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Toxicity to aquatic algae and cyanobacteria

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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:
EU Method C.3 (Algal Inhibition test)
Version / remarks:
, 1992
Qualifier:
according to
Guideline:
OECD Guideline 201 (Alga, Growth Inhibition Test)
Version / remarks:
, 1984
GLP compliance:
yes (incl. certificate)
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- Method: Since the test item hydrolyses in water very quickly, the hydrolysis products were tested, according to the draft guidance document on aquatic toxicity testing on difficult substances.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.
Endpoint:
toxicity to aquatic algae and cyanobacteria
Type of information:
read-across from supporting substance (structural analogue or surrogate)
Adequacy of study:
key study
Justification for type of information:
Please refer to the overall analogue justification attached in IUCLID Section 13.
Reason / purpose:
read-across source
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
Validity criteria fulfilled:
yes
Conclusions:
A 72 h EC10 of 68.03 mg/L, a 72 h NOEC of 33.5 mg/L and a 72 h EC50 of 117.42 mg/L have been determined for the effects of the read across substance CAS 23432-65-7 on growth rate of Desmodesmus subspicatus. Due to rapid hydrolysis of the substance the effects are predominantly attributed to the hydrolysis products. As detailed in the analogue justification, similar effects are expected by the target substance.

Description of key information

EC50 (72 h) = 117.42 mg/L and NOEC (72 h)= 33.5 mg/L (nominal, EU Method C.3) based on read across from CAS 23432-65-7.

Key value for chemical safety assessment

EC50 for freshwater algae:
117.42 mg/L
EC10 or NOEC for freshwater algae:
33.5 mg/L

Additional information

Experimental data on the toxicity of methyl-N-[3-(trimethoxysilyl)propyl]carbamate (CAS 23432-62-4) towards algae are not available. Therefore, in accordance with the Regulation (EC) No. 1907/2006 Annex XI, 1.5 “Grouping of substances and read across” and the read across assessment framework (RAAF, ECHA 2017) a read across from the analogue substance methyl-N-{[dimethoxy(methyl)silyl]methyl}carbamate (CAS 23432-65-7) has been performed. Details on the read-across justification can be found in the analogue justification attached in IUCLID Section 13.

 

The influence of the analogue substance methyl-N-{[dimethoxy(methyl)silyl]methyl}carbamate (CAS 23432-65-7) on the growth of green algae was investigated in a 72-hour static test according to the EU Method C.3 and GLP standards (2004). 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 ErC50 of 117.42 mg/l and a NOErC of 33.5 mg/L. The effects are mainly attributed to the hydrolysis products.

 

Based on the results of the analogues substance and the attached read across justification, similar effects are expected by the target substance methyl-N-[3-(trimethoxysilyl)propyl]carbamate (CAS 23432-62-4).