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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:
This study was conducted between 27 July 2017 and 14 November 2017
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: Reliability 1 is assigned because the study conducted according to OECD TG 201 in compliance with GLP, without deviations that influence the quality of the results.
Qualifier:
according to guideline
Guideline:
OECD Guideline 201 (Freshwater Alga and Cyanobacteria, Growth Inhibition Test)
Version / remarks:
2006
Deviations:
no
Qualifier:
according to guideline
Guideline:
EU Method C.3 (Algal Inhibition test)
Version / remarks:
EC No. 761/2009
Deviations:
no
GLP compliance:
yes (incl. QA statement)
Specific details on test material used for the study:
Information as provided by the Sponsor.
Identification: 4,4'-(1,3-Phenylenediisopropylidene) diphenylcyanate
Physical state/Appearance: Yellow viscous liquid
Batch: FAR366085A
Purity: Not provided
Expiry Date: 29 September 2019
Storage Conditions: Approximately 4 ºC in the dark
Analytical monitoring:
yes
Details on sampling:
Due to the low aqueous solubility and complex nature of the test item, for the purposes of the study the test medium was prepared as a Water Accommodated Fraction (WAF) of the test item.

Range-Finding Tests
A sample of each loading rate WAF was taken for chemical analysis at 0 and 72 hours in order to determine the stability of the test item over the test duration. All samples were stored frozen prior to analysis.

Definitive Test
Based on the results of the range-finding tests the following loading rates were assigned to the definitive test:1.0, 3.2, 10, 32 and 100 mg/L
The concentration and stability of the test item in the test preparations were verified by chemical analysis at 0 and 72 hours
Vehicle:
no
Details on test solutions:
Range-Finding Tests

The loading rates to be used in the definitive test were determined by a preliminary range-finding test.
The range-finding test was conducted by exposing Pseudokirchneriella subcapitata cells to nominal loading rates of 10 and 100 mg/L for a period of 72 hours.
The test was conducted in 250 mL glass conical flasks each containing 100 mL of test preparation and plugged with polyurethane foam bungs to reduce evaporation. Two replicate flasks were prepared for each control and test concentration.
Nominal amounts of test item (20 and 200 mg) were each separately weighed onto a glass slide and suspended within 2 liters of culture medium to give the 10 and 100 mg/L loading rates respectively. After the addition of the test item, the culture medium was stirred by magnetic stirrer using a stirring rate such that a vortex was formed to give a dimple at the water surface. The stirring was stopped after 23 hours and the mixtures allowed to stand for 1-Hour. Visual observations made on the WAFs indicated that a significant amount of dispersed test item was present in the water column and hence it was considered justifiable to remove the WAFs by filtering through a glass wool plug (2-4 cm in length). A wide bore glass tube, covered at one end with Nescofilm was submerged into the vessel, sealed end down, to a depth of approximately 5 cm from the bottom of the vessel. A length of Tygon tubing was inserted into the glass tube and pushed through the Nescofilm seal. A glass wool plug was inserted into the opposite end of the tubing and the WAF removed by mid-depth siphoning (the first 75-100 mL discarded). Further filtration through one sheet of filter paper was conducted to remove as much undissolved test item as possible. Dispersed test item was observed in the 100 mg/L loading rate after filtration, it was considered that further filtration would not have removed any more at this point.
An aliquot (500 mL) of each of the loading rate WAFs was separately inoculated with algal suspension (5.7 mL) to give the required test concentrations of 10 and 100 mg/L loading rate WAF.

Definitive Test
Based on the results of the range-finding test the following loading rates were assigned to the definitive test: 1.0, 3.2, 10, 32 and 100 mg/L.

Experimental Preparation
Nominal amounts of test item (20, 32, 20, 64 and 200 mg) were each separately weighed onto a glass slide and suspended within 20, 10, 2.0, 2.0 and 2.0 liters of culture medium to give the 1.0, 3.2, 10, 32 and 100 mg/L loading rates respectively. After the addition of the test item, the culture medium was stirred by magnetic stirrer using a stirring rate such that a vortex was formed to give a dimple at the water surface. The stirring was stopped after 23 hours and the mixtures allowed to stand for 1-Hour. A wide bore glass tube, covered at one end with Nescofilm was submerged into the vessel, sealed end down, to a depth of approximately 5 cm from the bottom of the vessel. A length of Tygon tubing was inserted into the glass tube and pushed through the Nescofilm seal. The aqueous phase or WAF was removed by mid-depth siphoning (the first 75-100 mL discarded) to give the 1.0, 3.2, 10, 32 and 100 mg/L loading rate WAFs. Microscopic inspection of the WAFs showed no micro-dispersions or undissolved test item to be present.
An aliquot (500 mL) of each of the loading rate WAFs was separately inoculated with algal suspension (4.0 mL) to give the required test concentrations of 1.0, 3.2, 10, 32 and 100 mg/L loading rate WAF
Test organisms (species):
Pseudokirchneriella subcapitata (previous names: Raphidocelis subcapitata, Selenastrum capricornutum)
Details on test organisms:
The test was carried out using Pseudokirchneriella subcapitata strain CCAP 278/4. Liquid cultures of Pseudokirchneriella subcapitata were obtained from the Culture Collection of Algae and Protozoa (CCAP), SAMS Research Services Ltd, Scottish Marine Institute, Oban, Argyll, Scotland. Master cultures were maintained in the laboratory by the periodic replenishment of culture medium (below). The master cultures were maintained in the laboratory under constant aeration and illumination at 21 ± 2”C.
Prior to the start of the test sufficient master culture was added to approximately 100 mL volumes of culture media contained in conical flasks to give an initial cell density of approximately 10^3 cells/mL. The flasks were plugged with polyurethane foam stoppers and kept under constant agitation by orbital shaker (100 to 150 rpm) and constant illumination at 24 ± 1”C until the algal cell density was approximately 10^4 to 10^5 cells/mL

Culture Medium
The culture medium used for both the range-finding and definitive tests was the same as that used to maintain the stock culture.

Culture Medium
NaNO3 25.5 mg/L
MgCl2.6H2O 12.16 mg/L
CaCl2.2H2O 4.41 mg/L
MgSO4.7H2O 14.6 mg/L
K2HPO4 1.044 mg/L
NaHCO3 15.0 mg/L
H3BO3 0.186 mg/L
MnCl2.4H2O 0.415 mg/L
ZnCl2 0.00327 mg/L
FeCl3.6H2O 0.160 mg/L
CoCl2.6H2O 0.00143 mg/L
Na2MoO4.2H2O 0.00726 mg/L
CuCl2.2H2O 0.000012 mg/L
Na2EDTA.2H2O 0.30 mg/L
The culture medium was prepared using reverse osmosis purified deionized water and the pH adjusted to 7.5 with 0.1N NaOH or HCl.
Test type:
semi-static
Water media type:
freshwater
Limit test:
no
Total exposure duration:
72 h
Hardness:
not reported
Test temperature:
Temperature was maintained at 24 ± 1 °C
pH:
The pH value of the control cultures was observed to increase from pH 7.4 at 0 hours to pH 8.1 at 72 hours. The pH deviation in the control cultures was less than 1.5 pH units after 72 hours and therefore was within the limits given in the Test Guidelines.
Dissolved oxygen:
Not reported
Salinity:
Not reported
Conductivity:
Not reported
Nominal and measured concentrations:
Chemical analysis of the test preparations at 0 and 72 hours showed measured test concentrations of less than the limit of quantification (LOQ) of the analytical method employed were obtained which was determined to be 0.070 mg/L. This does not infer that no test item was in solution, just that any dissolved test item was at a concentration of less than the LOQ.
Given that toxicity cannot be attributed to a single component or mixture of components but to the test item as a whole, the results were based on nominal loading rates only.
Details on test conditions:
Experimental Design and Study Conduct
Due to the low aqueous solubility and complex nature of the test item, for the purposes of the study the test medium was prepared as a Water Accommodated Fraction (WAF) of the test item.
Validation of Mixing Period
Preliminary work was carried out to determine whether stirring for a prolonged period produced significantly higher measured test concentrations in the WAF.

Range-Finding Tests
The loading rates to be used in the definitive test were determined by preliminary range-finding tests.
The initial range-finding test was conducted by exposing Pseudokirchneriella subcapitata cells to nominal loading rates of 10 and 100 mg/L for a period of 72 hours.
The test was conducted in 250 mL glass conical flasks each containing 100 mL of test preparation and plugged with polyurethane foam bungs to reduce evaporation. Two replicate flasks were prepared for each control and test concentration.

Nominal amounts of test item (20 and 200 mg) were each separately weighed onto a glass slide and suspended within 2 liters of culture medium to give the 10 and 100 mg/L loading rates respectively. After the addition of the test item, the culture medium was stirred by magnetic stirrer using a stirring rate such that a vortex was formed to give a dimple at the water surface. The stirring was stopped after 23 hours and the mixtures allowed to stand for 1-Hour. Visual observations made on the WAFs indicated that a significant amount of dispersed test item was present in the water column and hence it was considered justifiable to remove the WAFs by filtering through a glass wool plug (2-4 cm in length). A wide bore glass tube, covered at one end with Nescofilm was submerged into the vessel, sealed end down, to a depth of approximately 5 cm from the bottom of the vessel. A length of Tygon tubing was inserted into the glass tube and pushed through the Nescofilm seal. A glass wool plug was inserted into the opposite end of the tubing and the WAF removed by mid-depth siphoning (the first 75-100 mL discarded). Further filtration through one sheet of filter paper was conducted to remove as much undissolved test item as possible. Dispersed test item was observed in the 100 mg/L loading rate after filtration, it was considered that further filtration would not have removed any more at this point.
An aliquot (500 mL) of each of the loading rate WAFs was separately inoculated with algal suspension (5.7 mL) to give the required test concentrations of 10 and 100 mg/L loading rate WAF.
The control group was maintained under identical conditions but not exposed to the test item.
At the start of the range-finding test a sample of each test and control culture was removed and the cell density determined using a haemocytometer and light microscope. The flasks were then plugged with polyurethane foam bungs and incubated (INFORS Multitron Version 2 incubator) at 24 ± 1 ºC under continuous illumination (intensity approximately 7000 lux) provided by warm white lighting (380 – 730 nm) and constantly shaken at approximately 150 rpm for 72 hours.
After 72 hours the cell density of each flask was determined using a Coulter® Multisizer Particle Counter.
A sample of each loading rate WAF was taken for chemical analysis at 0 and 72 hours in order to determine the stability of the test item over the test duration. All samples were stored frozen prior to analysis.

Definitive Test
Based on the results of the range-finding test the following loading rates were assigned to the definitive test: 1.0, 3.2, 10, 32 and 100 mg/L.

Experimental Preparation
Nominal amounts of test item (20, 32, 20, 64 and 200 mg) were each separately weighed onto a glass slide and suspended within 20, 10, 2.0, 2.0 and 2.0 liters of culture medium to give the 1.0, 3.2, 10, 32 and 100 mg/L loading rates respectively. After the addition of the test item, the culture medium was stirred by magnetic stirrer using a stirring rate such that a vortex was formed to give a dimple at the water surface. The stirring was stopped after 23 hours and the mixtures allowed to stand for 1-Hour. A wide bore glass tube, covered at one end with Nescofilm was submerged into the vessel, sealed end down, to a depth of approximately 5 cm from the bottom of the vessel. A length of Tygon tubing was inserted into the glass tube and pushed through the Nescofilm seal. The aqueous phase or WAF was removed by mid-depth siphoning (the first 75-100 mL discarded) to give the 1.0, 3.2, 10, 32 and 100 mg/L loading rate WAFs. Microscopic inspection of the WAFs showed no micro-dispersions or undissolved test item to be present.
An aliquot (500 mL) of each of the loading rate WAFs was separately inoculated with algal suspension (4.0 mL) to give the required test concentrations of 1.0, 3.2, 10, 32 and 100 mg/L loading rate WAF.
The concentration and stability of the test item in the test preparations were verified by chemical analysis at 0 and 72 hours (see Annex 4).

Exposure Conditions
As in the range-finding test 250 mL glass conical flasks were used. Six flasks each containing 100 mL of test preparation were used for the control and three flasks each containing 100 mL were used for each treatment group.
The control group was maintained under identical conditions but not exposed to the test item.
Pre-culture conditions gave an algal suspension in log phase growth characterized by a cell density of 6.22 x 105 cells per mL. Inoculation of 500 mL of test medium with 4.0 mL of this algal suspension gave an initial nominal cell density of 5.00 x 103 cells per mL and had no significant dilution effect on the final test concentration.
The flasks were plugged with polyurethane foam bungs and incubated (INFORS Multitron Version 2 incubator) at 24 ± 1 °C under continuous illumination (intensity approximately 7000 lux) provided by warm white lighting (380 – 730 nm) and constantly shaken at approximately 150 rpm for 72 hours.

Assessments
Test Organism Observations
Samples were taken at 20, 48 and 72 hours and the cell densities determined using a Coulter® Multisizer Particle Counter. Three determinations were made for each sample. The nominally inoculated cell concentration (5.00 x 10^3 cells/mL) was taken as the starting cell density.
To determine the potential effect of the test item on the appearance of algal cells, a sample was removed from each test and control culture (replicates pooled) at the end of the test. The shape and size of the algal cells was inspected microscopically and any abnormalities recorded.

Water Quality Criteria
The pH of the control and each test concentration was determined at initiation of the test and after 72 hours exposure. The pH was measured using a Hach HQ30d Flexi handheld meter. The temperature within the incubator was recorded daily.
The appearance of the test media was recorded daily.
Vortex Depth Measurements
The vortex depth was recorded at the start and end of the mixing period.



Reference substance (positive control):
yes
Remarks:
Potassium dichromate
Duration:
72 h
Dose descriptor:
EL50
Effect conc.:
> 100 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
growth rate
Duration:
72 h
Dose descriptor:
NOELR
Effect conc.:
> 100 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
growth rate
Details on results:
Validation of Mixing Period
Preliminary investigational work (see Annex 3) indicated that there was no significant increase in the amount of dissolved test item when the preparation period was extended for longer than 24 hours. Therefore, for the purpose of testing the WAF was prepared using a stirring period of 23 hours followed by a 1-Hour settlement period.

Range-finding Tests
The cell densities and percentage inhibition of growth values from the exposure of Pseudokirchneriella subcapitata to the test item indicated an effect on growth at 10 and 100 mg/L loading rate WAF.
Based on this information loading rates of 1.0, 3.2, 10, 32 and 100 mg/L were selected for the definitive test.
Chemical analysis of the 10 and 100 mg/L loading rate WAF test preparations at 0 hours showed measured test concentrations of less than the LOQ, determined to be 0.070 mg/L, and 1.96 mg/L respectively were obtained. A decline in measured test concentrations was observed at 72 hours to less than the LOQ and 0.40 mg/L respectively indicating that the test item was unstable under the conditions of the test.

Definitive Test
Chemical Analysis of Test Loading Rates
Chemical analysis of the test preparations at 0 and 72 hours showed measured test concentrations of less than the limit of quantification (LOQ) of the analytical method employed were obtained which was determined to be 0.070 mg/L. This does not infer that no test item was in solution, just that any dissolved test item was at a concentration of less than the LOQ.
Given that toxicity cannot be attributed to a single component or mixture of components but to the test item as a whole, the results were based on nominal loading rates only.

Growth Data
Cell density values determined at each sampling time and pH values at 0 and 72 hours are given in Table 2. Growth rate and yield values for the control and test cultures after 72 hours and percentage inhibition values are given in Table 3.
From the data it is clear that the growth rate (r) and yield (y) of Pseudokirchneriella subcapitata (CCAP 278/4) were not affected by the presence of the test item over the 72-Hour exposure period.
The results obtained from the definitive test indicated that no inhibitory effects occurred up to the maximum loading rate of 100 mg/L. This result contradicts the effects seen in the range-finding test where significant inhibition of growth occurred at both 10 and 100 mg/L loading rate WAF. It was considered that the presence of dispersed test item which could not be removed by filtration in the range-finding test caused the effects seen and as such did not give an accurate picture of the intrinsic toxic properties of the dissolved and hence bioavailable content of test item.

Accordingly the following results were determined from the data:
Inhibition of Growth Rate
ErL10 (0 - 72 h) : >100 mg/L loading rate WAF
ErL20 (0 - 72 h) : >100 mg/L loading rate WAF
ErL50 (0 - 72 h) : >100 mg/L loading rate WAF

Where ErLx is the loading rate that reduced growth rate by x%.
Statistical analysis of the growth rate data was carried out for the control and all loading rates using one way analysis of variance incorporating Bartlett's test for homogeneity of variance (Sokal and Rohlf, 1981) and Dunnett's multiple comparison procedure for comparing several treatments with a control (Dunnett, 1955). There were no statistically significant differences (P0.05), between the control and all test groups and therefore the "No Observed Effect Loading Rate" (NOEL) based on growth rate was 100 mg/L loading rate WAF.

Inhibition of Yield
EyL10 (0 - 72 h) : >100 mg/L loading rate WAF
EyL20 (0 - 72 h) : >100 mg/L loading rate WAF
EyL50 (0 - 72 h) : >100 mg/L loading rate WAF

Where EyLx is the loading rate that reduced yield by x%.
Statistical analysis of the yield data was carried out as above. There were no statistically significant differences between the control and all test groups (P0.05) and therefore the "No Observed Effect Loading Rate" (NOEL) based on yield was 100 mg/L loading rate WAF

Validation Criteria
The following data show that the cell concentration of the control cultures increased by a factor of 250 after 72 hours. This increase was in line with the OECD Guideline that states the enhancement must be at least by a factor of 16 after 72 hours.
Nominal cell density of control at 0 hours : 5.00 x 10^3 cells per mL
Mean cell density of control at 72 hours : 1.25 x 10^6 cells per mL

The mean coefficient of variation for section by section specific growth rate for the control cultures was 8% and hence satisfied the validation criterion given in the OECD Guideline which states the mean must not exceed 35%.
The coefficient of variation for average specific growth rate for the control cultures over the test period (0 – 72 h) was 1% and hence satisfied the validation criterion given in the OECD Guideline which states that this must not exceed 7%.

Observations on Cultures
All test and control cultures were inspected microscopically at 72 hours. There were no abnormalities detected in any of the control or test cultures.

Water Quality Criteria
Temperature was maintained at 24 ± 1 ºC throughout the test.
The pH value of the control cultures was observed to increase from pH 7.4 at 0 hours to pH 8.1 at 72 hours. The pH deviation in the control cultures was less than 1.5 pH units after 72 hours and therefore was within the limits given in the Test Guidelines.

Observations on Test Item Solubility
Observations on the test media were carried out during the mixing and testing of the WAFs.
At the start of mixing all loading rate WAFs were observed to have formed clear colorless media columns with test item visible attached to the glass slides suspended within the media columns. After stirring, and following a 1-Hour standing period, all loading rates were observed to have formed clear colorless media columns with most test item free of the glass slide and settled on the bottom of the mixing vessels. Microscopic examination of the WAFs showed there to be no micro-dispersions of test item present.
At the start of the test all control and test cultures were observed to be clear colorless solutions. After the 72-Hour test period all control and test cultures were observed to be green dispersions.
Results with reference substance (positive control):
A positive control (Envigo Study Number FP48BQ) used potassium dichromate as the reference item at concentrations of 0.25, 0.50, 1.0, 2.0 and 4.0 mg/L.

Exposure conditions and data evaluation for the positive control were similar to those in the definitive test.

Exposure of Pseudokirchneriella subcapitata (CCAP 278/4) to the reference item gave the following results:

ErC50 (0 – 72 h) : 1.4 mg/L; 95% confidence limits 1.2 – 1.5 mg/L
EyC50 (0 – 72 h) : 0.60 mg/L; 95% confidence limits 0.52 – 0.69 mg/L

No Observed Effect Concentration (NOEC) based on growth rate: 0.25 mg/L
No Observed Effect Concentration (NOEC) based on yield: 0.25 mg/L
Lowest Observed Effect Concentration (LOEC) based on growth rate: 0.50 mg/L
Lowest Observed Effect Concentration (LOEC) based on yield: 0.50 mg/L

The results from the positive control with potassium dichromate were within the normal ranges for this reference item.

Table 2            Cell Densities and pH Values in the Definitive Test

Nominal Loading Rate

(mg/L)

pH

Cell Densities*(cells per mL)

pH

0 h

22 h

48 h

72 h

72 h

Control

R1

7.4

2.70E+04

1.81E+05

1.15E+06

8.1

R2

3.10E+04

2.08E+05

1.20E+06

R3

3.31E+04

2.03E+05

1.24E+06

R4

3.14E+04

2.08E+05

1.30E+06

R5

2.97E+04

1.86E+05

1.18E+06

R6

3.40E+04

2.03E+05

1.44E+06

Mean

3.10E+04

1.98E+05

1.25E+06

1.0

R1

7.3

3.04E+04

2.35E+05

1.46E+06

8.2

R2

3.46E+04

2.34E+05

1.38E+06

R3

3.29E+04

2.19E+05

1.49E+06

Mean

3.26E+04

2.30E+05

1.44E+06

3.2

R1

7.3

2.63E+04

1.92E+05

1.35E+06

8.2

R2

2.61E+04

1.94E+05

1.92E+06

R3

2.86E+04

2.16E+05

1.39E+06

Mean

2.70E+04

2.01E+05

1.56E+06

10

R1

7.3

2.96E+04

2.05E+05

1.32E+06

8.2

R2

2.70E+04

1.94E+05

1.37E+06

R3

3.50E+04

2.04E+05

1.44E+06

Mean

3.05E+04

2.01E+05

1.37E+06

32

R1

7.3

3.36E+04

2.28E+05

1.07E+06

8.3

R2

2.47E+04

2.11E+05

1.33E+06

R3

3.25E+04

1.72E+05

1.13E+06

Mean

3.03E+04

2.04E+05

1.18E+06

100

R1

7.3

2.47E+04

1.80E+05

1.33E+06

8.3

R2

2.77E+04

2.10E+05

1.39E+06

R3

3.14E+04

2.24E+05

1.40E+06

Mean

2.79E+04

2.05E+05

1.38E+06


*Cell densities represent the mean number of cells per mL calculated from the mean of the cell counts from 3 counts for each of the replicate flasks.

R1- R6= Replicates 1 to 6


Table 3: Inhibition of Growth Rate and Yield in the Definitive Test

Nominal Loading Rate
(mg/L)

Growth Rate (cells/mL/hour)

Yield (cells/mL)

0 – 72 h

% Inhibition

0 – 72 h

% Inhibition*

Control

R1

0.075

 

1.14E+06

 

R2

0.076

 

1.20E+06

 

R3

0.077

 

1.24E+06

 

R4

0.077

-

1.30E+06

-

R5

0.076

 

1.17E+06

 

R6

0.079

 

1.44E+06

 

Mean

0.077

 

1.25E+06

 

SD

0.001

 

1.09E+05

 

1.0

R1

0.079

[3]

1.45E+06

 

R2

0.078

[1]

1.38E+06

 

R3

0.079

[3]

1.49E+06

 

Mean

0.079

[2]

1.44E+06

[15]

SD

0.001

 

5.71E+04

 

3.2

R1

0.078

[1]

1.35E+06

 

R2

0.083

[8]

1.91E+06

 

R3

0.078

[1]

1.39E+06

 

Mean

0.080

[3]

1.55E+06

[24]

SD

0.003

 

3.14E+05

 

10

R1

0.077

0

1.31E+06

 

R2

0.078

[1]

1.36E+06

 

R3

0.079

[3]

1.43E+06

 

Mean

0.078

[1]

1.37E+06

[10]

SD

0.001

 

5.99E+04

 

32

R1

0.075

3

1.06E+06

 

R2

0.078

[1]

1.33E+06

 

R3

0.075

3

1.13E+06

 

Mean

0.076

2

1.17E+06

6

SD

0.002

 

1.38E+05

 

100

R1

0.078

[1]

1.32E+06

 

R2

0.078

[1]

1.39E+06

 

R3

0.078

[1]

1.40E+06

 

Mean

0.078

[1]

1.37E+06

[10]

SD

0.000

 

4.00E+04

 

*       In accordance with the OECD test guideline only the mean value for yield for each test concentration is calculated

R1-R6= Replicates 1 to 6

SD= Standard Deviation

[Increase in growth as compared to controls]

Validity criteria fulfilled:
yes
Remarks:
The data satisfied the validation criterion given in the OECD Guideline
Conclusions:
The effect of the test item on the growth of Pseudokirchneriella subcapitata has been investigated and gave EL50 values of greater than 100 mg/L loading rate WAF. The No Observed Effect Loading Rate was 100 mg/L loading rate WAF.
Executive summary:

A study was performed to assess the effect of the test item on the growth of the green algaPseudokirchneriella subcapitata. The method followed was designed to be compatible with the OECD Guidelines for Testing of Chemicals (2006) No 201, "Freshwater Alga and Cyanobacteria, Growth Inhibition Test" referenced as Method C.3 of Commission Regulation (EC) 761/2009.

Methods

Due to the low aqueous solubility and complex nature of the test item for the purposes of the test the test item was prepared as a Water Accommodated Fraction (WAF).

Following a preliminary range-finding test,Pseudokirchneriella subcapitatawas exposed to Water Accommodated Fractions (WAFs) of the test item over a range of nominal loading rates of 1.0, 3.2, 10, 32 and 100 mg/L (three replicate flasks per concentration) for 72 hours, under constant illumination and shaking at a temperature of 24 ± 1 °C.

Samples of the algal populations were removed daily and cell concentrations determined for each control and treatment group, using a Coulter®Multisizer Particle Counter.

 Results

Analysis of the 100 mg/L loading rate WAF test preparations at 0 and 72 hours showed measured test concentrations of less than the limit of quantification (LOQ) of the analytical method employed were obtained which was determined to be 0.070 mg/L. This does not infer that no test item was in solution, just that any dissolved test item was at a concentration of less than the LOQ.

Given that the toxicity cannot be attributed to a single component or a mixture of components but to the test item as a whole, the results were based on nominal loading rates only.

Exposure ofPseudokirchneriella subcapitatato the test item gave EL50values of greater than 100 mg/L loading rate WAF. The No Observed Effect Loading Rate was 100 mg/L loading rate WAF.

Description of key information

Key value for chemical safety assessment

EC10 or NOEC for freshwater algae:
100 mg/L

Additional information