4-methylmorpholine 4-oxide, monohydrate

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:

23 June 1999

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

Qualifier:

according to guideline

Guideline:

ISO 8192 (Water quality - Test for inhibition of oxygen consumption by activated sludge for carbonaceous and ammonium oxidation)

GLP compliance:

yes

Analytical monitoring:

no

Vehicle:

no

Test organisms (species):

activated sludge, domestic

Details on inoculum:

- Laboratory culture: yes, municipal sludge taken from a laboratory wastewater treatment fed with municipal sewage
- Preparation of inoculum for exposure: The inoculum was washed, brought to a concentration of 5 g/L dry substance and aerated for 24 hours.
50 mL were added to a total volume of 250 mL to obtain a concentration of 1 g/L dry substance in the test.

Test type:

static

Water media type:

freshwater

Limit test:

yes

Total exposure duration:

30 min

Test temperature:

20 ± 2°C

Dissolved oxygen:

Oxygen concentration during aeration: > 2.5 mg/L
Oxygen concentration immediately before measurement: > 6.5 mg/L

Nominal and measured concentrations:

Nominal: 1000 mg/L

Details on test conditions:

TEST SYSTEM
- Test vessel: Erlenmeyer-vessel
- Material, size, headspace, fill volume: glass, nominal volume: 250 mL, fill volume 250 mL
- No. of vessels per concentration (replicates): 1
- No. of vessels per control (replicates): 3

TEST MEDIUM / WATER PARAMETERS
- Source/preparation of dilution water: Synthetic medium: 8 mL/vessel 100-fold concentrated OECD medium

OTHER TEST CONDITIONS
- Adjustment of pH: yes

Reference substance (positive control):

yes

Remarks:

3,5-dichlorophenol

Key result

Duration:

30 min

Dose descriptor:

other: EC20

Effect conc.:

> 1 000 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

inhibition of total respiration

Remarks:

respiration rate

Duration:

30 min

Dose descriptor:

NOEC

Effect conc.:

>= 1 000 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

inhibition of total respiration

Results with reference substance (positive control):

- Results with reference substance valid? yes. EC50 of 3,5-dichlorophenol is in the range of 5-30 mg/L
- Relevant effect levels: 30 min EC20 = ca. 3.0 mg/L; 30-min EC50 = ca 15 mg/L; 30-min EC80 = ca. 50 mg/L (highest concentration tested: 100 mg/L)

Measured data - blank control (BC) and test substance (TS) after 30 minutes incubation time

	BC1	BC2	BC3	mv BC	TS1
Concentration of test substance (mg/L)	-	-	-	-	1001
Added volume of stock solution (mL/vessel)	-	-	-	-	125.0
Direct addition (mg/vessel)	-	-	-	-	-
Oxygen concentration start (mg O2/L)	7.8	8.1	7.9	-	8.1
Oxygen concentration after 6 min (mg O2/L)	6.2	6.6	6.2	-	6.5
Oxygen consumption rate (mg O2/L * 6 min)	1.6	1.5	1.7	1.6	1.6
Oxygen consumption rate (mg O2/L*h)	16	15	17	16	16
Specific oxygen consumption rate ( mg O2/g*h)	16	15	17	16	16
Change in oxygen consumption rate compared with the blank control (%)	-	-	-	-	0

mv BC = mean value of blank control

pH-values - blank control (BC) and test substance (TS) after 30 minutes incubation time

Vessel no.:	BC1	BC2	BC3	TS1
pH-value before adding the inoculum before correction: after correction:	6.2 7.3	6.2 7.3	6.2 7.4	6.3 7.4
pH-value after an incubation time of 30 min	-	-	-	7.4

Measured data - reference substance (RS) after 30 minutes incubation time

Vessel no.:	mv BC	RS1	RS2	RS3
Concentration of test substance (mg/L)	-	1	10	100
Added volume of stock solution (mL/vessel)	-	0.5	5.0	50.0
Oxygen concentration start (mg O2/L)	-	7.8	8.3	8.7
Oxygen concentration after 6 min (mg O2/L)	-	6.3	7.3	8.7
Oxygen consumption rate (mg O2/L * 6 min)	1.6	1.5	1.0	0.0
Oxygen consumption rate (mg O2/L*h)	16	15	10	0
Specific oxygen consumption rate ( mg O2/g*h)	16	15	10	0
Change in oxygen consumption rate compared with the blank control (%)	-	6	37	100

pH-values - reference substance (RS) after 30 minutes incubation time

Vessel no.:	RS1	RS2	RS3
pH-value before adding the inoculum before correction: after correction:	6.2 7.2	6.2 7.2	6.4 7.2

Validity criteria fulfilled:

yes

Conclusions:

No inhibition of respiration was measured at the concentration tested (1000 mg/L).

Executive summary:

The inhibitory effect of N-methylmorpholine oxide on activated sludge respiration was tested according to OECD guideline 209 (version 1999) during an exposure time of 30 min. One replicate of 1000 mg/L test substance was used in a limit test. The final concentration of solids in the test vessels was 1 g/L. Inhibition was not observed, therefore the NOEC is reported to be >= 1000 mg/L and the EC₂₀ is stated to be >1000 mg/L.

The study was valid at the time performed.

Description of key information

There is one study from BASF available. This result was chosen to derive PNEC-STP . The respiration inhibition test from BASF was performed according to a guideline (OECD 209) valid at that time including a test duration of 30 min. The 30 min. EC20 value of > 1000 mg/L is used for the CSA and derivation of the PNEC.

Key value for chemical safety assessment

EC10 or NOEC for microorganisms:

1 000 mg/L