Triethoxypropylsilane

Biodegradation in water: screening tests

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

biodegradation in water: ready biodegradability

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 justification for grouping of substances provided in IUCLID section 13.

Reason / purpose for cross-reference:

read-across source

Parameter:

% degradation (DOC removal)

Value:

50

Sampling time:

7 d

Parameter:

% degradation (DOC removal)

Value:

55

Sampling time:

14 d

Parameter:

% degradation (DOC removal)

Value:

54

Sampling time:

21 d

Parameter:

% degradation (DOC removal)

Value:

55

Sampling time:

27 d

Parameter:

% degradation (DOC removal)

Value:

54

Sampling time:

28 d

Interpretation of results:

other: not readily biodegradable

Conclusions:

A biodegradation result of 54% in 28 days was determined in a reliable study conducted according to an appropriate test protocol, and in compliance with GLP.

Reference 2

Endpoint:

biodegradation in water: ready biodegradability

Type of information:

experimental study

Adequacy of study:

key study

Study period:

1994-08-31 to 1994-11-02

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

EU Method C.4-A (Determination of the "Ready" Biodegradability - Dissolved Organic Carbon (DOC) Die-Away Test)

GLP compliance:

yes

Oxygen conditions:

aerobic

Inoculum or test system:

activated sludge, non-adapted

Details on inoculum:

The inoculum employed in the test was activated sludge from the Marl - Ost municipal sewage treatment plant. It was taken off on 1994-09-07 and centrifugated for 15 min at 3000 rpm. The supernatant was rejected and the sludge resuspended with mineral medium (washing). After another centrifugation step 15 min at 3000 rpm, the sludge was resuspended. The content of the dry matter in the inoculum used was 3.45 g/l. The determination of suspended solids was carried out before the inoculum. During this time the sludge had to be aerated by aerating tube. The content of the suspended solids in the test batches was 27.6 mg/l.

Duration of test (contact time):

28 d

Initial conc.:

11.2 mg/L

Based on:

DOC

Parameter followed for biodegradation estimation:

DOC removal

Details on study design:

Vessels: 2000 ml conial flasks with loose aluminium foil closure

Test batches:
2 flasks containing test substance (11.2 mg DOC/l after 3h) and inoculum
2 flasks without test substance, but with inoculum (= blank batch)
2 flasks containing control subsatnce (sodium benzoate: 10.8 mg DOC/l after 3 hours) and inoculum

Method:
Addition of inoculum corresponding to a dry matter content of 27.6 mg/test medium.
Filling up with about 2 l mineral medium.
30 ml/l test substance stock solution (20 ml/l control substance stock solution) were added to the test vessels.
The batches were filled up to 2.5 l with mineral medium.
From this batches two times 1000 ml were put into 2000 ml Erlenmeyer flasks.
The loosely covered flasks were incubated at 21.9 to 22.2 °C in the dark on a mechanical shaker for 28 days.

Reference substance:

benzoic acid, sodium salt

Parameter:

% degradation (DOC removal)

Value:

50

Sampling time:

7 d

Parameter:

% degradation (DOC removal)

Value:

55

Sampling time:

14 d

Parameter:

% degradation (DOC removal)

Value:

54

Sampling time:

21 d

Parameter:

% degradation (DOC removal)

Value:

55

Sampling time:

27 d

Parameter:

% degradation (DOC removal)

Value:

54

Sampling time:

28 d

Details on results:

Results with reference substance:
98% DOC decrease after 7 days
99% DOC decrease after 14 days
100% DOC decrease after 21 days
99% DOC decrease after 27 days
99% DOC decrease after 28 days

DOC measurements of the test item

 

	DOC concentration after n days (mg/l)
	Flask no.		O h (C0)	3h (C3)	7	14	21	27	28
Test batches (Mineral medium + test item + inoculum)	1	a1	13.58	13.59	7.53	6.16	6.43	6.78	6.83
		a2	13.32	14.13	7.41	6.31	6.43	7.02	6.74
		Ca (t) = (a1 + a2) /2	13.45	13.86	7.47	6.24	6.43	6.90	6.79
	2	b1	12.25	13.78	7.04	6.74	6.62	6.28	6.61
		b2	12.30	13.38	7.00	6.77	6.67	6.37	6.80
		Cb (t) = (b1+ b2) /2	12.28	13.58	7.02	6.76	6.65	6.33	6.71
Blank batches (Mineral medium + inoculum)	1	c1	0.52	0.36	0.61	0.50	0.43	0.60	0.62
		c2	0.56	0.39	0.54	0.44	0.42	0.65	0.62
		Cc (t) = (c1 + c2) /2	0.54	0.38	0.58	0.47	0.43	0.63	0.62
	2	d1	0.49	0.36	0.70	0.53	0.49	0.60	0,62
		d2	0.44	0.41	0.68	0.49	0.49	0.61	0.59
		Cd (t) 0 (d1 + d2) /2	0.47	0.39	0.69	0.51	0.49	0.61	0.61
	Cbl(t)=Cc(t)+Cd(t)/2		0.51	0.39	0.64	0.49	0.46	0.62	0.62

 

Validity criteria fulfilled:

yes

Interpretation of results:

other: not readily biodegradable

Conclusions:

A biodegradation result of 54% in 28 days was determined in a reliable study conducted according to an appropriate test protocol, and in compliance with GLP.

Description of key information

Biodegradation in water, screening tests: A biodegradation rate of 54 % in 28 days
Biodegradation in water, screening tests: Ethanol is readily biodegradable

Additional information

Note: A biodegradation screening study is currently ongoing for the registered substance (i.e. triethoxy(propyl)silane (CAS 2550-02-9)). This dossier will be updated once the final study report is available.

There are no reliable ready biodegradation data available for triethoxypropylsilane, therefore good quality data for the analogue substance, trimethoxypropylsilane, have been read across. Both substances share the same silanol hydrolysis product, propylsilanetriol; the other hydrolysis products being ethanol and methanol, respectively, which are readily biodegradable.

Both triethoxypropylsilane and trimethoxypropylsilane are within a wider analogue group than the analogue groups discussed in Section 1.4. Substances within this wider analogue group,in general, exhibit no evidence of any significant biodegradation once hydrolysis and subsequent biodegradation of alkoxy/acetoxy groups has been taken into account.

This wider analogue group for the ready biodegradability endpoint consists of a number of sub-classes of substances. However, read-across is carried out between substances within the same sub-class in most cases.

Table 4.1.4 presents ready biodegradation data available for substances within the sub-class (I-2) of alkoxysilanes, silanols, acetoxysilanes and chlorosilanes, etc, where the Si part is of low-biological reactivity, once any hydrolysis is accounted for.

Table 4.1.4 Ready biodegradation data available for substances within the relevant sub-class (I-2) of chemicals

CAS	Name	Readily biodegradable? Yes/no	Result: Biodegradation after 28 day	Guideline	Reliability	Corrected % biodegradation once alkoxy/acetoxy biodegradation is accounted for
001066-40-6	Hydroxytrimethylsilane	No	0%	OECD 310	1a	0
018748-98-6	Trimethyl(octadecyloxy)silane	No	68%	OECD 301B	1a	-18
017689-77-9	Triacetoxyethylsilane	Yes	74% in 21 days	EC C4-A	1a	-1
001067-25-0	Trimethoxypropylsilane	No	54%	Annex V C4-A	1a	4
002943-75-1	Triethoxyoctylsilane	No	31.5%	OECD 301D	1a	-11
016415-13-7	Triethoxyhexadecylsilane	No	43%	MITI	1c	16
087135-01-1	1,6-Bis(trimethoxysilyl)hexane	Yes, but not meeting 10-day window	74%	OECD 301B	1a	24
None45	Mixture of 1,1- and 1,2-bis(trimethoxysilyl)ethane	Yes	93%	"Biodegradation study of chemical substances by microorganisms and the like " stipulated in "Testing Method for New Chemical Substances etc." ( Kanhogyo No.5, Yakuhatsu 615, 49Kikyoku No.392, July 13, 1974 )	1a	18
013154-25-1	Chlorotri(3-methyl-propyl)silane	No	0%	OECD 301B	1a	0
035435-21-3	Triethoxy(2,4,4-trimethylpentyl)silane	No	13%	OECD310	1a	-30
018395-30-7	Trimethoxy(2-methylpropyl)silane	No	36 - 47%	OECD 301B	1a	4
142877-45-0	Silane, trimethoxy(1,1,2-trimethylpropyl)-	No	31%	OECD 301D	1a	-2
017980-47-1	Triethoxyisobutylsilane	Yes	75%	OECD 301D	1a	15
126990-35-0	Dicyclopentyldimethoxysilane	No	12%	OECD 301C	1	-5
139147-73-2	Silane, dichlorodicyclopentyl-	No	0.8%	OECD 301D	2b	1
017865-32-6	Cyclohexyldimethoxymethylsilane	No	15-17%	OECD 301D	1a	-5
None46	t-butoxycyclopentyldimethoxysilane	No	15%	OECD 301C	1a	7
000098-12-4	Cyclohexyltrichlorosilane	No	0%	OECD 301C	1a	0
000124-70-9	Dichloro(methyl)(vinyl)silane	No	-6.78%	OECD 301A	1a	0
001067-53-4	Tris(2-methoxyethoxy)vinylsilane	Yes	89%	Annex V C4-A	1a	7
002768-02-7	Trimethoxyvinylsilane	No	51%	OECD 301F	1a	-9

 

It is therefore considered valid to read-across the results for trimethoxypropylsilane to fill the data gap for the registered substance. Additional information is given in a supporting report (PFA, 2013f) attached in Section 13 of the IUCLID 5 dossier.

A biodegradation rate of 54 % in 28 days was reported for the trimethoxypropylsilane. The results from this study are likely to reflect the biodegradation of methanol, which would biodegrade rapidly (three of the six carbons in trimethoxypropylsilane are converted to methanol in a rapid hydrolysis reaction). Propylsilanetriol is not expected to biodegrade to any significant extent. This is supported by evidence that within a category of small molecule silicon-dominated organosilicon compounds, without reactive functional groups in the side chain, there is no evidence of any significant biodegradation in ready biodegradation tests. The second hydrolysis product ethanol is known to be readily biodegradable.

The study is considered to be reliability 1 (reliable without restrictions); the read across of the result is considered to be reliability 2 (reliable with restrictions).