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Ecotoxicological information

Toxicity to aquatic algae and cyanobacteria

Administrative data

Endpoint:
toxicity to aquatic algae and cyanobacteria
Type of information:
experimental study
Adequacy of study:
key study
Study period:
16 March - 4 April 2018
Reliability:
1 (reliable without restriction)

Data source

Reference
Reference Type:
study report
Title:
Unnamed
Year:
2018

Materials and methods

Test guideline
Qualifier:
according to guideline
Guideline:
OECD Guideline 201 (Alga, Growth Inhibition Test)
GLP compliance:
yes (incl. QA statement)

Test material

Constituent 1
Chemical structure
Reference substance name:
2-ethylhexyl 12-hydroxyoctadecanoate
EC Number:
249-793-7
EC Name:
2-ethylhexyl 12-hydroxyoctadecanoate
Cas Number:
29710-25-6
Molecular formula:
C26H52O3
IUPAC Name:
2-ethylhexyl 12-hydroxyoctadecanoate
Test material form:
other: Yellow Liquid
Details on test material:
Wickenol 171 Lot #424-9
2-Ethylhexyl Oxystearate
Specific details on test material used for the study:
Barch : A9859
Stable until 5 July 2018

Sampling and analysis

Analytical monitoring:
yes

Test solutions

Vehicle:
no
Details on test solutions:
The batch of the test substance was a clear yellowish liquid UVCB which was not completely soluble in test medium at the loading rates initially prepared. No correction was made for the purity of the test item.
Preparation of test solutions started with loading rates individually prepared at 1.0, 10 and 100 mg/L. A two day period of magnetic stirring was applied to ensure maximum dissolution of the test item in medium. The obtained mixtures were allowed to settle for an overnight period. Thereafter, the aqueous Water Accommodated Fractions (WAFs) were collected by means of siphoning and used as test concentrations. Immediately after siphoning, the obtained test solutions were checked for the presence of the Tyndall effect with the use of a laser pen. No light scattering was observed which indicates that only the dissolved part of the test item was present in the test solutions. All test solutions were clear and colorless at the end of the preparation procedure.
After preparation, volumes of 50 mL were added to each replicate of the respective test concentration. Subsequently, 1 mL of an algal suspension was added to each replicate providing a cell density of 104 cells/mL.
Any residual volumes were discarded.

Test organisms

Test organisms (species):
Pseudokirchneriella subcapitata (previous names: Raphidocelis subcapitata, Selenastrum capricornutum)
Details on test organisms:
Species Raphidocelis subcapitata (formerly known as Pseudokirchneriella subcapitata), strain: NIVA CHL 1
Source In-house laboratory culture.
Reason for selection This system is a unicellular algal species sensitive to toxic items in the aquatic ecosystem and has been selected as an internationally accepted species.

Study design

Test type:
static
Water media type:
freshwater
Limit test:
yes
Total exposure duration:
72 h

Test conditions

Hardness:
0.24mmol/L (24 mg CaCO3/L)
Test temperature:
21-24°C.
pH:
8.1 ± 0.2
Details on test conditions:
Test Concentrations
WICKENOL 171 WAFs individually prepared at loading rates of 1.0, 10 and 100 mg/L.
Control Test medium without test item or other additives
Replicates 3 replicates of each test concentration,
6 replicates of the control and limit concentration,
1 extra replicate of each test group for sampling purposes after 24 hours of exposure,
1 or 2 replicates of each test concentration without algae
Reference substance (positive control):
yes

Results and discussion

Effect concentrationsopen allclose all
Key result
Duration:
72 h
Dose descriptor:
EL50
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.:
> 0.003 mg/L
Nominal / measured:
meas. (TWA)
Conc. based on:
test mat.
Basis for effect:
growth rate
Duration:
72 h
Dose descriptor:
other: NOEL
Effect conc.:
>= 100 mg/L
Nominal / measured:
nominal
Conc. based on:
other: loading rate
Basis for effect:
growth rate
Duration:
72 h
Dose descriptor:
LOEC
Effect conc.:
>= 0.003 mg/L
Nominal / measured:
meas. (TWA)
Conc. based on:
test mat.
Basis for effect:
growth rate
Details on results:
Growth Rate And Percentage Inhibition For The Total Test Period

Test substance
Loading rate (mg/L) Mean Std. Dev. n %Inhibition
Control 1.825 0.0256 6
1.0 1.801 0.0113 3 1.3
10 1.809 0.0031 3 0.91
100 (0.0030) 1.808 0.0115 6 0.93
( ) – TWA concentration (mg/L).
Table 2
Growth Rate And Percentage Inhibition At Different Time Intervals

Test substance
Loading rate (mg/L) n 0 – 24 h 24 – 48 h 48 – 72h
Mean %Inhibition Mean %Inhibition Mean %Inhibition
Control 6 2.234 1.763 1.480
100 (0.0030) 6 2.320 -3.8 1.549 12 1.556 -5.2
( ) – TWA concentration (mg/L).
Table 3
Yield And Percentage Inhibition For The Total Test Period

Test substance
Loading rate (mg/L) Mean Std. Dev. n %Inhibition
Control 238.4 18.71 6
1.0 221.4 7.52 3 7.1
10 226.2 2.11 3 5.1
100 (0.0030) 226.1 7.83 6 5.2
( ) – TWA concentration (mg/L).
9.4. Determination of Effect Concentrations
Table 4 shows the effect parameters expressed as the loading rate and TWA of the limit concentration.
Table 4
Effect Parameters Expressed as Loading Rate and TWA concentration

Parameter (mg/L) NOEL NOEC EL50 EC50
Growth rate 100 0.0030 >100 >0.0030
Yield 100 0.0030 >100 >0.0030

Results with reference substance (positive control):
Potassium dichromate inhibited growth rate of this fresh water algae species at nominal concentrations of 0.18 mg/L and higher.
The EC50 for growth rate inhibition (72h-ERC50) was 0.86 mg/L with a 95% confidence interval ranging from 0.84 to 0.88 mg/L. The historical ranges for growth rate inhibition lie between 0.82 and 2.3 mg/L. The observed 72h-ERC50 for the algal culture tested corresponds with this range.
The EC50 for yield inhibition (72h-EYC50) was 0.34 mg/L with a 95% confidence interval ranging from 0.34 to 0.35 mg/L. The historical ranges for yield inhibition lie between 0.20 and 1.1 mg/L. The observed 72h-EYC50 for the algal culture tested corresponds with this range.

Applicant's summary and conclusion

Validity criteria fulfilled:
yes
Conclusions:
In conclusion, under the conditions of the present study with Raphidocelis subcapitata (formerly known as Pseudokirchneriella subcapitata), no significant inhibition of growth rate or inhibition of yield was recorded at any of the concentrations of the test substance tested.
The EL50-values for growth rate (72h-ERL50) and yield inhibition (72h-EYL50) exceeded a loading rate of 100 mg/L.
The EC50-values for growth rate (72h-EYL50) and yield inhibition (72h-EYC50) exceeded a TWA concentration of 0.0030 mg/L.
The 72h-NOEL for both growth rate and yield inhibition was at a loading rate of 100 mg/L.
The 72h-NOEC for both growth rate and yield inhibition was at a TWA concentration of 0.0030 mg/L.
Due to the very low solubility of the test substance in water, concentration levels that might be toxic for algae could not be reached.
Executive summary:

In conclusion, under the conditions of the present study with Raphidocelis subcapitata(formerly known asPseudokirchneriella subcapitata), no significant inhibition of growth rate or inhibition of yield was recorded at any of the concentrations of test substance tested.

The EL50-values for growth rate (72h-ERL50) and yield inhibition (72h-EYL50) exceeded a loading rate of 100 mg/L.

The EC50-values for growth rate (72h-EYL50) and yield inhibition (72h-EYC50) exceeded a TWA concentration of 0.0030 mg/L.

The 72h-NOEL for both growth rate and yield inhibition was at a loading rate of 100 mg/L.

The 72h-NOEC for both growth rate and yield inhibition was at a TWA concentration of 0.0030 mg/L.

Due to the very low solubility of test subtance in water, concentration levels that might be toxic for algae could not be reached.