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

Toxicity to microorganisms

Link to relevant study record(s)

Reference

Endpoint:

activated sludge respiration inhibition testing

Type of information:

experimental study

Adequacy of study:

key study

Study period:

2012-11-15 to 2012-11-16

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Remarks:

Read-across 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 209 (Activated Sludge, Respiration Inhibition Test

Deviations:

no

GLP compliance:

yes

Analytical monitoring:

no

Vehicle:

no

Details on test solutions:

PREPARATION AND APPLICATION OF TEST SOLUTION (especially for difficult test substances)
- Method: Directly weighing of the stock solution, 30 min ultrasound treatment at room temperature
- Eluate: Synthetic waste water acc. to OECD 209
- Differential loading: 100 - 180 - 320 - 560 - 1000 mg/L corresponding to 72.3 - 130 - 231 - 405 - 723 mg a.i./L
- Controls: Triplicates at the beginning of the test + triplicates at the end of the test

Test organisms (species):

activated sludge

Details on inoculum:

- Preparation of inoculum for exposure: Non adapted activated sludge from the sewage plant at Hildesheim (Municipal sewage treatment plant of 31137 Hildesheim, Germany)
- Pretreatment: Washed twice with autoclaved tap water and an adjustment to a dry weight concentration of 3.0 g/L +/- 10 % was not necessary. The sludge was used within 24 h after sampling
- Dry sludge concentration: 3.18 g/L corresponding to 1.59 g/L in the test vessel

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

3 h

Hardness:

Not determined

Test temperature:

19.8 °C

pH:

pH-value of the activated sludge 7.98
pH-value of the synthetic waste water 7.24

Salinity:

Not determined

Details on test conditions:

TEST SYSTEM
- Test vessel: 1000 mL Erlenmeyer flask, DIN 12380
- Aeration: Permanent
- No. of vessels per concentration (replicates): 5
- No. of vessels per control (replicates): 3
- Composition of test medium:

Test item concentration [mg/L]
100 180 320 560 1000
Inoculum 250
Synthetic waste water 16
Stock solution [g/L] 5
Volume stock solution [mL] 10 18 32 56 100
Demineralised water [mL] 224 216 202 178 134




EFFECT PARAMETERS MEASURED (with observation intervals if applicable) :
After 3 h incubation, the oxygen concentration of each control, reference item and test item replicate was determined by means of oximeter immediately after transferring the solution to the measuring cell and the oxygen depletion was recorded for at least 3 minutes on a flat bed recorder.

TEST CONCENTRATIONS
- Spacing factor for test concentrations:
- Range finding study

Test item concentration pH (test item in water) Inhibition [%]

[mg/L] [mg a.i./L]
10 7.23 - -10
100 72.3 - 11
1000 723 - #
100 72.3 6.61 5
1000 723 6.80 49

Reference substance (positive control):

yes

Remarks:

Copper (II) sulphate pentahydrate p.a.

Key result

Duration:

3 h

Dose descriptor:

NOEC

Effect conc.:

180 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Remarks:

is UVCB means 100% act.ingr.

Basis for effect:

inhibition of total respiration

Remarks:

respiration rate

Duration:

3 h

Dose descriptor:

EC50

Effect conc.:

513 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Remarks:

is UVCB means 100% act.ingr.

Basis for effect:

inhibition of total respiration

Remarks:

respiration rate

Remarks on result:

other: 95 CI 465-572 mg/L

Details on results:

- Any observations (e.g. precipitation) that might cause a difference between measured and nominal values: None

Results with reference substance (positive control):

- Results with reference substance valid? Yes
- Relevant effect levels: EC50: 94.6 mg/L

Reported statistics and error estimates:

The NOEC was determined by calculation of statistical significance of the inhibition of respiration in comparison to the control. One Way Analysis of Variance (ANOVA) and DUNNETT’s test was used for NOEC calculations. When running a One Way Analysis of Variance a Normality test and an Equal Variance test were done first. P-values for both Normality and Equal Variance test were 0.05. The -value (acceptable probability of incorrectly concluding that there is a difference) is a=0.05.

The EC-values of the test item were calculated by sigmoidal dose-response regression and the EC50-value of the reference item by linear regression using software GraphPad Prism, GRAPHPAD SOFTWARE, INC. Calculation of the confidence intervals for the EC50-values was carried out using standard procedures.

From the oxygen depletion the oxygen uptake rates were calculated in mg O₂/L×h, additionally the specific respiration rates based on the dry sludge concentration were calculated in mg O₂/g×h.

The inhibition of the oxygen uptake rates of the test and reference item concentrations in % was calculated in comparison with the oxygen uptake rates of the control.

Oxygen Uptake Rates, Specific Respiration Rates and Inhibition of the Respiration of the Control and Reference Item Concentrations

Test Item Concentration		Repl.	Oxygen Uptake Rate R	Specific Respiration Rate Rs	Inhibition	Mean Inhibition
[mg/L]	[mg a.i./L]		[mg O2/L×h]	[mg O2/g×h]	[%]	[%]
Control		1	24.0	15.1	–	–
		2	28.4	17.9
		3	28.4	17.9
		4	18.8	11.8
		5	20.4	12.8
		6	20.4	12.8
100	72.3	1	24.8		-6	-1
		2	23.2		1
		3	23.2		1
		4	24.4		-4
		5	24.8		-6
180	130	1	20.0		15	12
		2	21.2		9
		3	20.4		13
		4	21.2		9
		5	20.0		15
320	231	1	14.8		37	37
		2	14.4		38
		3	14.8		37
		4	14.0		40
		5	14.8		37
560	405	1	11.6		50	50
		2	11.6		50
		3	11.6		50
		4	11.2		52
		5	12.0		49
1000	723	1	10.0		57	57
		2	10.0		57
		3	10.8		54
		4	9.2		61
		5	10.8		54

Repl. = Replicate

Mean specific respiration rate of the control: 14.7 mg O₂/g×h

Coefficient of variation of oxygen uptake rates of the control: 18.1 %

Suspended solids in the test vessel: 1.59 g/L

Validity criteria fulfilled:

yes

Conclusions:

The NOEC of the read-across source substance Sodium methyl cocoyl taurate (SMCT) is 180 mg/L, corresponding to 130 mg a.i./L. The test item is not toxic up to the concentration of 180 mg/L, corresponding to 130 mg a.i./L, to activated sludge of a municipal sewage treatment plant. The EC50 is 513 mg/L, corresponding to 371 mg a.i./L.

Based on read-across, this microorganism respiration inhibition 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:

An actived sludge respiration Inhibition test (ASRIT) with activated sludge according to OECD Guideline No. 209 was carried out with the source substance Sodium methyl cocoyl taurate (SMCT; batch number: DEB4003323) from 2012-11-15 to 2012-11-16, with the definite study on 2012-11-16 at the Dr.U.Noack-Laboratorien, 31157 Sarstedt, Germany. Test system was activated sludge of the municipal treatment plant of 31137 Hildesheim, Germany. The test was carried out under static conditions with the substance concentrations 100 - 180 - 320 - 560 - 1000 mg/L, corresponding to 72.3 - 130 - 231 - 405 - 723 mg a.i./L. The respiration rates of the control, reference and test item replicates were measured after a contact time of three hours, and the inhibitory effects of the test and reference item were determined in comparison to the control respiration rates. The mean inhibition of respiration for the test item replicates ranged from -1 % to 57 %.

In order to check the activity of the test system and the test conditions a reference test was carried out with copper (II) sulphate pentahydrate as reference item and the reference toxicity was determined. The EC₅₀-value for the reference item was 94.6 mg/L.

IMPORTANT NOTE TO AVOID CONFUSION:

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

NOEC and EC-Values with Confidence Intervals of Sodium methyl cocoyl taurate

	EC-values [mg/L]	Confidence interval P = 95 [%] [mg/L]
NOEC*	180	–
EC20	215	204 - 226
EC50	513	465 - 572
EC80	> 1000	–

The NOEC of the test item Sodium methyl cocoyl taurate is 180 mg/L. The test item is not toxic at concentrations up to 180 mg/L to activated sludge of a municipal sewage treatment plant. The EC50 of the test item is 513 mg/L. Based on read-across, this microorganism respiration inhibition 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.

Description of key information

The NOEC of the read-across source substance Sodium methyl cocoyl taurate (SMCT) is 180 mg/L, corresponding to 130 mg a.i./L. The test item is not toxic up to the concentration of 180 mg/L, corresponding to 130 mg a.i./L, to activated sludge of a municipal sewage treatment plant. The EC50 is 513 mg/L, corresponding to 371 mg a.i./L.

Based on read-across, this microorganism respiration inhibition 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 microorganisms:

513 mg/L

EC10 or NOEC for microorganisms:

180 mg/L