Reaction mass of 4,4,13,13-tetraethoxy-3,14-dioxa-8,9-dithia-4,13-disilahexadecane and 4,4,14,14-tetraethoxy-3,15-dioxa-8,9,10-trithia-4,14-disilaheptadecane

Toxicity to microorganisms

Link to relevant study record(s)

Reference

Endpoint:

activated sludge respiration inhibition testing

Type of information:

experimental study

Adequacy of study:

key study

Study period:

2009-09-03 to 2009-09-03

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

guideline study with acceptable restrictions

Remarks:

The study was conducted according to an appropriate OECD test guideline, and in compliance with GLP, and was considered to be reliability 1 (reliable without restrictions). Read across to the registered substance is considered scientifically justified; the read across is considered to be reliability 2

Qualifier:

according to guideline

Guideline:

OECD Guideline 209 (Activated Sludge, Respiration Inhibition Test

Deviations:

no

GLP compliance:

yes

Analytical monitoring:

yes

Details on sampling:

- Sampling method: 46ul of the test substance which corresponds to 50 mg, was pipetted below the surface of the Milli-RO water and stirred briefly to mix (5 minutes). Synthetic sewage was subsequently feed and sludge added (final volume 500 ml) and the test was initiated. A loading rate of 100 mg/l was tested in duplicate.

- Sample storage conditions before analysis: Test substance stored at room temperature in the dark

Vehicle:

no

Test organisms (species):

activated sludge of a predominantly domestic sewage

Details on inoculum:

- Pretreatment: The sludge was coarsely sieved to remove large particles. The sludge was then washed by centrifuging at 1000 g for 10 minutes. The supernanted was decanted and replaced with ISO-medium. The washing step was performed three times. Small amount of the sludge was weighed and dried overnight at ca. 105°C to determine the amount of suspended solids.

Test type:

static

Water media type:

freshwater

Limit test:

yes

Total exposure duration:

3 h

Test temperature:

20 ± 2°C

pH:

7.4

Details on test conditions:

TEST SYSTEM
- Test vessel:All glass, approximately 300 ml oxygen bottles and 1 L test bottles

- Type (delete if not applicable): open

- Aeration: Strong aeration with clean, oil-free air

- No. of organisms per vessel:Number of micro-organisms was determined as the amount of mixed liquor suspended solids (MLSS) per litre of test medium.

- Biomass loading rate: 100 mg/l

TEST MEDIUM / WATER PARAMETERS
- Source/preparation of dilution water: Tap-water was purified by reverse osmosis (Mill-RO) and subsequently passed over activated carbon and ion-exchange cartridges (Mill-Q).

Reference substance (positive control):

yes

Duration:

3 h

Dose descriptor:

EC10

Effect conc.:

> 100 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

inhibition of total respiration

Remarks:

respiration rate

Results with reference substance (positive control):

- Results with reference substance valid? Yes

Table 2: Determination of the 3-hour EC50 value for 3,5-dicholophenol

Conc. (mg/l)	X Log conc. (mg/l)	Y Inhibition (%)
5.0	0.699	38
12	1.079	59
30	1.477	72

Table 3: Controls (C) and Bis[3-(triethoxysilyl)propyl]poluysulfides (T): pH, oxygen concentration, oxygen consumption and percentage inhibition of the respiration rate

Flask	loading rate (mg/l)	Oxygen conc. At the start (~mg O2/l)	Oxygen consumption (mg O2/l/h)	% Respiration rate	pH
C start T	0	7.4	29	-	8.2
C end T	0	7.9	28	-	8.3
T1	100	5.3	29	-2^1	8.1
T2	100	7.1	30	-5^1	8.2

¹: Negative values indicate stimulation of the respiration rate sludge. The values are considered not significant

Validity criteria fulfilled:

yes

Conclusions:

An ASRI 3hr EC10 value of >100 mg/L (loading rate) was determined in a reliable study conducted according to an appropriate test protocol, and in compliance with GLP.

Description of key information

Toxicity to microorganisms: ASRI 3-hour EC₅₀: >100 mg/l (loading rate) (OECD 209), read across from a structurally-related substance. Organisms were likely predominantly exposed to parent test substance.

Additional information

There are no microorganism toxicity data available for the reaction mass of S2 and S3, therefore good quality data for the structurally-related substance polysulfides, bis[3-(triethoxysilyl)propyl]- (CAS 211519-85-6), have been read across.

S2 and S3 are present as constituents in polysulfides, bis[3-(triethoxysilyl)propyl]- which is a multi-constituent substance. S2, S3 and the other constituent of polysulfides, bis[3-(triethoxysilyl)propyl]- hydrolyse at a moderate or slow rate to structurally similar silanol products; the other hydrolysis product being ethanol. Ethanol is not expected to have adverse effects on microorganisms.

Both substances are within an analogue group of substances that exhibit no evidence of significant toxicity to microorganisms.

This analogue group for the toxicity to microorganisms endpoint consists of a number of sub-classes of substances (based on structure/functionality). However, read-across is carried out between substances specifically containing sulphide groups. The table below presents microorganism toxicity data available for di- and poly-sulfides.

It is therefore considered valid to read across the results for polysulfides, bis[3-(triethoxysilyl)propyl]- to fill the data gap for the registered substance. Additional information is given in a supporting report (PFA, 2013j) attached in Section 13 of IUCLID.

A 3-hour EC50 value of >100 mg/l (exceeding the loading rate) was determined for polysulfides, bis[3-(triethoxysilyl)propyl]-.

Table: Microorganism toxicity data available for relevant substances

CAS	Name	Result: E(I)C50 (mg/l)	Result: NOEC (or EC10/ EC20) (mg/l)	Guideline Number	Test method	Species	Duration	Reliability
211519-85-6	Reaction mass of 4,4,15,15-tetraethoxy-3,16-dioxa-8,9,10,11-tetrathia-4,15-disilaoctadecane and 4,4,14,14-tetraethoxy-3,15-dioxa-8,9,10-trithia-4,14-disilaheptadecane and 4,4,13,13-tetraethoxy-3,14-dioxa-8,9-dithia-4,13-disilahexadecane	>100 mg/l		OECD 209	ASRI		3hr	1a

References:

PFA2013j: Peter Fisk Associates, STP Microorganism toxicity Main Analogue Group report, PFA.300.003.006