3-methoxy-N,N-dimethylpropionamide

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:

17 October 2011 - 19 October 2011

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 209 (Activated Sludge, Respiration Inhibition Test (Carbon and Ammonium Oxidation))

Version / remarks:

2010

Deviations:

no

Qualifier:

according to guideline

Guideline:

other: Official Journal of the European Communities, Ll33 A, Part C, Activated sludge respiration inhibition test.

Version / remarks:

1988

Deviations:

no

GLP compliance:

yes

Vehicle:

no

Details on test solutions:

Method of preparation: two stock solutions were prepared at a nominal rate of 5000 mg test item/L in reverse osmosis (RO) water, the day before use. These stocks were observed to be clear colourless solutions. The pH was was adjusted to 7.8 with hydrochloric acid. Test solutions were prepared by the addition of a known volume of this stock solution to a total volume of 500 mL RO water, synthetic sewage and activated sludge.
Control: containing activated sludge, synthetic sewage feed and dilution water only.
Abiotic control: containing reference substance, synthetic sewage feed, reference substance and dilution water only (no activated sludge).

Test organisms (species):

activated sludge of a predominantly domestic sewage

Details on inoculum:

- Name and location of sewage treatment plant where inoculum was collected: Totnes Sewage Works, Totnes, Devon, UK
- Method of cultivation: activated sludge was obtained 1 day prior to exposure. The activated sludge was settled, the supernatant decanted. The settled sludge was fed with 50 mL of OECD synthetic sewage feed per litre of sludge per day and aerated at room temperature, until it was used in the test.
- Preparation of inoculum for exposure: a synthetic sewage mixture was prepared as described by OECD 209.
- Initial biomass concentration: 4373 mg of filterable solids/L

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

3 h

Test temperature:

20 +/- 2 °C

pH:

Adjusted to 7.8 at the start of the test.

Nominal and measured concentrations:

Nominal concentrations: 10, 100 and 1000 mg/L

Details on test conditions:

TEST SYSTEM
- Test vessel: no detailed information on test vessels was provided; final flask fill volume: 500 mL
- Aeration: yes
- No. of vessels per concentration (replicates): one for 10 and 100 mg/L; three for 1000 mg/L
- No. of vessels per control (replicates): two
- No. of vessels per reference control (replicates): four (nominal concentrations of 3.2, 10, 32 and 100 mg/L)
- No. of vessels per abiotic control (replicates): one (100 mg/L)
- Sludge concentration (weight of dry solids per volume): 1500 mg/L
- Nutrients provided for bacteria: synthetic sewage feed

TEST MEDIUM / WATER PARAMETERS
- Source/preparation of dilution water: water treated with reverse osmosis

OTHER TEST CONDITIONS
- Adjustment of pH: yes, to 7.8 with hydrochloric acid

EFFECT PARAMETERS MEASURED (with observation intervals if applicable) : Respiration rate after 3 hours (microcathode oxygen electrodes, connected to an interface unit)

Reference substance (positive control):

yes

Remarks:

3,5-dichlorophenol

Key result

Duration:

3 h

Dose descriptor:

EC50

Effect conc.:

> 1 000 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

inhibition of total respiration

Duration:

3 h

Dose descriptor:

NOEC

Effect conc.:

1 000 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

inhibition of total respiration

Details on results:

- <10% inhibition was observed in all tested concentrations.

Results with reference substance (positive control):

- 3h-EC50: 9.1 mg/L
- Result was within the expected range and confirmed the sensitivity of the used sludge.

Study deviation: the control, abiotic control and reference substance flasks were aerated for 3.5 hours instead of 3 hours. This additional aeration did not compromise the data or invalidate the conclusion.

Table 1 Inhibition results

Test substance	Nominal test concentration (mg/L)	pH		Respiration rate (mg/L/h)	Percentage inhibition^a
		Start	End
Control	Control	7.0	6.2	13.4	-
3,5-DCP^b	100 (abiotic)	7.9	7.8	-5.6	-
3,5-DCP	100	8.0	7.7	0.5	96.2
3,5-DCP	32	7.1	7.8	3.1	78.4
3,5-DCP	10	7.0	7.7	6.7	53.1
3,5-DCP	3.2	7.0	7.7	12.2	14.9
Control	Control	6.9	6.2	15.3	-
Equamide M100	1000	6.9	6.4	13.5	<10
Equamide M100	1000	6.9	6.4	16.1	<10
Equamide M100	1000	6.9	6.7	18.1	<10
Equamide M100	100	6.9	6.5	13.6	<10
Equamide M100	10	6.9	6.6	13.8	<10

^a             calculated using mean control respiration rate of 14.4 mg/L/h
^b             3,5-dichlorophenol

Validity criteria fulfilled:

yes

Remarks:

Oxygen update in de controls was >20 mg O2/g activated sludge (e.g., >22 mg/g), the CV of oxygen uptake in the control was <30% (e.g., 9%) and the EC50 of the reference item was in the range of 2-25 mg/L (e.g., 9.1 mg/L)

Conclusions:

The 3h-EC50 for Equamide M100 based on inhibition of respiration was > 1000 mg/L. The NOEC was 1000 mg/L.

Executive summary:

In an activated sludge respiration inhibition test , according to OECD 209, Equamide M100 was tested for its effect on activated domestic sludge. Nominal concentrations of 10, 100 and 1000 mg/L were used, together with a control. The reference substance, 3,5 -dichlorophenol was tested at concentrations of 3.2, 10, 32 and 100 mg/L and an abiotic control (containing no sludge) was included as well. Results showed that Equamide M100 did not inhibit respiration up to the highest tested concentration.

Description of key information

In an activated sludge respiration inhibition test , according to OECD 209, Equamide M100 was tested for its effect on activated domestic sludge. Nominal concentrations of 10, 100 and 1000 mg/L were used, together with a control. The reference substance, 3,5 -dichlorophenol was tested at concentrations of 3.2, 10, 32 and 100 mg/L and an abiotic control (containing no sludge) was included as well. Results showed that Equamide M100 did not inhibit respiration up to the highest tested concentration.

Key value for chemical safety assessment

EC50 for microorganisms:

1 000 mg/L