Trimethoxy(2,4,4-trimethylpentyl)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

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 (incl. QA statement)

Analytical monitoring:

no

Details on test solutions:

Direct dispersion in water. 500 mg test substance was dispersed in approximately 250 ml of water and subjected to ultrasonication for approximately 30 minutes. Synthetic sewage (16 ml), activated sewage sludge (200 ml) and water were added to a final volume of 500 ml to give a test concentration of 1000 mg/l.

Test organisms (species):

activated sludge of a predominantly domestic sewage

Details on inoculum:

A mixed population of activated sewage sludge microorganisms was obtained on 7th April 1998 from the aeration stage of the Severn Trent Water Plc sewage treatment plant at Belper, Derbyshire, UK, which treats predominantly domestic sewage. The activated sewage sludge sample was maintained on continuous aeration in the laboratory at a temperature of 21°C and was used on the day of collection. The pH of the sample was 7.3 and the suspended solids equal to 3.7g/l prior to use.

Test type:

static

Water media type:

freshwater

Limit test:

yes

Total exposure duration:

3 h

Post exposure observation period:

At 30 minute and 3 hour contact times, aliquotes were removed from the conical flask and poured into the measuring vessel (250 ml darkened glass Biological Oxygen Demand (BOD) bottle) and the rate of respiration measured using a Yellow Spring dissolved oxygen meter fiitted with a BOD probe. The contents of the measuring vessel were stirred constantly be magnetic stirrer. The rate of respiration for each flask was measured over the linear portion of the oxygen consumption trace for an approximate 10 minute period.

Test temperature:

21°C

Nominal and measured concentrations:

Based on the results from a range finding study, the definitive test was carried out as a limit test at a test concentration of 1000 mg/l.

Details on test conditions:

TEST SYSTEM
- Test vessel: 500 ml conical flask

TEST MEDIUM / WATER PARAMETERS
- Source/preparation of dilution water: Laboratory dechlorinated tap water

TEST CONCENTRATIONS
- Spacing factor for test concentrations: limit test at 1000 mg/l, in triplicate

Reference substance (positive control):

yes

Remarks:

3,5-dichlorophenol

Duration:

3 h

Dose descriptor:

EC50

Effect conc.:

> 1 000 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

inhibition of total respiration

Remarks:

respiration rate

Duration:

3 h

Dose descriptor:

NOEC

Effect conc.:

>= 1 000 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
- Relevant effect levels: EC50 5.2 mg/l

Table 1: Controls, reference substance (3, 5-dichlorophenol) and test substance: oxygen consumption and percentage inhibition of the respiration rate.

Flask	Nominal concentration (mg/l)	Oxygen consumption rate (mg O2/l/min)	% Inhibition respiration rate
Inoculum control	-	0.48	-
Inoculum control	-	0.40	-
Test substance	1000	0.42	5
Test substance	1000	0.42	5
Test substance	1000	0.46	5
Reference substance	32	0.05	89
Reference substance	10	0.11	75
Reference substance	3.2	0.31	30

 

Validity criteria fulfilled:

yes

Conclusions:

An ASRI 3hr EC50 of >1000 mg/l and NOEC of >= 1000 mg/l were determined in a reliable study conducted according to an appropriate test protocol, and in compliance with GLP.

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 the attached justification for grouping of substances provided in IUCLID Section 13.

Reason / purpose for cross-reference:

read-across source

Reason / purpose for cross-reference:

read-across source

Duration:

3 h

Dose descriptor:

EC50

Effect conc.:

> 1 000 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

inhibition of total respiration

Remarks:

respiration rate

Remarks on result:

other: Source: Safepharm Laboratories 1998

Duration:

3 h

Dose descriptor:

NOEC

Effect conc.:

>= 1 000 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

inhibition of total respiration

Remarks:

respiration rate

Remarks on result:

other: Source: Hüls 1993

Duration:

5.8 h

Dose descriptor:

EC10

Effect conc.:

1 115 other: µl/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

inhibition of total respiration

Remarks on result:

other: (Test 1)

Duration:

5.75 h

Dose descriptor:

EC10

Effect conc.:

1 421 other: µl/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

inhibition of total respiration

Remarks on result:

other: (Test 2)

Reference 3

Endpoint:

activated sludge respiration inhibition testing

Type of information:

experimental study

Adequacy of study:

supporting study

Study period:

1993-09-28 to 1993-10-01

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Principles of method if other than guideline:

Method: Oxygen consumption test (Huls method)

GLP compliance:

yes

Analytical monitoring:

no

Vehicle:

yes

Details on test solutions:

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

- Method: A 5 l wide-necked bottle, with magnetic stirrer and 3520 ml distilled aqua, was covered with aluminum foil and autoclaved for 30 minutes at 120°C and 1 bar. After cooling down to room temperature, 200 ml of sterile stock solution and 90 ml seed suspension (liquid culture of the test organism, about 19 ​​hrs incubation, count 10 x 105 cells / ml) were stirred for 5 minutes.
The test substance was pipetted directly into the test bottles. Subsequently, the emulsifier was added. Then the flasks were completely filled with the inoculated culture solution and stoppered.
Emulsifier additive: Nonylphenol ethoxylated propoxylated (EO 10Mol PO 5Mol).

Test organisms (species):

Pseudomonas putida

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

5.8 h

Post exposure observation period:

At the end of the examination, 1 ml HgCl2 solution (final concentration about 3 mg HgCl2/l) was added to each flask to stop the biochemical reactions. Subsequently, the oxygen measurements were performed.

Test temperature:

Test 1: 24.7 - 25.0°C. Test 2: 24.8 - 25.1°C

Nominal and measured concentrations:

Test 1: 500, 1000, 1500, 2000 µl/L. Test 2: 1000, 1500, 1750, 2000 µl/L

Details on test conditions:

TEST SYSTEM

- Test vessel:

- Type (delete if not applicable): closed

- Material, size, headspace, fill volume: 100mL glass flasks with ground glass stopper

- No. of vessels per concentration (replicates): Four, two with HgCl2

- No. of vessels per blank (replicates): Nine, four with HgCl2


EFFECT PARAMETERS MEASURED (with observation intervals if applicable) : oxygen content of the test solutions measured using oxygen electrode.

Reference substance (positive control):

no

Duration:

5.8 h

Dose descriptor:

EC10

Effect conc.:

1 115 other: µl/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

inhibition of total respiration

Remarks:

respiration rate

Remarks on result:

other: (Test 1)

Duration:

5.75 h

Dose descriptor:

EC10

Effect conc.:

1 421 other: µl/l

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

inhibition of total respiration

Remarks:

respiration rate

Remarks on result:

other: (Test 2)

Details on results:

Mean bacteria-inhibiting concentration: 1268µl/l (1.3 ml/l to 2 significant figures)

Test 1:

	Control	Test substance concentration:
		500µl/L	1000µl/L	1500µl/L	2000µl/L
Oxygen concentration in flasks with HgCl2at start of incubation	8.44
	8.28
	8.63	8.65	8.55	8.57	8.52
	8.43	8.54	8.32	8.47	8.43
Average value	8.45	8.60	8.44	8.52	8.48
Oxygen concentration in flasks without HgCl2at end of incubation	4.07
	4.01
	4.04	4.03	4.36	4.62	5.14
	4.02	4.05	4.61	4.50	5.25
Average value	4.04	4.04	4.49	4.56	5.20
O2Consumption during incubation	4.41	4.56	3.95	3.96	3.28
Absolute difference during incubation		-0.14	0.46	0.45	1.13
% effect during incubation		-3.3	10.4	10.2	25.6

Test 2:

	Control	Test substance concentration:
		1000µl/L	1500µl/L	1750µl/L	2000µl/L
Oxygen concentration in flasks with HgCl2at start of incubation	8.22
	7.89
	8.05	8.23	8.11	8.10	8.08
	8.16	8.26	8.30	8.26	8.12
Average value	8.08	8.25	8.21	8.18	8.10
Oxygen concentration in flasks without HgCl2at end of incubation	4.04
	3.89
	3.90	4.25	4.64	4.70	4.94
	3.99	4.27	4.69	4.50	4.73
Average value	3.96	4.26	4.67	4.60	4.84
O2Consumption during incubation	4.13	3.99	3.54	3.58	3.27
Absolute difference during incubation		0.14	0.59	0.55	0.86
% effect during incubation		3.4	14.2	13.2	20.8

 

 

 

Conclusions:

A 5hr EC10 of 1.3 ml/l for toxicity to Pseudomonas putida was determined in a reliable study conducted according to an appropriate test protocol and in compliance with GLP.

Description of key information

3-h NOEC >= 1000 mg/L (OECD 209; read-across from CAS No. 142877-45-0).

Key value for chemical safety assessment

EC10 or NOEC for microorganisms:

1 000 mg/L

Additional information

Note: A study on the toxicity towards aquatic microorganisms according to OECD guideline 209 is currently ongoing for the analogue substance (i.e. trichloro(2,4,4 -trimethylpentyl)silane (CAS 18379-25 4)), which shares the same silanol hydrolysis product as the registered compound. This dossier will be updated with a read-across to the above mentioned analogue substance once the final study report is available.

There are no microorganism toxicity data available for trimethoxy(2,4,4-trimethylpentyl)silane (CAS No. 34396-03-7), therefore good quality data for the structurally analogue substances trimethoxy(2-methylpropyl)silane (CAS No. 18395-30-7) and (2,3-Dimethyl-2-butanyl)(trimethoxy)silane (CAS No. 142877-45-0) have been read across.

All substances share related hydrolysis products (2,4,4-trimethylpentyl)silanetriol, (2-methylpropyl)silanetriol and (1,1,2-trimethylpropyl)silanetriol; the other hydrolysis product is methanol. Methanol does not have adverse effects on microorganisms (OECD, 2004). Both substances are expected to undergo minimal hydrolysis within the timescale of an ASRI test.

All substances are within a wider analogue group than the trimethoxy(2,4,4-trimethylpentyl)silane analogue group. Substances within this wider analogue group, in general, exhibit no evidence of significant toxicity to microorganisms. It is therefore considered valid to read-across the results for trimethoxy(2-methylpropyl)silane (CAS No. 18395-30-7) and from (2,3-Dimethyl-2-butanyl)(trimethoxy)silane (CAS No. 142877-45-0) to fill the data gap for the registered substance. This wider analogue group for the toxicity to microorganisms endpoint consists of a number of sub-classes of substances. However, read-across is carried out between substances with the same sub-class in most cases. 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 any hydrolysis is accounted for.

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, 2013j) attached in Section 13 of the IUCLID dossier.

The influence of the test item on the respiration rate on the activated sludge was investigated in a 3-h limit test test according to the OECD guideline 209 and under GLP conditions (Safepharm, 1998). The concentration of the test item in the limit test was 1000 mg/l. Up to and including the concentration of 1000 mg/l, the test item had no significant inhibitory effect on the respiration rate of activated sludge after the incubation period of three hours. The EC50 was at > 1000 mg/l and the NOEC at ≥ 1000 mg/l. In view of the rapid hydrolysis it is likely that the test organisms were exposed predominantly to the hydrolysis products of the tested substance.

Based on the results with the read-across substance, no toxicity of trimethoxy(2,4,4-trimethylpentyl)silane (CAS No. 34396-03-7) and its silanol hydrolysis product (2,4,4-trimethylpentyl)silanetriol are expected towards activated sludge microorganisms for concentrations relevant for sewage treatment plants.

 

A second study with Pseudomonas putida was available (Hüls AG, 1993). A 5-hr EC10 of 1.3 ml/l for toxicity to Pseudomonas putida was determined in a reliable study conducted according to an appropriate test protocol and in compliance with GLP.