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Toxicity to aquatic algae and cyanobacteria

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Endpoint:
toxicity to aquatic algae and cyanobacteria
Type of information:
calculation (if not (Q)SAR)
Adequacy of study:
supporting study
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: The result was obtained by an appropriate predictive method.
Principles of method if other than guideline:
The ECOSAR ‘neutral organics’ QSARs for acute data have been applied and the effect concentrations calculated using log Kow and molar mass as input variables. An additional factor of *0.2 has been applied to the results.

The USEPA model ECOSAR was used as the basis for the estimation. This method is well-validated for ‘neutral organics’, i.e. those which act by a general narcotic mechanism, the potency of which is usually related to log Kow. Its scope is acute and long-term effects for the three standard trophic levels.
The method was validated for use with organosilicon compounds with a high weight percent of Si and limited or no additional functionality. Many of the reliable data for the category are limit values, therefore, the data were considered in terms of the range of theE(L)C50, in accordance with normal classification bands:    
E(L)C50 < 1 mg/l;
E(L)C50 in the range > 1 mg/l to 10 mg/l;
E(L)C50 in the range > 10 mg/l to 100 mg/l;
E(L)C50 > 100 mg/l.

In broad terms ECOSAR predicted correctly for most substances for each trophic level. However, performance was improved significantly by application of a factor of 0.2 to each predicted value (expressed in mg/l). This is equivalent to saying that the organosilicon substances are slightly more toxic than the general ECOSAR ‘neutral organics’ regression lines, although still well within the range of each model. The factor of 0.2 is applicable to fish,Daphniaand algae, across the whole range of log Kowvalues.
It is concluded that the acute effects of the substances in the sub-category can therefore be predicted from ECOSAR, with a minor modification.
Duration:
96 h
Dose descriptor:
EC50
Effect conc.:
8.6 mg/L
Basis for effect:
growth rate
Remarks on result:
other: Based on O[Si](O)(c1ccccc1)c2ccccc2 and log Kow of -2.4
Conclusions:
A 96 h EC50 values of 8.6 mg/L was obtained for the hydrolysis product of the submission substance using an appropriate calculation method . The results are considered to be reliable.
Endpoint:
toxicity to aquatic algae and cyanobacteria
Type of information:
experimental study
Adequacy of study:
key study
Study period:
2004-01-26 to 2004-02-04
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to
Guideline:
OECD Guideline 201 (Alga, Growth Inhibition Test)
Qualifier:
according to
Guideline:
EU Method C.3 (Algal Inhibition test)
Qualifier:
according to
Guideline:
EPA OPPTS 850.5400 (Algal Toxicity, Tiers I and II)
GLP compliance:
yes
Analytical monitoring:
yes
Details on sampling:
- Concentrations: 0 (Control), 0.47, 0.94, 1.9, 3.8, 7.5 and 15 mg/L.

- Sampling method: concentrations of the test substance. Samples at test initiation were collected from the individual batches of test solution prepared for each treatment and control group prior to addition of the algae. At test termination, samples were collected from the pooled replicates from each treatment and control group. All samples were collected in glass vials and were analyzed immediately without storage.



Vehicle:
no
Details on test solutions:
PREPARATION AND APPLICATION OF TEST SOLUTION

- Method: A primary stock solution was prepared by dissolving Diphenylsilanediol in freshwater algal medium at a nominal concentration of 15 mg/L. The stock was stirred approximately 1.5 hours using a magnetic stir plate and Teflon coated stir bar and appeared clear and colorless with particles floating throughout. After mixing the stock appeared clear and colorless. The primary stock was proportionally diluted with freshwater algal medium to prepare the five additional test solutions at nominal concentrations of 0.47, 0.94, 1.9, 3.8 and 7.5 mg/L. Test concentrations were not corrected for percent active ingredient in test substance. All test solutions appeared clear and colorless.

- Controls: Freshwater Algal Medium (OECD 201).
Test organisms (species):
Pseudokirchneriella subcapitata (previous names: Raphidocelis subcapitata, Selenastrum capricornutum)
Details on test organisms:
TEST ORGANISM

- Source (laboratory, culture collection): Original algal cultures were obtained from the University of Toronto Culture Collection, and had been maintained in culture medium at Wildlife International, Ltd., Easton, Maryland. Algal cells used in this test were obtained from Wildlife International, Ltd. cultures that had been actively growing in culture medium for at least two weeks prior to test initiation. The culture was last transferred to fresh medium three days prior to test initiation.

- Culture medium: The algal cells were cultured and tested in freshwater algal medium. Stock nutrient solutions were prepared by adding reagent-grade chemicals to purified Wildlife International, Ltd. well water. The test medium then was prepared by adding appropriate volumes of the stock nutrient solutions to purified well water (NANOpure® water). The pH of the medium was adjusted to 8.0 using 10% HCl and the medium was sterilized by filtration (0.22 μm) prior to use.

- Initial density: 10,000 cells/mL
Test type:
static
Water media type:
freshwater
Limit test:
no
Total exposure duration:
96 h
Post exposure observation period:
None
Test temperature:
23 to 33 ºC



pH:
7.9 at test initiation

7.9 to 9.1 at test termination
Dissolved oxygen:
Not applicable
Salinity:
Not applicable
Nominal and measured concentrations:
Nominal concentrations: Negative Control, 0.47, 0.94, 1.9, 3.8, 7.5 and 15 mg/L.

Mean measured test concentrations:
Details on test conditions:
TEST SYSTEM

- Test vessel: 250-mL Erlenmeyer flasks plugged with cotton stoppers containing 100 mL of test solution.

- Aeration: none

- Renewal rate of test solution (frequency/flow rate): static test

- Initial cells density: 10000 cells/mL

- No. of vessels per concentration (replicates): 3

- No. of vessels per control (replicates): 6


GROWTH MEDIUM

- Standard medium used: yes


TEST MEDIUM / WATER PARAMETERS

- Source/preparation of dilution water: Freshwater algal growth medium (OECD 201) madeup with NANOpure water (pH: 8.0)

- Culture medium different from test medium: no

- Intervals of water quality measurement: Start and end of test


OTHER TEST CONDITIONS

- Sterile test conditions: yes

- Adjustment of pH: no

- Photoperiod: Continuous

- Light intensity and quality: 3880 to 4660 lux, continuous cool-white fluorescent lighting


EFFECT PARAMETERS MEASURED: Cell densities measured at start of test and then at 24 hour intervals. Cell densities were used to determine effects on average-specific growth rate and biomass.


TEST CONCENTRATIONS

- Spacing factor for test concentrations: 2
Reference substance (positive control):
no
Duration:
72 h
Dose descriptor:
NOEC
Effect conc.:
0.55 mg/L
Nominal / measured:
meas. (arithm. mean)
Conc. based on:
test mat.
Basis for effect:
cell number
Duration:
72 h
Dose descriptor:
EC50
Effect conc.:
2.7 mg/L
Nominal / measured:
meas. (arithm. mean)
Conc. based on:
test mat.
Basis for effect:
cell number
Remarks on result:
other: 2.2-3.3
Duration:
96 h
Dose descriptor:
NOEC
Effect conc.:
1.1 mg/L
Nominal / measured:
meas. (arithm. mean)
Conc. based on:
test mat.
Basis for effect:
cell number
Duration:
96 h
Dose descriptor:
EC50
Effect conc.:
2.7 mg/L
Nominal / measured:
meas. (arithm. mean)
Conc. based on:
test mat.
Basis for effect:
cell number
Remarks on result:
other: 2.4-3.0
Duration:
72 h
Dose descriptor:
NOEC
Effect conc.:
0.55 mg/L
Nominal / measured:
meas. (arithm. mean)
Conc. based on:
test mat.
Basis for effect:
biomass
Duration:
72 h
Dose descriptor:
EC50
Effect conc.:
2.8 mg/L
Nominal / measured:
meas. (arithm. mean)
Conc. based on:
test mat.
Basis for effect:
biomass
Remarks on result:
other: 2.4-3.3
Duration:
96 h
Dose descriptor:
NOEC
Effect conc.:
0.55 mg/L
Nominal / measured:
meas. (arithm. mean)
Conc. based on:
test mat.
Basis for effect:
biomass
Duration:
96 h
Dose descriptor:
EC50
Effect conc.:
2.7 mg/L
Nominal / measured:
meas. (arithm. mean)
Conc. based on:
test mat.
Basis for effect:
biomass
Remarks on result:
other: 2.4-3.0
Duration:
72 h
Dose descriptor:
NOEC
Effect conc.:
1.1 mg/L
Nominal / measured:
meas. (arithm. mean)
Conc. based on:
test mat.
Basis for effect:
growth rate
Duration:
72 h
Dose descriptor:
EC50
Effect conc.:
9 mg/L
Nominal / measured:
meas. (arithm. mean)
Conc. based on:
test mat.
Basis for effect:
growth rate
Remarks on result:
other: 8.3-9.7
Duration:
96 h
Dose descriptor:
NOEC
Effect conc.:
2.2 mg/L
Nominal / measured:
meas. (arithm. mean)
Conc. based on:
test mat.
Basis for effect:
growth rate
Duration:
96 h
Dose descriptor:
EC50
Effect conc.:
11 mg/L
Nominal / measured:
meas. (arithm. mean)
Conc. based on:
test mat.
Basis for effect:
growth rate
Remarks on result:
other: 10-11
Details on results:
Was control response satisfactory: Yes

Observations: After 96 hours of exposure, there were no signs of adherence of cells to the test chambers or aggregation/flocculation of algae in the controls or in any treatment group. There were no noticeable changes in cell morphology at concentrations ≤4.4 mg/L when compared to the control. However, enlarged cells were noted in the 9.0 and 18 mg/L treatment groups at 96 hours.



Reported statistics and error estimates:
Statistical methods: Non-linear regression, linear interpolation and Dunnett's test

 

Table 1. Results of analysis of test media

 

Nominal test substance concentration (mg/L)

Mean measured concentration (mg/L)

Mean measured concentration as percentage of nominal

0 (Control)

-

-

0.47

0.55

117

0.94

1.1

117

1.9

2.2

116

3.8

4.4

116

7.5

9.0

120

15

18

120

 

 

Table 2. Test results – Mean cell density and percent inhibition

 

Mean measured test substance concentration (mg/L)

Initial cell density (cells/mL)

Mean cell density after 72 hours (cells/mL)

Mean percentage reduction in cell density after 72 hours

Mean cell density after 96 hours (cells/mL)

Mean percentage reduction in cell density after 96 hours

0 (Control)

10000

915718

-

3521655

-

0.55

10000

964501

-5.3

3380411

4.0

1.1

10000

729809*

20

3182383**

9.6

2.2

10000

536044*

41

2237855*

36

4.4

10000

305078*

67

815895*

77

9.0

10000

95305*

90

321212*

91

18

10000

32958*

96

62470*

98

*Statistically significant difference (p<0.05) at 72 and 96-hours from the negative control replicates using Dunnett’s test.

**While statistically different, a 9.6% inhibition from the control is not considered to be treatment related since this amount of inhibition is within an acceptable limit.

 

 

Table 3. Test results – Mean Area Under the Growth Curve (Biomass) and Percent Inhibition

 

Mean measured test substance concentration (mg/L)

Mean area under the growth curve 0-72 hours

Mean percentage inhibition in area relative to Control 0-72 hours

Mean area under the growth curve 0-96 hours

Mean percentage inhibition in area relative to Control 0-96 hours

0 (Control)

16277226

-

69285698

-

0.55

16735092

-2.8

68634040

0.94

1.1

13693204*

16

60399504*

13

2.2

9985224*

39

43032008*

38

4.4

5181820*

68

18393496*

73

9.0

2347128*

86

7105332*

90

18

786892*

95

1692032*

98

*Statistically significant difference (p<0.05) at 72 and 96-hours from the negative control replicates using Dunnett’s test.

 

 

Table 4. Test results – Mean Growth rate and Percent Inhibition

              

Mean measured test substance concentration (mg/L)

Mean area under the growth curve 0-72 hours

Mean percentage inhibition in area relative to Control 0-72 hours

Mean area under the growth curve 0-96 hours

Mean percentage inhibition in area relative to Control 0-96 hours

0 (Control)

0.0626

-

0.0611

-

0.55

0.0635

-1.2

0.0607

0.68

1.1

0.0596

4.8

0.0600

1.7

2.2

0.0553*

12

0.0563**

7.8

4.4

0.0474*

24

0.0458*

25

9.0

0.0313*

50

0.0361*

41

18

0.0163*

74

0.0191*

69

*Statistically significant difference (p<0.05) at 72 and 96-hours from the negative control replicates using Dunnett’s test.

**While statistically different, a 7.8% inhibition from the control is not considered to be treatment related since this amount of inhibition is within an acceptable limit.

 

Validity criteria fulfilled:
yes
Conclusions:
A 96-hour EC50 value of 2.7 mg/L and NOEC of 0.55 mg/L (based on biomass) have been determined for the effects of the test on growth rate of Selenastrum capricornutum (new name: Pseudokirchnerella subcapitata) based on mean measured concentrations of the test substance.
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 attached justification for grouping of substances in IUCLID Section 13.
Reason / purpose:
read-across source
Duration:
72 h
Dose descriptor:
NOEC
Effect conc.:
1.1 mg/L
Nominal / measured:
meas. (arithm. mean)
Conc. based on:
test mat.
Basis for effect:
growth rate
Duration:
72 h
Dose descriptor:
EC50
Effect conc.:
9 mg/L
Nominal / measured:
meas. (arithm. mean)
Conc. based on:
test mat.
Basis for effect:
growth rate
Remarks on result:
other: 8.3-9.7

Description of key information

72-hour EC50 = 9.0 mg/l and NOEC = 1.1 mg/l

Key value for chemical safety assessment

EC50 for freshwater algae:
9 mg/L
EC10 or NOEC for freshwater algae:
1.1 mg/L

Additional information

Measured data were not available for the test substance. However, as the substance hydrolysis rapidly to diphenylsilanediol, data for the hydrolysis product was considered more relevant. A 72 -hour EC50value of 9 mg/l and NOEC of 1.1 mg/l (based on growth rate) have been determined for the effects of the test on growth rate of Selenastrum capricornutum (new name: Pseudokirchnerella subcapitata) based on mean measured concentrations of the test substance and according to OECD guideline 201 (Wildlife international ltd, 2004). This study is considered reliable and was selected as key. This was also supported by predicted a predicted EC50 of 8.6 mg/l based on an appropriate QSAR.