(3-chloropropyl)dimethoxymethylsilane

Biodegradation in water: screening tests

Link to relevant study record(s)

Reference

Endpoint:

biodegradation in water: ready biodegradability

Type of information:

experimental study

Adequacy of study:

key study

Study period:

1994-06-08-06 to 1994-07-06

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)

Deviations:

no

GLP compliance:

yes

Oxygen conditions:

aerobic

Inoculum or test system:

activated sludge, domestic (adaptation not specified)

Details on inoculum:

- Source of inoculum/activated sludge (e.g. location, sampling depth, contamination history, procedure): activated sludge of a predominantly municipal wastewater treatment plant (Marl-east). Taken 08.06.94.

- Preparation of inoculum for exposure: Centrifuge 15 min at 3000 rpm. Supernatant was discarded and the sludge resuspended with mineral medium. Re-centrifugation: 15 min at 3000 rpm. Resuspension of the sludge. The sludge concentration was 3.77g dry weight per liter. The final concentration of the inoculum per flask test was 26.4 mg/l.

Duration of test (contact time):

28 d

Initial conc.:

11.2 mg/L

Based on:

other: COD (theoretical)

Parameter followed for biodegradation estimation:

DOC removal

Details on study design:

TEST CONDITIONS
- Composition of medium: Mineral salts solution, inoculum and test substance.

- Test temperature: temp 21.9 to 22.1°C


TEST SYSTEM
- Culturing apparatus: 2000 ml Erlenmeyer flask with a loose aluminium foil claps.

- Number of culture flasks/concentration: 2

SAMPLING
- Sampling frequency: At time 0 and after 3 hours, and at 7, 14, 21, 27 and 28 day.

CONTROL AND BLANK SYSTEM
- Inoculum blank: Yes

- Abiotic sterile control: No

- Toxicity control: No

Reference substance:

benzoic acid, sodium salt

Key result

Parameter:

% degradation (DOC removal)

Value:

56

Sampling time:

28 d

Details on results:

Biodegradation of reference substance 96% in 28d.

Table 1: Dissolved organic carbon (DOC) concentration (mg/l) and calculated % biodegradation for inoculum blank, test substance and reference substance

Type of suspension	0 h		3 h		7d		14d		21d		27d		28d
	DOC (mg/l)	(%) biodeg	DOC (mg/l)	(%) biodeg	DOC (mg/l)	(%) biodeg	DOC (mg/l)	(%) biodeg	DOC (mg/l)	(%) biodeg	DOC (mg/l)	(%) biodeg	DOC (mg/l)	(%) biodeg
Inoculum Blank (mean of two replicates with duplicate analyses)	0.76	-	0.75	-	1.16	-	1.01	-	0.17	-	0.97	-	0.63	-
Test sample Replicate 1 (mean of two analyses)	10.57	0.00	10.75	0.00	5.67	54.90	5.82	51.90	5.76	44.10	5.02	59.50	4.98	56.50
Test sample Replicate 2 (mean of two analyses)	10.33	0.00	10.87	0.00	5.36	58.50	5.87	51.98	6.24	40.02	4.85	61.66	5.13	55.53
Mean		0.00		0.00		56.70		51.94		42.06		60.58		56.02
Reference substance Replicate 1 (mean of two analyses)	11.77	0.00	11.89	0.00	1.46	97.31	1.04	99.73	0.17	100.00	1.12	98.65	0.99	96.77
Reference substance Replicate 2 (mean of two analyses)	11.65	0.00	11.37	0.00	1.56	96.23	1.02	99.91	0.16	100.09	0.98	99.91	1.05	96.05
Mean		0.00		0.00		96.77		99.82		100.05		99.28		96.41

 

Validity criteria fulfilled:

yes

Conclusions:

A biodegradation rate of 56 % 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:  56% in 28 days (EU Method C.4-A), read-across from an analogous substance. No significant biodegradation of the silanol hydrolysis product is expected.

Key value for chemical safety assessment

Biodegradation in water:

not biodegradable

Type of water:

freshwater

Additional information

There are no reliable ready biodegradation data available for 3-chloropropyl(dimethoxy)methylsilane, therefore good quality data for the analogous substance, 3-chloropropyl(diethoxy)methylsilane (CAS 13501-76-3) have been read across. Both substances share the same silanol hydrolysis product, 3-chloropropyl(methyl)silanediol; the other hydrolysis products being methanol and ethanol respectively. In view of the rapid hydrolysis, it is the silanol hydrolysis product that is relevant for environmental risk assessment.

 

Ethanol and methanol are readily biodegradable (OECD 2004a and OECD 2004b).

 

3-Chloropropyl(dimethoxy)methylsilane and 3-chloropropyl(diethoxy)methylsilane are within an analogue group of substances within which in general, there is 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 substances containing a number of different functional groups but specific read-across is between substances with similar functionality.

 

The table below presents ready biodegradation data available for substances relevant to 3-chloropropyl(dimethoxy)methylsilane.

 

It is therefore considered valid to read-across the result for 3-chloropropyl(diethoxy)methylsilane to fill the data gap for the registered substance since both substances generate the same silanol hydrolysis product.

 

Additional information is given in a supporting report (PFA 2021) attached in Section 13.

 

Table A.6         Ready biodegradation data for substances with functional side-chains

CAS	Name	Type (side-chain type)	Readily biodegradable?	Biodegradation after 28 days (%)	Guideline (test type)	Klimisch code	# carbons from OR^1	# carbons in side-chain(s)	% degradation if only OR degrades	Corrected % biodegradation^2	Study ID Code^3
002212-11-5	Silane, (chloromethyl)dimethoxymethyl-	Dialkoxy (Chloro)	No	30-34%	OECD 301F (BOD)	1	2	2	50	-16	5.2.049
013501-76-3	(3-chloropropyl)diethoxymethylsilane	Dialkoxy (Chloro)	No	56%	EC C4-A (DOC)	1	4	4	50	6	5.2.075
002530-87-2	3-chloropropyltrimethoxysilane	Trialkoxy (Chloro)	No	43%	OECD 301 B (CO2)	1	3	3	50	-7	5.2.008
005089-70-3	(3-chloropropyl)triethoxysilane	Trialkoxy (Chloro)	No	46%	EC C4-C (CO2)	1	6	3	67	-21	5.2.076

¹OR is the alkoxy/acetoxy group, which hydrolyses to give ROH.

²This is the measured percentage biodegradation minus the expected biodegradation if only the acetoxy/alkoxy by-products biodegrade. It is the biodegradation associated with the side-chain of the silanol hydrolysis product. The negative values in this column are where the biodegradation rate observed in the test is less than that expected if the substance fully hydrolyses and the alkoxy/acetoxy parts readily biodegrade. This could be due to low solubility of parent substance or low rates of hydrolysis. These values should in effect be considered as zero. Substances where significant biodegradation (≥10%) associated with the silanol hydrolysis product is observed are highlighted bold.

³This is a unique internal ID code which can be used to identify the reference for the study.

 

In the study with (3-chloropropyl)diethoxymethylsilane (CAS 13501-76-3), a biodegradation of 56% in 28 days was determined in a reliable study conducted according to an appropriate test protocol, and in compliance with GLP (EU Method C.4-A). (3-Chloropropyl)diethoxymethylsilane (CAS 13501-76-3) hydrolyses within the timescale of the ready biodegradation study to form 3-chloropropyl(methyl)silanediol and ethanol.

The biodegradation observed in the study is attributable to the biodegradation of the ethanol hydrolysis product.

 

No significant biodegradation is expected for the silanol hydrolysis product.

 

 

References: 

OECD (2004a): SIDS Initial Assessment Report for SIAM 19, Berlin, Germany, 18-20 October 2004, Methanol, CAS 67-56-1.

 

OECD (2004b): SIDS Initial Assessment Report for SIAM 19, Berlin, Germany, 19-22 October 2004, Ethanol, CAS 64-17-5.

 

PFA 2021: Background to persistence assessment of organosilicon compounds, Reference: PFA.923.001.001, February 2021.