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Ecotoxicological information

Toxicity to aquatic algae and cyanobacteria

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Reference
Endpoint:
toxicity to aquatic algae and cyanobacteria
Type of information:
experimental study
Adequacy of study:
key study
Study period:
2018
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
GLP compliance:
yes
Specific details on test material used for the study:
SOURCE OF TEST MATERIAL
- Source and lot/batch number of test material: Batch number 170808-29
- Expiration date of the lot/batch: 28/Aug/2019
- Purity test date: 99.71 % w/w
Analytical monitoring:
yes
Details on sampling:
At intervals of 0, 24, 48 and 72 hours of the test, aliquots of each one of the test solutions were taken from the flasks to determine the test substance
concentration
Vehicle:
yes
Details on test solutions:
The primary stock solution used in the range-finding test was prepared by dissolving 0.0250 g of the test substance in the volume was completed to 250 mL with OECD medium, resulting in a concentration of 100 mg.1. 1. The stock solution of 10 mg.L-1 was prepared from dilution of the primary stock solution.
The stock solution used in the definitive test was prepared by dissolving 0.100 g of the test substance in the volume was completed to 1000 mL with OECD medium, resulting in a concentration of 100 mg.L-1.
From these initial stock solutions, a series of dilutions was prepared in order to obtain the desired tested concentrations
Test organisms (species):
Pseudokirchneriella subcapitata (previous names: Raphidocelis subcapitata, Selenastrum capricornutum)
Details on test organisms:
The unicellular green alga species Pseudokirchneriella subcapitata used is part of the Chloroficeae group, Chlorococcales order.

The test system was obtained from Culture Collection of Algae at Goettingen University - SAG 61.81 on October, 08th, 2013and is recommended by the
Guideline OECD 201 (2011).

The stock culture was prepared and maintained under lab-controlled conditions in solid medium with protease peptone.
The inoculated solid medium was kept inside a culture room, with controlled temperature of 21 to 24°C and luminosity of 2100 ± 10% lux. After algae cultures
reached an ideal growth (about one week), they were maintained at temperature of 2 to 6°C and luminosity of 100 to 200 lux in order to slow down the algae
growth.
Test type:
static
Water media type:
freshwater
Total exposure duration:
72 h
Test temperature:
22.0 to 22.3°C
pH:
7.2 to 8.12
Nominal and measured concentrations:
Nominal concentration (mg.L-1)
Control
1 0.
3.2
10
32
100

Mean of effective concentration of test substance (mg.L-1)
0.9026
2.6836
8.1396
26.9469
81.9080
Details on test conditions:
A range-finding test was carried out using the following concentrations of test substance: control; 0.1; 1; 10 and 100 mg.L-1 of test substance, with two replicate per concentration. The algae inoculum was transferred aseptically to each test flask, with calculated volume to yield an initial cell concentration of 5 x 103

After 72 hours, samples of each test flask were taken in order to count the cells and to determine the concentrations, using a Neubauer chamber and a
microscope, that caused algal growth reduction.
Based on the results obtained in the range-finding test, the definitive test was carried out with the following concentrations of test substance: control;
1; 3.2; 10; 32 and 100 mg.L-1.
The test was performed with six replicates per each concentration and control, therefore tree replicate was prepared for determinations
of pH and chemical analysis. The algae inoculum was transferred aseptically to each test flask, with calculated volume to yield an initial cell concentration of 5 x 103 cells.mL-1.
All test flasks were randomly positioned in an incubating chamber with controlled temperature and kept under continuous shaking and lighting conditions.
Every day the flasks were relocated to different places inside the incubating chamber.

The definitive test was carried out under the conditions described below:
Temperature: 22.0 to 22.3°C
Light: 5991 lux (average)
Photoperiod: continuous light
Shaker velocity: 130.8 rpm (average)
Test duration: 72 hours
Temperature was measured daily using a digital thermometer. The pH was measured at the beginning of the test and at 72 hours .
One aliquot was taken from each test flask in order to determine the algal growth over the period of 24, 48 and 72 hours after the start of the test. A Neubauer
chamber and a microscope were used to determine the cell number (cells.mL-1).
A test with the reference substance, potassium dichromate, was also carried out in order to verify the sensitivity of the test system.
The procedure for this test was the same as for the definitive test described above, with initial cell concentration of 5 x 103 cells.mL-1 for each concentration and using nominal concentrations of 0 (control); 0.18; 0.32; 0.56; 1.00 and 1.80 mg/L and two replicates for each test concentrations.
Reference substance (positive control):
yes
Remarks:
Potassium dichromate
Key result
Duration:
72 h
Dose descriptor:
NOEC
Effect conc.:
ca. 1 mg/L
Basis for effect:
growth rate
Key result
Duration:
72 h
Dose descriptor:
EC50
Basis for effect:
growth rate
Remarks on result:
not determinable
Remarks:
because the highest tested concentration of 100 mg.L1, caused only 16% inhibition of growth rate.
Key result
Duration:
72 h
Dose descriptor:
LOEC
Effect conc.:
ca. 3.2 mg/L
Basis for effect:
growth rate
Details on results:
The 72-hours EC50 value of test substance, obtained in this study with Pseudokirchneriella subcapitata, was 23.42 mg.L-1 (95% confidence limits = 13.78 to 39.79 mg.L-1) and the the 72-hours EC50 value was not determined, because the highest tested concentration of 100 mg.L-1, caused only 16% inhibition of growth rate.
The highest test substance concentration which no observed significant adverse effect (NOEC) on algal growth was 1 mg.L-1 and the lowest test substance concentration at which was observed significant reducing effect on growth (LOEC) was 3.2 mg/L.
Results with reference substance (positive control):
The 72-hours EC50 value of the reference substance potassium dichromate was 0.64 mg/L (confidence limits at 95% = 0.59 to 0.70 mg1-1), demonstrating that the toxic sensitivity of the algae was within the accepted range (ISO, 1989), which report toxicity ranged between 0.60 and 1.03 mg.L-1.
Validity criteria fulfilled:
yes
Conclusions:
The 72-hours EyC50 value for alga Pseudokirchneriella subcapitata exposed to 2-(Benzyloxy) ethanol was 23.42 mg.L-1 (95% confidence limits = 13.78 to 39.79 mg.L-1) and the the 72-hours EC50 value was not determined, because the highest tested concentration of 100 mg.L1, caused only 16% inhibition of growth rate. The highest test substance concentration which no observed significant adverse effect (NOEC) on algal growth was 1 mg.L-1 and the lowest test substance
concentration at which was observed significant reducing effect on growth (LOEC) was 3.2 mg.L-1.

Description of key information

The 72-hours EyC50 value for alga Pseudokirchneriella subcapitata exposed to 2-(Benzyloxy) ethanol was 23.42 mg.L-1 (95% confidence limits = 13.78 to 39.79 mg.L-1) and the the 72-hours EC50 value was not determined, because the highest tested concentration of 100 mg.L1, caused only 16% inhibition of growth rate. The highest test substance concentration which no observed significant adverse effect (NOEC) on algal growth was 1 mg.L-1 and the lowest test substance

concentration at which was observed significant reducing effect on growth (LOEC) was 3.2 mg.L-1.

Key value for chemical safety assessment

Additional information