Octan-1-ol, ethoxylated

Toxicity to aquatic algae and cyanobacteria

Link to relevant study record(s)

Reference

Endpoint:

toxicity to aquatic algae and cyanobacteria

Type of information:

experimental study

Adequacy of study:

key study

Study period:

04 Feb 2019 - 04 Apr 2019

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 201 (Alga, Growth Inhibition Test)

Version / remarks:

2006

GLP compliance:

yes (incl. QA statement)

Analytical monitoring:

yes

Details on sampling:

- Sampling of all concentrations: 1.0, 3.2, 10, 32 and 100 mg/L
- Sampling method: Replicates at 0, 24, 48 and 72 hours were pooled.
- Sample storage conditions before analysis: stored frozen prior to analysis

Vehicle:

no

Details on test solutions:

PREPARATION AND APPLICATION OF TEST SOLUTION (especially for difficult test substances)
- Method: Nominal amounts of test item (50 and 16 mg) were dissolved in culture medium with the aid of ultrasonication for approximately 10 minutes and the volume adjusted to 500 mL to give 100 and 32 mg/L stock solutions respectively from which a series of dilutions was made to give further stock solutions of 10, 3.2 and 1.0 mg/L. An aliquot (450 mL) of each of the stock solutions was separately inoculated with algal suspension (1.5 mL) to give the required test concentrations of 1.0, 3.2, 10, 32 and 100 mg/L.
The stock solutions were inverted several times to ensure adequate mixing and homogeneity.

Test organisms (species):

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

Details on test organisms:

TEST ORGANISM
- Common name: green algae
- Strain: CCAP 278/4
- Source (laboratory, culture collection): Culture Collection of Algae and Protozoa (CCAP), SAMS Research Services Ltd, Scottish Marine Institute, Oban, Argyll, Scotland.
- Method of cultivation:The master cultures were maintained under constant agitation by orbital shaker (approximately 150 rpm) and constant illumination at 24 ±1 °C.

CULTUR
- Culturing media and conditions (same as test or not): same as test conditions

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

72 h

Test temperature:

24 ±1 ºC

pH:

Control: 7.8 - 8.3
Test concentrations: 7.6 - 8.6

Nominal and measured concentrations:

Nominal test substance concentrations: 1.0, 3.2, 10, 32 and 100 mg/L
Geometric mean measured test concentrations: 0.81, 2.6, 8.0, 23 and 105 mg/L.

Analysis of the test preparations at 0, 24 and 48 hours showed measured test concentrations to range from 0.92 to 110 mg/L (86% to 110% of the nominal test concentrations). A significant decline in measured test concentrations was observed in the 1.0, 3.2, 10 and 32 mg/L test preparations at 72 hours with concentrations in the range of 0.31 to 4.0 mg/L (13% to 59% of the nominal test concentrations). Analysis of the 100 mg/L test preparation at 72 hours showed a measured test concentration of 125% of nominal was obtained.

Details on test conditions:

TEST SYSTEM
- Test vessel: glass conical flasks (nominal volume 250 mL)
- Type (delete if not applicable): plugged with polyurethane foam bungs
- Fill volume: 100 mL
- Initial cells density: 5.00E+03 cells per mL
- Control end cells density: 1.25E+06cells per mL
- No. of vessels per concentration (replicates): 3
- No. of vessels per control (replicates): 6

GROWTH MEDIUM
- Standard medium used: yes

TEST MEDIUM / WATER PARAMETERS
- Source/preparation of dilution water: The culture medium was prepared using reverse osmosis purified deionized water* and the pH adjusted to 7.5 ± 0.1 with 0.1N NaOH or HCl.
- Culture medium different from test medium: no
- Intervals of water quality measurement: temperature and appearance were recorded daily. The pH was recored at test start and after 72 h.

OTHER TEST CONDITIONS
- Adjustment of pH: no
- Photoperiod: continuous illumination
- Light intensity and quality: 7000 lux provided by warm white lighting (380 to 730 nm)


EFFECT PARAMETERS MEASURED
- Determination of cell concentrations: electronic particle counter (Coulter® Multisizer Particle Counter) at 27, 48 and 72 hours


TEST CONCENTRATIONS
- Range finding study: yes
- Test concentrations: 0.10, 1.0, 10 and 100 mg/L
- Results used to determine the conditions for the definitive study: no effects at 0.10 and 1 mg/L, reduced growth at 10 and 100 mg/L

Reference substance (positive control):

yes

Remarks:

Potassium dichromate

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

14 mg/L

95% CI:

>= 12 - <= 17

Nominal / measured:

meas. (geom. mean)

Conc. based on:

test mat.

Basis for effect:

growth rate

Duration:

72 h

Dose descriptor:

EC10

Effect conc.:

5.9 mg/L

Nominal / measured:

meas. (geom. mean)

Conc. based on:

test mat.

Basis for effect:

growth rate

Details on results:

- Exponential growth in the control (for algal test): yes
- Results based on Yield: EyC10 (72h): 2.7 mg/L, EyC20 (72h): 3.7 mg/L, EyC50 (72h): 6.4 mg/L
- Observation of abnormalities (for algal test): enlarged cells were observed in the 7.0 mg/L test cultures whilst cell debris was observed in the 18 mg/L test cultures. No intact cells were observed to be present in the 105 mg/L test cultures.
- NOEC based on growth rate was 2.5 mg/L. Correspondingly the LOEC based on growth rate was 7.0 mg/L. NOEC based on yield was 2.5 mg/L. Correspondingly the LOEC based on yield was 7.0 mg/L.

Results with reference substance (positive control):

ErC50 (0 to 72 hour): 1.5 mg/L; 95% confidence limits 1.3 to 1.7 mg/L
Test was conducted between 12 November 2018 and 03 December 2018.

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).

Table 1: Test concentrations

Nominal Test Concentration (mg/L)	Geometric Mean Measured Test Concentration (mg/L)	Expressed as a Percentage of the Nominal Test Concentration (%)
1.0	0.72	72
3.2	2.5	78
10	7.0	70
32	18	56
100	105	105

Table 2: Inhibition of Growth Rate and Yield in the Definitive Test

Geometric Mean Measured Test Concentration (mg/L)		Growth Rate (cells/mL/hour)		Yield (cells/mL)
		0 to 72 Hour	% Inhibition	0 to 72 Hour	% Inhibition*
Control	Mean	0.076		1.24E+06
	SD	0.004		3.47E+05
0.72	Mean	0.077	[1]	1.29E+06	[4]
	SD	0.000		3.00E+04
2.5	Mean	0.075	2	1.08E+06	13
	SD	0.002		1.18E+05
7.0	Mean	0.066	13	5.79E+05	53
	SD	0.004		1.40E+05
18	Mean	0.026	66	2.91E+04	98
	SD	0.005		1.25E+04
105	Mean	0.009	88	4.29E+03	100
	SD	0.001		4.39E+02

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

SD =Standard Deviation

- = Not applicable

[ ] = Increase in growth compared to controls

Table 3: Validity criteria for OECD 201.

Criterion from the guideline	Outcome	Validity criterion fulfilled
The biomass in the control cultures should have increased exponentially by a factor of at least 16 within the 72-hour test period.	250	yes
The mean coefficient of variation for section-by-section specific growth rates (days 0-1, 1-2 and 2-3, for 72-hour tests) in the control cultures must not exceed 35%	5%	yes
The coefficient of variation of average specific growth rates during the whole test period in replicate control cultures must not exceed 7% in tests with Pseudokirchneriella subcapitata and Desmodesmus subspicatus. For other less frequently tested species, the value should not exceed 10%.	5%	yes

 

 

Validity criteria fulfilled:

yes

Remarks:

For further details please refer to table 3 in “Any other information on results incl. tables”.

Description of key information

ErC50 (72 h): 14 mg/L (nominal), OECD 201

ErC10 (72 h): 5.9 mg/L (nominal), OECD 201