Polysulfides, bis[3-(triethoxysilyl)propyl]

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:

1991-09-17 to 1991-09-27

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

guideline study with acceptable restrictions

Remarks:

Guideline study with acceptable restrictions. The study was conducted according to an appropriate OECD test guideline, with acceptable restrictions. The restriction was that the presence of undissolved test material (turbidity) in the water-accommodated fractions may have contributed to effects observed in the test.

Qualifier:

according to guideline

Guideline:

OECD Guideline 201 (Alga, Growth Inhibition Test)

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Analytical monitoring:

no

Vehicle:

no

Details on test solutions:

PREPARATION AND APPLICATION OF TEST SOLUTION

- Method: Water-accommodated fractions of the test substance were prepared individually for each treatment. Appropriate amounts of the substance were added to 1 litre bottles and 1 litre of algal growth medium added. The media were then stirred vigorously for 24 hours at room temperature and then allowed to stand for 20 hours. After standing the upper approximately 350 mL of medium in each bottle was siphoned off for use as the test water-accommodated fractions. A parallel set of test media were prepared by direct addition of the substance to algal growth medium with no further treatment.

- Controls: algal growth medium

- Evidence of undissolved material (e.g. precipitate, surface film, etc): there was evidence of turbidity in the water-accommodated fractions.

Test organisms (species):

Desmodesmus subspicatus (previous name: Scenedesmus subspicatus)

Details on test organisms:

TEST ORGANISM

- Strain: SAG 86.81

- Source (laboratory, culture collection): Collection of Algal Cultures, Institute for Plant Physiology, University of Göttingen, Germany.

- Method of cultivation: not described

ACCLIMATION

- Culturing media and conditions: The test cultures were grown in algal growth medium prepared in accordance with the OECD guideline except that it contained 150 mg/l NaHCO3 and not 50 mg/l.

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

96 h

Remarks on exposure duration:

Nominal

Hardness:

no data

Test temperature:

23+/-1ºC

pH:

8.0-8.1 at start of test

7.9-8.3 throughout test

Dissolved oxygen:

no data

Salinity:

not applicable

Nominal and measured concentrations:

Nominal loading rates in water-accommodated fraction test: 0(Control), 320, 560, 1000, 1800, 3200 and 10000 mg/L.

Nominal loading rates in direct addition test: 0(Control), 10, 32, 100, 320 and 1000 mg/L.

There was evidence of turbidity in the water-accommodated fractions.

Details on test conditions:

TEST SYSTEM

- Test vessel: Conical flask

- Type: covered with silicone sponge caps

- Material, size, headspace, fill volume: glass, 200 mL with 100 ml of test medium

- Aeration: none

- Initial cells density: 12000-13000 cells/mL

- Control end cells density: 2500000-2840000 cells/mL

- No. of vessels per concentration (replicates): 2

- No. of vessels per control (replicates): 4


GROWTH MEDIUM

- Standard medium used: no

- Detailed composition if non-standard medium was used: OECD medium except that 150 mg/L of NaHCO3 was used instead of 50 mg/L


TEST MEDIUM / WATER PARAMETERS

- Source/preparation of dilution water: The dilution water (algal growth medium) was prepared by addition of concentrated stock solutions of salts and nutrients to Milli-Q filtered water. The final medium was filter-sterilized before use.

- 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: 120 μmol/s/m2 +/-20% from fluorescent lights in a Gallenkamp orbital shaker


EFFECT PARAMETERS MEASURED (with observation intervals if applicable):

- Determination of cell concentrations: Coulter Counter TAII and Perking Elmer 3000 Fluorescence Spectrometer


TEST CONCENTRATIONS

- Spacing factor for test concentrations: 1.8 (water-accommodated fraction test), 3.3 (direct addition test)

- Range finding study

- Test concentrations: 10, 100, 1000, 10000 mg/L

- Results used to determine the conditions for the definitive study: Results indicated that toxic effects could be expected at loading rates of >100 mg/L.

Reference substance (positive control):

no

Duration:

96 h

Dose descriptor:

EL10

Effect conc.:

1 600 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Remarks:

water-accommodated fraction

Basis for effect:

other: yield after logistic growth based on cell numbers

Duration:

96 h

Dose descriptor:

EL50

Effect conc.:

2 600 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Remarks:

water-accommodated fraction

Basis for effect:

other: yield after logistic growth based on cell numbers

Remarks on result:

other: 2000-3400

Duration:

96 h

Dose descriptor:

EL10

Effect conc.:

< 320 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Remarks:

water-accommodated fraction

Basis for effect:

other: area under the growth curve based on cell numbers

Duration:

96 h

Dose descriptor:

EL50

Effect conc.:

2 100 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Remarks:

water-accommodated fraction

Basis for effect:

biomass

Remarks:

area under the growth curve based on cell numbers

Duration:

72 h

Dose descriptor:

EL10

Effect conc.:

60 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Remarks:

water-accommodated fraction

Basis for effect:

other: yield after logistic growth based on fluorescence measurements

Duration:

96 h

Dose descriptor:

EL50

Effect conc.:

700 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Remarks:

water-accommodated fraction

Basis for effect:

other: yield after logistic growth based on fluorescence measurements

Remarks on result:

other: 230-2300

Duration:

72 h

Dose descriptor:

EL10

Effect conc.:

> 1 000 - < 1 800 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Remarks:

water-accommodated fraction

Basis for effect:

other: area under the growth curve based on fluorescence measurements

Duration:

96 h

Dose descriptor:

EL50

Effect conc.:

> 1 800 - < 32 000 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Remarks:

water-accommodated fraction

Basis for effect:

other: area under the growth curve based on fluorescence measurements

Duration:

96 h

Dose descriptor:

NOELR

Effect conc.:

1 000 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Remarks:

water-accommodated fraction

Basis for effect:

other: yield and biomass

Duration:

96 h

Dose descriptor:

NOELR

Effect conc.:

1 000 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Remarks:

added directly to medium

Basis for effect:

other: yield and biomass

Details on results:

- Exponential growth in the control (for algal test): yes

- Observation of abnormalities (for algal test): no

- Any stimulation of growth found in any treatment: no

- Effect concentrations exceeding solubility of substance in test medium: yes, there was evidence of turbidity in the water-accommodated fractions. The results are above the expected water solubility of the substance (<1 mg/L).

Reported statistics and error estimates:

The area under the growth curve (biomass) and logistic growth parameters were calculated from the cell concentration data in accordance with the description of the test method.

ELx values with respect to logistic growth were calculated using a parametric model developed by Kooijman et al (1983).

NOELR values were determined by visual comparison of the growth curves for treated and control cultures.

Kooijman, S.A.L.M., A.O. Hanstveit and H. Oldersma. (1983). Parametric analysis of population growth in bioassays. Water Research, 17: 527-538.

Table 1. Results of test with test media prepared as water-accommodated fractions (mean cell concentrations in cells/ml in each treatment loading rate)

Time (hours)	Control	Control	0.32 g/L	0.56 g/L	1.0 g/L	1.8 g/L	3.2 g/L	10 g/L
0	13000	12000	12000	12000	12000	12000	12000	12000
23.5	56000	62000	58000	197000	142000	39000	-	94000
48.5	278000	306000	304000	300000	170000	294000	248000	3000
73.5	879000	1216000	851000	410000	836000	815000	245000	313000
97.0	1961000	3070000	1665000	728000	1648000	1416000	385000	725000

Table 2. Results of test with test substance added directly (mean cell concentrations in cells/ml in each treatment loading rate)

Time (hours)	Control	Control	10 mg/L	32 mg/L	100 mg/L	320 mg/L	1000 mg/L
0	12000	12000	12000	12000	12000	12000	12000
19.5	43000	39000	43000	44000	40000	50000	36000
46.5	333000	329000	345000	327000	330000	337000	333000
71.5	1250000	1126000	1132000	960000	1001000	1009000	1040000
93.5	3005000	2675000	2803000	2228000	2536000	2479000	2209000

Validity criteria fulfilled:

yes

Conclusions:

A 96-h EL50 value of 700 mg/L and a 96-h EL10 of 60 mg/L have been determined for the effects of the test substance on yield of Scenedesmus subspicatus as determined by fluorescence measurement. A NOELR of 1000 mg/l has been estimated from the test results by the report authors but does not seem realistic given the EL50 and EL10 values. The results are above the expected water solubility of the test substance (<1 mg/L). There was evidence of undissolved test material (turbidity) in the water-accommodated fractions and this may have contributed to effects observed at the high test substance loading rates utilised in the test.

Description of key information

EL₅₀ (96 h) >1000 mg/l (nominal) and EL₁₀ (96 h): >1000 mg/l (nominal) based on: biomass and yield in Scenedesmus subspicatus (new name: Desmodesmus subspicatus), in media prepared by direct addition, and an EL₅₀ of 700 mg/l (nominal) based on: yield in Scenedesmus subspicatus (new name: Desmodesmus subspicatus), in media prepared by water accommodated fraction. The EL₅₀ value of 700 mg/l is selected as the key value for this endpoint as it is a definitive value, not a limit value (>).

Additional information

A 96-hour EL₅₀ value of 700 mg/l and a 96-hour EL₁₀ of 60 mg/l have been determined for the effects of bis[3-triethoxysilylpropyl]polysulfides (CAS 211519-85-6, EC 915-673-4) on the yield of Scenedesmus subspicatus as determined by fluorescence measurement (Evonik Degussa, 1992a). A NOELR of 1000 mg/l has been estimated from the test results by the report authors but does not seem realistic given the EL₅₀ and EL₁₀ values. This test was conducted in media prepared by Water Accommodated Fractions (WAFs). The results are above the expected water solubility of the test substance (approximately 0.01 mg/l at 20°C). There was evidence of undissolved test material (turbidity) in the water-accommodated fractions and this may have contributed to effects observed at the high test substance loading rates utilised in the test. Based on the test media preparation methods and static exposure regime, it is likely that the test organisms would have been exposed to a mixture of the parent substance, the hydrolysis products and undissolved test substance and/or precipitated by-products. Insoluble oligomers may have precipitated out of solution to an extent during the media preparation and in the course of the test. The test results have been interpreted in this context. This is reflected in the observation of turbidity in test media, although no analytical verification was performed. In view of the media preparation method and duration of study, the effects seen are attributed to precipitated oligomeric or cross-linked by-products. Physical effects are likely to have dominated any intrinsic toxic effects.

In the same study, a 96-hour EL₅₀ value of >1000 mg/l (nominal) and an EL₁₀ of >1000 mg/l (nominal, highest concentration tested) have been determined for the effects of bis[3-triethoxysilylpropyl]polysulfides (CAS 211519-85-6) on the yield of Scenedesmus subspicatus as determined by fluorescence measurement (Evonik Degussa, 1992a). This test was conducted in media prepared by direct addition, intending to represent the properties of the parent substance. Based on the test media preparation methods and static exposure regime, it is likely that the test organisms would have been exposed to a mixture of the parent substance, the hydrolysis products and undissolved test substance and/or precipitated by-products. Insoluble oligomers may have precipitated out of solution to an extent in the course of the test. The test results have been interpreted in this context. No analytical verification was performed. In view of the media preparation method and duration of study, the effects seen are attributed to a mixture of parent, silanol hydrolysis product and oligomeric or cross-linked by-products. Physical effects such as decrease in light intensity could have contributed by affecting growth rate.

The 96-hour EL₅₀ value of 700 mg/l is considered to be the appropriate value for the registration substance.