Dimethyl carbonate

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:

February 5 2003

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: Study conducted in accordance with OECD & EU guidelines and to GLP.

Qualifier:

according to guideline

Guideline:

OECD Guideline 209 (Activated Sludge, Respiration Inhibition Test

Deviations:

no

Qualifier:

according to guideline

Guideline:

EU Method C.11 (Biodegradation: Activated Sludge Respiration Inhibition Test)

GLP compliance:

yes (incl. QA statement)

Analytical monitoring:

no

Vehicle:

no

Test organisms (species):

activated sludge of a predominantly domestic sewage

Details on inoculum:

- Laboratory culture:
- Method of cultivation:
- Preparation of inoculum for exposure: The sludge was washed by centrifugation and the supernatant liquid phase was decanted. The solid material was resuspended in tap water and again centrifuged. The latter procedure was repeated twice. An aliquot of the final sludge suspension was
weighed, dried and the ratio of wet sludge (g) to its dry weight (g) determined. Based on this ratio, calculated aliquots of washed sludge suspension, corresponding to 4 g dry material per litre, were made up with tap water. To this mixture, 50 mL synthetic sewage feed per litre was added one day
prior to use, and the sludge was kept at room temperature under continuous aeration until use. Immediately before use, the dry weight of the activated sludge was determined, and adjusted to 4 g/L with tap water. The pH of the activated sludge was determined to be pH 7.8.
- Pretreatment:
- Initial biomass concentration:

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

3 h

Post exposure observation period:

10 minutes

Test temperature:

19-20°C

pH:

pH measurements given in Tables 2 and 3 in results section

Dissolved oxygen:

Measurements given in Tables 2 and 3 in results section

Nominal and measured concentrations:

Nominal concentrations are presented in Table 1.

Details on test conditions:

TEST SYSTEM
- Test vessel: Glass flasks 1L and Karlsruher flasks 250 mL
- Type (delete if not applicable): open
- Material, size, headspace, fill volume:
- Aeration: Compressed air (0.6 L/minute)
- Type of flow-through (e.g. peristaltic or proportional diluter):
- Renewal rate of test solution (frequency/flow rate): None
- No. of organisms per vessel:
- No. of vessels per concentration (replicates): 1
- No. of vessels per control (replicates): 1
- No. of vessels per vehicle control (replicates):
- Biomass loading rate:

TEST MEDIUM / WATER PARAMETERS
- Source/preparation of dilution water:
- Total organic carbon:
- Particulate matter:
- Metals:
- Pesticides:
- Chlorine:
- Alkalinity:
- Ca/mg ratio:
- Conductivity:
- Culture medium different from test medium:
- Intervals of water quality measurement:

OTHER TEST CONDITIONS
- Adjustment of pH:
- Photoperiod:
- Light intensity:

EFFECT PARAMETERS MEASURED (with observation intervals if applicable) :

TEST CONCENTRATIONS
- Spacing factor for test concentrations: 3.2
- Justification for using less concentrations than requested by guideline:
- Range finding study
- Test concentrations: 10, 32, 100, 320, 1000 mg/L
- Results used to determine the conditions for the definitive study:

Reference substance (positive control):

yes

Remarks:

3,5-Dichlorophenol

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.:

10 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
- Relevant effect levels: 3-hour EC50 of reference substance 6.7 mg/L
- Other:

Table 2 below gives results for the reference substance, table 3 gives results for dimethylcarbonate.

Table 2. Influence of 3,5-Dichlorophenol on oxygen consumption of activated sludge

Flask No.	Treatment	Concentration (mg/L)	Oxygen Consumption (mg O2/L min)	Inhibition %	pH Values			Oxygen concentration (mg O2/L)
					start*	end*		start*	end*
1	Control	-	0.506		7.4		8.3	8.0	7.7
10	Control	-	0.470		7.4		8.2	8.2	7.6
Mean % deviation			0.488
			7.1
2	3,5-DCP	32	0.060	87.7	7.5		8.4	7.8	8.3
3	3,5-DCP	10	0.170	65.2	7.5		8.4	7.7	8.3
4	3,5-DCP	3.2	0.360	26.2	7.4		8.4	7.8	8.0

*: start and end of 3-hour aeration

3,5-DCP: 3,5-Dichlorophenol

Table 3. Influence of dimethylcarbonate (DMC) on oxygen consumption of activated sludge

Flask No.	Treatment	Concentration (mg/L)	Oxygen Consumption (mg O2/L min)	Inhibition %	pH Values			Oxygen concentration (mg O2/L)
					Start*	End*		Start*	End*
1	Control	-	0.506		7.4		8.3	8.0	7.7
10	Control	-	0.470		7.4		8.2	8.2	7.6
Mean % deviation			0.488
			7.1
5	DMC	1000	0.310	36.5	7.4		8.3	7.8	8.2
6	DMC	320	0.320	34.4	7.4		8.3	8.0	7.8
7	DMC	100	0.380	22.1	7.4		8.3	8.1	7.9
8	DMC	32	0.440	9.8	7.5		8.3	8.1	7.8
9	DMC	10	0.500	-2.5	7.4		8.2	8.0	7.1

* start and end of 3-hour aeration

Validity criteria fulfilled:

yes

Conclusions:

Based on measured inhibition rates, the 3-hour EC 50 could not be quantified because up to the highest nominal test concentration of 1000 mg/L less than 50 % inhibition was noted after three hours incubation. Nevertheless, the 3 hour EC 50 is clearly higher than 1000 mg/L nominal under the present test conditions. The 3-hour EC 20 was calculated to be 92 mg test item/L. The lowest test concentration of 10 mg/L (nominal) can be regarded as the NOEC.

Description of key information

Based on measured inhibition rates, the 3-hour EC 50 could not be quantified because up to the highest nominal test concentration of 1000 mg/L less than 50 % inhibition was noted after three hours incubation. Nevertheless, the 3 hour EC 50 is clearly higher than 1000 mg/L nominal under the present test conditions. The 3-hour EC 20 was calculated to be 92 mg test item/L. The lowest test concentration of 10 mg/L (nominal) can be regarded as the NOEC.

Key value for chemical safety assessment

EC50 for microorganisms:

1 000 mg/L

EC10 or NOEC for microorganisms:

10 mg/L

Additional information

The study was performed by Institut für Biologische Analytik und Consulting IBACON GmbH, Arheilger Weg l7, 64380 Rossdorf Germany. Study conducted to GLP according to OECD Guideline 209 and EU Method C.11.

Based on measured inhibition rates, the 3-hour EC 50 could not be quantified because up to the highest nominal test concentration of 1000 mg/L less than 50 % inhibition was noted after three hours incubation. Nevertheless, the 3 hour EC 50 is clearly higher than 1000 mg/L nominal under the present test conditions. The 3-hour EC 20 was calculated to be 92 mg test item/L.