Alcohols, C12-13, branched and linear, ethoxylated

Toxicity to aquatic algae and cyanobacteria

Link to relevant study record(s)

Reference

Endpoint:

effects on growth of green algae

Type of information:

experimental study

Adequacy of study:

key study

Study period:

23 Nov - 21 Dec 2020

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, corrected 2011

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Analytical monitoring:

yes

Details on sampling:

- Concentrations: all concentrations
- Sampling method: sampling at 0h (fresh solutions) and aftter 24, 48 and 72 h (aged solutions)
- Sample storage conditions before analysis: The samples were mixed with 10 mL acetonitrile and stored deep-frozen (≤ - 18 °C) until analysis.

Vehicle:

no

Details on test solutions:

PREPARATION AND APPLICATION OF TEST SOLUTION (especially for difficult test substances)
- Method: A stock solution with a nominal concentration of 12 mg/L was prepared by adding the necessary amount of test item to a volumetric flask. Test medium was added and the solution was homogenised by by shaking. The solution was observed to be clear and transparent. Test item concentrations were prepared by dilution with test medium.

Test organisms (species):

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

Details on test organisms:

TEST ORGANISM
- Strain: SAG 61.81
- Source (laboratory, culture collection): purchased from MBM Sciencebridge GmbH, Göttingen, Germany
- Method of cultivation: The algae are grown semi-continuously in sterile cultures in the laboratory. Old medium is periodically replaced by fresh mineral solution in order to keep the algae in an exponential growth state.

ACCLIMATION
- Acclimation period: 3 to 4 days
- Culturing media and conditions (same as test or not): same

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

72 h

Test temperature:

22.5 – 23.1 °C

pH:

7.36 - 8.01

Nominal and measured concentrations:

Nominal test item concentrations: 0.0750, 0.150, 0.300, 0.600, 1.20 mg/L
Geometric mean measured test item concentrations: 0.0165, 0.0435, 0.0960, 0.288, 0.516 mg/L(based on 3 representative constituents)

Details on test conditions:

TEST SYSTEM
- Test vessel: Erlenmeyer flasks (glass), nominal volume 100 mL
- Type (delete if not applicable): covered by aluminium caps
- Fill volume: ~70 mL
- Initial cells density: 0.5 × E*4 cells/mL
- Control end cells density: 72.20 × E*4 cells/mL
- No. of vessels per concentration (replicates): 3
- No. of vessels per control (replicates): 6

GROWTH MEDIUM
- Standard medium used: yes acc. to AAP-Medium (according to Annex 3 of OECD 201)

TEST MEDIUM / WATER PARAMETERS
- Culture medium different from test medium: no
- Intervals of water quality measurement: pH at test start and test end; temperature continously

OTHER TEST CONDITIONS
- Adjustment of pH: no
- Photoperiod:continous illumination
- Light intensity and quality: 95.0 µEm-2s-1 (mean light intensity)

EFFECT PARAMETERS MEASURED (with observation intervals if applicable) :
- Determination of cell concentrations: cell densities were determined by a fluorimeter at time points. 0, 24, 48 and 72 h

TEST CONCENTRATIONS
- Range finding study
- Test concentrations: 0.0100, 0.100, 1.00 and 10.0 mg/L
- Results used to determine the conditions for the definitive study: EC50 (72h): >0.10 - < 1.0 mg/L

Reference substance (positive control):

yes

Remarks:

Potassium dichromate

Duration:

72 h

Dose descriptor:

EC10

Effect conc.:

0.099 mg/L

95% CI:

>= 0.092 - <= 0.106

Nominal / measured:

meas. (geom. mean)

Conc. based on:

other: based on three representative constituents

Remarks:

C12EO2, C12EO3 and C12EO6

Basis for effect:

growth rate

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

0.179 mg/L

95% CI:

>= 0.171 - <= 0.187

Nominal / measured:

meas. (geom. mean)

Conc. based on:

other: based on three representative constituents

Remarks:

C12EO2, C12EO3 and C12EO6

Basis for effect:

growth rate

Duration:

72 h

Dose descriptor:

NOEC

Effect conc.:

0.043 mg/L

Nominal / measured:

meas. (geom. mean)

Conc. based on:

other: based on three representative constituents

Remarks:

C12EO2, C12EO3 and C12EO6

Basis for effect:

growth rate

Details on results:

- Exponential growth in the control (for algal test): yes

Results with reference substance (positive control):

- ErC50 (72 h): 1.35 mg/L (NOErC(72 h): 0.320 mg/L)
- Other: test performed Aug 2020

Reported statistics and error estimates:

The NOEC and LOEC were determined using a multiple comparison method (Dunnetts-t-test, left sided, for growth rate and yield). The EC10, 20, 50-values were determined following Probit analysis using linear max. likelihood regression for growth rate and following Weibull analysis using linear max. likelihood regression for yield.

Table 1: Validity criteria for OECD 201 (2006)

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.	136.23	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%	19%	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%.	2.5%	yes

Table 2:  Percentage inhibition of growth rate

Nominal Conc.	% Inhibition of growth rate
[mg/L]	0 h – 24 h	0 h –48 h	0 h – 72 h
Control	0.0	0.0	0.0
0.0750	-23.9	-9.8	-5.0
0.150	-10.8	-9.5	-4.6
0.300	16.2	15.9	8.9*
0.600	121.8	116.3	84.8*
1.20	149.0	181.8	145.9*

* Statistically significant different to the control (left-sided, p≤0.05)

Validity criteria fulfilled:

yes

Remarks:

please see table 1 at "Any other information on results incl. tables"

Description of key information

EC50 (72 h): 0.179 mg/L (geom. mean)

EC10 (72 h): 0.0994 mg/L (geom. mean)

Additional information

The key study investigating the toxicity Alcohols, C12-13, branched and linear, ethoxylated to aquatic algae was conducted according to OECD 201. In the GLP guideline study the growth inhibition of green algae (Raphidocelis subcapitata) at nominal test item concentrations of 0.0750, 0.150, 0.300, 0.600, 1.20 mg/L was monitored. The test concentrations were analytically monitored by HPLC-MS/MS. The time weighted mean measured concentrations, based on three representative constituents of the UVCB substance, were 0.0165, 0.0435, 0.0960, 0.288, 0.516 mg/L. Based on the algal growth rate an EC50 (72 h) of 0.179 mg/L (geom. mean) was observed. The determined EC10 (72 h) was 0.0994 mg/L (geom. mean).