Isoalkanes, C17 -C22 linear and branched

Biodegradation in water: screening tests

Link to relevant study record(s)

Reference

Endpoint:

biodegradation in water: ready biodegradability

Type of information:

(Q)SAR

Adequacy of study:

key study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

results derived from a valid (Q)SAR model and falling into its applicability domain, with limited documentation / justification

Justification for type of information:

Modelling to confirm low biodegradation rates is a common approach for polyolefins
The substance is a mix of liner C17 and branched C22 and each of the two key components were assessed.
The very low water solubility means that standard screening methods are not suitable.

Qualifier:

no guideline followed

Principles of method if other than guideline:

Use of BIOWin model to cofnrim low rate of biodegradation

Oxygen conditions:

aerobic

Inoculum or test system:

activated sludge, non-adapted

Remarks:

Model assumes non-adapted

Duration of test (contact time):

ca. 42 d

Parameter followed for biodegradation estimation:

DOC removal

Reference substance:

not required

Parameter:

probability of ready biodegradability (QSAR/QSPR)

Remarks on result:

not readily biodegradable based on QSAR/QSPR prediction

Parameter:

half-life in days (QSAR/QSPR)

Value:

ca. 29

Remarks on result:

readily biodegradable based on QSAR/QSPR prediction

Details on results:

Probability of Rapid Biodegradation (BIOWIN v4.10):
Biowin1 (Linear Model) : 0.8432
Biowin2 (Non-Linear Model) : 0.9562
Expert Survey Biodegradation Results:
Biowin3 (Ultimate Survey Model): 3.2334 (weeks )
Biowin4 (Primary Survey Model) : 4.0187 (days )
MITI Biodegradation Probability:
Biowin5 (MITI Linear Model) : 0.7465
Biowin6 (MITI Non-Linear Model): 0.8899
Anaerobic Biodegradation Probability:
Biowin7 (Anaerobic Linear Model): 0.4573
Ready Biodegradability Prediction: YES

Hydrocarbon Biodegradation (BioHCwin v1.01):
LOG BioHC Half-Life (days) : 1.4689
BioHC Half-Life (days) : 29.4350

Removal In Wastewater Treatment (recommended maximum 95%):
Total removal: 96.34 percent
Total biodegradation: 0.55 percent
Total sludge adsorption: 80.38 percent
Total to Air: 15.41 percent
(using 10000 hr Bio P,A,S)

Validity criteria fulfilled:

yes

Interpretation of results:

inherently biodegradable, not fulfilling specific criteria

Conclusions:

In view of low water solubility (< 0.01 mg/l), screening testing is considered meaninless
Publications indicate ultimate biodegradation for linear and branched olefins and modelling confirms slow but ultimate degradation under aerobic conditions.
Hydrcarbons are not considered 'P' Persistent.

Description of key information

The very low solubility in water makes this type of screening test difficult to perform and most research considers longer term biodegradation.

The class of substance is accepted to be ultimately biodegradable in water and waste treatment systems, but this will be a slow process determined by the bioavailablity of the substance in water.

REF: Abbasian, F., Lockington, R., Mallavarapu, M. and Naidu, R., 2015. A comprehensive review of aliphatic hydrocarbon biodegradation by bacteria. Applied Biochemistry and Biotechnology, 176(3), 670-699.

Modelling applied:

Hydrocarbon Biodegradation (BioHCwin v1.01):

    LOG BioHC Half-Life (days) :  1.4689

    BioHC Half-Life (days)    : 29.4350

 

Key value for chemical safety assessment

Biodegradation in water:

inherently biodegradable, not fulfilling specific criteria

Type of water:

freshwater