Bis(triethoxysilylpropyl)amine

Biodegradation in water: screening tests

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

biodegradation in water: ready biodegradability

Type of information:

experimental study

Adequacy of study:

key study

Study period:

08 Aug - 05 Sep 2013

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

other: Method for Testing the Biodegradability of Chemical Substances by Microorganisms" stipulated in the "Testing Methods for New Chemical Substances" (No. 110331009, Environmental Policy Bureau, Ministry of the Environment, Japan)

Qualifier:

according to guideline

Guideline:

OECD Guideline 301 C (Ready Biodegradability: Modified MITI Test (I))

GLP compliance:

yes

Remarks:

based on statement of the study director

Oxygen conditions:

aerobic

Inoculum or test system:

other: see details on inoculum

Details on inoculum:

- Source of inoculum/activated sludge (e.g. location, sampling depth, contamination history, procedure): on-site sludge sampling was carried out at 10 locations in Japan (samples were from surface water and surface soil of rivers, lakes, and inland sea; return sludges from sewage plants). Sampling period: Mar 2012, initiation date of use: 9 Apr 2012
- Laboratory culture: activated sludge was prepared and controlled in the laboratory
- Method of cultivation: the synthetic sewage was prepared according to the following method; glucose, peptone, and potassium dihydrogenphosphate were dissolved in purified water. The pH of the solution was adjusted to 7.0 ± 1.0. Synthetic sewage was cultivated for 19 h and then used for the experiments.
- Concentration of sludge: additive amount of activated sludge into the test vessel was 2.74 mL (on the basis of the concentration of suspended solid in the activated sludge which was determined by Japanese Industrial Standards (JIS) K 0102-2010)

Duration of test (contact time):

28 d

Initial conc.:

100 mg/L

Based on:

test mat.

Parameter followed for biodegradation estimation:

O2 consumption

Parameter followed for biodegradation estimation:

DOC removal

Details on study design:

TEST CONDITIONS
- Composition of medium: basal culture medium was prepared with purified water which was added to each 3 mL aliquot of the solutions A B C D in order to prepare 1 L of medium. The pH was then adjusted to 7
- Volume of test solution: 300 mL
- Test temperature: 25 ± 1 °C
- pH: 7 - 7.5 in vessels with sludge and test item, 9.4 - 9.6 in vessels with water and test item
- pH adjusted: yes, where needed
- Suspended solids concentration: 30 mg/L
- Continuous darkness: yes

TEST SYSTEM
- Culturing apparatus: OM7000A (Ohkura Electric)
- Number of culture flasks/concentration: 3 replicates, sludge (2.28 mL) + test item (100 mg/L)
- Details of trap for CO2: soda lime
- Other: each test solution was stirred by a stirrer for 30 min

SAMPLING
- Sampling method: measurement of BOD with a closed system oxygen consumption measuring apparatus and determination of DOC by total organic carbon analysis

CONTROL AND BLANK SYSTEM
- Inoculum control: 1 replicate, sludge (2.28 mL) + aniline (100 mg/L)
- Abiotic control: 1 replicate, water + test item (100 mg/L)
- Contol blank: 1 replicate, sludge (2.28 mL)

Reference substance:

aniline

Parameter:

% degradation (O2 consumption)

Value:

57

Sampling time:

28 d

Parameter:

% degradation (DOC removal)

Value:

62

Sampling time:

28 d

Details on results:

All of the test item was hydrolyzed rapidly and converted to methanol and N,N-bis (3- trihydroxysilylpropyl) amine under the test conditions of this study. Ethanol was biodegraded while N,N-bis (3- trihydroxysilylpropyl) amine was not biodegraded.

The test item hydrolyzes rapidly in water (result of hydrolysis test). Therefore, the % biodegradation of the test item could not be calculated. Ethanol and silanol form [N,N- bis (3-trihydroxysilylpropyl) amine] are produced as hydrolysis products. From the results of the quantitative analysis, the % production of ethanol was 100% in the test solutions (water + test item) and 0% in the test solutions (sludge + test item) each. On the other hand, the % production of silanol form was 101% in the test solution (water+test item) and 98-103% in the test solutions (sludge+test item). These results suggest that ethanol and silanol form were produced by hydrolysis in ethoxysilane group of the test item and ethanol was biodegraded, whereas silanol form was not biodegraded. Biodegradation based on BOD was 56-58%. The calculated biodegradation when the theoretical amount of ethanol was biodegraded was 63%*, based on BOD and agreed with the experimental % biodegradation of BOD. Therefore the rising of BOD was considered to proceed from biodegradation of ethanol.

*Ethanol: C2H6O + 3O2à2CO2 + 3 H2O  3O2/C2H6O=2.08

Calculated value of TOD = 19.8 (theoretical amount of ethanol) x 2.08 = 41.2 mg

% biodegradation by BOD = 41.2/65.9 (TOD of test item) x 100 = 63%

Table 1: Validity criteria

		Value in this test	Value of criterion
Difference between extremes of replicate values of % biodegradation	% biodegradation by BOD	2%	<20%
	% biodegradation of test item	2%
% biodegradation of aniline by BOD	After 7 days	82%	>40%
	After 14 days	89%	>65%
BOD value of control blank	After 28 d	10.6 mg	<60 mg/L

Table 2: Analytical results of the test solutions after 28 d.

		Water+ test item	Sludge+test item			Theoretical amount
		Vessel No. 1	Vessel No. 2	Vessel No. 3	Vessel No. 4
BOD*	mg	0.7	36.8	37.7	38.2	65.9
Residual amount* and percentage residue of DOC	mgC	16.5	6.2	6.5	6.2	15.5
	%	106	40	42	40	-
Residual amount and percentage residue of DOC	-	The determination oft he test item could not be performed because the test item is hydrolyzed rapidly in water
Residual amount and % residue of test item	mg	19.7	0	0	0	19.8
	%	100	0	0	0	-
Produced amount and % production of ethanol (GC)	mg	18.5	18.9	18	18.4	18.4
	%	101	103	98	100	-

*The value of the test solution (control blank) was substracted from the values of the test solutions (sludge + test item)

Table 3: Measured and calculated DOC amount.

		Water + test item	Sludge + test item
		Vessel No. 1	Vessel No. 2	Vessel No. 3	Vessel No. 4
Measured amount of DOC	mgC	16.5	6.2	6.5	6.2
Calculated amount of DOC (derived from produced amount of ethanol*)	mgC 1	10.3	0	0	0
Calculated amount of DOC (derived from produced amount of silanol form**)	mgC 2	5.2	5.3	5	5.2
Calculated amount of DOC 1+2	mgC 1+2	15.5	5.3	5	5.2

*Calculated amount of DOC from produced amount of ethanol (mgC) = produced amount of ethanol (mg) x 2C/C2H6O

**Calculated amount of DOC from produced amount of silanol form (mgC) = produced amount of silanol form (mg) x 6C/C6H19NO6Si

Table 4: % biodegradation by BOD.

Vessel No.	7th day		14th day		21st day		28th day		Mean
	BOD (mg)	Deg.(%)	BOD (mg)	Deg.(%)	BOD (mg)	Deg.(%)	BOD (mg)	Deg.(%)	Deg.(%)
1	0	-	0	-	0.1	-	0.7	-	-
2	36.1	51	43.5	58	46	60	47.4	56	57
3	35.8	51	42.6	57	46.3	60	48.3	57
4	35.8	51	42.7	57	46.7	61	48.8	58
5	2.3	-	5.2	-	6.7	-	10.6	-	-
6	61.9	82	69.9	89	71.9	90	74.3	88	-

Table 5: Produced amount of ethanol over 2 h.

Sampling point			Production of ethanol (GC)
			Right after preparation	0.5 h	1 h	2 h
Water + test item	1	mg	10	19.3	19.2	19.7
		%	51	99	98	101
	2	mg	12	18.9	19.1	19.2
		%	62	97	98	99
Theoretical amount (mg)			19.5

Validity criteria fulfilled:

yes

Interpretation of results:

other: not readily biodegradable

Conclusions:

The test item was found to hydrolyze rapidly in water. The products are ethanol and bis(trihydroxysilylpropyl)amine. Ethanol is biodegraded to 100% but the silanol hydrolysis product does not biodegrade rapidly. DOC analysis showed a biodegradation lower than 70% (62%). Therefore, based on the guideline, it is concluded that the substance is not readily biodegradable.

Reference 2

Endpoint:

biodegradation in water: ready biodegradability

Type of information:

experimental study

Adequacy of study:

key study

Study period:

09 Dec 2004 - 07 Feb 2005

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: GLP guideline study

Qualifier:

according to guideline

Guideline:

other: OECD 306

GLP compliance:

yes

Oxygen conditions:

aerobic

Inoculum or test system:

other: seawater

Details on inoculum:

- Source of inoculum: North Sea , 53°50,86'N 7° 59,86'E (sampling was performed by the "Bundesamt für Seeschifffahrt und Hydrogeographie, Hamburg"), typical coastal seawater from 12 m depth, sampling date 28th 2004
- Salinity: 31.83 PSU (practical salanity units [g/L])
- DOC: 0.958 mg/L (measured by Hydrotox)
- other: the inoculum was aged prior the testing for 8 days at 18 °C; before testing the seawater was sedimented for 1.5 h

Duration of test (contact time):

60 d

Initial conc.:

41.72 other: %

Based on:

other: TOC

Initial conc.:

40 mg/L

Based on:

other: organic carbon

Parameter followed for biodegradation estimation:

DOC removal

Details on study design:

TEST CONDITIONS
- Composition of medium: mineral medium is according to OECD 306, excepted for Disodium hydrogenphosphate dihydrate 33.40 g (OECD 306: 33.30 g) and Calcium chloride 36.4 g (OECD 306: 27.50 g)
- Test temperature: range between 15 - 20 °C (+/- 2 °C)


TEST SYSTEM
- Culturing apparatus: reactor
- Number of culture flasks/concentration: 7 reactors
- Measuring equipment: Total carbon analyser TOC-5000A, Shimadzu Deutschland, Duisburg
- Other: Materials: Erlenmeyer flask (volume 3000 mL); orbital shaker GFL, 3020, Burgwedel; pipettes: 5 mL, 1 mL, 100 µL; precision balance, Sartorius AG Göttingen; membrane filters F-30/0.45 µm, Schleicher & Schüll

SAMPLING
- Sampling frequency: day: 0, 4, 7, 11, 14, 21, 25, 28, 36, 42, 49, 53, 60
- Sampling method: 10 - 20 mL of test splutions were taken, filtered through membrane filters
- Sample storage before analysis: For longer storage samples were kept at <-18 °C.

CONTROL AND BLANK SYSTEM
- Inoculum blank: 2
- Toxicity control: 2

Reference substance:

benzoic acid, sodium salt

Parameter:

% degradation (DOC removal)

Value:

64.5

Sampling time:

28 d

Parameter:

% degradation (DOC removal)

Value:

71

Sampling time:

60 d

Details on results:

- The degradation of the test item reached a plateau on day 36
- Reference item: The biodegradability was 66% within 4 days and 96% with 28 days
- Toxicity control: Degradation was 71% with 28 days; after day 28 there was a high variation of the DOC-measurements in the toxicity control
- Blank: The DOC was between 0.8 and 6.4 mg/L

Results with reference substance:

The biodegradability was 66% within 4 days and 96% with 28 days.

Degradation of chemicals in seawater has generally been found to be slower than that in freshwater tests inoculated with activated sludge and sewage effluent [ECHA, 2008, Guidance on information requirements and chemical safety assessment, Chapter R.7b: Endpoint specific guidance]. Therefore the screening test for biodegradability in seawater (Test Guideline 306) may be seen as seawater parallel to the ready biodegradability tests in freshwater [OECD, 2001 Series on testing and assessment Number 33]. In the present case the degradation of the substance did not reach the pass level of > 70% DOC removal within 28 days. Hence, 3-(triethoxysilyl)-N-[3-(triethoxysilyl)propyl]-1-propanamine cannot be regarded as readily biodegradable.

Validity criteria fulfilled:

yes

Interpretation of results:

other: not readily biodegradable

Conclusions:

The biodegradation of the test item was 64.5% within 28 days and 71% within 60 days. In the present case the degradation of the substance did not reach the pass level of > 70% DOC removal within 28 days. Furthermore the observed biodegradation is considered to result from the biodegradation of ethanol while no significant biodegradation is expected for the silanol hydrolysis product. Hence,the substance cannot be regarded as readily biodegradable.

Description of key information

No evidence of biodegradation (OECD 301 C, OECD 306)

Key value for chemical safety assessment

Biodegradation in water:

not biodegradable

Type of water:

freshwater

Additional information

Two studies are available testing the biodegradability of 3-(triethoxysilyl)-N-[3-(triethoxysilyl)propyl]-1-propanamine (CAS 13497-18-2). Both studies showed that the substance is not readily biodegradable. Due to the fast hydrolysis half-life of 11.9 h at pH 7 and 20 °C of the substance and the duration of the biodegradation studies (28 days), it can be expected that mainly the hydrolysis products of the registered compound were available.

 

In the first study the biodegradability of the substance was tested according to OECD guideline 301 C and GLP (2013). The inoculum used for the test was a mixture of freshwater samples from 10 locations in Japan, consisting of sludge from surface water, surface soil of rivers, lakes, and inland sea, and return sludges from sewage plants, and was exposed to 100 mg test mat./L for 28 d. The substance hydrolyses rapidly to ethanol and 3-(trihydroxysilyl)-N-[3-(hydroxysilyl)propyl]-1-propanamine. After 28 d a biodegradation of 62% and 57% based on DOC and BOD was determined, respectively.

 

The second available study was conducted according to OECD guideline 306 and GLP (2005). Coastal seawater was used as inoculum and was exposed to an initial test item concentration of 40 mg/L (organic carbon). 64.5% of the substance was biodegraded after 28 days.

 

In both studies the degradation of the substance did not reach the pass level of > 70% DOC removal within 28 days. The observed biodegradation is considered to result from the biodegradation of ethanol while no significant biodegradation is expected for the silanol hydrolysis product. Hence, the silanol hydrolysis product cannot be regarded as readily biodegradable.