Carbamic acid, N-[(dimethoxymethylsilyl)methyl]-, methyl ester

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:

19 Aug 2003

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

Version / remarks:

adopted 1984

GLP compliance:

yes (incl. QA statement)

Remarks:

Hessisches Ministerium für Umwelt, Energie, Landwirtschaft und Forsten, Wiesbaden, Germany

Analytical monitoring:

no

Vehicle:

no

Details on test solutions:

PREPARATION AND APPLICATION OF TEST SOLUTION (especially for difficult test substances)
- Method: Since the test item hydrolyses in water very quickly, the hydrolysis products were tested, according to the draft guidance document on aquatic toxicity testing on difficult substances. Therefore, 1000 mg test item were filled up to 200 mL with deionized water and were completely dissolved by stirring for 24 h. Thus a concentration of 5 g/L was obtained. Then, adequate volumes of the intensively stirred stock solution were dosed into the test flasks.
- Eluate: no
- Differential loading: no
- Controls: yes, test medium control

Test organisms (species):

activated sludge, domestic

Details on inoculum:

- Source of inoculum: Sewage treatment plant Groß-Zimmern, Germany
- Laboratory culture: no
- 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 2.5 g dry material per litre, were made up with tap water. The activated sludge was used of the test directly after conditioning. The pH of the sludge was 7.4.

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

3 h

Test temperature:

21 - 22 °C

pH:

7.2 - 8.3

Dissolved oxygen:

7.6 - 8.1 (start)
7.0 - 7.5 (end)

Nominal and measured concentrations:

nominal: control, 10, 32, 100, 320, 1000 mg/L

Details on test conditions:

TEST SYSTEM
- Test vessel: Glass flasks of approx. 1 L volume and Karlsruher flasks of 250 mL volume
- Aeration: with compressed air (approx. 0.6 L/min)
- No. of vessels per concentration (replicates): 5
- No. of vessels per control (replicates): 2

TEST MEDIUM / WATER PARAMETERS
- Source/preparation of dilution water: according to guideline

OTHER TEST CONDITIONS
- Adjustment of pH: no

EFFECT PARAMETERS MEASURED
Respiration rate was measured in Karlsruher flasks after exactly 3 h with an oxygen electrode and was recorded for about 10 min. During measurement the samples were continuously stirred on a magnetic stirrer. The O2 consumption was determined from the most linear part of the respiration curve.

TEST CONCENTRATIONS
- Spacing factor for test concentrations: 3.125

Reference substance (positive control):

yes

Remarks:

3,5-dichlorophenol

Duration:

3 h

Dose descriptor:

other: EC20

Effect conc.:

> 1 000 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Remarks:

but the exposure was to hydrolysis products

Basis for effect:

inhibition of total respiration

Remarks:

respiration rate

Duration:

3 h

Dose descriptor:

EC50

Effect conc.:

> 1 000 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Remarks:

but the exposure was to hydrolysis products

Basis for effect:

inhibition of total respiration

Remarks:

respiration rate

Results with reference substance (positive control):

EC50 (3 h): 6.9 mg/L

Table 2: Inhibition of respiration after 3 h

Flask	Concentration [mg/L]	Oxygen consumption [mg O2/L min]	Inhibition [%]
5	1000	0.330	10.8
6	320	0.380	-2.7
7	100	0.400	-8.1
8	32	0.400	-8.1
9	10	0.390	-5.4
1	control	0.350	--
10	control	0.390	--

Validity criteria fulfilled:

yes

Conclusions:

An 3 h EC50 > 1000 mg/L has been determined for the effects of the test substance on respiration rate of activated sludge microorganisms. The results are expressed relative to nominal concentrations of the test substance. However, the substance is subject to rapid hydrolysis and under the test conditions it is therefore likely that exposure will have been to its hydrolysis products.

Description of key information

EC50 (3 h): > 1000 mg/L based on respiration of activated sludge microorganisms (OECD 209)

Additional information

One experimental study is available investigating the toxicity of methyl-N-{[dimethoxy(methyl)silyl]methyl}carbamate (CAS 23432-65-7) to activated sludge microorganisms (Hertl, 2003). This study was performed according to OECD 209 (GLP). Activated sludge from a domestic sewage treatment plant was exposed to nominal concentrations of 10, 32, 100, 320 and 1000 mg/l. Since the substance is expected to hydrolyse rapidly in contact with water (DT50: 1.9 h at 20 - 25 °C, pH 7), the result from this study mainly investigated the possible effects of the hydrolysis products (Methyl-N-{[dihydroxy(methyl)silyl]methyl}carbamate und methanol). During stock solution preparation it was ensured by intensive stirring that the parent substance hydrolyses and mainly the hydrolysis products are tested. After an exposure of 3 h an inhibition of respiration of 10.8% was recorded in the highest concentration tested, resulting in an EC50 > 1000 mg/l.