Triethoxy(methyl)silane

Toxicity to microorganisms

Link to relevant study record(s)

Reference

Reference 1

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:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 209 (Activated Sludge, Respiration Inhibition Test

GLP compliance:

yes

Analytical monitoring:

no

Vehicle:

no

Details on test solutions:

PREPARATION AND APPLICATION OF TEST SOLUTION
53 µl of the test substance, Milli-RO water, synthetic sewage feed (16 ml) and activated sludge (200 ml) were mixed and made up to 500 ml with Milli-RO water in a 1 litre bottle.

Test organisms (species):

activated sludge of a predominantly domestic sewage

Details on inoculum:

Preparation of inoculum for exposure: The sludge was coarsely sieved to remove large particles. The sludge was then washed by centrifuging at 1000 g for 10 minutes. The supernatant was decanted and replaced with ISO-medium. The washing step was performed three times. The pH was 7.7 on the day of testing. The batch of sludge was used one day after collection; therefore 50 ml of synthetic sewage feed was added per litre of activated sludge at the end of the collection day. The sludge was kept aerated at test temperature until use.

- Initial biomass concentration: 3.8 g/L

Test type:

static

Water media type:

freshwater

Limit test:

yes

Total exposure duration:

3 h

Post exposure observation period:

Oxygen consumption was measured and recorded for approximately 10 minutes.

Test temperature:

19.9-20.3°C

pH:

8.2 to 8.3

Nominal and measured concentrations:

100 mg/l (loading rate). Performance of a limit concentration at 100 mg/l is acceptable, because 100 mg/l exceeds the expected concentration in a Sewage Treatment Plant.

Details on test conditions:

Test vessel:
- Material, size, headspace, fill volume: glass, 300ml oxygen bottles, 1L test bottles

- Aeration: continuous

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

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

TEST MEDIUM / WATER PARAMETERS

- Source/preparation of dilution water: tap water purified by reverse osmosis (Milli-RO) and subsequently passed over activated carbon and ion-exchange cartridges (Milli-Q)


EFFECT PARAMETERS MEASURED (with observation intervals if applicable) :
After the 3-hour contact time, a well mixed sample of the contents of the reaction mixture was poured into a 300 ml oxygen bottle, and the flask was sealed with an oxygen electrode connected to a recorder, forcing the air out of the vessel. WTW inolab Oxi 730 supplied with a WTW CellOx 325 oxygen electrode, electrolyte type ELY/G

TEST CONCENTRATIONS

- Spacing factor for test concentrations: 100 mg/L only, tested in duplicate

- Justification for using less concentrations than requested by guideline: No significant inhibition of respiration rate of the sludge was recorded for the test substance at a loading rate of 100 mg/L in both replicates and therefore no further testing was required.

Reference substance (positive control):

yes

Remarks:

(3,5-Dichlorophenol)

Key result

Duration:

3 h

Dose descriptor:

EC50

Effect conc.:

> 100 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

inhibition of total respiration

Remarks:

respiration rate

Key result

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

Details on results:

The two controls had a difference in respiration rate of 6%, which is less than the 15% limit required by the guideline for a valid study.

Results with reference substance (positive control):

A positive control test with 3, 5-dichlorophenol yielded an EC50 of 8.7 mg/L, which is within the accepted range of 5 to 30 mg/l required by the guideline for a valid study.

Table 1: Results of the activated sludge respiration inhibition test

Test sample	Loading rate (mg/l)	Oxygen conc. at start (mg O2/l)	Oxygen consumption (mg O2/l/h)	% Inhibition respiration rate	pH
Initial control	0	7.3	34	-	8.3
Final control	0	6.5	32	-	8.2
Trimethoxy(methyl)silane replicate (1)	100	7.1	33	0	8.3
Trimethoxy(methyl)silane replicate (2)	100	7.1	31	6	8.3
3,5-dichlorophenol	5	-	-	38	-
	12	-	-	59	-
	30	-	-	72	-

 

 

Validity criteria fulfilled:

yes

Conclusions:

An activated sludge respiration inhibition 3hr EC50 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. This indicates that the test substance was not toxic to waste water (activated sludge) bacteria at a loading rate of 100 mg/l.

Reference 2

Endpoint:

activated sludge respiration inhibition testing

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 overall summary (IUCLID Section 6.1.7) and attached justification for grouping in IUCLID Section 13.

Reason / purpose for cross-reference:

read-across source

Key result

Duration:

3 h

Dose descriptor:

EC50

Effect conc.:

> 100 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

inhibition of total respiration

Remarks:

respiration rate

Key result

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

Validity criteria fulfilled:

yes

Conclusions:

An activated sludge respiration inhibition 3 hour EC50 value of >100 mg/l (loading rate) was determined for the read across substance in a reliable study conducted according to an appropriate test protocol, and in compliance with GLP. Therefore the target substance is considered not to be toxic activated sludge bacteria at loading rates up to 100 mg/l.

Description of key information

3 hour EC50 >100 mg/l; based on RA to trimethoxy(methyl)silane 

Additional information

No data are available on the toxicity of triethoxy(methyl)silane to microorganisms. Therefore, good quality data for the analogue substance, trimethoxy(methyl)silane, have been read across. Both substances share the same silanol hydrolysis product, methylsilanetriol. Both triethoxy(methyl)silane and trimethoxy(methyl)silane are within an analogue group of substances that exhibit no evidence of significant toxicity to microorganisms. It is therefore considered valid to read-across the results from trimethoxy(methyl)silanet o fill the data gap for the registered substance.

Table 7.4.2 presents microorganism toxicity data available for substances within the sub-class of alkoxysilanes, silanols, acetoxysilanes and chlorosilanes, etc, where the Si part is of low-biological reactivity, once hydrolysis has been taken into account. Both trimethoxyoctylsilane and triethoxyoctylsilane are members of this sub-class.

Table 7.4.2 Microorganism toxicity data available for substances within the relevant sub-class of chemicals.

CAS	Name	Result: E(I)C50 (mg/l)	Result: NOEC (or EC10/ EC20) (mg/l)	Guideline Number	Test method	Species	Duration	Reliability
001000-50-6	Butylchlorodimethylsilane	>340		88/302/EC	ASRI		3h	1a
001066-40-6	Hydroxytrimethylsilane	6670		OECD 209 and ISO 1892	ASRI		Uncertain	1a
001185-55-3	Trimethoxy(methyl)silane	>100		OECD 209	ASRI		3hr	1a
031795-24-1	Potassium methylsilanetriolate	>100		OECD 209	ASRI		3 h	1a
087135-01-1	1,6-Bis(trimethoxysilyl)hexane	>1000		OECD 209	ASRI		3h	1a
017980-47-1	Triethoxyisobutylsilane	>1000	≥1000	OECD 209	ASRI		3h	1a
005894-60-0	Trichloro(hexadecyl)silane	>1000		OECD 209	ASRI		3h	1a
016415-12-6	Hexadecyltrimethoxysilane	>1000		OECD 209	ASRI		3 hr	1a
002943-75-1	Triethoxyoctylsilane	>1000		OECD 209	ASRI		3 hr	1a
016068-37-4	4,4,7,7-tetraethoxy-3,8-dioxa-4,7-disiladecane	>8000	8000	DIN 38 412, Part 8 (Pseudomonas cell multiplication inhibition test)	growth inhibition test	P putida	16 h	1c
035435-21-3	Triethoxy(2,4,4-trimethylpentyl)silane	>100		OECD 209	ASRI		3hr	1a
018395-30-7	Trimethoxy(2-methylpropyl)silane		EC10 1.3 ml/l	Huls AG method	oxygen consumption	P putida	5.8 h	2c -don't use to derive PNEC
142877-45-0	Silane, trimethoxy(1,1,2-trimethylpropyl)-	>1000	≥1000	OECD 209	ASRI		3 hr	1a
013154-25-1	Chlorotri(3-methyl-propyl)silane	>1000	100	OECD 209	ASRI		3 hr	2b
126990-35-0	Dicyclopentyldimethoxysilane	>water solubility		OECD 209//EU C11/Huls AG method (WOE)	ASRI/ASRI/oxygen consumption P putida		3 hr	1a/1a/2c
139147-73-2	Silane, dichlorodicyclopentyl-	>100		OECD 209	ASRI		3 hr	1a

 

Additional information is given in a supporting report (PFA, 2013) attached in Section 13 of the IUCLID dossier.

An activated sludge respiration inhibition 3 hour EC₁₀value of >100 mg/l (loading rate) was determined in a reliable study conducted according to an appropriate test protocol, and in compliance with GLP (2009). On this basis it is assumed that trimethoxy(methyl)silane is not toxic to activated sludge bacteria at loading rates up to 100 mg/l.