Diethyl sulphate, compound with 2-(heptadec-8-enyl)-4,5-dihydro-1H-imidazole-1-ethanol (1:1)

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:

2018-09-04 to 2018-09-27

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:

2011

Qualifier:

according to guideline

Guideline:

EU Method C.3 (Algal Inhibition test)

Version / remarks:

2016

GLP compliance:

yes (incl. QA statement)

Specific details on test material used for the study:

SOURCE OF TEST MATERIAL
- batch No. of test material: 170825
- Expiration date of the batch: 2019-06-19

STABILITY AND STORAGE CONDITIONS OF TEST MATERIAL
- Storage condition of test material: Dark, dry place at room temperature
- Solubility and stability of the test substance in the solvent/vehicle: soluble in water

TREATMENT OF TEST MATERIAL PRIOR TO TESTING
- Treatment of test material prior to testing: no

Analytical monitoring:

no

Vehicle:

no

Details on test solutions:

Stock solution, media preparation:
10.0 mg test item/L was freshly prepared with dilution water. The dispersion was agitated until the solution was visually clear. The stock solution was checked via laser beam (Tyndall effect) for undissolved test item. The Tyndall effect was negative.

Test concentrations (nominal):
The stock solution was diluted to get the required test item concentrations. Six concentrations were tested in a geometrical series with a spacing factor of 2: 0.00500 - 0.0100 - 0.0200 - 0.0400 - 0.0800 - 0.160 mg/L. The concentrations are based on the results of a preliminary range finding test.

Test organisms (species):

Raphidocelis subcapitata (previous names: Pseudokirchneriella subcapitata, Selenastrum capricornutum)

Details on test organisms:

TEST ORGANISM
- Common name: Pseudokirchneriella subcapitata
- Strain: HINDÁK CCAP 278/4
- Source (laboratory, culture collection): Culture Collection of Algae and Protozoa (CCAP), SAMS Research Services Ltd., Dunstaffnage Marine Laboratory Dunbeg, OBAN; Argyll PA37 1QA; Scotland, UK

- Age of inoculum (at test initiation): 3 d
- Method of cultivation: Fresh stocks are prepared every month on Z-Agar. Light intensity amounts 2567 – 5130 lux for 24 hours per day. Nutrient medium Z according to LÜTTGE et al. (1994)

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

72 h

Test temperature:

22.0 - 24.0°C; mean value: 23.0 °C

pH:

Start: 7.12 - 7.44
End: 7.37 to 8.98

Conductivity:

Ultrapure water was used to prepare the dilution water (conductivity max. 0.1 µS/cm)

Nominal and measured concentrations:

Nominal 0.16 mg/L, 0.08 mg/L, 0.04 mg/L, 0.02 mg/L, 0.01 mg/L, 0.005 mg/L

Details on test conditions:

TEST SYSTEM
- Test vessel: Sterile Erlenmeyer flasks
- Type (delete if not applicable): closed
- Material, size, headspace, fill volume: Glass, 250 mL
- Aeration: no
- Initial cells density:
Nominal: approximately 5 x 10exp3 - 10exp4 cells/mL
Actual: 6442 cells/mL
- Control end cells density: yes
- No. of organisms per vessel: 1250 x 10exp3 - 10exp4
- No. of vessels per concentration (replicates): 2
- No. of vessels per control (replicates): 6

GROWTH MEDIUM
- Standard medium used: yes
- Detailed composition if non-standard medium was used: Nutrient medium Z according to LÜTTGE et al. (1994)

TEST MEDIUM / WATER PARAMETERS
- Source/preparation of dilution water: Ultrapure water (conductivity max. 0.1 µS/cm)
- Conductivity: max. 0.1 µS/cm
- Culture medium different from test medium: no

OTHER TEST CONDITIONS
- Sterile test conditions: yes
- Adjustment of pH: The pH of the test medium has to be 7.5  0.1 and may be adjusted prior to testing with addition of 1 M NaOH or HCl.
- Photoperiod: 24 h/d
- Light intensity and quality: Approximately 4440 to 8880 lux, corresponding to 60 to 120 µE*m-2*s-1

EFFECT PARAMETERS MEASURED (with observation intervals if applicable) :
- Determination of cell concentrations: The cell density was measured daily via Chlorophyll-a-fluorescence, excitation at 436 nm, emission at 685 nm.
- Chlorophyll measurement: see above

TEST CONCENTRATIONS
- Spacing factor for test concentrations: geometrical series
- Range finding study: yes
- Test concentrations: 10 mg/L, 1 mg/L, 0.100 mg/L, 0.0100 mg/L
- Results used to determine the conditions for the definitive study: yes

Reference substance (positive control):

yes

Remarks:

Potassium dichromate

Key result

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

ca. 0.024 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

growth rate

Duration:

72 h

Dose descriptor:

NOEC

Effect conc.:

ca. 0.005 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

growth rate

Details on results:

- Exponential growth in the control (for algal test): yes
- Observation of abnormalities (for algal test): no
- Unusual cell shape: no
- Colour differences: no
- Flocculation: no
- Adherence to test vessels: no
- Aggregation of algal cells: no
- Other: none reported
- Any stimulation of growth found in any treatment: no
- 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: no

Results with reference substance (positive control):

- Results with reference substance valid? yes
- EC50: 0.799 mg/L
- Other:

Reported statistics and error estimates:

The NOEC and LOEC were determined by calculation of statistically significant differences of growth rates and yield. As a standard, One Way Analysis of Variance (ANOVA) and DUNNETT’s test were used for NOEC/LOEC calculations. When running a One Way Analysis of Variance, a Normality test and an Equal Variance test were done first. P-values for both Normality and Equal Variance tests are 0.05. The alpha-value (acceptable probability of incorrectly concluding that there is a difference) is alpha=0.05.

Validity criteria fulfilled:

yes

Conclusions:

In this study, diethyl sulphate, compound with 2-(heptadec-8-enyl)-4,5-dihydro-1H-imidazole-1-ethanol (1:1) was found to inhibit the growth of the freshwater green alga Pseudokirchneriella subcapitata after 72 hours with the following effect values (based on nominal test item concentrations): The EC50-values with 95% confidence intervals for inhibition of growth rate (ErC50) and yield (EyC50) after 72 hours were 0.0235 (0.0202 – 0.0340) mg/L and 0.0216 (0.0194 – 0.0315) mg/L of the nominal test item concentration, respectively. The NOEC-values for both inhibition of growth rate and yield after 72 hours were 0.00500 mg/L of the nominal test item concentration.

Executive summary:

The toxictity of diethyl sulphate, compound with 2-(heptadec-8-enyl)-4,5-dihydro-1H-imidazole-1-ethanol (1:1) towards algae was determined in a guideline study according to OECD 105.

 

The substance was found to inhibit the growth of the freshwater green alga Pseudokirchneriella subcapitata after 72 hours with the following effect values (based on nominal test item concentrations): The EC50-values with 95% confidence intervals for inhibition of growth rate (ErC50) and yield (EyC50) after 72 hours were 0.0235 (0.0202 – 0.0340) mg/L and 0.0216 (0.0194 – 0.0315) mg/L of the nominal test item concentration, respectively. The NOEC-values for both inhibition of growth rate and yield after 72 hours were 0.00500 mg/L of the nominal test item concentration.

Description of key information

The toxicity of Diethyl sulphate, compound with 2-(heptadec-8-enyl)-4,5-dihydro-1H-imidazole-1-ethanol (1:1) to the unicellular freshwater green alga Pseudokirchneriella subcapitata was determined according to the principles of OECD 201. The EC₅₀-values with 95% confidence intervals for inhibition of growth rate (E_rC₅₀) and yield (E_yC₅₀) after 72 hours were 0.0235 (0.0202 – 0.0340) mg/L and 0.0216 (0.0194 – 0.0315) mg/L of the nominal test item concentration, respectively. The NOEC-values for both inhibition of growth rate and yield after 72 hours were 0.00500 mg/L of the nominal test item concentration.

Key value for chemical safety assessment

EC50 for freshwater algae:

0.024 mg/L

EC10 or NOEC for freshwater algae:

0.005 mg/L