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Diss Factsheets

Environmental fate & pathways

Biodegradation in water: screening tests

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Administrative data

Link to relevant study record(s)

Reference
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
Reason / purpose for cross-reference:
exposure-related information
Parameter:
% degradation (DOC removal)
Value:
54
Sampling time:
28 d
Remarks on result:
other: Result from 5.2.010 Enste-Diefenbach 1994
Parameter:
% degradation (O2 consumption)
Value:
31.5
Sampling time:
28 d
Remarks on result:
other: 5.2.032 Williams 1995
Remarks:
Closed bottle test
Parameter:
% degradation (CO2 evolution)
Value:
18.7
Sampling time:
29 d
Remarks on result:
other: 5.2.032 Williams 1995
Remarks:
CO2 evolution test
Parameter:
% degradation (CO2 evolution)
Value:
3.35
Sampling time:
29 d
Remarks on result:
other: 5.2.032 Williams 1995
Remarks:
CO2 evoution test with radiolabelled test substance
Interpretation of results:
not readily biodegradable

Description of key information

Not readily biodegradable: 54% after 28 d (DOC removal, EU Method C.4-A)

Key value for chemical safety assessment

Additional information

There are no data on biodegradation for hexyl(trimethoxy)silane (CAS 3069-19-0). 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 substances trimethoxy(propyl)silane (CAS 1067-25-0) and triethoxyoctylsilane (CAS 2943-75-1) has been applied to support the environmental hazard assessment of hexyl(trimethoxy)silane (CAS 3069-19-0). Details on read across justifications 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 (1994) investigating the biodegradation of the analogue substance trimethoxy(propyl)silane (CAS 1067-25-0) was conducted according to EU Method C.4-A, under GLP conditions. The inoculum (non-adapted activated sludge from a sewage treatment plant) was exposed for 28 days to the test substance and biodegradation was calculated based on DOC removal. A biodegradation of 54% was recorded after 28 d. Thus, the substance is not readily biodegradable according to the OECD criteria. 

The available study (1995) investigating the biodegradation of the analogue substance triethoxyoctylsilane (CAS 2943-75-1) was conducted equivalent or similar to standard OECD guidelines (OECD 301B+OECD 301D). The inoculum (non-adapted activated sludge from a sewage treatment plant) was exposed for 28 days to the test substance and biodegradation was calculated based on O2 consumption and CO2 evolution. After 28 d a biodegradation rate of 31.5% based on O2 consumption and 18.7% based on CO2 evolution was recorded. Thus, the substance is not readily biodegradable according to the OECD criteria. 

Based on the results of the analogue substance, hexyl(trimethoxy)silane (CAS 3069-19-0) is not assumed to be readily biodegradable.