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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:
read-across from supporting substance (structural analogue or surrogate)
Adequacy of study:
key study
Justification for type of information:
REPORTING FORMAT FOR THE ANALOGUE APPROACH
Please refer to the Read-across statement attached under section 13.

1. HYPOTHESIS FOR THE ANALOGUE APPROACH
This Read-Across is based on the hypothesis that the target and the source substances have similar environmental fate and (eco)toxicological properties because both substances have the same common compound octyl sulfonate while another main constituent of the target substance octyl disulfonate is considered to have similar level of toxicity as octyl sulfonate. Other non-common compounds represented by impurities are considered not to influence the read-across validity because they are either structurally identical in the target and in the source substances or, if different, do not contribute to the toxicity effects because they are also anionic sulfonates with the same functional groups and their content is very low.

2. SOURCE AND TARGET CHEMICAL(S) (INCLUDING INFORMATION ON PURITY AND IMPURITIES)
Please refer to the Read-across statement attached under section 13.

3. ANALOGUE APPROACH JUSTIFICATION
The aquatic toxicity of the ANS category members is influenced mainly by the length of alkyl chain. Numerous studies demonstrate increasing toxicity with the chain length. Since all sulfonate containing constituents of the target substance are octyl derivatives, they are considered not to possess higher toxicity potential to aquatic environment than the source substance. Taking into account the similar predicted environmental fate and behavior as well as the similar mode of ecotoxic action due to its surfactant properties, the second sulfonate group of the main constituent octyl disulfonate is considered not to result in a higher toxicity to aquatic life than the source substance. Thus, the results of the acute toxicity study in algae available for the source substance are considered to be the same if a study with the target substance was conducted.

4. DATA MATRIX
Please refer to the Read-across statement attached under section 13.
Reason / purpose:
read-across source
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
Remarks on result:
other: predicted result from the source substance
Duration:
72 h
Dose descriptor:
EC20
Effect conc.:
> 100 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
growth rate
Remarks on result:
other: predicted result from the source substance
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
Remarks on result:
other: predicted result from the source substance
Key result
Duration:
72 h
Dose descriptor:
EC50
Effect conc.:
> 100 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
other: yield
Remarks on result:
other: predicted result from the source substance
Duration:
72 h
Dose descriptor:
EC20
Effect conc.:
> 100 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
other: yield
Remarks on result:
other: predicted result from the source substance
Key result
Duration:
72 h
Dose descriptor:
EC10
Effect conc.:
> 100 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
other: yield
Remarks on result:
other: predicted result from the source substance
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 on result:
other: predicted result from the source substance
Duration:
72 h
Dose descriptor:
NOEC
Effect conc.:
100 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
other: yield
Remarks on result:
other: predicted result from the source substance
Duration:
72 h
Dose descriptor:
LOEC
Basis for effect:
growth rate
Remarks on result:
not determinable
Remarks:
No statistically significant inhibitory effects
Duration:
72 h
Dose descriptor:
LOEC
Basis for effect:
other: yield
Remarks on result:
not determinable
Remarks:
No statistically significant inhibitory effects
Details on results:
- Exponential growth in the control (for algal test): yes
- Observation of abnormalities (for algal test): Microscopically observed at the end of the test, all cells were considered normal for the control and all test item concentrations.
- Unusual cell shape: None
- Colour differences: None
- Flocculation: None
- Adherence to test vessels: None reported
- Aggregation of algal cells: None reported
- Other: N/A
- Any stimulation of growth found in any treatment:
- Any observations (e.g. precipitation) that might cause a difference between measured and nominal values: None
- Effect concentrations exceeding solubility of substance in test medium: None

Results with reference substance (positive control):
- Results with reference substance valid?
- EC50: Growth rate: 1.23 mg/L (nominal); Yield: 0.685 mg/L
- Other: The EC50 values calculated in the reference test (performed in a separate study twice a year by the laboratory) were considered to be within an acceptable range therefore it can be considered that the test organism is sensitive.
Reported statistics and error estimates:
After 72 h at termination of the test no statistically significant inhibition of growth rate or yield was observed for test item concentrations up to and including 100 mg/L. Due to an inhibition below 10, 20 and 50 % for growth rate and yield, the calculation of the EC10, 20, 50 was not indicated.
The statistical evaluation for the 72 hours period was performed for growth rate and yield using SAS® (2002–2010). A test for normality of the data was performed by calculating the Shapiro-Wilk statistic and the homogeneity of variance of the data was evaluated by calculating the Levene Test. The NOEC and LOEC were determined by using a multiple comparison method (Dunnetts-t-test, two-tailed, for growth rate, Jonckheere Terpstra test, two-tailed, for yield).

Validity criteria of the study:

Biomass: Cell numbers, measured in the controls between 0 h and 72 hours, were found to increase by a factor of 54.20, which exceeds the threshold of 16. It corresponds to a growth rate of 1.32937 d-1.

Coefficient of Variation (section by section): The mean coefficient of variation for the section-by-section specific growth rates (hours 0 - 24, 24 - 48 and 48 - 72) in the control cultures was 20 % and did not exceed 35 %.

Coefficient of Variation (average growth rate): The coefficient of variation of average growth rate in replicate control cultures was 2.6 % and did not exceed 7 % for the whole test period.

Results:

After 72 h at termination of the test no statistically significant inhibition of growth rate or yield was observed for test item concentrations up to and including 100 mg/L

Table 2. Average cell numbers for each sampling time and concentration

Conc.

Average cell numbers [104/mL]

[mg/L]

0 h

24 h

48 h

72 h

Control

0.55

1.61

7.18

29.81

0.954

0.55

2.03

8.01

32.76

3.05

0.55

2.14

9.79

38.78

9.77

0.55

2.31

13.54

58.10

31.3

0.55

2.33

14.55

56.73

100

0.55

1.95

14.51

62.16

Table 3. Percentage inhibition of growth rate

Conc.

% Inhibition of growth rate1)

[mg/L]

0 h – 24 h

0 h – 48 h

0 h – 72 h

9.5

-1.6

-4.4

-2.2

-7.3

0.3

Control

10.9

4.2

3.4

11.4

8.5

1.2

-18.7

1.6

-0.9

-10.9

-5.4

0.4

Mean

0.0

0.0

0.0

-18.7

-0.5

1.8

0.954

-21.5

-12.0

-7.0

-23.7

0.0

-1.4

Mean

-21.3

-4.2

-2.2

-29.4

-13.7

-9.7

3.05

-27.7

-14.9

-4.3

-21.9

-8.2

-5.8

Mean

-26.3

-12.3

-6.6

-31.4

-27.8

-19.0

9.77

-31.4

-26.1

-15.3

-37.0

-21.0

-16.1

Mean

-33.3

-25.0

-16.8

-30.6

-28.6

-14.2

31.3

-38.6

-27.0

-17.0

-33.9

-27.9

-17.4

Mean

-34.4

-27.8

-16.2

-18.7

-27.7

-17.8

100

-17.7

-28.4

-20.4

-16.3

-27.1

-17.2

Mean

-17.6

-27.7

-18.5

Table 4. Percentage inhibition of yield

Conc.

% Inhibition of yield1)

[mg/L]

0 h – 24 h

0 h – 48 h

0 h – 72 h

3.8

-16.6

-34.1

-3.8

-21.2

1.8

Control

15.1

10.4

11.8

18.9

23.3

6.9

-17

17.3

9.8

-17

-12.8

3.8

Mean

0.0

0.1

0.0

-34

-0.3

7.4

0.954

-39.6

-37.7

-32.3

-44.3

1.1

-5.3

Mean

-39.3

-12.3

-10.1

-56.6

-44.3

-47.3

3.05

-52.8

-48.9

-18.5

-40.6

-24.2

-26.2

Mean

-50

-39.1

-30.7

-61.3

-110.5

-114.5

9.77

-61.3

-101.1

-84.6

-74.5

-75.3

-91

Mean

-65.7

-95.6

-96.7

-59.4

-115.2

-76.8

31.3

-78.3

-106.2

-98.2

-67

-111.1

-101

Mean

-68.2

-110.8

-92

-34

-109.9

-104.6

100

-32.1

-113.9

-127.2

-29.2

-106.8

-99.9

Mean

-31.8

-110.2

-110.6

Table 5. pH measurements during test

Conc.

t = 0 h

t = 72 h

[mg/L]

Control

7.23

8.12

0.954

7.25

8.10

3.05

7.27

8.05

9.77

7.26

8.05

31.3

7.27

8.13

100

7.28

8.34

Table 6. Temperature during the test

Time

Temperature[°C] min

Temperature[°C] max

[h]

0

23.0

24

22.6

23.1

48

22.6

23.1

72

22.6

23.1

Table 7. Control, growth rates

Growth rates, µ [d-1]

0 h – 24 h

0 h – 48 h

0 h – 72 h

0.97273

1.30075

1.38780

1.09861

1.37480

1.32503

Control

0.95825

1.22658

1.28389

0.95266

1.17215

1.31350

1.27629

1.26036

1.34178

1.19280

1.34969

1.32424

Mean

1.07522

1.28072

1.32937

Std. Dev.

0.13712

0.07634

0.03445

CV [%]

12.8

6.0

2.6

Std.Dev.:Standard deviation

CV: Coefficient of variation

Validity criteria fulfilled:
yes
Conclusions:
The same result is predicted for the target substance.
No statistically significant inhibitory effects on any parameter (growth rate, yield) were observed at any of the source substance concentrations, including the highest test item concentration of 100 mg/L (nominal) at test end. Thus the overall LOEC was not determinable and the overall NOEC was observed to be at 100 mg/L (nominal).
The EC10, EC20 and EC50 for growth rate and yield were considered to be > 100 mg/L (nominal).

Executive summary:

This GLP-compliant study with the source substance sodium octane-1 -sulfonate was conducted in accordance with the OECD guideline 201; “Freshwater Alga and Cyanobacteria, Growth Inhibition Test" (28 July 2011), in order to determine the effects of the test item on the growth and yield of green alga Pseudokirchneriella subcapitata. Initial target cell densities of 0.5 × 104 cells/mL were employed for the individual replicates. The increase of cell numbers was assessed over a test period of 72 hours. A static test with nominal test item concentrations of 100, 31.3, 9.77, 3.05, 0.954 mg/L and control was performed. Six replicates were employed for the control and three for each test item concentration. The test was performed in 100 mL Erlenmeyer flasks each containing ~ 50 mL test solution. Analytical samples were analysed from control and test item concentration 100 mg/L at 0 hours (initial value) from fresh test solutions and after 72 hours from aged solutions. The measured initial concentration of the test item was 91.2 % of nominal in the highest test item concentration of 100 mg/L. In the aged samples the measured concentrations was 102.6 %.

No statistically significant inhibitory effects on any parameter (growth rate, yield) were observed at any test item concentrations up to the highest concentration tested (100 mg/L, nominal) at test end. No abnormalities in the cells were observed at test end.

The overall LOEC was not determinable and the overall NOEC was observed to be 100 mg/L (nominal). The EC10, EC20 and EC50 for growth rate and yield were considered to be > 100 mg/L (nominal).

Description of key information

Read-across: OECD 201, GLP, P. subcapitata, NOEC = 100 mg/L, EC50 > 100 mg/L (nominal)

Key value for chemical safety assessment

EC10 or NOEC for freshwater algae:
100 mg/L

Additional information

This study was conducted in accordance with the OECD guideline 201; “Freshwater Alga and Cyanobacteria, Growth Inhibition Test" (28 July 2011), in order to determine the effects of the test item on the growth and yield of green alga Pseudokirchneriella subcapitata. Initial target cell densities of 0.5 × 104 cells/mL were employed for the individual replicates. The increase of cell numbers was assessed over a test period of 72 hours. A static test with nominal test item concentrations of 100, 31.3, 9.77, 3.05, 0.954 mg/L and control was performed. Six replicates were employed for the control and three for each test item concentration. The test was performed in 100 mL Erlenmeyer flasks each containing ~ 50 mL test solution. Analytical samples were analysed from control and test item concentration 100 mg/L at 0 hours (initial value) from fresh test solutions and after 72 hours from aged solutions. The measured initial concentration of the test item was 91.2 % of nominal in the highest test item concentration of 100 mg/L. In the aged samples the measured concentrations was 102.6 %.

No statistically significant inhibitory effects on any parameter (growth rate, yield) were observed at any test item concentration up to the highest concentration tested (100 mg/L, nominal) at test end. No abnormalities in the cells were observed at test end.

The overall LOEC was not determinable and the overall NOEC was observed to be 100 mg/L (nominal). The EC10, EC20 and EC50 for growth rate and yield were considered to be > 100 mg/L (nominal).