Dichloro(diphenyl)silane

Toxicity to aquatic algae and cyanobacteria

Link to relevant study record(s)

Reference

Reference 1

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

Guideline:

OECD Guideline 201 (Alga, Growth Inhibition Test)

Qualifier:

according to guideline

Guideline:

EU Method C.3 (Algal Inhibition test)

Qualifier:

according to guideline

Guideline:

EPA OPPTS 850.5400 (Algal Toxicity, Tiers I and II) (January 2012)

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):

Raphidocelis subcapitata (previous names: Pseudokirchneriella 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:

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:

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:

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

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:

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

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.

Reference 2

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 for cross-reference:

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 (measured arithmetic mean, OECD 201, RA CAS No. 947-42-2)

72 -hour NOEC = 1.1 mg/l (measured arithmetic mean, OECD 201, RA CAS No. 947-42-2)

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

There is no data available on toxicity to aquatic algae for dichloro(diphenyl)silane (CAS 80-10-4). Therefore, good quality data from the analogous substance, diphenylsilanediol (CAS 947-42-2), which is one of the two hydrolysis products of the target substance, have been read across. Details on read across justifications can be found in IUCLID Section 13.

The study with the hydrolysis product diphenylsilanediol (CAS 947-42-2) was performed according to OECD 201 (GLP). Pseudokirchneriella subcapitata was exposed to six concentrations of the substance (0.47, 0.94, 1.9, 3.8, 7.5 and 15 mg/L nominal) and a control under static conditions for 96 hours. The test concentrations remained stable for the duration of the study resulting in a mean measured test concentrations of 0.55, 1.1, 2.2, 4.4, 9.0 and 18 mg/L (116 – 120% of nominal). Inhibition of growth rate was recorded after 72 h resulting in an EC50 (72 h) = 9.0 mg/L and a NOEC (72 h) = 1.1 mg/L based on arithmetic mean measured concentrations.

Because the target compound dichloro(diphenyl)silane (CAS 80-10-4) hydrolyses rapidly under environmental conditions (DT50 = 10 sec) to diphenylsilanediol (CAS 947-42-2) and hydrochloric acid, it is more relevant to consider the hydrolysis product diphenylsilanediol for the toxicity assessment towards aquatic organisms. Because under conditions relevant to ecotoxicity testing, exposure will predominantly be to the hydrolysis products. The second hydrolysis product hydrochloric acid readily dissociates in water into hydrated protons and chloride anions. Thus, it is ionised and neutralisation depends on the buffer capacity of the receiving water. Toxicity only occurs when the buffering capacity of the receiving water is exceeded and pH values fall below pH 6. The pH in rivers and lakes fluctuates within a natural range. The natural pH range in aquatic systems is generally not expected to be perturbed to a relevant extent by anthropogenic emissions when appropriate risk control measures are in place. Variations in effect values of experimental studies can largely be explained by variations in the buffer capacity of the test media (OECD, 2002).

References:

OECD, 2002. Hydrogen Chloride - SIDS Initial Assessment Report for SIAM 15, Boston, USA: UNEP Publications.