Fatty acids, C16-18, stearyl esters

Biodegradation in water: screening tests

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)

Remarks:

Summary of available data used for the endpoint assessment of the target substance.

Adequacy of study:

key study

Justification for type of information:

Refer to the analogue approach justification provided in IUCLID section 13.

Reason / purpose for cross-reference:

read-across source

Reason / purpose for cross-reference:

read-across source

Parameter:

% degradation (CO2 evolution)

Value:

68.1

Sampling time:

29 d

Remarks on result:

other: bottle A

Remarks:

Source: RA-A, CAS 93803-87-3, Notox, 1998

Parameter:

% degradation (CO2 evolution)

Value:

71.7

Sampling time:

29 d

Remarks on result:

other: bottle B

Remarks:

Source: RA-A, CAS 93803-87-3, Notox, 1998

Parameter:

% degradation (O2 consumption)

Value:

90

Sampling time:

28 d

Remarks on result:

other: mean of all replicates

Remarks:

Source: RA-A, CAS 101227-09-2, Henkel, 2001

Conclusions:

The target substance is readily biodegradable based on experimental studies with two structurally and chemically closely related source substances (66.1 - 71.7% in 29 d, OECD 301 B, 90% in 28 d, OECD 301 D); read-across

Description of key information

Readily biodegradable (90% in 28 d, ISO 10708; 68.1 - 71.7% in 28 d, OECD 301B); read-across

Key value for chemical safety assessment

Biodegradation in water:

readily biodegradable

Additional information

There are no studies available, in which the ready biodegradability of the target substanceFatty acids, C16-18, stearyl esters (CAS 85536-04-5) was assessed.Therefore, the data requirements for this endpoint were met by (Q)SAR prediction (VEGA v1.2.3) in combination with read-across to the two structurally and chemically closely related source substances Fatty acids, C16-18, 2-hexyldecyl esters (CAS 101227-09-2) and 2-octyldodecyl isooctadecanoate (CAS 93803-87-3). Read-across was conducted in accordance with Regulation (EC) No. 1907/2006 Annex XI, 1.5. The source substances are characterized by similar fatty acid chain lengths and alcohol components as the target substance and are therefore considered suitable representatives for the assessment of the ready biodegradability of the target substance. A detailed justification of the analogue approach is provided in IUCLID section 13.

The available study with the source substance Fatty acids, C16-18, 2-hexyldecyl esters (CAS 101227-09-2) was conducted according to ISO 10708 (equivalent or similar to OECD 301 D) using activated sludge from a domestic sewage treatment plant as inoculum for 100 mg/L test item (based on ThOD/L). After 28 d, the mean degradation of the test item was 90% based on O2 consumption. Therefore, the substance is readily biodegradable according to the OECD criteria (biodegradation > 60% after 28 d, and the fulfilment of the 14 d window).

The available study with source substance 2-octyldodecyl isooctadecanoate (CAS 93803-87-3) was conducted according to OECD 301 B using domestic activated sludge as inoculum with approx. 14.5 mg/L test item. After 28 d, the substance was degraded by 68.1 - 71.7%. According to ECHA Guidance Chapter R. 7b (2017), the 10-day window does not need to be applied if the test is carried out on a mixture of structurally similar constituents and if it is anticipated that a sequential biodegradation of the individual components is taking place, based on the OECD “Guidelines for the Testing of Chemicals, Revised Introduction To The OECD Guidelines For Testing of Chemicals (Section 3, Part I, OECD, 2006b). Thus, the % degradation at the end of exposure is used instead to assess the ready biodegradability of the substance as a whole. Since degradation was > 60 % after 28 d, the substance is regarded as readily biodegradable.

Furthermore, the (Q)SAR model for ready biodegradability (VEGA v1.2.3, IRFMN 1.0.9) predicts ready biodegradability. The two constituents of the substance lie within the applicability domain of the model and fulfilled all the measured applicability domain scores listed in the attached VEGA report. The overall model performance is very good. Thus, the result appears reliable and is considered adequate for regulatory purposes under REACh regulation (EC) No 1907/2006.

Based on the high degree of structural and chemical similarity between the target and the selected source substances, the target substance is expected to exhibit a similar environmental fate profile as the source substances. Therefore, it is concluded that the target substanceFatty acids, C16-18, stearyl esters (CAS 85536-04-5) is readily biodegradable according to OECD guideline criteria, based on the available experimental results and QSAR prediction.