Polysulfides, bis[3-(triethoxysilyl)propyl]

Short-term toxicity to aquatic invertebrates

Link to relevant study record(s)

Reference

Endpoint:

short-term toxicity to aquatic invertebrates

Type of information:

experimental study

Adequacy of study:

key study

Study period:

2009-08-26 to 2009-11-19

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 202 (Daphnia sp. Acute Immobilisation Test)

GLP compliance:

yes

Analytical monitoring:

yes

Details on sampling:

Samples of the WAFs were taken after preparation and turbidity measurements made in order to assess whether they contained any undissolved test substance.

Vehicle:

no

Details on test solutions:

PREPARATION AND APPLICATION OF TEST SOLUTION (especially for difficult test substances)

- Method: A WAF was prepared at a loading rate of 10 mg/L by means of magnetic stirring for 4 days followed by overnight settling. This resulted in a clear solution containing that also contained finely dispersed material. The dispersion was left to stabilise overnight after which the undissolved material was mainly present floating at the surface or as precipitate. The water phase was collected and centrifuged for 30 minutes at 10000 rpm (18480 g). The supernatant was collected with a pipette and used for testing.

- Controls: Dilution water

Test organisms (species):

Daphnia magna

Details on test organisms:

TEST ORGANISM

- Source: In-house laboratory stock culture

- Age at study initiation (mean and range, SD): <24 hours

- Method of breeding: acyclical parthenogenesis

- Feeding during test: none


ACCLIMATION

- Acclimation period: continuous

- Acclimation conditions (same as test or not): same except that M7 medium was used for culture and adjusted ISO medium was used for the test.

- Feeding frequency: Daily with a suspension of algae

Test type:

semi-static

Water media type:

freshwater

Limit test:

yes

Total exposure duration:

48 h

Hardness:

180 mg/L as CaCO3

Test temperature:

20.0-20.5ºC

pH:

7.6-7.8

Dissolved oxygen:

8.7-9.2 mg/L

Salinity:

Not applicable

Nominal and measured concentrations:

Nominal loading rate: 0 (Control) and 10 mg/L

Details on test conditions:

TEST SYSTEM


- Test vessel:

- Type (delete if not applicable): open

- Material, size, headspace, fill volume: 100 mL with 80 mL of test medium

- Aeration: none

- Renewal rate of test solution: Daily

- No. of organisms per vessel: 5

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

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

- Biomass loading rate: 1 daphnid/16 mL of test medium


TEST MEDIUM / WATER PARAMETERS

- Source/preparation of dilution water: Adjusted ISO medium prepared with reverse-osmosis treated water

- Culture medium different from test medium: yes

- Intervals of water quality measurement: Daily


OTHER TEST CONDITIONS
- Adjustment of pH: No

- Photoperiod: 16 hours light and 8 hours dark


EFFECT PARAMETERS MEASURED (with observation intervals if applicable): Mobility after 24 and 48 hours


TEST CONCENTRATIONS

- Spacing factor for test concentrations: Limit test

- Range finding study
- Test concentrations: Loading rates of 1, 10 and 100 mg/L

- Results used to determine the conditions for the definitive study: Effects were demonstrated at 1, 10 and 100 mg/L but were attributed to the presence of undissolved test material.

Reference substance (positive control):

yes

Remarks:

Potassium dichromate

Duration:

48 h

Dose descriptor:

EL50

Effect conc.:

> 10 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

mobility

Duration:

48 h

Dose descriptor:

NOELR

Effect conc.:

>= 10 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

mobility

Details on results:

- Immobilisation in control: 10%

- Effect concentrations exceeding solubility of substance in test medium: The test media were WAFs that were prepared at a loading rate (10 mg/L) that exceeded the solubility of the substance.

Results with reference substance (positive control):

48 h EC50: 0.75 mg/L (95% confidence interval: 0.56-1.0 mg/L)

Reported statistics and error estimates:

No significant effects on mobility were observed in the test and therefore statistical analysis of the results was not required.

Table 1. Test results

Nominal loading rate (mg/L)	Percentage immobilisation after 24 hours	Percentage immobilisation after 24 hours
0 (Control)	5	10
10	0	0

UV/VIS spectral scans of the 10 mg/L test WAFs at 200 and 900 nm showed that they did not contain significant amounts of undissolved material.

Validity criteria fulfilled:

yes

Conclusions:

A 48-hour EL50 value of >10 mg/L and NOELR of ≥10 mg/L have been determined for the effects of the test substance on mobility of Daphnia magna. It is likely that, because of the prolonged test medium preparation phase, the test organisms were exposed to the hydrolysis products of the substance.

Description of key information

EL₅₀ (48 h): >10 mg/l (nominal, highest concentration tested) based on mobility of Daphnia magna (OECD Guideline 202 (Daphnia sp. Acute Immobilisation Test)).

Additional information

A 48-hour EL₅₀ value >10 mg/l (nominal, highest concentration tested) have been determined for the effects of bis[3-(triethoxysilyl)propyl]polysulfides (CAS 211519-85-6, EC 915-673-4) on mobility of Daphnia magna in a test conducted according to OECD TG 202 (Reconsile, 2009). The water solubility of the substance (<1 mg/l, measured; 0.01 - 0.014 mg/l, estimated) was exceeded at the tested loading rates and undissolved test substance was observed to be present in the test media. It is likely that, because of the prolonged test medium preparation phase, the test organisms were exposed to a mixture of the parent constituents and a mixture of the monomeric silanol hydrolysis products and siloxane oligomers. 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.

A disregarded study has also been included in the dataset for short-term toxicity to aquatic invertebrates (Evonik Degussa, 1992c). In this study, two tests were conducted with the test material, bis[3-(triethoxysilyl)propyl]polysulfides (CAS 211519-85-6). The first test displayed evidence of undissolved test material on the appendages of the daphnids (Daphnia magna), suggesting physical impairment. The second test used filtered test media, which rendered the culture medium unsuitable for survival of the daphnids. For these reasons, the results of this study have been disregarded, the study has been assigned Reliability 3 and not considered further.