Sodium 2-[methyl(1-oxododecyl)amino]ethanesulphonate

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:

2012-11-19 to 2012-11-22

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Justification for type of information:

This study for the source substance SMCT is used as read-across to the registered (target) substance SMLT. See section 13 for the full read-across justification.

Reason / purpose for cross-reference:

read-across: supporting information

Qualifier:

according to guideline

Guideline:

OECD Guideline 201 (Alga, Growth Inhibition Test)

Deviations:

no

GLP compliance:

yes

Analytical monitoring:

yes

Details on sampling:

- Concentrations: 1.00 - 3.16 - 10.0 - 31.6 - 100 mg/L
- Sampling method: The concentrations of the test item were analytically determined from all test concentrations and the control after 0 hours (test start) and 72 hours (test end). Samples at test start were taken from an additional replicate without algae. At end of the test samples were taken directly from the pooled test replicates.
- Sample storage conditions before analysis:All original samples were stored at room temperature until sample preparation. Prepared samples were stored at room temperature until analysis.

Vehicle:

no

Details on test solutions:

PREPARATION AND APPLICATION OF TEST SOLUTION (especially for difficult test substances)
- Method: A stock solution of 100 mg/L was freshly prepared with dilution water. Dispersion treatment was agitation.
- Eluate: Dilution water
- Differential loading: 1.00 - 3.16 - 10.0 - 31.6 - 100 mg/L
- Controls: Six replicates (without test item) were tested under the same test conditions as the test replicates.

Test organisms (species):

Desmodesmus subspicatus (previous name: Scenedesmus subspicatus)

Details on test organisms:

TEST ORGANISM
- Common name: Desmodesmus subspicatus Chodat
- Strain: SAG 86.81
- Source (laboratory, culture collection): SAG Pflanzenphysiologisches Institut der Universitaet Goettingen, Nikolausberger Weg 18, D-37073 Goettingen, Germany
- Age of inoculum (at test initiation): 3 days
- Method of cultivation: Fresh stocks were prepared every month on Z-Agar. Light intensity amounted to 35 - 70 µE x m-2 x s-1 for 24 h per day.

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

72 h

Post exposure observation period:

No

Hardness:

0.24 mmol Ca+Mg/l

Test temperature:

min.: 22.0 max.: 23.5, mean value: 22.8 °C

pH:

Nominal concentration pH-value
Test item
[mg/L] Active ingredient
[mg a.i./L] Start; 0 hours End; 72 hours
100 72.3 7.86 7.69
31.6 22.8 7.85 7.89
10.0 7.23 7.83 7.94
3.16 2.28 7.91 8.03
1.00 0.723 7.86 8.13
Control 7.94 8.25

Dissolved oxygen:

Not measured

Salinity:

Not measured, freshwater conditions

Details on test conditions:

TEST SYSTEM
- Test vessel: 250 mL Erlenmeyer flasks
- Type (delete if not applicable): open, cotton wool plugs
- Material, size, headspace, fill volume: sterile 250 mL Erlenmeyer flasks, test volume 100 mL
- Aeration: Test containers were placed on a rotary shaker and oscillated at appr. 70 rpm
- Type of flow-through (e.g. peristaltic or proportional diluter): None
- Renewal rate of test solution (frequency/flow rate): One application at test start
- Initial cells density: Nominal: approximately 2 - 5 x 103 cells/mL, Actual: mean 4332 cells/mL
- Control end cells density: Mean 631901 cells/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:
Composition of Dilution Water
according to the guideline
Component Concentration [mg/L]
NH4Cl 15
MgCl2  6 H2O 12
CaCl2  2 H2O 18
MgSO4  7 H2O 15
KH2PO4 1.6
FeCl3  6 H2O 0.064
Na2EDTA  2 H2O 0.1
H3BO3 0.185
MnCl2  4 H2O 0.415
ZnCl2 3 x 10-3
Na2MoO4  2 H2O 7 x 10-3
CoCl2  6 H2O 1.5 x 10-3
CuCl2  2 H2O 1 x 10-5
NaHCO3 50
pH 8.1  0.2




OTHER TEST CONDITIONS
- Sterile test conditions: no
- Adjustment of pH: no
- Photoperiod: 24 h
- Light intensity and quality: 60 - 120 µE x m-2 x s-1, mean value: 67.9



EFFECT PARAMETERS MEASURED (with observation intervals if applicable) :
- Determination of cell concentrations: [counting chamber; electronic particle counter; fluorimeter; spectrophotometer; colorimeter] fluorimeter, Cell density and self fluorescence was measured daily via Chlorophyll-a- fluorescence, excitation at 436 nm, emission at 685 nm. Dilution water was used as background signal.



TEST CONCENTRATIONS

Results of the Range Finding Test (0-72 hours)
Nominal Test Item Concentration
[mg/L] Growth Rate Inhibition [%] Yield Inhibition [%]
100 75 98
10.0 2 12
1.00 1 3
0.1 3 15
0.01 0 0

Reference substance (positive control):

yes

Remarks:

Potassium dichromate

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

> 100 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Remarks:

is UVCB means 100% act. ingr.

Basis for effect:

growth rate

Duration:

72 h

Dose descriptor:

EC10

Effect conc.:

36.2 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Remarks:

is UVCB means 100% act.ingr.

Basis for effect:

growth rate

Remarks on result:

other: 95% CI 28-46 mg/L

Details on results:

- Exponential growth in the control (for algal test): yes
- Observation of abnormalities (for algal test):
- Unusual cell shape: No
- Colour differences: No
- Flocculation: No
- Adherence to test vessels: No
- Aggregation of algal cells: No
- Other: No
- Any observations (e.g. precipitation) that might cause a difference between measured and nominal values: No
- Effect concentrations exceeding solubility of substance in test medium: No

Results with reference substance (positive control):

- Results with reference substance valid? Yes

Current Study Valid Range (average ± 3 x SD)
Growth Rate Inhibition
ErC50 0.631 0.682 ± 0.452
95 %
confidence
interval 0.583 - 0.687
Yield Inhibition
EyC50 0.256 0.314 ± 0.144
95 %
confidence
interval 0.247 - 0.265
SD = Standard deviation

Reported statistics and error estimates:

NOEC/LOEC were determined by calculation of statistical significance of growth rate and yield. As standard One Way Analysis of Variance (ANOVA) and DUNNETT’s test were used for NOEC/LOEC calculations. When running a One Way Analysis of Variance a Normality test and an Equal Variance test were done first. The SHAPIRO-WILK-Test was used to test for normally distributed populations. The Levene median test was used for equal variance. P-values for both Normality and Equal Variance tests are 0.05. The a-value (acceptable probability of incorrectly concluding that there is a difference) is a=0.05.

Cell Densities

	Nominal concentration			Replicate		Cell density [cells/mL]
Test item [mg/L]		Active ingredient [mg a.i./L]	No.		0 hours		24 hours	48 hours	72 hours
100		72.3	1		4332		8838	19141	110142
			2		4332		7426	16676	84866
			3		4332		7272	14068	72374
			Mean		4332		7845	16628	89127
31.6		22.8	1		4332		10417	67257	456538
			2		4332		9301	66653	387254
			3		4332		10622	67691	419522
			Mean		4332		10113	67200	421105
10.0		7.23	1		4332		11455	80422	542460
			2		4332		15537	81252	603033
			3		4332		12637	76465	562085
			Mean		4332		13210	79380	569193
3.16		2.28	1		4332		11930	57463	596287
			2		4332		12568	55243	495159
			3		4332		12345	50865	493209
			Mean		4332		12281	54524	528218
1.00		0.723	1		4332		15804	105739	693388
			2		4332		12738	77415	601900
			3		4332		15949	97361	660429
			Mean		4332		14830	93505	651906
Control			1		4332		15977	120457	732386
			2		4332		12930	92750	584792
			3		4332		14106	107094	618585
			4		4332		13446	88410	636873
			5		4332		12971	88174	611021
			6		4332		12637	96493	607750
			Mean		4332		13678	98896	631901

Evaluation after 72 hours

                   Statistically significant differences of growth rates and yield compared to

                   control values are marked (+), not significant differences are marked (-).

Nominal concentration		Replicate	Growth rate		Growth rate inhibition	Yield		Inhibition of yield
Test item [mg/L]	Active ingredient [mg a.i./L]	No.	[d^-1]		[%]	[cells/mL]		[%]
100	72.3	1		1.08	35.0		105810	83.1
		2		0.992	40.3		80534	87.2
		3		0.939	43.5		68042	89.2
		Mean	(+)	1.00	39.6	(+)	84795	86.5
31.6	22.8	1		1.55	6.47		452206	27.9
		2		1.50	9.78		382922	39.0
		3		1.52	8.17		415190	33.8
		Mean	(+)	1.53	8.14	(+)	416773	33.6
10.0	7.23	1		1.61	3.01		538128	14.3
		2		1.65	0.89		598701	4.60
		3		1.62	2.30		557753	11.1
		Mean	(-)	1.63	2.07	(-)	564861	9.99
3.16	2.28	1		1.64	1.11		591955	5.67
		2		1.58	4.84		490827	21.8
		3		1.58	4.92		488877	22.1
		Mean	(-)	1.60	3.62	(+)	523886	16.5
1.00	0.728	1		1.69	-1.92		689056	-9.80
		2		1.65	0.92		597568	4.78
		3		1.68	-0.94		656097	-4.55
		Mean	(-)	1.67	-0.65	(-)	647574	-3.19
Control		1		1.71			728054
		2		1.64			580460
		3		1.65			614253
		4		1.66			632541
		5		1.65			606689
		6		1.65			603418
		Mean		1.66			627569

Section-by-Section and Average Specific Growth Rates of the Control Group

                   (0 – 72 hours)

	Replicate No.	Specific growth rate [d^-1]			Mean (0 - 72 h)	SD ±	CV [%]	Mean CV [%]
		section-by-section
		0 - 24 hours	24 - 48 hours	48 - 72 hours
Control	1	1.31	2.02	1.81	1.71	0.367	21.5	27.4
	2	1.09	1.97	1.84	1.64	0.473	29.0
	3	1.18	2.03	1.75	1.65	0.432	26.1
	4	1.13	1.88	1.98	1.66	0.462	27.8
	5	1.10	1.92	1.94	1.65	0.479	29.0
	6	1.07	2.03	1.84	1.65	0.509	30.9
				Mean	1.66
				SD ±	0.03
				CV [%]	1.58

Validity criteria fulfilled:

yes

Conclusions:

In this study Sodium methyl cocoyl taurate was found to inhibit the growth of the freshwater green alga Desmodesmus subspicatus after 72 hours. The NOEC-values of the test item for inhibition of growth rate and inhibition of yield after 72 hours were nominal 10.0 mg/L and 1.00 mg/L, respectively. The LOEC-values of the test item for inhibition of growth rate and inhibition of yield after 72 hours were nominal 31.6 mg/L and 3.16 mg/L, respectively. The EC50-values of the test item for inhibition of growth rate (ErC50) and yield (EyC50) with 95 % Confidence Intervals after 72 hours were > 100 and 43.7 (35.0 – 55.5) mg/L, respectively.

The corresponding NOEC-values of the active ingredient inhibition of growth rate and inhibition of yield after 72 hours were 7.23 mg a.i./L and 0.723 mg a.i./L, respectively. The LOEC-values of the active ingredient for inhibition of growth rate and inhibition of yield after 72 hours were 22.8 mg a.i./L and 2.28 mg a.i./L, respectively. The EC50-values of the active ingredient for inhibition of growth rate (ErC50) and yield (EyC50) with 95 % Confidence Intervals after 72 hours were > 72.3 and 31.6 (25.2 – 40.1) mg a.i./L, respectively.

All effect levels are given based on nominal test item and active ingredient concentrations of Sodium methyl cocoyl taurate.

Based on read-across, this algae toxicity result is applied to the registration (target) substance SMLT. This is a conservative read-across since the available data on other alkyl taurate amide salts indicates toxicity increases with increasing chain length, and SMCT contains constituents with chain lengths in the range C12-C18 whilst SMLT is essentially 'pure' C12.

Executive summary:

The toxicity of Sodium methyl cocoyl taurate(batch number: DEB4003323)to the unicellular freshwater green alga Desmodesmus subspicatus was determined according to the principles of OECD 201 at Dr.U.Noack-Laboratorienin 31157 Sarstedt, Germany from 2012-11-19 to 2012-11-22. The aim of the study was to assess the effects on growth rate and yield over a period of 72 hours.

The study was conducted under static conditions with an initial cell density of 4332 cells/mL. Based on a preliminary test 5 concentration levels were tested in a geometrical series with a nominal dilution factor of Ö10: 1.00 - 3.16 - 10.0 - 31.6 - 100 mg/L corresponding to active ingredient concentrations of 0.723 - 2.28 - 7.23 - 22.8 - 72.3 mg a.i./L. Three replicates were tested for each test item concentration and six replicates for the control. Environmental conditions were determined to be within the acceptable limits.

The concentrations of Sodium methyl cocoyl taurate were analytically verified by LC-MS/MS at test start and test end of all test concentrations and the control.

The measured concentrations of the active ingredient of Sodium methyl cocoyl taurateat test start were in the range of 105 to 111 % and after 72 hours in the range of 111 to 114 % of the nominal values. Therefore, all effect values given are based on the nominal test item and active ingredient concentrations Sodium methyl cocoyl taurate.

IMPORTANT NOTE TO AVOID CONFUSION:

As the registration substance is a UVCB this means that the test item is 100% active ingredient.

NOEC, LOEC, EC - values and 95 % Confidence Intervals of Sodium methyl cocoyl taurate
(0-72 hours)

                   based on nominal test item concentrations [mg/L]

                               

	Growth Rate Inhibition
	[mg/L]
NOEC	10.0
LOEC	31.6
ErC10	36.2 (28.4 – 45.7)
ErC20	58.4 (49.7 – 66.2)
ErC50	> 100
	Inhibition of Yield
NOEC	1.00
LOEC	3.16
EyC10	10.9 ( – 20.5)
EyC20	21.2 (14.5 – 29.4)
EyC50	43.7 (35.0 – 55.5)

Based on read-across, this algae toxicity result is applied to the registration (target) substance SMLT. This is a conservative read-across since the available data on other alkyl taurate amide salts indicates toxicity increases with increasing chain length, and SMCT contains constituents with chain lengths in the range C12-C18 whilst SMLT is essentially 'pure' C12. See attached read-across justification in section 13 for additional details

Description of key information

In this study Sodium methyl cocoyl taurate was found to inhibit the growth of the freshwater green alga Desmodesmus subspicatus after 72 hours. The NOEC-values of the test item for inhibition of growth rate and inhibition of yield after 72 hours were nominal 10.0 mg/L and 1.00 mg/L, respectively. The LOEC-values of the test item for inhibition of growth rate and inhibition of yield after 72 hours were nominal 31.6 mg/L and 3.16 mg/L, respectively. The EC50-values of the test item for inhibition of growth rate (ErC50) and yield (EyC50) with 95 % Confidence Intervals after 72 hours were > 100 and 43.7 (35.0 – 55.5) mg/L, respectively.

The corresponding NOEC-values of the active ingredient inhibition of growth rate and inhibition of yield after 72 hours were 7.23 mg a.i./L and 0.723 mg a.i./L, respectively. The LOEC-values of the active ingredient for inhibition of growth rate and inhibition of yield after 72 hours were 22.8 mg a.i./L and 2.28 mg a.i./L, respectively. The EC50-values of the active ingredient for inhibition of growth rate (ErC50) and yield (EyC50) with 95 % Confidence Intervals after 72 hours were > 72.3 and 31.6 (25.2 – 40.1) mg a.i./L, respectively.

All effect levels are given based on nominal test item and active ingredient concentrations of Sodium methyl cocoyl taurate.

Based on read-across, this algae toxicity result is applied to the registration (target) substance SMLT. This is a conservative read-across since the available data on other alkyl taurate amide salts indicates toxicity increases with increasing chain length, and SMCT contains constituents with chain lengths in the range C12-C18 whilst SMLT is essentially 'pure' C12.

Key value for chemical safety assessment

EC50 for freshwater algae:

100 mg/L

EC10 or NOEC for freshwater algae:

36 mg/L