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Toxicity to aquatic algae and cyanobacteria

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Endpoint:
toxicity to aquatic algae and cyanobacteria
Type of information:
read-across from supporting substance (structural analogue or surrogate)
Adequacy of study:
key study
Study period:
2013
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: see 'Remark'
Remarks:
Guideline study performed under GLP; minor deviations not impacting the validity of the study (OECD TG 201 does not mandate positive controls only that they are desirable and may be used). The source substance, and both components of the target substance have an aldehyde group at the 1-carbon position and either a terminal (10-position) or an internal alkene (9-position or 8-position; with the terminal alkyl group no larger than an ethyl group and/or should not multiply substituted). From an aquatic toxicity perspective, this puts both structurally similar substances into the mono-aldehyde chemical class. The mono-aldehyde group in this substance is the entity responsible for excess toxicity of both substances. As both source and target substances are composed of (9E)-9-Undecenal, (9Z)-9-Undecenal and/or undec-10-enal, the mono-aldehyde component is the toxicity-driving group.
Justification for type of information:
REPORTING FORMAT FOR THE ANALOGUE APPROACH
Further information is included in attachment to IUCLID section 13.

1. HYPOTHESIS FOR THE ANALOGUE APPROACH
The read-across is based on the hypothesis that the source and target substances have common structural features in the same relative positions. The source and target have similar physico-chemical, toxicological properties and because of common metabolism they share common or have similar breakdown products and therefore potential mechanisms of action. Further information is included in attachment to IUCLID section 13.

2. SOURCE AND TARGET CHEMICAL(S) (INCLUDING INFORMATION ON PURITY AND IMPURITIES)
The source and target chemicals have comparable chemical similarity. Further information is included in attachment to IUCLID section 13

3. ANALOGUE APPROACH JUSTIFICATION
The source substance is a chemically similar substance with common metabolism and common or similar degradants of the target substance. Further information is included in attachment to IUCLID section 13

4. DATA MATRIX
Further information is included in attachment to IUCLID section 13.
Reason / purpose for cross-reference:
read-across source
Reason / purpose for cross-reference:
read-across: supporting information
Qualifier:
according to guideline
Guideline:
OECD Guideline 201 (Alga, Growth Inhibition Test)
Deviations:
yes
Remarks:
no positive control completed; pH of the control medium exceeded the guideline recommendations of the guideline potentially caused by use of sealed vessel to prevent test item losses; associated population densities and test validity criteria were met.
Qualifier:
equivalent or similar to guideline
Guideline:
EU Method C.3 (Algal Inhibition test)
GLP compliance:
yes (incl. QA statement)
Remarks:
inspected May 2012; signature: September 2012
Analytical monitoring:
yes
Vehicle:
no
Test organisms (species):
Raphidocelis subcapitata (previous names: Pseudokirchneriella subcapitata, Selenastrum capricornutum)
Details on test organisms:
TEST ORGANISM
- Common name: Pseudokirchneriella subcapitata
- Strain: CCAP 278/4
- Source (laboratory, culture collection): Culture Collection of Algae and Protozoa (CCAP), obtained from a concentrated liquid slope culture from the Culture Collection of Algae and Protozoa (CCAP), SAMS Research Services Ltd., Oban, UK
- Age of inoculum (at test initiation): Not reported.
- Method of cultivation: Not reported.

ACCLIMATION
- Acclimation period: Yes, 72 hours until algal cell density was approximately 10^4 cells/mL
- Culturing media and conditions (same as test or not): Yes. 72 hours inccubation prior to the start of the test.
Medium : NaNO3 50 mg/L; MgCl2.6H2O 12 mg/L; CaCl2.2H2O 18 mg/L; MgSO4.7H2O 15 mg/L; KH2PO 1.6 mg/L; FeCl3.6H2O 0.08 mg/L; Na2EDTA.2H2O 0.1 mg/L; H3BO3 0.185 mg/L; MnCl2.4H2O 0.415 mg/L; ZnCl2 0.003 mg/L; CoCl2.6HO 0.0015 mg/L; CuCl2.2H2O 0.00001 mg/L; Na2MoO4.2H2O 0.007 mg/L; NaHCO3 50 mg/L; pH 7.6 ± 0.1
- Any deformed or abnormal cells observed: None reported.
Test type:
static
Water media type:
freshwater
Limit test:
yes
Total exposure duration:
72 h
Post exposure observation period:
All test and control cultures were inspected at 72 hours.
Test temperature:
Temperature within the incubator was recorded daily. 22.6 to 23.6 °C
pH:
The pH of the control and each test preparation was determined at initiation of the test and after 72 hours exposure. pH = 7.9 ± 0.2 in test item vessels at 72 hours and pH 8.38 in the controls.
Nominal and measured concentrations:
Combined limit/range-finder test: 0.010, 0.1, 1.0, 10 and 100% v/v saturated solution (<0.0096, 0.023, 0.23, 2.2 and19 mg/L based on initial measured concentrations).
Final test: The definitive test was conducted as nominal test concentrations of 0.25, 0.5, 1.0, 2.0, 4.0 and 8.0% v/v saturated solution (0.043, 0.083, 0.15, 0.34, 0.84 and 1.7 mg/L based on geometric mean measured concentrations of the 0 and 24 hour results
Details on test conditions:
TEST SYSTEM
- Test vessel: Glass
- Type (delete if not applicable): Closed
- Static- Material, size, headspace, fill volume: Glass, 250 ml, containing 100 ml of test solution
- Aeration: Vessel shaken continuously.- Initial cells density: (Mean cell density of control at 0 hours): 5.41 x 10^3 cells/ml ; RF and definitive tests: ca. 5 x 10^3 cells/ml
- Control end cells density: Mean (of replicates after 72 hours) 6.16 x10^5 cells/ml.
- No. of vessels per concentration (replicates): 3 replicates of each test concentration- No. of vessels per control (replicates): 6 replicates of the control.
- No. of vessels per vehicle control (replicates): Not applicable.

GROWTH MEDIUM
- Standard medium used: Yes. EC medium
- Detailed composition if non-standard medium was used: NaNO3 50 mg/L MgCl2.6H2O 12 mg/L; CaCl2.2H2O 18 mg/L; MgSO4.7H2O 15 mg/L; KH2PO 1.6 mg/L; FeCl3.6H2O 0.08 mg/L; Na2EDTA.2H2O 0.1 mg/L; H3BO3 0.185 mg/L; MnCl2.4H2O 0.415 mg/L; ZnCl2 0.003 mg/L; CoCl2.6HO 0.0015 mg/L; CuCl2.2H2O 0.00001 mg/L; Na2MoO4.2H2O 0.007 mg/L; NaHCO3 50 mg/L; pH 7.6 ± 0.1

TEST MEDIUM / WATER PARAMETERS
- Source/preparation of dilution water: reverse osmosis (RO) water
- Culture medium different from test medium: No.
- Intervals of water quality measurement: Not reported.

OTHER TEST CONDITIONS
- Sterile test conditions: No.
- Adjustment of pH: No.
- Photoperiod: 24 hours ; continuous
- Light intensity and quality: 4440 to 8880 Lux at 400-730 nm
- Salinity (for marine algae): Not applicable.

EFFECT PARAMETERS MEASURED (with observation intervals if applicable) :
- Determination of cell concentrations: particle counter (Z2 Coulter Counter®)

TEST CONCENTRATIONS- Spacing factor for test concentrations: 3.2 or in definitive test justified from the results of the range finding study.
- Justification for using less concentrations than requested by guideline: Not applicable.
- Range finding study: Yes.
- Test concentrations: Two replicates per concentration were exposed to dilutions representing nominal concentrations 0 (control), 0.1, 1.0, 10 and 100% (v/v) saturated solution. Definitive test: six replicates for control and three replicates at each test concentration.
- Results used to determine the conditions for the definitive study: Yes.
Reference substance (positive control):
no
Duration:
72 h
Dose descriptor:
EC50
Effect conc.:
1.1 mg/L
Nominal / measured:
meas. (geom. mean)
Conc. based on:
test mat.
Basis for effect:
growth rate
Remarks on result:
other: 95% CL: 0.63 and 1.3 mg/L
Duration:
72 h
Dose descriptor:
EC50
Effect conc.:
0.28 mg/L
Nominal / measured:
meas. (geom. mean)
Conc. based on:
test mat.
Basis for effect:
other: yield
Duration:
72 h
Dose descriptor:
EC10
Effect conc.:
0.18 mg/L
Nominal / measured:
meas. (geom. mean)
Conc. based on:
test mat.
Basis for effect:
growth rate
Remarks on result:
other: 95% CL: 0.053 and 0.41 mg/L
Duration:
72 h
Dose descriptor:
EC10
Effect conc.:
0.037 mg/L
Nominal / measured:
meas. (geom. mean)
Conc. based on:
test mat.
Basis for effect:
other: yield
Duration:
72 h
Dose descriptor:
NOEC
Effect conc.:
0.34 mg/L
Nominal / measured:
meas. (geom. mean)
Conc. based on:
test mat.
Basis for effect:
growth rate
Duration:
72 h
Dose descriptor:
EC20
Effect conc.:
0.42 mg/L
Nominal / measured:
meas. (geom. mean)
Conc. based on:
test mat.
Basis for effect:
growth rate
Remarks on result:
other: 95% CL: 0.31 and 0.52 mg/L
Details on results:
- Exponential growth in the control (for algal test): Yes.
- Any stimulation of growth found in any treatment: Yes.
- Any observations (e.g. precipitation) that might cause a difference between measured and nominal values: During the exposure period the measured concentrations decreased in the range finder and definitive test from nominal values. No observations were made to account for the difference.
- Effect concentrations exceeding solubility of substance in test medium: No.
Reported statistics and error estimates:
Statistical analysis of the growth rate and yield data was carried out for the control and all test concentrations using statistical analysis was conductedusing the CETIS program v 1.8.6. Linear interpolation analysis was performed in order to estimate EC10, EC20 and EC50 values. Where possible, 95% confidence limits were calculated for the EC10, EC20 and EC50 values. Recent scientific developments have led to a recommendation, documented within the OECD 201 test guideline, to abandon the concept of the no observed effect concentration (NOEC) and replacing it with regression-based point estimates ECx.A range of 10 to 20% appears appropriate and, therefore, the NOEC was determined by the highest test concentration below the determined ExC20. Significant inhibition was therefore considered to have occurred at treatment levels greater than the NOEC. To distinguish between ECx values determined using areas under the growth curve, final yield and growth rates, the symbols EbCx, EyCx and ErCx were used, respectively.

Table 1 Measured concentrations versus nominal concentrations and mean cell densities: Definitive test

 Nominal Test Concentration

(% (v/v) Saturated Solution)

 

Geometric Mean Measured Test

Concentration (mg/L)

pH (0 hours)*

Mean Cell Concentration (x10^4 /mL) 24-hours

Mean Cell Concentration (x10^4 /mL) 48-hours

Mean Cell Concentration (x10^4 /mL) 72-hours

pH (72 hours)*

 

 

 

 

 

 

 

Control

-

7.66

7.77

39.1

220

10.33

0.25

0.043

7.67

6.09

32.6

195

9.82

0.50

0.083

7.70

5.57

30.0

173

9.59

1.00

0.15

7.69

4.41

23.4

138

8.72

2.00

0.34

7.71

3.30

17.5

98.9

8.50

4.00

0.84

7.71

1.46

5.72

20.7

8.01

8.00

1.70

7.70

1.26

3.39

7.40

7.92

 

 

 

 

 

 

 

* Measured pH values are determined using samples of test media from volumetric flasks at 0 hours and from each individual test vessel at 72 hours

 

Table 2 Inhibition Yield in the Definitive Test

Geometric Mean Measured Test

Concentration (mg/L)

Initial Cell Density (cells x10^4 /mL)

Mean growth rate (cells x 10 ^ -2 /mL)

# Mean final yield per treatment (cells x10^4 /mL)

% Inhibition in Final Yield relative to control

 

 

0-24 h

0-48 h

0-72 h

 

 

Control

1

8.52

7.63

7.48

219

-

0.043

1

7.52

7.26

7.32

194

11.4

0.083

1

7.15

7.08

7.16

172

21.3

0.15

1

6.16

6.54

6.81

137

37.4

0.34

1

4.96

5.95

6.36

97.9

55.2

0.84

1

1.57

3.60

4.18

19.7

91.0

1.70

1

0.938

2.54

2.76

6.40

97.1

# Final yield (cells/mL) = cell density (cells/mL) at 72 hours – initial cell density (cells/mL)

- Not applicable

 

Table 3 Inhibition of Growth Rate in the Definitive Test

Geometric Mean Measured Test

Concentration (mg/L)

Reduction in average specific growth

rates relative to the control (%)

Section by section growth rate inhibition % (relative to control)

 

0-24 h

0-24 h

0-48 h

0-72 h

0-48 h

0-72 h

Control

-

-

-

-

-

-

0.043

11.7

4.94

2.15

-3.59

-3.69

-3.81

0.083

16.1

7.19

4.32

-4.09

-2.92

-1.83

0.15

27.7

14.4

8.99

-2.42

-2.47

-2.51

0.34

41.8

22.0

14.9

-2.94

-1.50

-0.153

0.84

81.6

52.8

44.1

16.4

21.1

25.5

1.70

89.0

66.8

63.0

38.7

47.1

55.1

Negative percentage inhibition values relative to the common control are considered to be 0%

Validity criteria fulfilled:
yes
Conclusions:
The target substance 48h-EC50 (growth rate reduction) is expected to be 1.1 mg/L (95% CL: 0.63 - 1.3 mg/L) based on GMM concentrations.
Executive summary:

The algal growth inhibition to Pseudokirchneriella subcapitata, was carried out on a source substance according to OECD 201 Freshwater Alga and Cyanobacteria, Growth Inhibition Test and EU Method C.3 guidelines. Following a preliminary range-finding test, P.subcapitata was exposed to solutions of the test item at nominal test concentrations of 0.25, 0.5, 1.0, 2.0, 4.0 and 8.0% v/v saturated solution (0.043, 0.083, 0.15, 0.34, 0.84 and 1.7 mg/L based on geometric mean measured concentrations of the 0 and 24 hour results) within three replicate flasks per concentration for 72 hours, under constant illumination and shaking at a temperature of 24 ± 2 °C. The test item solutions were prepared by the use of a saturated solution method of preparation, followed by filtration, was the most appropriate method of preparation for the test substance given that the measured concentration was comparable to the water solubility of the test substance. This saturated solution was then further diluted as necessary, to provide the remaining test groups. Samples of the algal populations were removed daily and cell concentrations determined for each control and treatment group. Analysis of the 72 hour samples without algae showed slightly higher measured test concentrations. At the three highest test concentrations, where algal growth had been inhibited, the measured test concentrations in the 72 hour samples without algae were 75 to 78% of the initial measured concentration. This indicated that the decrease in measured concentration over the 72 hour test period was, at least in part, due to possible adsorption to algae. However, since the measured test concentrations in the 72 hour samples without algae were <80% of the 0 hour measured concentration, it was considered appropriate to base the results on the geometric mean measured test concentrations in order to give a worst case analysis of the data. The study met the acceptability criteria prescribed by the guideline. The 72h-NOEC for growth rate reduction based on GMM concentrations was 0.34 mg/L. The EC50 for growth rate reduction (72h-ERC50) based on GMM concentrations was 1.1 mg/L (95% CL: 0.63 – 1.3 mg/L).

 

The target substance is expected to have 48h-EC50 (growth rate reduction) of 1.1 mg/L (95% CL: 0.63 - 1.3 mg/L) based on GMM concentrations.

Endpoint:
toxicity to aquatic algae and cyanobacteria
Type of information:
experimental study
Adequacy of study:
key study
Study period:
2013
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: see 'Remark'
Remarks:
Guideline study performed under GLP; minor deviations not impacting the validity of the study (OECD TG 201 does not mandate positive controls only that they are desirable and may be used). The source substance, and both components of the target substance have an aldehyde group at the 1-carbon position and either a terminal (10-position) or an internal alkene (9-position or 8-position; with the terminal alkyl group no larger than an ethyl group and/or should not multiply substituted). From an aquatic toxicity perspective, this puts both structurally similar substances into the mono-aldehyde chemical class. The mono-aldehyde group in this substance is the entity responsible for excess toxicity of both substances. As both source and target substances are composed of (9E)-9-Undecenal, (9Z)-9-Undecenal and/or undec-10-enal, the mono-aldehyde component is the toxicity-driving group.
Reason / purpose for cross-reference:
read-across source
Qualifier:
according to guideline
Guideline:
OECD Guideline 201 (Alga, Growth Inhibition Test)
Deviations:
yes
Remarks:
no positive control completed; pH of the control medium exceeded the guideline recommendations of the guideline potentially caused by use of sealed vessel to prevent test item losses; associated population densities and test validity criteria were met.
Qualifier:
equivalent or similar to guideline
Guideline:
EU Method C.3 (Algal Inhibition test)
GLP compliance:
yes (incl. QA statement)
Remarks:
inspected May 2012; signature: September 2012
Analytical monitoring:
yes
Vehicle:
no
Test organisms (species):
Raphidocelis subcapitata (previous names: Pseudokirchneriella subcapitata, Selenastrum capricornutum)
Details on test organisms:
TEST ORGANISM
- Common name: Pseudokirchneriella subcapitata
- Strain: CCAP 278/4
- Source (laboratory, culture collection): Culture Collection of Algae and Protozoa (CCAP), obtained from a concentrated liquid slope culture from the Culture Collection of Algae and Protozoa (CCAP), SAMS Research Services Ltd., Oban, UK
- Age of inoculum (at test initiation): Not reported.
- Method of cultivation: Not reported.

ACCLIMATION
- Acclimation period: Yes, 72 hours until algal cell density was approximately 10^4 cells/mL
- Culturing media and conditions (same as test or not): Yes. 72 hours inccubation prior to the start of the test.
Medium : NaNO3 50 mg/L; MgCl2.6H2O 12 mg/L; CaCl2.2H2O 18 mg/L; MgSO4.7H2O 15 mg/L; KH2PO 1.6 mg/L; FeCl3.6H2O 0.08 mg/L; Na2EDTA.2H2O 0.1 mg/L; H3BO3 0.185 mg/L; MnCl2.4H2O 0.415 mg/L; ZnCl2 0.003 mg/L; CoCl2.6HO 0.0015 mg/L; CuCl2.2H2O 0.00001 mg/L; Na2MoO4.2H2O 0.007 mg/L; NaHCO3 50 mg/L; pH 7.6 ± 0.1
- Any deformed or abnormal cells observed: None reported.
Test type:
static
Water media type:
freshwater
Limit test:
yes
Total exposure duration:
72 h
Post exposure observation period:
All test and control cultures were inspected at 72 hours.
Test temperature:
Temperature within the incubator was recorded daily. 22.6 to 23.6 °C
pH:
The pH of the control and each test preparation was determined at initiation of the test and after 72 hours exposure. pH = 7.9 ± 0.2 in test item vessels at 72 hours and pH 8.38 in the controls.
Nominal and measured concentrations:
Combined limit/range-finder test: 0.010, 0.1, 1.0, 10 and 100% v/v saturated solution (<0.0096, 0.023, 0.23, 2.2 and19 mg/L based on initial measured concentrations).
Final test: The definitive test was conducted as nominal test concentrations of 0.25, 0.5, 1.0, 2.0, 4.0 and 8.0% v/v saturated solution (0.043, 0.083, 0.15, 0.34, 0.84 and 1.7 mg/L based on geometric mean measured concentrations of the 0 and 24 hour results
Details on test conditions:
TEST SYSTEM
- Test vessel: Glass
- Type (delete if not applicable): Closed
- Static- Material, size, headspace, fill volume: Glass, 250 ml, containing 100 ml of test solution
- Aeration: Vessel shaken continuously.- Initial cells density: (Mean cell density of control at 0 hours): 5.41 x 10^3 cells/ml ; RF and definitive tests: ca. 5 x 10^3 cells/ml
- Control end cells density: Mean (of replicates after 72 hours) 6.16 x10^5 cells/ml.
- No. of vessels per concentration (replicates): 3 replicates of each test concentration- No. of vessels per control (replicates): 6 replicates of the control.
- No. of vessels per vehicle control (replicates): Not applicable.

GROWTH MEDIUM
- Standard medium used: Yes. EC medium
- Detailed composition if non-standard medium was used: NaNO3 50 mg/L MgCl2.6H2O 12 mg/L; CaCl2.2H2O 18 mg/L; MgSO4.7H2O 15 mg/L; KH2PO 1.6 mg/L; FeCl3.6H2O 0.08 mg/L; Na2EDTA.2H2O 0.1 mg/L; H3BO3 0.185 mg/L; MnCl2.4H2O 0.415 mg/L; ZnCl2 0.003 mg/L; CoCl2.6HO 0.0015 mg/L; CuCl2.2H2O 0.00001 mg/L; Na2MoO4.2H2O 0.007 mg/L; NaHCO3 50 mg/L; pH 7.6 ± 0.1

TEST MEDIUM / WATER PARAMETERS
- Source/preparation of dilution water: reverse osmosis (RO) water
- Culture medium different from test medium: No.
- Intervals of water quality measurement: Not reported.

OTHER TEST CONDITIONS
- Sterile test conditions: No.
- Adjustment of pH: No.
- Photoperiod: 24 hours ; continuous
- Light intensity and quality: 4440 to 8880 Lux at 400-730 nm
- Salinity (for marine algae): Not applicable.

EFFECT PARAMETERS MEASURED (with observation intervals if applicable) :
- Determination of cell concentrations: particle counter (Z2 Coulter Counter®)

TEST CONCENTRATIONS- Spacing factor for test concentrations: 3.2 or in definitive test justified from the results of the range finding study.
- Justification for using less concentrations than requested by guideline: Not applicable.
- Range finding study: Yes.
- Test concentrations: Two replicates per concentration were exposed to dilutions representing nominal concentrations 0 (control), 0.1, 1.0, 10 and 100% (v/v) saturated solution. Definitive test: six replicates for control and three replicates at each test concentration.
- Results used to determine the conditions for the definitive study: Yes.
Reference substance (positive control):
no
Duration:
72 h
Dose descriptor:
EC50
Effect conc.:
1.1 mg/L
Nominal / measured:
meas. (geom. mean)
Conc. based on:
test mat.
Basis for effect:
growth rate
Remarks on result:
other: 95% CL: 0.63 and 1.3 mg/L
Duration:
72 h
Dose descriptor:
EC50
Effect conc.:
0.28 mg/L
Nominal / measured:
meas. (geom. mean)
Conc. based on:
test mat.
Basis for effect:
other: yield
Duration:
72 h
Dose descriptor:
EC10
Effect conc.:
0.18 mg/L
Nominal / measured:
meas. (geom. mean)
Conc. based on:
test mat.
Basis for effect:
growth rate
Remarks on result:
other: 95% CL: 0.053 and 0.41 mg/L
Duration:
72 h
Dose descriptor:
EC10
Effect conc.:
0.037 mg/L
Nominal / measured:
meas. (geom. mean)
Conc. based on:
test mat.
Basis for effect:
other: yield
Duration:
72 h
Dose descriptor:
NOEC
Effect conc.:
0.34 mg/L
Nominal / measured:
meas. (geom. mean)
Conc. based on:
test mat.
Basis for effect:
growth rate
Duration:
72 h
Dose descriptor:
EC20
Effect conc.:
0.42 mg/L
Nominal / measured:
meas. (geom. mean)
Conc. based on:
test mat.
Basis for effect:
growth rate
Remarks on result:
other: 95% CL: 0.31 and 0.52 mg/L
Details on results:
- Exponential growth in the control (for algal test): Yes.
- Any stimulation of growth found in any treatment: Yes.
- Any observations (e.g. precipitation) that might cause a difference between measured and nominal values: During the exposure period the measured concentrations decreased in the range finder and definitive test from nominal values. No observations were made to account for the difference.
- Effect concentrations exceeding solubility of substance in test medium: No.
Reported statistics and error estimates:
Statistical analysis of the growth rate and yield data was carried out for the control and all test concentrations using statistical analysis was conductedusing the CETIS program v 1.8.6. Linear interpolation analysis was performed in order to estimate EC10, EC20 and EC50 values. Where possible, 95% confidence limits were calculated for the EC10, EC20 and EC50 values. Recent scientific developments have led to a recommendation, documented within the OECD 201 test guideline, to abandon the concept of the no observed effect concentration (NOEC) and replacing it with regression-based point estimates ECx.A range of 10 to 20% appears appropriate and, therefore, the NOEC was determined by the highest test concentration below the determined ExC20. Significant inhibition was therefore considered to have occurred at treatment levels greater than the NOEC. To distinguish between ECx values determined using areas under the growth curve, final yield and growth rates, the symbols EbCx, EyCx and ErCx were used, respectively.

Table 1 Measured concentrations versus nominal concentrations and mean cell densities: Definitive test

 Nominal Test Concentration

(% (v/v) Saturated Solution)

 

Geometric Mean Measured Test

Concentration (mg/L)

pH (0 hours)*

Mean Cell Concentration (x10^4 /mL) 24-hours

Mean Cell Concentration (x10^4 /mL) 48-hours

Mean Cell Concentration (x10^4 /mL) 72-hours

pH (72 hours)*

 

 

 

 

 

 

 

Control

-

7.66

7.77

39.1

220

10.33

0.25

0.043

7.67

6.09

32.6

195

9.82

0.50

0.083

7.70

5.57

30.0

173

9.59

1.00

0.15

7.69

4.41

23.4

138

8.72

2.00

0.34

7.71

3.30

17.5

98.9

8.50

4.00

0.84

7.71

1.46

5.72

20.7

8.01

8.00

1.70

7.70

1.26

3.39

7.40

7.92

 

 

 

 

 

 

 

* Measured pH values are determined using samples of test media from volumetric flasks at 0 hours and from each individual test vessel at 72 hours

 

Table 2 Inhibition Yield in the Definitive Test

Geometric Mean Measured Test

Concentration (mg/L)

Initial Cell Density (cells x10^4 /mL)

Mean growth rate (cells x 10 ^ -2 /mL)

# Mean final yield per treatment (cells x10^4 /mL)

% Inhibition in Final Yield relative to control

 

 

0-24 h

0-48 h

0-72 h

 

 

Control

1

8.52

7.63

7.48

219

-

0.043

1

7.52

7.26

7.32

194

11.4

0.083

1

7.15

7.08

7.16

172

21.3

0.15

1

6.16

6.54

6.81

137

37.4

0.34

1

4.96

5.95

6.36

97.9

55.2

0.84

1

1.57

3.60

4.18

19.7

91.0

1.70

1

0.938

2.54

2.76

6.40

97.1

# Final yield (cells/mL) = cell density (cells/mL) at 72 hours – initial cell density (cells/mL)

- Not applicable

 

Table 3 Inhibition of Growth Rate in the Definitive Test

Geometric Mean Measured Test

Concentration (mg/L)

Reduction in average specific growth

rates relative to the control (%)

Section by section growth rate inhibition % (relative to control)

 

0-24 h

0-24 h

0-48 h

0-72 h

0-48 h

0-72 h

Control

-

-

-

-

-

-

0.043

11.7

4.94

2.15

-3.59

-3.69

-3.81

0.083

16.1

7.19

4.32

-4.09

-2.92

-1.83

0.15

27.7

14.4

8.99

-2.42

-2.47

-2.51

0.34

41.8

22.0

14.9

-2.94

-1.50

-0.153

0.84

81.6

52.8

44.1

16.4

21.1

25.5

1.70

89.0

66.8

63.0

38.7

47.1

55.1

Negative percentage inhibition values relative to the common control are considered to be 0%

Validity criteria fulfilled:
yes
Conclusions:
The test substance 48h-EC50 (growth rate reduction) was 1.1 mg/L (95% CL: 0.63 - 1.3 mg/L) based on GMM concentrations.
Executive summary:

The algal growth inhibition to Pseudokirchneriella subcapitata, was carried out according to OECD 201 Freshwater Alga and Cyanobacteria, Growth Inhibition Test and EU Method C.3 guidelines. Following a preliminary range-finding test, P.subcapitata was exposed to solutions of the test item at nominal test concentrations of 0.25, 0.5, 1.0, 2.0, 4.0 and 8.0% v/v saturated solution (0.043, 0.083, 0.15, 0.34, 0.84 and 1.7 mg/L based on geometric mean measured concentrations of the 0 and 24 hour results) within three replicate flasks per concentration for 72 hours, under constant illumination and shaking at a temperature of 24 ± 2 °C. The test item solutions were prepared by the use of a saturated solution method of preparation, followed by filtration, was the most appropriate method of preparation for the test substance given that the measured concentration was comparable to the water solubility of the test substance. This saturated solution was then further diluted as necessary, to provide the remaining test groups. Samples of the algal populations were removed daily and cell concentrations determined for each control and treatment group. Analysis of the 72 hour samples without algae showed slightly higher measured test concentrations. At the three highest test concentrations, where algal growth had been inhibited, the measured test concentrations in the 72 hour samples without algae were 75 to 78% of the initial measured concentration. This indicated that the decrease in measured concentration over the 72 hour test period was, at least in part, due to possible adsorption to algae. However, since the measured test concentrations in the 72 hour samples without algae were <80% of the 0 hour measured concentration, it was considered appropriate to base the results on the geometric mean measured test concentrations in order to give a worst case analysis of the data. The study met the acceptability criteria prescribed by the guideline. The 72h-NOEC for growth rate reduction based on GMM concentrations was 0.34 mg/L. The EC50 for growth rate reduction (72h-ERC50) based on GMM concentrations was 1.1 mg/L (95% CL: 0.63 – 1.3 mg/L)..

Description of key information

EC50-72h (Read-Across: undec-10-enal ; aquatic algae; growth rate) = 1.1 mg/L (C.I. 0.63 -1.3 mg/L), 72 hour, freshwater, OECD TG 201, 2013

NOEC (Read-across: undec-10-enal ; aquatic algae; growth rate) = 0.34 mg/L, 72 hour, freshwater, OECD TG 201, 2013

Key value for chemical safety assessment

EC50 for freshwater algae:
1.1 mg/L
EC10 or NOEC for freshwater algae:
0.34 mg/L

Additional information

Key study: OECD TG 201, 2013 : Read-Across - SOURCE (undec-10-enal): The algal growth inhibition to Pseudokirchneriella subcapitata, was carried out according to OECD 201 Freshwater Alga and Cyanobacteria, Growth Inhibition Test and EU Method C.3 guidelines. Following a preliminary range-finding test, P.subcapitata was exposed to solutions of the test item at nominal test concentrations of 0.25, 0.5, 1.0, 2.0, 4.0 and 8.0% v/v saturated solution (0.043, 0.083, 0.15, 0.34, 0.84 and 1.7 mg/L based on geometric mean measured concentrations of the 0 and 24 hour results) within three replicate flasks per concentration for 72 hours, under constant illumination and shaking at a temperature of 24 ± 2 °C. The study met the acceptability criteria prescribed by the guideline. The 72h-NOEC for growth rate reduction based on GMM concentrations was 0.34 mg/L. The EC50 for growth rate reduction (72h-ERC50) based on GMM concentrations was 1.1 mg/L (95% CL: 0.63 – 1.3 mg/L).