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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:

weight of evidence

Study period:

14 November 2017 to 15 January 2018

Reliability:

1 (reliable without restriction)

Justification for type of information:

Reliable experimental study following OECD 301 guidelines (1992) and EC No. 440/2008 Method C.4-C adopted 2008 and GLP standards.

Qualifier:

according to guideline

Guideline:

OECD Guideline 301 B (Ready Biodegradability: CO2 Evolution Test)

Version / remarks:

1992

Deviations:

no

Qualifier:

according to guideline

Guideline:

EU Method C.4-C (Determination of the "Ready" Biodegradability - Carbon Dioxide Evolution Test)

Version / remarks:

2008

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Specific details on test material used for the study:

The test substance is listed as ATHC. The test substance is a pale yellow slightly viscous liquid. The test substance was obtained from the Sponsor, Vertellus Holdings LLC and stored at room temperature in the dark.

Oxygen conditions:

aerobic

Inoculum or test system:

activated sludge, domestic (adaptation not specified)

Details on inoculum:

A mixed population of activated sewage sludge micro-organisms was obtained on 13 November 2017 from the aeration stage of the Severn Trent Water Plc sewage treatment plant at Loughborough, Leicestershire, UK, which treats predominantly domestic sewage.

Duration of test (contact time):

60 d

Initial conc.:

15.6 mg/L

Based on:

test mat.

Initial conc.:

10 mg/L

Based on:

TOC

Parameter followed for biodegradation estimation:

CO2 evolution

Details on study design:

The test item, at a concentration of 10 mg carbon/L, was exposed to activated sewage sludge micro-organisms with mineral medium in sealed culture vessels in the dark at measured temperatures of between 20 and 24 °C for 60 days. At the request of the Sponsor the study was extended from 28 to 60 days. The biodegradation of the test item was assessed by the determination of carbon dioxide produced. Control solutions with inoculum and the reference item, sodium benzoate, together with a toxicity control were used for validation purposes.

Reference substance:

benzoic acid, sodium salt

Key result

Parameter:

% degradation (CO2 evolution)

Value:

26

Sampling time:

28 d

Key result

Parameter:

% degradation (CO2 evolution)

Value:

42

Sampling time:

60 d

Details on results:

The test item attained 26% biodegradation after 28 days and 42% biodegradation after 60 days and therefore cannot be considered to be readily biodegradable under the strict terms and conditions of OECD Guideline No. 301B.

Validity criteria fulfilled:

yes

Remarks:

IC content < 5% (protocol ≤ 5%); CO2 emitted by controls 33.52 mg/L (protocol <70 mg/L; difference reps. <20% (protocol ≤20 %); degradation positive control 80% at 14 d (protocol ≤14 d to achieve >60%); degradation toxicity d 14, 49% (protocol > 25%).

Interpretation of results:

not readily biodegradable

Conclusions:

The test item attained 26% biodegradation after 28 days and 42% biodegradation after 60 days and therefore cannot be considered to be readily biodegradable under the strict terms and conditions of OECD Guideline No. 301B.

Reference 2

Endpoint:

biodegradation in water: screening test, other

Type of information:

(Q)SAR

Remarks:

(Q)SAR BIOWINv4.10

Adequacy of study:

weight of evidence

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 adequate and reliable documentation / justification

Justification for type of information:

Modeling report of BIOWIN v4.10, a model contained within EPI-Suite version 4.1, a reliable (Q)SAR model.

Qualifier:

no guideline followed

Principles of method if other than guideline:

BIOWIN v4.10 a model with U.S. EPA's EPI-Suite, a reliable QSAR model included in the OECD QSAR Toolbox.

GLP compliance:

no

Remarks:

Not Applicable.

Parameter followed for biodegradation estimation:

other:

Remarks:

(Q)SAR Model biodegradation prediction.

Key result

Parameter:

probability of ready biodegradability (QSAR/QSPR)

Remarks:

BIOWIN5 Value

Value:

> 0.5

Sampling time:

28 d

Remarks on result:

readily biodegradable based on QSAR/QSPR prediction

Remarks:

BIOWIN 5 prediction of 1.5486 is > 0.5, indicating that the substance biodegrades fast.

BIOWIN (v4.10) Program Results:

==============================

SMILES : O=C(C(CC(=O)OCCCCCC)(CC(=O)OCCCCCC)OC(=O)C)OCCCCCC

CHEM : 1,2,3-Propanetricarboxylic acid, 2-(acetyloxy)-, trihexyl ester

MOL FOR: C26 H46 O8

MOL WT : 486.65

--------------------------- BIOWIN v4.10 Results ----------------------------

Biowin1 (Linear Model Prediction) : Biodegrades Fast

Biowin2 (Non-Linear Model Prediction): Biodegrades Fast

Biowin3 (Ultimate Biodegradation Timeframe): Days-Weeks

Biowin4 (Primary Biodegradation Timeframe): Hours-Days

Biowin5 (MITI Linear Model Prediction) : Biodegrades Fast

Biowin6 (MITI Non-Linear Model Prediction): Biodegrades Fast

Biowin7 (Anaerobic Model Prediction): Does Not Biodegrade Fast

Ready Biodegradability Prediction: YES

------+-----+--------------------------------------------+---------+---------

TYPE | NUM | Biowin1 FRAGMENT DESCRIPTION | COEFF | VALUE

------+-----+--------------------------------------------+---------+---------

Frag | 3 | Linear C4 terminal chain [CCC-CH3] | 0.1084 | 0.3253

Frag | 4 | Ester [-C(=O)-O-C] | 0.1742 | 0.6967

Frag | 1 | Carbon with 4 single bonds & no hydrogens | -0.1839 | -0.1839

MolWt| * | Molecular Weight Parameter | | -0.2317

Const| * | Equation Constant | | 0.7475

============+============================================+=========+=========

RESULT | Biowin1 (Linear Biodeg Probability) | | 1.3539

============+============================================+=========+=========

------+-----+--------------------------------------------+---------+---------

TYPE | NUM | Biowin2 FRAGMENT DESCRIPTION | COEFF | VALUE

------+-----+--------------------------------------------+---------+---------

Frag | 3 | Linear C4 terminal chain [CCC-CH3] | 1.8437 | 5.5311

Frag | 4 | Ester [-C(=O)-O-C] | 4.0795 | 16.3180

Frag | 1 | Carbon with 4 single bonds & no hydrogens | -1.7232 | -1.7232

MolWt| * | Molecular Weight Parameter | | -6.9105

============+============================================+=========+=========

RESULT | Biowin2 (Non-Linear Biodeg Probability) | | 1.0000

============+============================================+=========+=========

A Probability Greater Than or Equal to 0.5 indicates --> Biodegrades Fast

A Probability Less Than 0.5 indicates --> Does NOT Biodegrade Fast

------+-----+--------------------------------------------+---------+---------

TYPE | NUM | Biowin3 FRAGMENT DESCRIPTION | COEFF | VALUE

------+-----+--------------------------------------------+---------+---------

Frag | 3 | Linear C4 terminal chain [CCC-CH3] | 0.2983 | 0.8950

Frag | 4 | Ester [-C(=O)-O-C] | 0.1402 | 0.5608

Frag | 1 | Carbon with 4 single bonds & no hydrogens | -0.2121 | -0.2121

MolWt| * | Molecular Weight Parameter | | -1.0754

Const| * | Equation Constant | | 3.1992

============+============================================+=========+=========

RESULT | Biowin3 (Survey Model - Ultimate Biodeg) | | 3.3675

============+============================================+=========+=========

------+-----+--------------------------------------------+---------+---------

TYPE | NUM | Biowin4 FRAGMENT DESCRIPTION | COEFF | VALUE

------+-----+--------------------------------------------+---------+---------

Frag | 3 | Linear C4 terminal chain [CCC-CH3] | 0.2691 | 0.8072

Frag | 4 | Ester [-C(=O)-O-C] | 0.2290 | 0.9158

Frag | 1 | Carbon with 4 single bonds & no hydrogens | -0.1534 | -0.1534

MolWt| * | Molecular Weight Parameter | | -0.7021

Const| * | Equation Constant | | 3.8477

============+============================================+=========+=========

RESULT | Biowin4 (Survey Model - Primary Biodeg) | | 4.7152

============+============================================+=========+=========

Result Classification: 5.00 -> hours 4.00 -> days 3.00 -> weeks

(Primary & Ultimate) 2.00 -> months 1.00 -> longer

------+-----+--------------------------------------------+---------+---------

TYPE | NUM | Biowin5 FRAGMENT DESCRIPTION | COEFF | VALUE

------+-----+--------------------------------------------+---------+---------

Frag | 4 | Ester [-C(=O)-O-C] | 0.3437 | 1.3749

Frag | 1 | Carbon with 4 single bonds & no hydrogens | 0.0676 | 0.0676

Frag | 4 | Methyl [-CH3] | 0.0004 | 0.0016

Frag | 17 | -CH2- [linear] | 0.0494 | 0.8401

MolWt| * | Molecular Weight Parameter | | -1.4478

Const| * | Equation Constant | | 0.7121

============+============================================+=========+=========

RESULT | Biowin5 (MITI Linear Biodeg Probability) | | 1.5486

============+============================================+=========+=========

------+-----+--------------------------------------------+---------+---------

TYPE | NUM | Biowin6 FRAGMENT DESCRIPTION | COEFF | VALUE

------+-----+--------------------------------------------+---------+---------

Frag | 4 | Ester [-C(=O)-O-C] | 2.4462 | 9.7846

Frag | 1 | Carbon with 4 single bonds & no hydrogens | 0.3990 | 0.3990

Frag | 4 | Methyl [-CH3] | 0.0194 | 0.0777

Frag | 17 | -CH2- [linear] | 0.4295 | 7.3014

MolWt| * | Molecular Weight Parameter | |-14.0490

============+============================================+=========+=========

RESULT |Biowin6 (MITI Non-Linear Biodeg Probability)| | 0.9976

============+============================================+=========+=========

A Probability Greater Than or Equal to 0.5 indicates --> Readily Degradable

A Probability Less Than 0.5 indicates --> NOT Readily Degradable

------+-----+--------------------------------------------+---------+---------

TYPE | NUM | Biowin7 FRAGMENT DESCRIPTION | COEFF | VALUE

------+-----+--------------------------------------------+---------+---------

Frag | 3 | Linear C4 terminal chain [CCC-CH3] | -0.3177 | -0.9532

Frag | 4 | Ester [-C(=O)-O-C] | 0.1719 | 0.6874

Frag | 1 | Carbon with 4 single bonds & no hydrogens | -0.3342 | -0.3342

Frag | 4 | Methyl [-CH3] | -0.0796 | -0.3183

Frag | 17 | -CH2- [linear] | 0.0260 | 0.4418

Const| * | Equation Constant | | 0.8361

============+============================================+=========+=========

RESULT | Biowin7 (Anaerobic Linear Biodeg Prob) | | 0.3596

============+============================================+=========+=========

A Probability Greater Than or Equal to 0.5 indicates --> Biodegrades Fast

A Probability Less Than 0.5 indicates --> Does NOT Biodegrade Fast

Ready Biodegradability Prediction: (YES or NO)

Criteria for the YES or NO prediction: If the Biowin3 (ultimate survey

model) result is "weeks" or faster (i.e. "days", "days to weeks", or

"weeks" AND the Biowin5 (MITI linear model) probability is >= 0.5, then

the prediction is YES (readily biodegradable). If this condition is not

satisfied, the prediction is NO (not readily biodegradable). This method

is based on application of Bayesian analysis to ready biodegradation data

(see Help). Biowin5 and 6 also predict ready biodegradability, but for

degradation in the OECD301C test only; using data from the Chemicals

Evaluation and Research Institute Japan (CERIJ) database.

Validity criteria fulfilled:

yes

Remarks:

Validated QSAR, part of the OECD (Q)SAR Toolbox

Interpretation of results:

readily biodegradable

Conclusions:

The BIOWIN v4.10 model predicted that the substance is readily biodegradable. The BIOWIN1 value = 1.3539 and the BIOWIN2 value = 1.000 were both greater than 0.5 and indicated fast biodegradation. The BIOWIN3 value = 3.3675 indicated a timeframe of days to weeks to ultimate biodegradation, and the BIOWIN4 value of 4.7152 indicated a timeframe of hours to days to primary degradation. The BIOWIN5 value = 1.5486 and the BIOWIN6 value = 0.9976 were both greater than 0.5, and both indicated the substance is readily biodegradable. The BIOWIN7 value of 0.35961 was less than 0.5, and indicated that it does not biodegrade fast under anaerobic conditions.

Description of key information

The test substance has been shown to exhibit inherent, primary degradability and significant mineralisation in the environment, based on a weight-of-evidence demonstration.  Although the substance did not exhibit ready degradability in a CO₂ evolution test conducted in accordance with OECD Guideline 301B, degradation rates of 26% in 28 days and 42% in 60 days were observed.  In accordance with ECHA guidance, the observed degradation rate is evidence of inherent, primary degradability (i.e., degradation of 20% or more in a biodegradability assay) and significant mineralisation (>40% degradation).   Additionally, a validated QSAR model (EPI Suite BIOWIN 4.10) predicted that the substance is readily biodegradable, based on two modules within the model: BIOWIN 3, which predicts ultimate degradation of the substance in the timeframe of “days-weeks”, and BIOWIN 5, which predicts that the substance “biodegrades fast” with a probability > 0.5. Three additional modules within the model (BIOWIN 1, BIOWIN 2 and BIOWIN 6) predict that the substance “biodegrades fast”; one module (BIOWIN 4) predicts that primary degradation occurs within the timeframe of “hours-days”.  Thus, the substance exhibits inherent, primary degradability in a laboratory test and is not refractory to ultimate degradation as indicated by QSAR predictions based on structural components of the substance.  Therefore, although the substance has not been shown to be readily biodegradable and may exhibit limited persistence in the environment,  there are no structural impediments to its aerobic degradation and has been shown to undergo significant mineralisation under strict conditions.  Therefore, the substance is not expected to be highly persistent in the environment based on multiple lines of evidence.

Key value for chemical safety assessment

Biodegradation in water:

inherently biodegradable

Type of water:

freshwater