N-(dimethylvinylsilyl)-1,1-dimethyl-1-vinylsilylamine

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:

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

Vehicle:

no

Details on test solutions:

PREPARATION AND APPLICATION OF TEST SOLUTION
46 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:

19.7-20.3°C

pH:

7.6

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 SYSTEM

- 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

- 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:

EC10

Effect conc.:

> 100 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Details on results:

The two controls had a difference in respiration rate of 7%, 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	6.8	30	-	8.2
Final control	0	6.5	32	-	8.2
Dichloro(methyl)(vinyl)silane replicate (1)	100	6.3	29	6	7.6
Dichloro(methyl)(vinyl)silane replicate (2)	100	5.8	30	3	7.6
3,5-dichlorophenol	5	-	-	38	-
	12	-	-	59	-
	30	-	-	72	-

 

Validity criteria fulfilled:

yes

Conclusions:

An activated sludge respiration inhibition 3 hr 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 EC10 >100 mg/L (loading rate) (OECD 209), read-across from an analogue substance.

Key value for chemical safety assessment

EC10 or NOEC for microorganisms:

100 mg/L

Additional information

There are no microorganism toxicity data available for N-(dimethylvinylsilyl)-1,1-dimethyl-1-vinylsilylamine, therefore good quality data for the structurally-related substance dichloro(methyl)(vinyl)silane (CAS 124-70-9), have been read across.

N-(Dimethylvinylsilyl)-1,1-dimethyl-1-vinylsilylamine and dichloro(methyl)(vinyl)silane hydrolyse very rapidly to structurally-related silanol hydrolysis products, dimethylvinylsilanol and methylvinylsilanediol respectively. The other hydrolysis products are ammonia and hydrochloric acid respectively.

N-(Dimethylvinylsilyl)-1,1-dimethyl-1-vinylsilylamine and dichloro(methyl)(vinyl)silane are within a wider group of substances within which in general, there is no evidence of significant toxicity to microorganisms.

This group consists of a number of substances containing a number of different functional groups but specific read-across is between substances with similar functionality. In this case however, this is not possible as no data are available for the relevant group containing silazanes. Therefore, data have been read across from the related group containing alkoxysilanes, silanols, acetoxysilanes and chlorosilanes, etc, where the Si part is of low-biological reactivity, once any hydrolysis is accounted for.

The table below presents microorganism toxicity data available for substances within this group. Additional information is given in a supporting report (PFA, 2013j) attached in Section 13.

Table: Microorganism toxicity data for other relevant substances

CAS	Name	Result: E(I)C50 (mg/L)	Result: NOEC (or EC10/ EC20) (mg/L)	Guideline Number	Test method	Species	Duration (hours)	Reliability
1000-50-6	Butylchlorodimethylsilane	>340		88/302/EC	ASRI		3	1
1066-40-6	Hydroxytrimethylsilane	6670		OECD 209 and ISO 1892	ASRI		Uncertain	1
1185-55-3	Trimethoxy(methyl)silane	>100		OECD 209	ASRI		3	1
31795-24-1	Potassium methylsilanetriolate	>100		OECD 209	ASRI		3	1
87135-01-1	1,6-Bis(trimethoxysilyl)hexane	>1000		OECD 209	ASRI		3	1
17980-47-1	Triethoxyisobutylsilane	>1000	≥1000	OECD 209	ASRI		3	1
5894-60-0	Trichloro(hexadecyl)silane	>1000	≥1000	OECD 209	ASRI		3	1
16415-12-6	Hexadecyltrimethoxysilane	>1000		OECD 209	ASRI		3	1
2943-75-1	Triethoxyoctylsilane	>1000		OECD 209	ASRI		3	1
16068-37-4	4,4,7,7-tetraethoxy-3,8-dioxa-4,7-disiladecane	>8000	8000	DIN 38 412, Part 8 (Pseudomonascell multiplication inhibition test)	growth inhibition test	P. putida	16	1
35435-21-3	Triethoxy(2,4,4-trimethylpentyl)silane	>100		OECD 209	ASRI		3	1
18395-30-7	Trimethoxy(2-methylpropyl)silane		EC101.3 ml/L	Huls AG method	oxygen consumption	P. putida	5.8	2 -don't use to derive PNEC
142877-45-0	Silane, trimethoxy(1,1,2-trimethylpropyl)-	>1000	≥1000	OECD 209	ASRI		3	1
13154-25-1	Chlorotri(3-methyl-propyl)silane	>1000	100	OECD 209	ASRI		3	2
126990-35-0	Dicyclopentyldimethoxysilane	>water solubility		Weight of evidence of three studies: OECD 209//EU C11/Huls AG method (WOE)	ASRI/ASRI/oxygen consumption P. putida		3	1/1/2
139147-73-2	Silane, dichlorodicyclopentyl-	>100		OECD 209	ASRI		3	1
124-70-9	Dichloro(methyl)(vinyl)silane	>100		OECD 209	ASRI		3	1
75-94-5	Trichloro(vinyl)silane	>100		OECD 209	ASRI		3	1
1067-53-4	Tris(2-methoxyethoxy)vinylsilane		EC10> 2 ml/L	Huls AG method	oxygen consumption	P. putida	5	2 -don't use to derive PNEC
2768-02-7	Trimethoxy(vinyl)silane		EC101.1 ml/L	Huls AG method	oxygen consumption	P. putida	5	2 -don't use to derive PNEC

In the study with dichloro(methyl)(vinyl)silane (CAS 124-70-9), a 3 hour ASRI EC₁₀ value of >100 mg/L (loading rate) was determined in a reliable study conducted according to an appropriate standard method and in compliance with GLP.

The other hydrolysis product of N-(dimethylvinylsilyl)-1,1-dimethyl-1-vinylsilylamine is ammonia. Typical levels of free ammonia in municipal WWTPs range from approximately 12-50 mg/L in the WWTP collection system (Lehr, 2005. Lehr, Jay; Keeley, Jack; Lehr, Janet Water Encyclopedia, Volumes 1-5. (section 1.4.49). John Wiley & Sons). For the registration substance, the predicted environmental concentrations of the hydrolysis product ammonia in a sewage treatment plant are negligible compared to this typical level (CSR Section 9).

Hydrochloric acid does not have adverse effects on microorganisms in a sewage treatment plant, where the pH is maintained within a favourable range.

Reference:

PFA (2013j). Peter Fisk Associates, STP Microorganism toxicity Main Analogue Group report, PFA.300.003.006