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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:
15 January 2018 to 18 January 2018
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to guideline
Guideline:
OECD Guideline 201 (Alga, Growth Inhibition Test)
Deviations:
yes
Remarks:
no analytical confirmation os the tested concentrations due to the absence of a suitable analytical method
GLP compliance:
yes (incl. QA statement)
Analytical monitoring:
no
Remarks:
it was not possible to develop a suitable analytical method for this substance
Vehicle:
yes
Details on test solutions:
A primary stock concentrate of the substance with a nominal concentration of 10 g/L was prepared by weighing a nominal 0.1 g of test substance (actual weight: 0.09997 g) into a 10 mL volumetric flask and making up to volume with tetrahydrofuran (THF). The volumetric flask was manually shaken to mix and the resultant stock was observed to be clear and colourless.
Max amount of THF solvent used in all exposure solutions with the exception of the control was 100 µL/L.
Test solutions were prepared by the direct addition of the appropriate amount of concentrate to dilution water via a microliter syringe into a stirring solution in a volumetric flask. The solvent control was prepared in the same way using solvent only. The control consisted of culture medium only.
Test organisms (species):
Pseudokirchneriella subcapitata (previous names: Raphidocelis subcapitata, Selenastrum capricornutum)
Details on test organisms:
TEST ORGANISM
- Common name: Pseudokirchneriella subcapitata
- Strain: CCAP 278/4
- Source: laboratory culture:
- Age of inoculum (at test initiation): 3 days
- Method of cultivation: similar to test conditions

Test type:
static
Water media type:
freshwater
Limit test:
no
Total exposure duration:
72 h
Test temperature:
21.8-22.2 ˚C
pH:
7.09-7.62
Nominal and measured concentrations:
nominal: 0.0625, 0.125, 0.25, 0.5 and 1.0 mg/L (highest concentration selected based on low solubility)
Details on test conditions:
TEST SYSTEM
- Test vessel: glass conical flasks of 250 mL
- Type: closed with foam bung
- Fill volume: 100 mL
- Aeration: none
- Initial cells density: nominal 0.5E04 cells/mL; measured 0.459E04 cells/mL
- Control end cells density: 46.7E04 cells/mL (medium controls); 35.9E04 cells/mL (vehicle controls)
- No. of vessels per concentration (replicates): 3
- No. of vessels per control (replicates): 6
- No. of vessels per vehicle control (replicates): 6

GROWTH MEDIUM
- Standard medium used: yes AAP medium

TEST MEDIUM / WATER PARAMETERS
- Source/preparation of dilution water: AAP medium according to the guideline

OTHER TEST CONDITIONS
- Sterile test conditions: yes
- Adjustment of pH: no
- Photoperiod: continuous
- Light intensity: 6485 lux

EFFECT PARAMETERS MEASURED: at 24, 48 and 72 h cell density, growth rate and yield
- Determination of cell concentrations: couter counter
- Chlorophyll measurement: not included
- Other: at 72 h microscopic observations of one replicate of controls and substance concentrations

TEST CONCENTRATIONS
- Range finding study: at 0.0625, 0.125, 0.25, 0.5 and 1.0 mg/L in THF
- Results used to determine the conditions for the definitive study: mean biomass at 72 h (times E04 cells/mL): 18.70, 14.10, 12.70, 13.83, 14.30, 14.23 and 12.57 at 0, 0 (THF), 0.0625, 0.125, 0.25, 0.5 and 1.0 mg/L
Reference substance (positive control):
no
Duration:
72 h
Dose descriptor:
EC50
Effect conc.:
> 1 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
growth rate
Duration:
72 h
Dose descriptor:
NOELR
Effect conc.:
0.5 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
growth rate
Duration:
72 h
Dose descriptor:
EC50
Effect conc.:
> 1 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
biomass
Remarks:
yield
Duration:
72 h
Dose descriptor:
NOELR
Effect conc.:
0.25 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
biomass
Remarks:
yield
Details on results:
The microscopic observations, made at the end of the test, showed that compared to the control the algal cells sampled from the solvent control and all test concentrations appeared normal.

Mean growth rates over the test period

Nominal concentration

(mg/L)

Mean growth rate/day

(0-72 hours)

Mean growth rate/day

95% Cl

Percentage of solventcontrol (%)

Culture medium control

1.54

1.52-1.56

106

Solvent control

1.45

1.44-1.47

-

0.0625

1.42

1.39-1.45

98

0.125

1.44

1.38-1.49

99

0.25

1.42

1.39-1.46

98

0.5

1.41

1.38-1.44

97

1.0

1.37 *

1.28-1.46

94

* Significant difference (p <0.05) from the solvent control.

All biological measurements are quoted to 3 significant figures and percentages to the nearest integer.

Mean yields over the test period

Nominal concentration

(mg/L)

Mean yield

(0-72 hours)

(104cells/ml)

Mean yield

95% Cl

(104cells/ml)

Percentage of solventcontrol (%)

Culture medium control

46.2

43.0-49.4

130

Solvent control

35.5

33.5-37.4

-

0.0625

32.1

29.0-35.2

90

0.125

33.7

28.2-39.1

95

0.25

32.2

28.6-35.8

91

0.5

31.2 *

28.4-34.1

88

1.0

27.6 *

20.2-34.9

78

* Significant difference (p <0.05) from the solvent control.

Mean yield values are quoted to 3 significant figures.

Validity criteria fulfilled:
yes
Conclusions:
The ErC50 is > 1.0 mg/L, the NOELR (growth rate) is 0.5 mg/L
Executive summary:

In a study according to OECD 201, algae were exposed to 0, 0.0625, 0.125, 0.25, 0.5 and 1.0 mg/L (vehicle THF) of the substance during 72 hours. The highest concentration was based on the limited solubility of the substance.

Effects on growth rate were seen at 1.0 mg/L, while effects on yield were observed at 0.5 mg/L. EC50 values for both growth rate and yield were > 1.0 mg/L.

Description of key information

In a study according to OECD 201, algae were exposed to 0, 0.0625, 0.125, 0.25, 0.5 and 1.0 mg/L (vehicle THF) of the substance during 72 hours. The highest concentration was based on the limited solubility of the substance. Effects on growth rate were seen at 1.0 mg/L, while effects on yield were observed at 0.5 mg/L. EC50 values for both growth rate and yield were > 1.0 mg/L.

Key value for chemical safety assessment

EC50 for freshwater algae:
1 mg/L
EC10 or NOEC for freshwater algae:
0.5 mg/L

Additional information