3-methyl-4-phenylbutan-2-ol

Toxicity to aquatic algae and cyanobacteria

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

toxicity to aquatic algae and cyanobacteria

Type of information:

experimental study

Adequacy of study:

key study

Study period:

Between 1 November 2011 and 9 December 2011.

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Justification for type of information:

This information is used for read across to Muguesia

Reason / purpose for cross-reference:

read-across: supporting information

Qualifier:

according to guideline

Guideline:

EU Method C.3 (Algal Inhibition test)

Deviations:

no

Qualifier:

according to guideline

Guideline:

OECD Guideline 201 (Alga, Growth Inhibition Test)

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Analytical monitoring:

yes

Details on sampling:

Range-finding test
The test concentrations 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 a series of nominal test concentrations of 0.10, 1.0, 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 evaporative losses of the test solutions. Two replicate flasks were used for each control and test concentration. The test item was dissolved directly in culture medium.
An amount of test item (50 mg) was dissolved in culture medium with the aid of ultrasonication for approximately 10 minutes and the volume adjusted to 500 ml to give a 100 mg/l stock solution. A series of dilutions was made from this stock solution to give further stock solutions of 10, 1.0 and 0.10 mg/l. An aliquot (450 ml) of each of the stock solutions was separately inoculated with algal suspension (2.4 ml) to give the required test concentrations of 0.10, 1.0, 10 and 100 mg/l.
The stock solutions and each of the prepared concentrations were inverted several times to ensure adequate mixing and homogeneity.
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 Coulter® Multisizer Particle Counter. The flasks were then plugged with polyurethane foam bungs and incubated (INFORS Multitron Version 2 incubator) at 24 ± 1ºC 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.
Samples were taken from the range-finding test preparations at 0 and 72 hours in order to determine the stability of the test item under test conditions. All samples were stored at approximately -20°C prior to analysis.
Definitive test
Based on the results of the range-finding test the following test concentrations were assigned to the definitive test: 0.10, 0.32, 1.0, 3.2, 10 and 32 mg/l.

Verification of test concentrations
Samples were taken from the control (replicates R1 - R6 pooled) and each test group (replicates R1 - R3 pooled) at 0 and 72 hours for quantitative analysis. All 0-Hour samples were stored at approximately -20°C prior to analysis. Duplicate samples were taken at 0 and 72 hours and stored at approximately -20ºC for further analysis if necessary.
Given that chemical analysis of the range-finding test preparations showed a concentration dependant decline in measured test concentrations over the 72-Hour test period it was considered likely that the test item was adsorbing to the algal cells present, particularly at the lower test concentrations employed.. As such additional test samples were prepared with the omission of algal cells and incubated alongside the test to provide samples for analysis at 72 hours in order to confirm this.

Vehicle:

no

Details on test solutions:

Experimental Preparation
For the purpose of the definitive test, the test item was dissolved directly in culture medium.
An amount of test item (32 mg) was dissolved in culture medium with the aid of ultrasonication for approximately 3 minutes and the volume adjusted to 1 litre to give a 32 mg/l stock solution from which a series of dilutions was made to give further stock solutions of 10, 3.2, 1.0, 0.32 and 0.10 mg/l. An aliquot (500 ml) of each of the stock solutions was separately inoculated with algal suspension (2.9 ml) to give the required test concentrations of 0.10, 0.32, 1.0, 3.2, 10 and 32 mg/l.
The stock solutions and each of the prepared concentrations were inverted several times to ensure adequate mixing and homogeneity.
The concentration and stability of the test item in the test preparations were verified by chemical analysis at 0 and 72 hours.

Test organisms (species):

Pseudokirchneriella subcapitata (previous names: Raphidocelis subcapitata, Selenastrum capricornutum)

Details on test organisms:

Test Species
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 (Section 3.2). The master cultures were maintained in the laboratory under constant aeration and illumination at 21 ± 1°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 103 cells/ml. The flasks were plugged with polyurethane foam stoppers and kept under constant agitation by orbital shaker (100 – 150 rpm) and constant illumination at 24 ± 1°C until the algal cell density was approximately 104 - 105 cells/ml.
A positive control (Harlan Laboratories Ltd Project Number: 41104038) used potassium dichromate as the reference item.

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

72 h

Post exposure observation period:

Not applicable

Hardness:

Not recorded.

Test temperature:

Temperature was maintained at 24 ± 1ºC throughout the test. The temperature within the incubator was recorded daily.

pH:

The pH value of the control cultures (see Table 2) was observed to increase from pH 7.6 at 0 hours to pH 8.7 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.
The pH of each control and test flask was determined at initiation of the test and after 72 hours exposure. The pH was measured using a WTW pH 320 pH meter.

Dissolved oxygen:

Not recorded.

Salinity:

freshwater used

Nominal and measured concentrations:

The test concentrations 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 a series of nominal test concentrations of 0.10, 1.0, 10 and 100 mg/l for a period of 72 hours.

Details on test conditions:

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 characterised by a cell density of 8.60 x 105 cells per ml. Inoculation of 500 ml of test medium with 2.9 ml of this algal suspension gave an initial nominal cell density of 5 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.
Samples were taken at 0, 25, 48 and 72 hours and the cell densities determined using a Coulter® Multisizer Particle Counter.

Physico-chemical measurements
The pH of the control and each test preparation was determined at initiation of the test and after 72 hours exposure. The pH was measured using a WTW pH 320 pH meter. The temperature within the incubator was recorded daily.

Reference substance (positive control):

yes

Remarks:

potassium dichromate

Key result

Duration:

72 h

Dose descriptor:

EC10

Effect conc.:

11 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

other: growth rate

Key result

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

20 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

growth rate

Remarks on result:

other: 18-23 mg/l 95% confidence limits

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

12 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

cell number

Remarks:

Yield

Remarks on result:

other: 95% confidence limits 11-13 mg/l loading rate

Duration:

72 h

Dose descriptor:

EC10

Effect conc.:

7.4 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

cell number

Remarks:

yield

Details on results:

Range-finding Test
The results showed no effect on growth at the test concentration of 0.10 mg/l. However, growth was observed to be reduced at 1.0, 10 and 100 mg/l.
Based on this information test concentrations of 0.10, 0.32, 1.0, 3.2, 10 and 32 mg/l were selected for the definitive test.
Chemical analysis of the test preparations at 0 hours showed measured test concentrations in the range of 92% to 107% of nominal were obtained. A concentration dependant decline in measured test concentration was observed at 72 hours in the range of less than the limit of quantitation (LOQ) of the analytical method employed at 0.10 mg/l through to 99% of nominal at 100 mg/l. This decline was considered to be due to adsorption of the test item to the algal cells present rather than instability.

Definitive Test
Validation criteria
The following data show that the cell concentration of the control cultures increased by a factor of 194 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.
Mean cell density of control at 0 hours : 4.21 x 103 cells per ml
Mean cell density of control at 72 hours : 8.14 x 105 cells per ml
The mean coefficient of variation for section by section specific growth rate for the control cultures was 25% 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 6% and hence satisfied the validation criterion given in the OECD Guideline which states that this must not exceed 7%.

Growth data
From the data given in Tables 2 and 4, it is clear that the growth rate (r) and yield (y) of Pseudokirchneriella subcapitata (CCAP 278/4) were affected by the presence of the test item over the 72-Hour exposure period.
Accordingly the following results were determined from the data:
Inhibition of growth rate
ErC10 (0 - 72 h) : 11 mg/l
ErC20 (0 - 72 h) : 14 mg/l
ErC50 (0 - 72 h) : 20 mg/l; 95% confidence limits 18 - 23 mg/l
where ErCx is the test concentration that reduced growth rate by x%.
Statistical analysis of the growth rate data was carried out for the control and all test concentrations 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 between the control, 0.10, 0.32, 1.0, 3.2 and 10 mg/l test concentrations (P0.05), however the 32 mg/l test concentration was significantly different (P<0.05) and, therefore the "No Observed Effect Concentration" (NOEC) based on growth rate was 10 mg/l. Correspondingly the "Lowest Observed Effect Concentration" (LOEC) based on growth rate was 32 mg/l.

Inhibition of yield
EyC10 (0 - 72 h) : 7.4 mg/l
EyC20 (0 - 72 h) : 8.8 mg/l
EyC50 (0 - 72 h) : 12 mg/l; 95% confidence limits 11 - 13 mg/l
where EyCx is the test concentration that reduced yield by x%.
Statistical analysis of the yield data was carried out as in Section 5.2.2.1. There were no statistically significant differences between the control, 0.10, 0.32, 1.0, 3.2 and 10 mg/l test concentrations (P0.05), however the 32 mg/l test concentration was significantly different (P<0.05) and, therefore the "No Observed Effect Concentration" (NOEC) based on yield was 10 mg/l. Correspondingly the "Lowest Observed Effect Concentration" (LOEC) based on yield was 32 mg/l.

Observations on cultures
All test and control cultures were inspected microscopically at 72 hours. After 72 hours there were no abnormalities detected in the control or test cultures at 0.10, 0.32, 1.0, 3.2 and 10 mg/l, however cell debris was observed to be present in the test cultures at 32 mg/l.

Observations on test item solubility
At the start of the test all control and test cultures were observed to be clear colourless solutions. After the 72-Hour test period all control, 0.10, 0.32, 1.0, 3.2 and 10 mg/l test cultures were observed to be pale green dispersions whilst the 32 mg/l test cultures were observed to be clear colourless solutions.

Physico-chemical measurements
Temperature was maintained at 24 ± 1ºC throughout the test.

Verification of test concentrations
Analysis of the test preparations at 0 hours (see Appendix 4) showed measured test concentrations to range from 92% to 100% of nominal. A concentration dependant decline in measured test concentrations was observed at 72 hours in the range of 28% of nominal at 0.10 mg/l through to 90% of nominal at 32 mg/l.
As a concentration dependant decline in measured test concentrations was observed during the range-finding test it was considered likely that the test item was adsorbing to the algal cells present. As such, in order to demonstrate this, additional test samples were prepared at 0 hours with the omission of algal cells. These additional samples were incubated alongside the test and sent for analysis at 72 hours. Analysis of these samples showed measured test concentrations in the range of 81% to 98% of nominal were obtained thereby confirming that the decline observed in the samples containing algal cells was due to adsorption of the test item to the algal cells present rather than instability.

Results with reference substance (positive control):

Positive Control
A positive control (Harlan Laboratories Ltd Project No: 41104038) 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 – 1.7 mg/l
EyC50 (0 – 72 h) : 0.59 mg/l, 95% confidence limits 0.53 – 0.65 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.

Reported statistics and error estimates:

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) was carried out on the growth rate and yield data after 72 hours for the control and all test concentrations to determine any statistically significant differences between the test and control groups. All statistical analyses were performed using the SAS computer software package (SAS 1999 - 2001).

Table1              Cell Densities and Percentage Inhibition of Growth from the Range-finding Test

Nominal Concentration (mg/l)		Cell Densities*(cells per ml)		Inhibition Values (%)
		0 Hours	72 Hours	Growth Rate	Yield
Control	R1	7.55E+03	1.19E+06
	R2	7.26E+03	9.24E+05	-	-
	Mean	7.41E+03	1.06E+06
0.10	R1	4.63E+03	1.03E+06
	R2	6.99E+03	1.07E+06	[4]	1
	Mean	5.81E+03	1.05E+06
1.0	R1	4.74E+03	6.34E+05
	R2	5.25E+03	6.14E+05	3	41
	Mean	4.99E+03	6.24E+05
10	R1	5.73E+03	5.22E+05
	R2	5.94E+03	4.67E+05	10	53
	Mean	5.84E+03	4.95E+05
100	R1	6.42E+03	1.53E+04
	R2	6.75E+03	8.42E+03	88	99
	Mean	6.59E+03	1.19E+04

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

R₁and R₂= Replicates 1 and 2

[Increase in growth compared to controls]

Table2              Cell Densities and pH Values in the DefinitiveTest

Nominal Concentration (mg/l)		pH	Cell Densities*(cells per ml)				pH
		0 h	0 h	25 h	48 h	72 h	72 h
Control	R1	7.6	5.25E+03	1.65E+04	1.10E+05	4.98E+05	8.7
	R2		4.30E+03	2.50E+04	1.95E+05	1.09E+06
	R3		4.10E+03	1.96E+04	1.76E+05	9.06E+05
	R4		3.63E+03	1.62E+04	1.57E+05	8.13E+05
	R5		3.90E+03	2.28E+04	1.72E+05	8.91E+05
	R6		4.05E+03	2.26E+04	1.65E+05	6.92E+05
	Mean		4.21E+03	2.05E+04	1.62E+05	8.14E+05
0.10	R1	7.5	5.00E+03	1.58E+04	1.27E+05	5.91E+05	8.6
	R2		4.53E+03	1.36E+04	1.75E+05	9.17E+05
	R3		4.47E+03	2.05E+04	1.32E+05	7.82E+05
	Mean		4.67E+03	1.66E+04	1.45E+05	7.63E+05
0.32	R1	7.5	4.66E+03	1.64E+04	1.31E+05	8.22E+05	8.5
	R2		4.84E+03	1.67E+04	1.47E+05	7.73E+05
	R3		2.93E+03	1.58E+04	1.52E+05	8.24E+05
	Mean		4.14E+03	1.63E+04	1.43E+05	8.07E+05
1.0	R1	7.5	4.14E+03	1.80E+04	1.48E+05	7.61E+05	8.4
	R2		4.13E+03	1.54E+04	1.47E+05	8.47E+05
	R3		3.92E+03	1.72E+04	1.45E+05	8.08E+05
	Mean		4.06E+03	1.69E+04	1.47E+05	8.05E+05
3.2	R1	7.4	3.88E+03	1.53E+04	1.67E+05	8.62E+05	8.4
	R2		3.84E+03	1.24E+04	1.59E+05	7.81E+05
	R3		4.30E+03	1.96E+04	1.73E+05	8.12E+05
	Mean		4.01E+03	1.58E+04	1.66E+05	8.18E+05
10	R1	7.4	4.79E+03	1.60E+04	1.22E+05	6.03E+05	8.4
	R2		3.94E+03	1.31E+04	1.07E+05	4.97E+05
	R3		3.94E+03	1.50E+04	1.09E+05	5.72E+05
	Mean		4.22E+03	1.47E+04	1.12E+05	5.57E+05
32	R1	7.4	3.59E+03	3.02E+03	5.45E+03	1.28E+04	8.2
	R2		3.98E+03	3.42E+03	6.61E+03	1.04E+04
	R3		4.90E+03	4.24E+03	6.33E+03	9.49E+03
	Mean		4.16E+03	3.56E+03	6.13E+03	1.09E+04

 

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

R₁- R₆= Replicates 1 to 6

Table 3              Daily Specific Growth Rates for the Control Cultures in the Definitive Test

		Daily Specific Growth Rate (cells/ml/hour)
		Day 0 - 1	Day 1 - 2	Day 2 - 3
Control	R1	0.048	0.083	0.063
	R2	0.064	0.089	0.072
	R3	0.055	0.095	0.068
	R4	0.047	0.099	0.069
	R5	0.061	0.088	0.069
	R6	0.060	0.086	0.060
	Mean	0.056	0.090	0.067

 

R₁- R₆= Replicates 1 to 6

Table 4              Inhibition of Growth Rate and Yield in the Definitive Test

Nominal Concentration (mg/l)		Growth Rate (cells/ml/hour)		Yield (cells/ml)
		0 – 72 h	% Inhibition	0 – 72 h	% Inhibition*
Control	R1	0.064		4.93E+05
	R2	0.075		1.08E+06
	R3	0.072		9.01E+05
	R4	0.071	-	8.09E+05	-
	R5	0.072		8.88E+05
	R6	0.068		6.88E+05
	Mean	0.070		8.10E+05
	SD	0.004		2.02E+05
0.10	R1	0.066	6	5.86E+05
	R2	0.072	[3]	9.13E+05
	R3	0.070	0	7.78E+05
	Mean	0.069	1	7.59E+05	6
	SD	0.003		1.64E+05
0.32	R1	0.071	[1]	8.18E+05
	R2	0.070	0	7.68E+05
	R3	0.071	[1]	8.22E+05
	Mean	0.071	[1]	8.03E+05	1
	SD	0.001		2.96E+04
1.0	R1	0.070	0	7.57E+05
	R2	0.071	[1]	8.43E+05
	R3	0.071	[1]	8.04E+05
	Mean	0.071	[1]	8.01E+05	1
	SD	0.001		4.30E+04
3.2	R1	0.072	[3]	8.59E+05
	R2	0.070	0	7.77E+05
	R3	0.071	[1]	8.08E+05
	Mean	0.071	[1]	8.14E+05	[1]
	SD	0.001		4.14E+04
10	R1	0.067	4	5.98E+05
	R2	0.064	9	4.93E+05
	R3	0.066	6	5.68E+05
	Mean	0.066	6	5.53E+05	32
	SD	0.002		5.42E+04
32	R1	0.013	81	9.22E+03
	R2	0.010	86	6.38E+03
	R3	0.009	87	4.59E+03
	Mean	0.011	85	6.73E+03	99
	SD	0.002		2.33E+03

[ ]

*In accordance with the OECD test guideline only thean 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

Conclusions:

The effect of the test item on the growth of Pseudokirchneriella subcapitata has been investigated over a 72-Hour period and gave the following results: 72h-ErC50 = 20 mg/L, 72h-ErC10 = 11 mg/L and NOECr = 10 mg/L.

Executive summary:

A study according to OECD 201 was performed to assess the effect of the test item on the growth of the green alga Pseudokirchneriella subcapitata. Following a preliminary range-finding test, Pseudokirchneriella subcapitata was exposed to an aqueous solution of the test item at concentrations of 0.10, 0.32, 1.0, 3.2, 10 and 32 mg/l (three replicate flasks per concentration) for 72 hours, under constant illumination and shaking at a temperature of 24 ± 1°C. Exposure of Pseudokirchneriella subcapitata to the test item gave the following results: 72h-ErC50 = 20 mg/L, 72h-ErC10 = 11 mg/L and NOECr = 10 mg/L. Analysis of the test preparations at 0 hours showed measured test concentrations to range from 92% to 100% of nominal. A concentration dependant decline in measured test concentrations was observed at 72 hours in the range of 28% of nominal at 0.10 mg/l through to 90% of nominal at 32 mg/l. As a concentration dependant decline in measured test concentrations was observed during the range-finding test it was considered likely that the test item was adsorbing to the algal cells present. As such, in order to demonstrate this, additional test samples were prepared at 0 hours with the omission of algal cells. These additional samples were incubated alongside the test and sent for analysis at 72 hours. Analysis of these samples showed measured test concentrations in the range of 81% to 98% of nominal were obtained thereby confirming that the decline observed in the samples containing algal cells was due to adsorption of the test item to the algal cells present rather than instability. As such it was considered that the algal cells were exposed to near nominal test concentrations throughout the duration of the test. Therefore the results are based on nominal test concentrations only.

Reference 2

Endpoint:

toxicity to aquatic algae and cyanobacteria

Type of information:

read-across from supporting substance (structural analogue or surrogate)

Adequacy of study:

key study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: Reliability is 2 because the information is based on read across

Justification for type of information:

The executive summary for the read across from Pamplefleur to Muguesia is presented and includes the information on Daphnia. The full read across is in the overall aquatic Endpoint summary. The accompaning files are attached there as well.
Executive summary: Muguesia has the same aquatic toxicity as Pamplefleur because both substances are very similar in structure. Structural similarities and differences: The target and the source chemicals both have a phenyl-butyl backbone and an alcohol functional group. The differences are that an additional methyl is present on the butyl chain of Pamplefleur, and while Muguesia is a secondary alcohol, Pamplefleur is a primary alcohol. Overall, Pamplefleur has one more carbon than Muguesia, resulting in a slightly higher molecular weight and hence log Kow.
Bioavailability: The source chemical and the target chemical have similar bioavailability based on the similarity in chemical structure and physico-chemical properties. The molecular weight of the target substance (Muguesia) is 164.25, whereas for the source (Pamplefleur) it is 178.75. They are both liquids. They have similar vapour pressures, 1.1 and 0.3 Pa. The water solubility of Muguesia (3300 mg/L) is somewhat higher possibly due to the one methyl group less. This, however did not result in a lower log Kow (3.1) compared to Pamplefleur (log Kow is 3.0). The calculated log Kows did show a higher log Kow for Pamplefleur (ECOSAR) as expected.
Mode of Action and the prediction of the aquatic toxicity information: Muguesia and Pamplefleur have the same Neutral organic Mode of Action (OECD Toolbox and Verhaar rules).
Uncertainty of the prediction: There is no remaining uncertainty in view of the reasoning above. It is not thought necessary to convert the values of Pamplefleur towards Muguesia in view of the minor differences in both molecular weight and log Kow.

Reason / purpose for cross-reference:

read-across source

Key result

Duration:

72 h

Dose descriptor:

EC10

Effect conc.:

11 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

other: growth rate

Key result

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

20 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

growth rate

Remarks on result:

other: 18-23 mg/l 95% confidence limits

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

12 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

cell number

Remarks:

Yield

Remarks on result:

other: 95% confidence limits 11-13 mg/l loading rate

Duration:

72 h

Dose descriptor:

EC10

Effect conc.:

7.4 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

cell number

Remarks:

yield

Validity criteria fulfilled:

yes

Conclusions:

For Muguesia the 72 h ErC50 and ErC10 value for algae is 20 mg/L and 11 mg/L respectively, based on the read-across substance Pamplefleur. The effect of the test item on the growth of Pseudokirchneriella subcapitata has been investigated.

Executive summary:

For Muguesia the 72 h ErC50 and ErC10 value for algae have been derived from the read across substance Pamplefleur and were concluded at 20 mg/L and 11 mg/L respectively. A study according to OECD 201 was performed to assess the effect of the test item on the growth of the green alga Pseudokirchneriella subcapitata. Following a preliminary range-finding test, Pseudokirchneriella subcapitata was exposed to an aqueous solution of the test item at concentrations of 0.10, 0.32, 1.0, 3.2, 10 and 32 mg/l (three replicate flasks per concentration) for 72 hours, under constant illumination and shaking at a temperature of 24 ± 1°C. Exposure of Pseudokirchneriella subcapitata to the test item gave the following results: 72h-ErC50 = 20 mg/L, 72h-ErC10 = 11 mg/L and NOECr = 10 mg/L.

Analysis of the test preparations at 0 hours showed measured test concentrations to range from 92% to 100% of nominal. A concentration dependant decline in measured test concentrations was observed at 72 hours in the range of 28% of nominal at 0.10 mg/l through to 90% of nominal at 32 mg/l. As a concentration dependant decline in measured test concentrations was observed during the range-finding test it was considered likely that the test item was adsorbing to the algal cells present. As such, in order to demonstrate this, additional test samples were prepared at 0 hours with the omission of algal cells. These additional samples were incubated alongside the test and sent for analysis at 72 hours. Analysis of these samples showed measured test concentrations in the range of 81% to 98% of nominal were obtained thereby confirming that the decline observed in the samples containing algal cells was due to adsorption of the test item to the algal cells present rather than instability. As such it was considered that the algal cells were exposed to near nominal test concentrations throughout the duration of the test. Therefore the results are based on nominal test concentrations only.

Description of key information

Muguesia is concluded to have a 72h ErC50 value of 20 mg/L and ErC10 value of 11 mg/L, based on the results of the read across substance Pamplefleur. The values are based on nominal concentrations. A study according to OECD 201 was performed with the test material Pamplefleur to assess the effect of the test item on the growth of the green alga Pseudokirchneriella subcapitata. Following a preliminary range-finding test, Pseudokirchneriella subcapitata was exposed to an aqueous solution of the test item at concentrations of 0.10, 0.32, 1.0, 3.2, 10 and 32 mg/l (three replicate flasks per concentration) for 72 hours, under constant illumination and shaking at a temperature of 24 ± 1°C. Exposure of Pseudokirchneriella subcapitata to the test item gave the following results: 72h-ErC50 = 20 mg/L, 72h-ErC10 = 11 mg/L and NOECr = 10 mg/L. The results are based on nominal test concentrations only. The measured concentrations fit within the range 80 to 120% of the nominal concentrations, which means the results can be based only upon the nominal concentrations.

Key value for chemical safety assessment

EC50 for freshwater algae:

20 mg/L

EC10 or NOEC for freshwater algae:

11 mg/L