Trichloro(octadecyl)silane

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:

13 Apr - 13 Jun 2016

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 301 F (Ready Biodegradability: Manometric Respirometry Test)

Version / remarks:

1992

GLP compliance:

yes (incl. QA statement)

Remarks:

Staatliches Gewerbeaufsichtsamt Hildesheim, Hildesheim, Germany

Specific details on test material used for the study:

TREATMENT OF TEST MATERIAL PRIOR TO TESTING
- Treatment of test material prior to testing: the test material was melted at 30 - 50 °C until it was completely dissolved. 47.5 mg test item were weighed and 5 mL silicone oil were added. Mixture was vortexed and homogenized. 250 mL inoculated test medium was filled in brown glass bottles and 500 µL test item - silicone oil stock solution was pipetted directly into the inoculated test medium.

Oxygen conditions:

aerobic

Inoculum or test system:

activated sludge, domestic, non-adapted

Details on inoculum:

- Source of inoculum/activated sludge: municipal sewage treatment plant, Hildesheim, Germany
-Pretreatment: activated sludge was washed twice with chlorine free tap water. Thereafter settled sludge was resuspended in mineral salts medium and was aerated for 2 h. Sludge was then homogenized with a blender. After sedimentation the supernatant was decanted and maintained in an aerobic condition by aeration with air for 5 d.
- Concentration of sludge: 10 mL/L were used to initiate inoculation
- Initial cell/biomass concentration: approx. 1.13 x 10^7 CFU/L in the final test solution

Duration of test (contact time):

60 d

Initial conc.:

19 mg/L

Based on:

test mat.

Initial conc.:

52.8 mg/L

Based on:

ThOD

Initial conc.:

2.78 other: mg O2/mg

Based on:

ThOD

Parameter followed for biodegradation estimation:

CO2 evolution

Details on study design:

TEST CONDITIONS
- Composition of medium: mineral salts medium according to OECD 301 F
- Test temperature: 20 - 21 °C
- pH: 7.60 - 7. 90
- pH adjusted: no
- Concentration of sludge: 10 mL/L were used to initiate inoculation
- Continuous darkness: yes
- Other: continuous stirring

TEST SYSTEM
- Number of culture flasks/concentration: 2
- Measuring equipment: OxiTop® measuring heads, WTW Stirring platform, WTW
- Test performed in closed vessels: yes
- Details of trap for CO2: a rubber sleeve with soda lime was hung into the opening of the bottles to absorb evolved CO2
- Other: separate replicates of test item and toxicity control were prepared for measurement of pH at test start

SAMPLING
- Sampling frequency: 1080 measuring points during the 60 d incubation period

CONTROL AND BLANK SYSTEM
- Inoculum control: 2
- Inoculum control with silicone oil: 2 (500 µL silicone oil were pipetted directly into the inoculated test medium)
- Toxicity control: 1
- Functional control: 1

Reference substance:

benzoic acid, sodium salt

Remarks:

45 mg/L

Parameter:

% degradation (CO2 evolution)

Value:

57

Sampling time:

28 d

Parameter:

% degradation (CO2 evolution)

Value:

65

Sampling time:

60 d

Details on results:

- Reference substance: 100% degradation after 23 d (pass level of > 60% was reached after 3 d)
- Toxicity control: 75% degradation after 28 d (82% degradation after 60 d)

Both test item replicates reached the 10% biodegradation level on day 4. The 60% pass level was reached by the mean of replicates on day 39. The mean biodegradation on day 60 was 65%.

Table 1: % biodegradation over time

[d]	Functional Control	Biodegradation [%]		Toxicity Control
		Test item
		1	2
1	7	0	0	4
2	50	0	0	31
3	62	3	1	37
4	73	16	14	43
5	79	26	25	48
6	82	31	29	52
7	84	35	34	55
8	86	38	35	58
9	88	40	38	61
10	89	42	40	62
11	90	42	42	63
12	91	44	42	64
13	93	45	44	65
14	93	46	44	66
15	94	47	45	67
16	96	48	46	68
17	97	49	48	69
18	98	51	49	70
19	98	52	50	70
20	99	52	50	71
21	98	52	50	71
22	99	52	52	72
23	100	53	52	72
24	100	54	52	73
25	100	54	52	74
26	100	56	53	74
27	100	60	53	74
28	100	60	54	75
29	100	64	53	75
30	100	64	53	76
31	100	63	52	75
32	100	63	53	76
33	100	64	53	77
34	100	64	52	77
35	100	64	52	77
36	100	65	54	77
37	100	65	54	78
38	100	65	54	78
39	100	66	54	78
40	100	66	53	79
41	100	66	54	79
42	100	67	54	79
43	100	67	53	79
44	100	66	53	79
45	100	67	54	80
46	100	68	53	80
47	100	68	54	80
48	100	68	55	80
49	100	68	55	80
50	100	68	55	81
51	100	68	55	80
52	100	69	54	81
53	100	70	54	81
54	100	70	54	81
55	100	70	54	81
56	100	70	54	81
57	100	69	55	81
58	100	70	57	81
59	100	70	58	81
60	100	71	58	82

Validity criteria fulfilled:

yes

Interpretation of results:

inherently biodegradable

Conclusions:

A biodegradation study according to OECD 301F resulted in a biodegradation of 57% after 28 d and 65% after 60 d.

Reference 2

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 attached justification below and the overall justification for grouping of substances attached in IUCLID Section 13.

Reason / purpose for cross-reference:

read-across source

Parameter:

% degradation (CO2 evolution)

Value:

57

Sampling time:

28 d

Parameter:

% degradation (CO2 evolution)

Value:

65

Sampling time:

60 d

Details on results:

- Reference substance: 100% degradation after 23 d (pass level of > 60% was reached after 3 d)
- Toxicity control: 75% degradation after 28 d (82% degradation after 60 d)

Description of key information

Trichloro(octadecyl)silane (CAS 112-04-9) is inherently biodegradable (57% after 28 d and 65% after 60 d, OECD 301F) based on read across from CAS 18643-08-8

Key value for chemical safety assessment

Biodegradation in water:

inherently biodegradable

Additional information

There are no data on biodegradation for trichloro(octadecyl)silane (CAS 112-04-9). In accordance with Regulation (EC) No. 1907/2006 Annex XI, 1.5 “Grouping of substances and read across” and in accordance with the read across assessment framework (RAAF, ECHA 2017) a read across from the analogue substance octadecyldimethylchlorosilane (CAS 18643-08-8) has been applied to support the environmental hazard assessment of the substance. Details on the read across justification can be found in the attached justification in the respective target entry and in the overall justification for grouping of substances attached in IUCLID Section 13.

The available study (2016) investigating the biodegradation of the analogue substance octadecyldimethylchlorosilane (CAS 18643-08-8) was conducted according to OECD guidance 301F and GLP conditions. The inoculum (non-adapted activated sludge from a sewage treatment plant) was exposed for 60 days to 19 mg/L test substance and biodegradation was calculated based on CO2 evolution. The substance reached a biodegradation value of 57% after 28 d and 65% after 60 d. Therefore, the read across substance is considered as inherently biodegradable.

Based on the results of the analogue substance, trichloro(octadecyl)silane (CAS 112-04-9) is assumed to be inherently biodegradable.