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Biodegradation in water: screening tests

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Description of key information

Readily biodegradable (whole substance): 66 - 72% (CO2 evolution) in 28 d (OECD 301B) 

Key value for chemical safety assessment

Biodegradation in water:
readily biodegradable

Additional information

A measured ready biodegradation value of 66 - 72% (CO2 evolution) in 28 days was determined for the whole substance in accordance with OECD 301B test method and in compliance with GLP (Desmares-Koopmans, 1996).

The registered substance is a substance of unknown or variable composition (UVCB) containing linear and branched alcohols with carbon number in the range C14-C20; the constituents share a common chemistry, incorporating an alcohol functional group on an alkyl chain with carbon number in the range C14 -C20, predominantly C16 -C18. The alkyl structures are predominantly monobranched (methyl or ethyl branching at or beyond the 6 -carbon position) and may be considered essentially linear.

A recent study using OECD 301B methodology using an appropriate loading method for the low solubility of the substance

(Federle 2009) contains results for biodegradation of linear alcohols which are significant and fit for purpose even though the study was not conducted to GLP. This study gave results of 82.2% (C14), 82.4% (C16), 95.6 (C18) and 88.4% (C20) in 28 days (OECD 301B). All were readily biodegradable, meeting the ten-day window.

A more recent test using OECD 301B methodology using an appropriate loading method for the low solubility of the substance, has confirmed that docosan-1-ol (C22) is readily biodegradable, meeting the ten-day window, in a GLP-compliant study (Flach, 2012).The biodegradation level was 87.5% after 28 days.

These findings are consistent with very high levels of removal in other types of test systems (see Sections 6 and 5.2.2) and with the rapid degradation and metabolism in micro-organisms and a range of trophic levels for alcohols in the range C6-24 (see Sections 5.3, 7.1, and 6.1.5).

Rapid degradation in water is also indicated by the difficulties encountered in aquatic toxicity tests (chronic Daphnia reproduction) for long chain aliphatic alcohols (Schäfers, C., 2005a-d). Alcohols in the range C10-C15 were found to be rapidly removed from the test medium. This was attributed to metabolism by algae present as a food source in tests, and in later stages of the 21-day tests to bacterial degradation by microbes adsorbed onto the carapace of the test daphnids, despite daily cleaning of the animals.

There are older supporting studies available which suggest that chain lengths above C18 are not readily biodegradable, however those studies used loading techniques which, while in general are still reliable, did not make allowance for the reduced bioavailability caused by the low water solubility of these highest chains. Where the substances are introduced into the test vessels by coating onto the flask (Federle, 2009 and Flach, 2012), very rapid biodegradation was confirmed at all chain lengths tested.

Branched alcohols (mainly methyl and ethyl) are present in the registered substance. No measured results are available for branched alcohols specifically. It is possible that branched constituents might degrade at slightly different rates than linear ones, but this would not be picked up in a standard study.

Prediction using the SRC BIOWIN v4.10 program allows for a screening assessment of persistence, and results are shown in the table below. 

BIOWIN results for constituents of Fatty alcohols C16 – C18 (even numbered), branched and linear

Molecular formula

SMILE

Biowin1 (Linear Model Prediction)

Biowin2 (Non-Linear Model Prediction)

Biowin3 (Ultimate Biodegradation Timeframe)

Biowin4 (Primary Biodegradation Timeframe)

Biowin5 (MITI Linear Model Prediction)

Biowin6 (MITI Non-Linear Model Prediction)

Biowin7 (Anaerobic Model Prediction)

Ready Biodegradability Prediction

C14 H30 O1 (Tetradecanol)

OCCCCCCCCCCCCCC

Biodegrades Fast

Biodegrades Fast

Weeks

Days

Biodegrades Fast

Biodegrades Fast

Biodegrades Fast

Yes

C16 H34 O1

OCCCCCCC(C)CCCCCCCC

Biodegrades Fast

Biodegrades Fast

Weeks

Days

Biodegrades Fast

Biodegrades Fast

Biodegrades Fast

Yes

C16 H34 O1

OCCCCCCC(CC)CCCCCCC

Biodegrades Fast

Biodegrades Fast

Weeks

Days

Biodegrades Fast

Biodegrades Fast

Biodegrades Fast

Yes

C16 H34 O1

OCCCCCCCCCCC(C)CCCC

Biodegrades Fast

Biodegrades Fast

Weeks

Days

Biodegrades Fast

Biodegrades Fast

Biodegrades Fast

Yes

C16 H34 O1

OCCCCCCCCCCCCC(CC)C

Biodegrades Fast

Biodegrades Fast

Weeks

Days-weeks

Biodegrades Fast

Biodegrades Fast

Biodegrades Fast

Yes

C16 H34 O1

OCCCCCCCCCCCCCC(C)C

Biodegrades Fast

Biodegrades Fast

Weeks

Days-weeks

Biodegrades Fast

Biodegrades Fast

Biodegrades Fast

Yes

C16 H34 O1 (Hexadecan-1-ol)

OCCCCCCCCCCCCCCCC

Biodegrades Fast

Biodegrades Fast

Weeks

Days

Biodegrades Fast

Biodegrades Fast

Biodegrades Fast

Yes

C18 H38 O1

OCCCCCC(CC)CCCCCCCCCC

Biodegrades Fast

Biodegrades Fast

Weeks

Days

Biodegrades Fast

Biodegrades Fast

Biodegrades Fast

Yes

C18 H38 O1

OCCCCCCC(CC)CCCCCCCCC

Biodegrades Fast

Biodegrades Fast

Weeks

Days

Biodegrades Fast

Biodegrades Fast

Biodegrades Fast

Yes

C18 H38 O1

OCCCCCCCC(C)CCCCCCCCC

Biodegrades Fast

Biodegrades Fast

Weeks

Days

Biodegrades Fast

Biodegrades Fast

Biodegrades Fast

Yes

C18 H38 O1

OCCCCCCCCCC(C)C(C)CCCCC

Biodegrades Fast

Biodegrades Fast

Weeks

Days

Biodegrades Fast

Biodegrades Fast

Does Not biodegrade Fast

Yes

C18 H38 O1

OCCCCCCCCCC(C)CCC(C)CCC

Biodegrades Fast

Biodegrades Fast

Weeks

Days-weeks

Biodegrades Fast

Biodegrades Fast

Biodegrades Fast

Yes

C18 H38 O1

OCCCCCCCCCCC(C)CCCCCC

Biodegrades Fast

Biodegrades Fast

Weeks

Days

Biodegrades Fast

Biodegrades Fast

Biodegrades Fast

Yes

C18 H38 O1

OCCCCCCCCCCCC(CC)CCCC

Biodegrades Fast

Biodegrades Fast

Weeks

Days

Biodegrades Fast

Biodegrades Fast

Biodegrades Fast

Yes

C18 H38 O1

OCCCCCCCCCCCCC(C)CCCC

Biodegrades Fast

Biodegrades Fast

Weeks

Days

Biodegrades Fast

Biodegrades Fast

Biodegrades Fast

Yes

C18 H38 O1

OCCCCCCCCCCCCCCC(C)CC

Biodegrades Fast

Biodegrades Fast

Weeks

Days-weeks

Biodegrades Fast

Biodegrades Fast

Biodegrades Fast

Yes

C18 H38 O1

OCCCCCCCCCCCCCCCC(C)C

Biodegrades Fast

Biodegrades Fast

Weeks

Days

Biodegrades Fast

Biodegrades Fast

Biodegrades Fast

Yes

C18 H38 O1 (Octadecan-1-ol)

OCCCCCCCCCCCCCCCCCC

Biodegrades Fast

Biodegrades Fast

Weeks

Days

Biodegrades Fast

Biodegrades Fast

Biodegrades Fast

Yes

C20 H42 O1

OCCCCCCC(C)CC(CC)CCCCCCCC

Biodegrades Fast

Biodegrades Fast

Weeks

Days

Biodegrades Fast

Biodegrades Fast

Does Not Biodegrade Fast

Yes

C20 H42 O1

OCCCCCCCCCCCCCCCC(CC)CC

Biodegrades Fast

Does Not Biodegrade Fast

Weeks-months

Days-weeks

Biodegrades Fast

Biodegrades Fast

Biodegrades Fast

No

C20 H42 O1

OCCCCCCCCC(CC)CCCCCCCCC

Biodegrades Fast

Biodegrades Fast

Weeks

Days

Biodegrades Fast

Biodegrades Fast

Biodegrades Fast

Yes

C20 H42 O1 (Icosan-1-ol)

OCCCCCCCCCCCCCCCCCCCC

Biodegrades Fast

Biodegrades Fast

Weeks

Days

Biodegrades Fast

Biodegrades Fast

Biodegrades Fast

Yes

 

For some structural configurations, branched isomers could be slightly less rapidly degradable, though for the type of branched structures occurring in this substance, (Q)SAR (BIOWIN) indicates that as a general rule mono-branched structures degrade at essentially the same rate as the linear unsaturated alcohol of equivalent carbon number. These conclusions are supported by reliable measured data for branched alcohols.

The available data are considered to be reliable and used as weight of evidence.

References:

Schäfers, C. (2005a).Daphnia magna, reproduction test in closed vessels following OECD 211. C10 fatty alcohol. GLP code: SDA-005/4-21. FraunhoferInstitute for Molecular Biology and Applied Ecology (IME) 57377 Schmallenberg, Germany.

Schäfers, C. (2005b).Daphnia magna, reproduction test in closed vessels following OECD 211. C12 fatty alcohol. GLP code: SDA-001/4-21. Fraunhofer Institute for Molecular Biology and Applied Ecology (IME) 57377 Schmallenberg, Germany.

Schäfers, C. (2005c).Daphnia magna, reproduction test in closed vessels following OECD 211. C14 fatty alcohol. GLP code: SDA-006/4-21. Fraunhofer Institute for Molecular Biology and Applied Ecology (IME) 57377 Schmallenberg, Germany.

Schäfers, C. (2005d).Daphnia magna, reproduction test in closed vessels following OECD 211. C15 fatty alcohol. GLP code: SDA-002/4-21. Fraunhofer Institute for Molecular Biology andApplied Ecology (IME) 57377 Schmallenberg, Germany.