effect conc.:

0.86 mg/L

Nominal / measured:

meas. (not specified)

Conc. based on:

test mat.

Basis for effect:

growth rate

Duration:

72 h

Dose descriptor:

LOEC

Effect conc.:

1.9 mg/L

Nominal / measured:

meas. (not specified)

Conc. based on:

test mat.

Basis for effect:

growth rate

Duration:

72 h

Dose descriptor:

EC10

Effect conc.:

0.66 mg/L

Nominal / measured:

meas. (not specified)

Conc. based on:

test mat.

Basis for effect:

biomass

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

1.2 mg/L

Nominal / measured:

meas. (not specified)

Conc. based on:

test mat.

Basis for effect:

biomass

Duration:

72 h

Dose descriptor:

EC90

Effect conc.:

2.2 mg/L

Nominal / measured:

meas. (not specified)

Conc. based on:

test mat.

Basis for effect:

biomass

Duration:

72 h

Dose descriptor:

NOEC

Effect conc.:

0.39 mg/L

Nominal / measured:

meas. (not specified)

Conc. based on:

test mat.

Basis for effect:

biomass

Duration:

72 h

Dose descriptor:

LOEC

Effect conc.:

0.86 mg/L

Nominal / measured:

meas. (not specified)

Conc. based on:

test mat.

Basis for effect:

biomass

Details on results:

The microscopic examination of the algal cells after 72 hours exposure showed no difference between the algae growing in test medium with reduced algal growth (nominal 2.2 mg/L) and the algal cells in the controls. There were no obvious effects on the shape and size of the algal cells growing in test media containing the test item at up to and including this nominal concentration.

The validity criterion of increase of cell density by at least a factor of 16 over the duration of the study was fulfilled.

No remarkable observations were made concerning the appearance of the test media. All test media were clear solutions throughout the test period

Results with reference substance (positive control):

The latest result of the positive control test showed that the toxic performance was valid and within the historical range in the RCC laboratory.

Validity criteria fulfilled:

not specified

Conclusions:

The 72 hour ErC50 of the test material to Desmodesmus subspicatus was determined to be 1.6 mg/l under the conditions of the test.

Description of key information

The study provided was conducted to recognised testing guidelines and with GLP certification.

Key value for chemical safety assessment

EC50 for freshwater algae:

1.6 mg/L

EC10 or NOEC for freshwater algae:

0.86 mg/L

Additional information

In a GLP study performed according to OECD guideline 201 algal growth in presence of the test substance was tested. Scenedesmus subspicatus was exposed to the substance for 72 hours. Based on growth rate an EC50 of 1.6 mg/L was determined (RCC, 2005). The NOEC and the ErC10 after 72 h were 0.86 and 0.96 mg/L, respectively.