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

Toxicity to aquatic algae and cyanobacteria

Link to relevant study record(s)

Reference

Endpoint:

toxicity to aquatic algae and cyanobacteria

Type of information:

experimental study

Adequacy of study:

key study

Study period:

21 - 24 Jun 2004

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

EU Method C.3 (Algal Inhibition test)

Version / remarks:

1992

Qualifier:

according to guideline

Guideline:

OECD Guideline 201 (Alga, Growth Inhibition Test)

Version / remarks:

1984

GLP compliance:

yes (incl. QA statement)

Remarks:

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

Analytical monitoring:

yes

Details on sampling:

- Concentrations: control, 6.25, 12.5, 25, 50, 100, 200 mg/L
- Sampling method: Duplicate samples were taken at the start of the test from the freshly prepared test media (without algae).
- Sample storage conditions before analysis: analysed directly

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- Method: Since the test item hydrolyses in water very quickly, the hydrolysis products were tested, according to the draft guidance document on aquatic toxicity testing on difficult substances.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, a stock solution of nominal 200 mg/L was prepared by dosing 259.9 mg test item into 1300 mL test water. The stock solution was stirred for 24 h. Then, adequate volumes of the stock solution were diluted with test water to prepare the test concentrations.
- Eluate: no
- Differential loading: no
- Controls: yes, test medium control

Test organisms (species):

Desmodesmus subspicatus (previous name: Scenedesmus subspicatus)

Details on test organisms:

TEST ORGANISM
- Common name: green algae
- Strain: 86.81 SAG
- Source (laboratory, culture collection): Sammlung von Algenkulturen, Pflanzenphysiologisches Institut der Universität Göttingen, Göttingen, Germany
- Method of cultivation: Cultivated in the laboratory under standardised conditions according to the test guidelines.

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

72 h

Hardness:

0.24 mmol/L (= 24 mg/L) as CaCO3

Test temperature:

23 °C

pH:

7.2 - 8.1 (start)
8.2 - 10.5 (end)

Nominal and measured concentrations:

nominal: control, 6.25, 12.5, 25, 50, 100 and 200 mg/L
measured: Since it is possible to recalculate the values to the initially applied concentration of test item, the reported analytical results are related to test item. During the test period of 72 hours in the mean between 67 % and 75 % of the nominal concentrations were found. Therefore, the reported results are related to the analytically determined concentrations of the test item. The recovery rate of the lowest test concentration was not determined, since its concentration was below the Limit of Quantification.

Details on test conditions:

TEST SYSTEM
- Test vessel: Erlenmeyer flasks
- Material, size, headspace, fill volume: glass, 50 mL, headspace: 0 mL, fill volume: 50 mL
- Aeration: continuously stirred
- Initial cells density: 10000 cells/mL
- Control end cells density: 160.13 x 10000 cells/mL
- No. of vessels per concentration (replicates): 3
- No. of vessels per control (replicates): 6
- No. of vessels per blank control (replicates): 1

GROWTH MEDIUM
- Standard medium used: yes, according to guideline

TEST MEDIUM / WATER PARAMETERS
- Source/preparation of dilution water: deionised water
- Conductivity: < 5 µS/cm
- Culture medium different from test medium: no

OTHER TEST CONDITIONS
- Adjustment of pH: no
- Photoperiod: continuous illumination
- Light intensity and quality: 7487 lux (mean), range: 6900 - 7820 lux, fluorescent tubes

EFFECT PARAMETERS MEASURED
- Determination of cell concentrations: spectrophotometrically after 24, 48 and 72 h
- Other: Cell shape at the highest test concentration was examined microscopically after 72 h.

TEST CONCENTRATIONS
- Spacing factor for test concentrations: 2
- Range finding study: A range-finding study was performed but not reported in detail.

Reference substance (positive control):

no

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

117.42 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Remarks:

but the exposure was to hydrolysis products

Basis for effect:

growth rate

Remarks on result:

other: 95% CL: 103.48 - 130.99 mg/L

Duration:

72 h

Dose descriptor:

EC10

Effect conc.:

68.03 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Remarks:

but the exposure was to hydrolysis products

Basis for effect:

growth rate

Remarks on result:

other: 95% CL: 48.72 - 81.49 mg/L

Duration:

72 h

Dose descriptor:

NOEC

Effect conc.:

33.5 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Remarks:

but the exposure was to hydrolysis products

Basis for effect:

growth rate

Duration:

72 h

Dose descriptor:

LOEC

Effect conc.:

69 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Remarks:

but the exposure was to hydrolysis products

Basis for effect:

growth rate

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

76.17 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Remarks:

but the exposure was to hydrolysis products

Basis for effect:

biomass

Remarks on result:

other: 95% CL: 37.41 - 166.54 mg/L

Duration:

72 h

Dose descriptor:

EC10

Effect conc.:

40.48 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Remarks:

but the exposure was to hydrolysis products

Basis for effect:

biomass

Remarks on result:

other: 95% CL: 0.696 - 61.31 mg/L

Duration:

72 h

Dose descriptor:

NOEC

Effect conc.:

8.75 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Remarks:

but the exposure was to hydrolysis products

Basis for effect:

biomass

Duration:

72 h

Dose descriptor:

LOEC

Effect conc.:

17 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Remarks:

but the exposure was to hydrolysis products

Basis for effect:

biomass

Details on results:

- Exponential growth in the control (for algal test): yes
- Observation of abnormalities (for algal test): not observed
- Unusual cell shape: not observed
- Any stimulation of growth found in any treatment: no

Results with reference substance (positive control):

For the evaluation of the quality of the algae and the experimental conditions the substance potassium dichromate p.A. is tested at least twice a year to demonstrate satisfactory test conditions.

Reported statistics and error estimates:

For the determination of the LOEC and NOEC, the calculated mean biomass and growth rates r at the test concentrations were tested on significant differences to the control values by Dunnett-tests.

This increase of the pH during the test was obviously caused by the CO2-consumption of the algae due to their rapid growth respectively their high densities (although the test media have been intensively stirred).

Table 1: Cell densities during the test period

Concentration [mg/L]		Density of algal cells (x 10000/mL)
		24 h	48 h	72 h
control	1	5.1	44.6	162.7
	2	4.4	43.9	164.1
	3	5.4	42.5	170.7
	4	4.7	41.4	156.1
	5	5.1	47.4	156.1
	6	4.7	42.5	151.1
	m	4.90	43.72	160.13
	s	0.36	2.13	7.04
6.25	1	5.2	45.6	166.4
	2	5.1	45.4	154.7
	3	6.3	46.5	160.5
	m	5.2	45.5	160.6
	s	0.1	0.1	8.3
8.75	1	4.8	43.4	165.7
	2	5.9	43.1	163.0
	3	5.8	46.1	165.2
	m	5.50	44.20	164.63
	s	0.61	1.65	1.44
17.0	1	4.3	40.7	154.1
	2	5.1	38.8	129.7
	3	5.4	45.1	151.1
	m	4.93	41.87	144.97
	s	0.57	2.84	13.31
33.5	1	3.7	41.3	143.5
	2	4.8	43.9	136.0
	3	5.6	42.9	139.6
	m	4.7	42.7	139.7
	s	0.95	1.31	3.75
69.0	1	0.4	37.4	95.0
	2	1.6	31.8	93.9
	3	2.5	32.7	93.1
	m	1.5	33.97	94.00
	s	1.05	3.01	0.95
150	1	2.7	0.5	5.0
	2	1.1	0.8	3.6
	3	2.6	2.9	4.1
	m	2.13	1.40	4.23
	s	0.90	1.31	0.71

Validity criteria fulfilled:

yes

Conclusions:

A 72 h EC10 of 68.03 mg/L, a 72 h NOEC of 33.5 mg/L and an 72 h EC50 of 117.42 mg/L have been determined for the effects of the test substance on growth rate of Desmodesmus subspicatus. 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 (72 h): 117.42 mg/L based on growth rate of Desmodesmus subspicatus (EU Method C.3)

NOEC (72 h): 33.5 mg/L based on growth rate of Desmodesmus subspicatus (EU Method C.3)

Additional information

One experimental study is available investigating the toxicity of methyl-N-{[dimethoxy(methyl)silyl]methyl}carbamate (CAS 23432-65-7) to freshwater algae (Spatz & Wydra, 2004). This study was performed according to EU Method C.3 (GLP). Desmodesmus subspicatus was exposed to nominal concentrations of 6.25, 12.5, 25, 50, 100 and 200 mg/L. Analysis of the dissolved organic carbon (DOC) revealed a mean recovery of 67-75%. 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 72 h an inhibition of growth was observed resulting in an EC50 of 117.42 mg/l and a NOEC of 33.5 mg/l. The effects are mainly attributed to the hydrolysis products.