Oligomerisation products of 2,2'-[(1-methylethylidene)bis(4,1-phenyleneoxymethylene)]bisoxirane with acrylic acid and lauric 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:

October 26, 2020 to 02 November, 2020

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 201 (Alga, Growth Inhibition Test)

Qualifier:

according to guideline

Guideline:

EU Method C.3 (Algal Inhibition test)

GLP compliance:

yes (incl. QA statement)

Analytical monitoring:

yes

Details on sampling:

At the start and at the end of the test, the content of the test item in the test solutions was
estimated by determination of the total organic carbon (TOC) content in the test solutions
using a carbon analyser.

Vehicle:

no

Details on test solutions:

Due to the poor water solubility, water-accommodated fractions (WAFs) were prepared for the test. This was done by mixing the nominal loads of 0, 1, 3.2, 10, 32 and 100 mg/L test substance with the corresponding amount of algal medium (demineralised water enriched with minerals but without algae) and shaking vigorously for 24 hours. After a settling time of 1 hour the resulting solutions were filtered through 0.45 μm PTFE filters.

Test organisms (species):

Desmodesmus subspicatus (previous name: Scenedesmus subspicatus)

Details on test organisms:

Genus: Desmodesmus
Species: subspicatus
SAG Strain Number: 86.81
Taxonomic position: Chlorophyta - Chlorophyceae

Origin and Culture
The culture of Desmodesmus subspicatus was obtained in May 2020 by MBM Sciencebridge
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.

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

72 h

Test temperature:

21.7 – 22.2°C

pH:

7.5-7.9

Nominal and measured concentrations:

Only in the two highest tested concentrations 32 mg/L and 100 mg/L, TOC was clearly detectable.
The other tested concentrations were too low and the measurement method is too
inaccurate to get meaningful results. Because clear toxicity was observed, it was shown that
the test item was present throughout the test in the test solutions and therefore, the determination of the results was based on the nominal loading rate of the WAFs.

Details on test conditions:

Range of light intensity: 4440-8880 lux

Reference substance (positive control):

yes

Remarks:

The 72h-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).

Key result

Duration:

72 h

Dose descriptor:

EL50

Effect conc.:

25.41 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

growth rate

Remarks on result:

other: 95% CI 22.91 mg/L – 28.09 mg/L

Key result

Duration:

72 h

Dose descriptor:

NOELR

Effect conc.:

1 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

growth rate

Key result

Duration:

72 h

Dose descriptor:

EL50

Effect conc.:

6.44 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

other: Yield

Remarks on result:

other: 95% CI: 2.97 mg/L – 13.79 mg/L

Key result

Duration:

72 h

Dose descriptor:

NOELR

Effect conc.:

1 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

other: Yield

Details on results:

The study was performed using 5 concentrations ranging from 1 to 100 mg/L (nominal).
Incubation time (test system Desmodesmus subspicatus) was 72 hours. The cell concentration
of each replicate was determined by measuring the cell numbers every 24 ± 1 hours with an electronic particle counter. Growth rate and the yield were determined from the cell number at the respective observation times. Significant inhibition of algal growth was observed at the following concentrations: 0, 3.2, 10, 32 and 100 mg/L for the endpoint yield and 0, 1, 3.2, 10, 32 and 100 mg/L for the endpoint growth rate.
At the start and at the end of the test, the content of the test item in the test solutions was
estimated by determination of the total organic carbon (TOC) content in the test solutions
using a carbon analyser.
Only in the two highest tested concentrations 32 mg/L and 100 mg/L, TOC was clearly detectable.
The other tested concentrations were too low and the measurement method is too inaccurate to get meaningful results. Because clear toxicity was observed, it was shown that the test item was present throughout the test in the test solutions and therefore, the determination of the results was based on the nominal loading rate of the WAFs.

Results with reference substance (positive control):

The 72h-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).

Validity criteria fulfilled:

yes

Remarks:

Cell Density Increase in Control Cultures: > 16-fold; Coefficient of Variation of Sectional (Daily) Growth Rates in Control Cultures: < 35 % ; Coefficient of Variation of Average Growth between Control Cultures: < 7 %

Executive summary:

A study was conducted to determine the acute toxicity of the test substance to the Desmodesmus subspicatus according to OECD Guideline 201 and EU Method C.3, in compliance with GLP. Three replicates of exponentially growing algal cultures were exposed to WAFs prepared at loading rates of 0, 1, 3.2, 10, 32 and 100 mg/L. In addition, six replicates were exposed to a control. The initial cell density was 2.3E+3 cells/mL and the total test period was 72 h. Samples for analytical confirmation of actual exposure concentrations were taken at the start and the end of the test. At the start and at the end of the test, the content of the test item in the test solutions was estimated by determination of the total organic carbon (TOC) content in the test solutions using a carbon analyser. Only in the two highest tested concentrations 32 mg/L and 100 mg/L, TOC was clearly detectable.
The other tested concentrations were too low and the measurement method is too
inaccurate to get meaningful results. Because clear toxicity was observed, it was shown that the test item was present throughout the test in the test solutions and therefore, the determination of the results was based on the nominal loading rate of the WAFs The study met the acceptability criteria prescribed by the protocol and was considered valid. The test substance reduced the growth of the algae at various concentrations. Based on the observations, the following results were obtained. The EC50 for growth rate reduction (ErC50: 0-72 h) was 25.41 mg/L. The EC50 for yield inhibition (EyC50: 0-72h) was 6.44 mg/L. The NOE(L)R for both growth rate reduction and yield inhibition was 1 mg/L. Under the study conditions, 72 h ErC50 and NOE(L)R for the test substance were determined to be 25.41 and 1 mg/L (Meisner, 2020).

 

Key value for chemical safety assessment

EC50 for freshwater algae:

25.41 mg/L

EC10 or NOEC for freshwater algae:

1 mg/L

Additional information

A study was conducted to determine the acute toxicity of the test substance, to the Desmodesmus subspicatus according to OECD Guideline 201 and EU Method C.3, in compliance with GLP. Three replicates of exponentially growing algal cultures were exposed to WAFs prepared at loading rates of 0, 1, 3.2, 10, 32 and 100 mg/L. In addition, six replicates were exposed to a control. The initial cell density was 2.3E+3 cells/mL and the total test period was 72 h. Samples for analytical confirmation of actual exposure concentrations were taken at the start and the end of the test. At the start and at the end of the test, the content of the test item in the test solutions was estimated by determination of the total organic carbon (TOC) content in the test solutions using a carbon analyser. Only in the two highest tested concentrations 32 mg/L and 100 mg/L, TOC was clearly detectable.
The other tested concentrations were too low and the measurement method is too
inaccurate to get meaningful results. Because clear toxicity was observed, it was shown that the test item was present throughout the test in the test solutions and therefore, the determination of the results was based on the nominal loading rate of the WAFs The study met the acceptability criteria prescribed by the protocol and was considered valid. The test substance reduced the growth of the algae at various concentrations. Based on the observations, the following results were obtained. The EC50 for growth rate reduction (ErC50: 0-72 h) was 25.41 mg/L. The EC50 for yield inhibition (EyC50: 0-72h) was 6.44 mg/L. The NOE(L)R for both growth rate reduction and yield inhibition was 1 mg/L. Under the study conditions, 72 h ErC50 and NOE(L)R for the test substance were determined to be 25.41 and 1 mg/L (Meisner, 2020).