Methylsilanetriyl triacetate

Long-term toxicity to aquatic invertebrates

Link to relevant study record(s)

Reference

Endpoint:

long-term toxicity to aquatic invertebrates

Type of information:

experimental study

Adequacy of study:

key study

Study period:

2008-11-14 to 2008-12-05

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: Guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 211 (Daphnia magna Reproduction Test)

GLP compliance:

yes (incl. QA statement)

Analytical monitoring:

yes

Details on sampling:

- Sampling method: One sample from the freshly prepared stock solution and duplicate samples from the freshly prepared test media of all treatments were taken taken at a pretreatment period in the first, second and third weeks of the test (days 3, 10 and 14).

The stability of the test media was determined over periods of 48 and 72 hours using sub-samples of the test media that did not contain food or daphnia.

- Sample storage conditions before analysis: Samples were analysed directly on the day of collection.

Vehicle:

no

Details on test solutions:

A 100 mg/L stock suspension of the test substance was prepared by adding the test substance to dilution water. Immediately after adding the substance the pH of the water was adjusted to 8.0 - 8.1. The mixture was then stirred for 24 hours in the dark to dissolve as much test substance as possible. The resulting medium was filtered (0.45 µm cellulose nitrate filter). After filtration the pH was adjusted again to 8.0.Undiluted filtrate and 1:2, 1:4, 1:8 and 1:16 dilutions of the filtrate were tested.

Test organisms (species):

Daphnia magna

Details on test organisms:

TEST ORGANISM

- Strain/clone: Clone 5

- Source: Laboratory stock culture

- Feeding during test

- Food type: Green algae (Desmodesmus subspicatus)

- Amount: 0.10 mg TOC/daphnid on days 0 - 4, 0.15 mg TOC/daphnid on days 5-20

- Frequency: daily


ACCLIMATION

- Type and amount of food: Daily with algae (Desmodesmus subspicatus) and weekly with Tetra Min-extract

Test type:

semi-static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

21 d

Hardness:

250 mg/L as CaCO3

Test temperature:

19 - 22ºC

pH:

7.7 - 8.0 in freshly prepared media

7.6 - 8.7 in aged media

Dissolved oxygen:

7.0 - 9.0 mg/L in freshly prepared media

8.1 - 10.4 mg/L in aged media

Salinity:

Not applicable

Nominal and measured concentrations:

Nominal treatments: 0 (Control), filtered 100 mg/L loading rate and 1:2, 1:4, 1:8 and 1:16 dilutions of the filtrate

Measured concentrations: The mean measured Total carbon content of the nominal 100 mg/L filtrate was 10 mg/L. The mean measured concentrations in the 1:2 and 1:4 dilutions of the filtrate were 5.2 and 2.9 mg/L. No analysis results were reported for the 1:8 and 1:16 dilution treatments.

Details on test conditions:

TEST SYSTEM

- Test vessel:

- Type (delete if not applicable): open

- Material, size, headspace, fill volume: 100 mL glass beakers containing 80 mL of test medium

- Aeration: none

- Renewal rate of test solution (frequency/flow rate): every 2 or 3 days

- No. of organisms per vessel: 1

- No. of vessels per concentration (replicates): 10

- No. of vessels per control (replicates): 10

- Biomass loading rate: 1 daphnid/80 mL of test medium


TEST MEDIUM / WATER PARAMETERS

- Source/preparation of dilution water: Elendt M4 medium prepared by adding analytical grade salts and additives to deionised water

- Culture medium different from test medium: no

- Intervals of water quality measurement: On the occasions of test medium renewal in fresh and old medium


OTHER TEST CONDITIONS

- Adjustment of pH: yes

- Photoperiod: 16 hours light, 8 hours dark

- Light intensity: 50-1200 lux


EFFECT PARAMETERS MEASURED (with observation intervals if applicable): Daily observations of dead parental daphnia. At the same time offspring (dead and alive) were counted and removed.


VEHICLE CONTROL PERFORMED: no


RANGE-FINDING STUDY: no

Reference substance (positive control):

no

Duration:

21 d

Dose descriptor:

NOEC

Effect conc.:

>= 100 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

mortality

Duration:

21 d

Dose descriptor:

NOEC

Effect conc.:

>= 100 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

reproduction

Duration:

21 d

Dose descriptor:

NOEC

Effect conc.:

>= 10 mg/L

Nominal / measured:

meas. (arithm. mean)

Conc. based on:

other: Total Organic Carbon

Basis for effect:

other: Adult survival and reproduction

Details on results:

- Mortality of parent animals: 0

- No. of offspring in the Control after 21 days: 60.2 per surviving parental daphnid

Reported statistics and error estimates:

There were no effects in the highest treatment and therefore statistical analysis of the results was not required.

Table 1. Analysis of test media

 

Nominal treatment	Mean measured TOC concentration with (SD) (mg/L)
<LOQ	100
1:16 dilution	Not determined
1:8 dilution	Not determined
1:4 dilution	2.87 (0.067)
1:2 dilution	5.23 (0.068)
Undiluted 100 mg/L nominal concentration	9.96 (0.048)

Table 2. Test results

Treatment	Percentage of surviving parental daphnia at end of test	Average number of offspring per surviving parental daphnia at end of test	Average number of of offspring as a percentage of Control
0 (Control)	100	60.2	-
1:16 dilution	100	38.4	63.8*
1:8 dilution	100	59.8	99.3
1:4 dilution	100	69.4	115
1:2 dilution	90	67.3	112
Undiluted 100 mg/L nominal concentration	100	60.1	99.8

*significantly different from Control

Validity criteria fulfilled:

yes

Conclusions:

A 21-day NOEC value of =100 mg/L has been determined for the effects of the test substance on survival and reproduction of Daphnia magna when expressed in terms of nominal concentrations. When expressed in terms of mean measured TOC concentration in the test medium the NOEC was =10 mg/L. It is likely that the test organisms were primarily exposed to the hydrolysis products of the substance.

Description of key information

Long-term toxicity to invertebrates: 21 day NOEC=100 mg/l (highest concentration tested) (OECD 211), read-across from a structurally related substance, trichloro(ethyl)silane (CAS 115-21-9). The NOEC is equivalent to=66 mg/l expressed in terms of ethylsilanetriol.

Additional information

There are no reliable long-term invertebrate toxicity data available for methylsilanetriyl triacetate (CAS 4253-34-3), therefore good quality data for an appropriate structural analogue, trichloro(ethyl)silane (CAS 115-21-9), have been read across. Both substances have structurally similar silanol hydrolysis products, methylsilanetriol and ethylsilanetriol, respectively. The other hydrolysis products are acetic acid and hydrochloric acid, respectively.

 

A 21 day NOEC value of =100 mg/l (highest concentration tested) has been determined for the effects of trichloro(ethyl)silane (CAS 115-21-9) on reproduction of Daphnia magna. In view of the exposure regime it is likely that the test organisms were exposed predominantly to the hydrolysis products of the tested substance. The results may be expressed in terms of concentration of the hydrolysis product, ethylsilanetriol, by applying a molecular weight correction: (MW of silanol = 108.17 / MW of parent = 163.51) * [CONCENTRATION OF PARENT = =100 mg/l] = =66 mg/l.

 

Refer Section 6 endpoint summary (Section 7.0 of CSR) for further discussion of the approach to chemical safety assessment for this registration substance, and justification for read-across used.