[2-(2-methoxyethoxy)ethoxy]acetic acid

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:

from 2018-01-19 to 2018-04-24

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)

Deviations:

no

Qualifier:

according to guideline

Guideline:

EU Method C.3 (Algal Inhibition test)

Deviations:

no

Qualifier:

according to guideline

Guideline:

EPA OPPTS 850.5400 (Algal Toxicity, Tiers I and II) (January 2012)

Deviations:

no

Qualifier:

according to guideline

Guideline:

other: Guidance Document on Aquatic Toxicity Testing of Difficult Substances and Mixtures, section 3.1.2 Media preparation methods, Direct addition. OECD Series on Testing and Assessment No. 23, Paris September 2000

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Specific details on test material used for the study:

Batch No.: 08/2016_R_JM
Purity: 96.8 %

Analytical monitoring:

yes

Details on sampling:

Three parallel samples were measured from each test concentration and six replicates from the control. The samples were prepared immediately after sampling.

Vehicle:

no

Details on test solutions:

A stock solution of 100 mg/L (nominal concentration) was prepared by dissolving 0.08 g of test item in 808 mL OECD Medium. The pH value (5.68) of the stock solution was adjusted to the pH of the OECD Medium - 7.87 (according to OECD 23). The adjusted pH level of the stock solution was 8.14. Further test solutions were prepared by appropriate dilution of this stock solution.

Test organisms (species):

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

Details on test organisms:

TEST ORGANISM
- Common name: green algae
- Strain: 61.81 SAG
- Source: Collection of Algal Cultures, Inst. Plant Physiology, University of Göttingen, Untere Karspüle 2, D-37073 Göttingen, Germany
- Age of inoculum (at test initiation): 3 days

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

72 h

Test temperature:

22.0 – 22.6 °C

pH:

7.87 – 8.95

Nominal and measured concentrations:

nominal concentration: 6.25, 12.5, 25, 50, 100 mg/L
measured concentration: within ± 20 % of the nominal concentrations

Details on test conditions:

TEST SYSTEM
- Test vessel: Erlenmeyer flasks
- Material, size, headspace, fill volume: glass, ~250 mL volume, 100 mL test medium
- Initial cells density: 1 x 10^4 cells/mL
- Control end cells density: 50.50 x 10^4 cells/mL
- No. of organisms per vessel: 0.1 mL algal biomass (10^7 algal cells per mL)
- No. of vessels per concentration (replicates): 6
- No. of vessels per control (replicates): 6

GROWTH MEDIUM
- Standard medium used: yes

TEST MEDIUM / WATER PARAMETERS
- Source/preparation of dilution water: OECD Medium prepared according to OECD 201

OTHER TEST CONDITIONS
- Adjustment of pH: yes
- Photoperiod: continuously illuminated
- Light intensity and quality: 7453 lux

TEST CONCENTRATIONS
- Range finding study; yes, 2 tests, with and without pH adjustment
- Test concentrations: 0.1, 1, 10, 100 mg/L

EFFECT PARAMETERS MEASURED :
- Determination of cell concentrations: microscope with counting chambe at 24, 48 and 72 hours

Reference substance (positive control):

yes

Remarks:

Potassium dichromate (K2Cr2O7)

Key result

Duration:

72 h

Dose descriptor:

EC10

Effect conc.:

> 100 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

growth rate

Key result

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

> 100 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

growth rate

Duration:

72 h

Dose descriptor:

NOEC

Effect conc.:

100 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

growth rate

Remarks:

and yield

Duration:

72 h

Dose descriptor:

EC10

Effect conc.:

66.72 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

biomass

Remarks:

yield

Remarks on result:

other: 95% CI: 31.421 - 158.832 mg/L

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

> 100 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

biomass

Remarks:

yield

Duration:

72 h

Dose descriptor:

LOEC

Effect conc.:

> 100 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

growth rate

Remarks:

and yield

Details on results:

- Cell shape: No morphological abnormalities were observed in the control and in the concentrations of 6.25, 12.5, 25.0 and 50.0 mg/L during the experiment. In the highest test item group (100.0 mg/L) thin cells were observed together with normal cells at 48 and 72 hours.
- Cell density in the control: The cell density in the control has increased from nominal N = 1E+4 cells/mL at the start of the test (0 hours) to N = 50.50E+4 cells/mL (mean value) after 72 hours in the untreated control.

Results with reference substance (positive control):

The date of the last study with the reference item Potassium dichromate was: 26 February - 01 March 2018. The following results were obtained:
The 72h ErC50: 1.08 mg/L, (95 % confidence limits: 0.79 – 1.51 mg/L)
The 72h EyC50: 0.561 mg/L, (95 % confidence limits: 0.49 – 0.76 mg/L)

Pre-experiments

In the preliminary tests, the test item showed 15 % growth inhibition at 100 mg/L tets concentration when the pH of the test item solution was not adjusted. After adjustment of the pH, the inhibition at 100 mg/L concentration level was 9.93 %. In the second preliminary test, performed with adjusted pH, the inhibition of the algae was at a maximum of 4.99 % at treatment level of 100 mg/L.

Validity criteria

- Cell density in the control cultures increased by a factor of more than 16 (by a factor of 50.50) within 72 hours.

- The mean coefficient of variation for section-by-section specific growth rates (days 0-1, 1-2 and 2-3, for 72 h-tests) in the control cultures did not exceed 35 %.

- CV for section-by-section growth rate day 0-1: 12.44 %

- CV for section-by-section growth rate day 1-2: 24.19 %

- CV for section-by-section growth rate day 2-3: 15.00 %

The mean coefficient of variation for section-by-section specific growth rates: 17.21 %.

- The coefficient of variation of average specific growth rates during the whole test period in replicate control cultures did not exceed 7 % in test.

- CV for average specific growth rate day 0-3: 4.59 %

All validity criteria were met, therefore, the study is considered as valid.

Analytical results

Three parallel samples were measured from each test concentration and six replicates from the control. The measured concentration of the test item varied in the range from 96 % to 100 % in comparison to the nominal values.

Validity criteria fulfilled:

yes

Conclusions:

The 72-h EC10 and EC50 of the test item based on growth rate of green algae were determined to be >100 mg/L, respectively. The NOEC was determined to be 100 mg/L.

Executive summary:

The effect of the test item on the growth of a unicellular green algal species Raphidocelis subcapitata was determined according to OECD 201, Regulation (EC) No. 226/2016 Method C.3 and EPA OPPTS 850.5400 and under GLP. The study was conducted under static conditions with an initial cell density of 1E+4 cells/mL for a period of 72 hours. Five test concentrations - 6.25, 12.5, 25, 50 amd 100 mg/L, and control were tested. The measured concentrations of the test item at the start and at the end of the test were in the range of 99 - 100 % of the nominal concentration. The measured concentrations deviated not more than 20 % from the nominal concentration, therefore, the nominal concentrations were used to determine exposure concentrations. The EC50-values for inhibition of growth rate (ErC50) and for inhibition of yield (EyC50) were >100 mg/L. The ErC10 was determined to be >100 mg/L. The EyC50 was 66.72 mg/L and the NOEC was determined to be 100 mg/L. The test item showed no toxic effects on the growth of the Raphidocelis subcapitat up to the concentration of 100 mg/L.

Description of key information

The 72-h EC10 and EC50 of the test item based on growth rate of green algae were determined to be >100 mg/L, respectively. The NOEC was determined to be 100 mg/L.

Additional information

The effect of the test item on the growth of a unicellular green algal species Raphidocelis subcapitata was determined according to OECD 201, Regulation (EC) No. 226/2016 Method C.3 and EPA OPPTS 850.5400 and under GLP. The study was conducted under static conditions with an initial cell density of 1E+4 cells/mL for a period of 72 hours. Five test concentrations - 6.25, 12.5, 25, 50 amd 100 mg/L, and control were tested. The measured concentrations of the test item at the start and at the end of the test were in the range of 99 - 100 % of the nominal concentration. The measured concentrations deviated not more than 20 % from the nominal concentration, therefore, the nominal concentrations were used to determine exposure concentrations. The EC50-values for inhibition of growth rate (ErC50) and for inhibition of yield (EyC50) were >100 mg/L. The ErC10 was determined to be >100 mg/L. The EyC50 was 66.72 mg/L and the NOEC was determined to be 100 mg/L. The test item showed no toxic effects on the growth of the Raphidocelis subcapitat up to the concentration of 100 mg/L.