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Environmental fate & pathways

Biodegradation in water: screening tests

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Endpoint:
biodegradation in water: ready biodegradability
Type of information:
read-across from supporting substance (structural analogue or surrogate)
Adequacy of study:
key study
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: read-across from a guideline study
Justification for type of information:
The information is derived from Zenolide. The read across rationale is presented in the Biodegradation Enpoint summary. The accompanying files are also attached there.
Reason / purpose:
read-across source
Key result
Parameter:
% degradation (inorg. C analysis)
Value:
100
Sampling time:
28 d
Remarks on result:
other: read-across from Zenolide
Validity criteria fulfilled:
yes
Remarks:
Annex XI criteria are fulfilled presented in the read across rationale.
Interpretation of results:
readily biodegradable
Conclusions:
Oenanthic ether is readily biodegradable based on read across from Zenolide, which was teste in an OECDTG 301B.
Endpoint:
biodegradation in water: ready biodegradability
Type of information:
experimental study
Adequacy of study:
key study
Study period:
Between 24 July and 21 August 1997 (reported July 2000)
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: Reliability 1 is assigned because the study was conducted according to OECD TG 301, without deviations that influence the quality of the results.
Qualifier:
according to
Guideline:
OECD Guideline 301 B (Ready Biodegradability: CO2 Evolution Test)
GLP compliance:
yes
Oxygen conditions:
aerobic
Inoculum or test system:
other: Secondary effluent obtained from a laboratory rolling tube treatment unit which is fed on 100% settled sewage obtained from Newton Abbot sewage treatment works
Details on inoculum:
The inoculum used was secondary effluent obtained from a laboratory rolling tube treatment unit which is fed on 100% settled sewage obtained from Newton Abbot sewage treatment works, which treats sewage of predominantly domestic origin. This effluent was collected overnight on the day before the start of the test, after which it was filtered through a GF/C filter paper to remove any solids and sparged with nitrogen to reduce its dissolved inorganic carbon content to less than 1%. During sparging, its pH was maintained within the range 6.8-7.2 using mineral acid and alkali.
Duration of test (contact time):
28 d
Initial conc.:
10 mg/L
Based on:
ThIC
Parameter followed for biodegradation estimation:
inorg. C analysis
Details on study design:
The method uses septum sealed bottles with a 156 mL volume and measures the evolution of CO2 generated as a result of mineralisation of organic carbon arising from biodegradation. Each test bottle was filled with 95 mL inoculated mineral medium, made up to 100 mL with test substance or reference substance solution and/or water as applicable. After sparging the effluent was added to the test medium at 100 mL per litre of final medium. The bottles were sealed with butyl rubber septa and aluminium crimp caps and placed in an orbital incubator at a nominal test temperature of 20 ± 2°C. They were incubated for 28 days in the dark whilst being shaken at a nominal 150 rpm. Biodegradation was monitored by regular analysis of sacrificial test bottles to determine the amount of inorganic carbon evolved.

Reference substance:
aniline
Key result
Parameter:
% degradation (inorg. C analysis)
Value:
100
Sampling time:
28 d
Details on results:
The percentage biodegradation is expressed as a ratio of evolved carbon dioxide to the initial theoretical carbon added as test substance
Results with reference substance:
The reference substance, aniline, degraded by 100% (based on theoretical carbon concentration) during the 28 days of the test, confirming the viability of the inoculum. The total carbon content of the 258 mg aniline stock solution (theoretical 200 mg C/L) was measured as 166 mg C/L.

Test Article 97-215-03 meets the criterion outlined in the OECD guidelines, and can, therefore, be considered readily biodegradable.

Inorganic Carbon measurement and biodegradation results

Bottle contents

Inorganic Carbon (mg C/L)

Day 4

Day 7

Day 14

Day 21

Day 28

Blank control

0.59

0.80

1.1

1.0

1.5

0.65

0.76

1.0

1.1

1.4

0.67

0.75

1.1

1.1

1.7

Mean

0.64

0.77

1.1

1.1

1.5

Aniline (10 mg C/L)

6.1

7.0

8.6

8.1

9.7

5.9

7.6

8.7

7.9

9.6

5.7

6.7

8.0

7.8

8.8

Mean

5.9

7.1

8.4

7.9

9.4

Mean (blank corrected)

5.3

6.3

7.4

6.9

7.8

Total inorganic C in test bottle (mg)

0.84

1.0

1.2

1.1

1.3

% Biodegradation

84

101

118

110

125

Zenolide (10 mg C/L)

4.5

5.3

7.7

7.4

8.9

4.7

5.6

7.7

8.3

8.5

5.3

5.6

7.9

7.5

8.6

Mean

4.8

5.5

7.8

7.7

8.7

Mean (blank corrected)

4.2

4.7

6.7

6.7

7.1

Total inorganic C in test bottle (mg)

0.67

0.76

1.1

1.1

1.1

% Biodegradation

67

76

107

107

114

 

Validity criteria fulfilled:
yes
Interpretation of results:
readily biodegradable
Conclusions:
A 100% biodegradation of the test substance was observed within the 28-day test period in the CO2 evolution test fulfilling the 10-day time window criterion for ready biodegradable compounds.
Executive summary:

The ready biodegradability of the substance was determined in a study conducted according to OECD TG 301B (CO2 evolution test) and GLP. In this study, 10 mg/L of test substance (based on ThIC) is exposed for 28 days to secondary activated sludge from a wastewater plant treating predominantly domestic wastewater. After the 28-day exposure period 100% of the test substance was biodegraded. The pass level of 60% was reached within 4 days after the start of the test, and thus the 10-day time window criterion was met. Based on these findings, the test substance may be classified as readily biodegradable.

Description of key information

Oenanthic ether is readily biodegradable based on read across from Zenolide, which is tested in an OECD TG 301B.

Key value for chemical safety assessment

Biodegradation in water:
readily biodegradable
Type of water:
freshwater

Additional information

Ready biodegradability of Oenanthic ether is based on read-across from Zenolide's biodegradation information of which the summary is presented below.

Zenolide's ready biodegradability:

For Zenolide, the ready biodegradability of the substance was determined in a studyconducted according to OECD TG 301B (CO2 evolution test) and GLP. In this study, 10 mg/L of test substance (based on ThIC) is exposed for 28 days to secondary activated sludge from a wastewater plant treating predominantly domestic wastewater. After the 28-day exposure period 100% of the test substance was biodegraded. The pass level of 60% was reached within 4 days after the start of the test, and thus the 10-day time window criterion was met. Based on these findings, the substance is qualified as readily biodegradable.

Biodegradation of Oenanthic ether based on read across from data available for Zenolide (CAS #54982-83-1).

 

Introduction and hypothesis for the analogue approach

Oenanthic ether consists of 3 main constituents and a number of impurities. All are ethyl esters, despite the name ether, of long chain carboxylic acids. The major constituent has a C12 chain, the two minor ones have C14 and C16 saturated carbon chain. For Oenanthic ether there are no experimental biodegradation data available.In accordance with Article 13 of REACH, lacking information can be generated by means other than experimental testing, i.e. applying alternative methods such as QSARs, grouping and read-across.For assessing the biodegradation of Oenanthic ether, the analogue approach is selected becausefora close structural analogue, Zenolide, experimental data is available which can be used for read across.

Hypothesis: Oenanthic ether has the same ready biodegradability as Zenolide. The ready biodegradability of Zenolide is considered to be representative for all constituents and impurities of Oenanthic ether.

Available information: For Zenolide, the ready biodegradability of the substance was determined in a study conducted according to OECD TG 301B (CO2 evolution test, Rel. 1). In this study, 10 mg/L of test substance (based on ThIC) was exposed for 28 days to secondary activated sludge from a wastewater plant treating predominantly domestic wastewater. After the 28-day exposure period 100% of the test substance was biodegraded. The pass level of 60% was reached within 4 days after the start of the test, and thus the 10-day time window criterion was met and therefore Zenolide is readily biodegradable.

Target chemical and source chemical(s)

Chemical structures of the target chemical and the source chemical(s) are shown in the data matrix, including physico-chemical properties and available environmentalfateinformation. A full list of constituents and impurities of Oenanthic ether, including information relevant for read-across, is given in Appendix 1.

Purity / Impurities

The purity, and unidentified impurities, of Oenanthic ether and Zenolide are not expected to influence the potential for biodegradation.

Analogue approach justification

According to Annex XI 1.5 read across can be used to replace testing when the similarity can be based on a common backbone and a common functional group.When using read across the result derived should be applicable for C&L and/or risk assessment and it should be presented with adequate and reliable documentation, which is presented below.

Analogue selection: For Oenanthic ether Zenolide was selected as an analogue being a similar fatty acid type of acetic (ethyl) ester.

Structural similarities and differences: All constituents of Oenanthic ether and Zenolide contain ethyl esters and a long alkane chain (C8-C18 and C12, respectively) and therefore have a similar backbone and functional group: i.e. esters of long chain carboxylic acids. The difference is that all constituents of Oenanthic ether have linear alkyl chains, while Zenolide has a cyclic aliphatic alkyl chain, connected by Ethylene glycol, which will not affect the biodegradability.

Bioavailability: Oenanthic ether and Zenolide are fatty acid type of esters and based on their log Kows Oenanthic ether may be somewhat less bioavailable compared to Zenolide. After the ester cleavage this difference is not existing anymore and therefore will not affect the biodegradability.

Biodegradable fragments: Firstly the ester bond will be cleaved in both Oenanthic ether and Zenolide by abundantly available carboxyl esterases (Wheelock et al, 2008) resulting in fatty acids of >=C8 and ethanol in the case of Oenanthic ether and Ethylene glycol for Zenolide. These acids and alcohols all are readily biodegradable. This is further supported by Fisk et al. (2009) who has reviewed long chain alcohols for their biodegradability. During metabolism primary alcohols and acids can be easily converted into each other.

Further support for ready biodegradability using BIOWIN predictions:

BIOWIN (v4.10) predictions are made for both the Oenanthic ether and Zenolide to provide further insight on the biodegradation potential of these substances and the possible effect of structural differences on biodegradation. Only the BIOWIN modules 5 (‘MITI-linear’) and 6 (‘MITI-non-linear’) are used because these two models are based on ready biodegradability tests, which is the endpoint to be predicted.

 

Table: BIOWIN predictions for Oenanthic ether and Zenolide and the contribution of the fragments for the prediction of ready and non-ready biodegradability

Constituent/structural analogue

BIOWIN 5

BIOWIN 6

Ethyl octanoate

0.8901

0.9545

Ethyl decanoate

0.9055

0.9566

Ethyl dodecanoate

0.9208

0.9586

Ethyl tetradecanoate

0.9362

0.9605

Ethyl hexadecanoate

0.9516

0.9623

Ethyl octadecanoate

0.9670

0.9641

Ethyl (9Z)-octadec-9-enoate

0.8865

0.9273

Ethyl (9Z,12Z)octadeca,12di enoate

0.8060

0.8584

ZENOLIDE (structural analogue)

0.8737

0.9456

 

From these BIOWIN predictions it can be seen that the different constituents of Oenanthic ether as well as Zenolide have BIOWIN scores all exceeding 0.8 probability, which is well above the cut-off value of 0.5 and are therefore predicted to be readily biodegradable with high certainty.

Uncertainty of the prediction: As presented aboveZenolide has a lower log Kow value and a higher water solubility than Oenanthic ether. The substance is therefore likely to have higher bioavailability towards microorganisms in STP sludge and in the environment. This will not impact the ready biodegradability because long-chain hydrocarbons (hexadecane, ECHA website), alcohols (Fisk et al. 2009) and acids (SIDS dossier on Dodecanedioc acid) are known to be readily biodegradable. There are no other remaining uncertainties than already discussed above.

Data matrix

The relevant information on physico-chemical properties and environmental fate properties are presented in the data matrix below.

Conclusions for biodegradability

For Oenanthic ether no information on ready biodegradability is available and Zenolide information on this endpoint is used for read across.When using read across the result derived should be applicable for C&L and/or risk assessment and be presented with adequate and reliable documentation. This documentation is presented in the current. Zenolide is readily biodegradable and therefore Oenanthic ether is also readily biodegradable based on similarities in structure and degradation pathways.

Final conclusion on biodegradation: Oenanthic ether is readily biodegradable.

 

Data matrix presenting the information relevant for read across toOenanthic ether from Zenolide

References


Data matrix: Overview of data available for the different constituents of Oenanthic ether and the structural analogue Zenolide to support the read across for biodegradation

Chemical names for

 

Oenanthic ether#

ethyl octanoate (C8*)

ethyl decanoate (C10*)

ethyl dodecanoate (C12*)

ethyl tetra-decanoate (C14*)

ethyl hexa-decanoate (C16*)

ethyl octa-decanoate (C18*)

ethyl (9Z)-octadec-9-enoate (C18*)

ethyl (9Z,12Z)‐octadeca‐,12‐di enoate (C18*)

Zenolide

(‘C12’)

Target

 

 

 

 

 

 

 

 

Source

CAS#

106-32-1

110-38-3

106-33-2

124-06-1

628-97-7

111-61-5

544-35-4

111-62-6

5982-83-1

Structure

% in product

<10

<10

35-55

15-30

5-15

<10

<10

<10

 

EC No.

945-734-0#

 

 

 

 

 

 

 

 

259-423-6

Vp (Pa)

0.12 meas)#

 31.4

(est.)

 5.70

(est.)

 1.17

(est.)

 0.34

(est.)

0.036

(est.)

 0.0084

(est.)

 0.0081

(est.)

 0.0067

(est.)

0.028

 (exp.)

WS (mg/L)

1.6 (meas)#

 45.6

(est.)

 4.8

(est.)

 0.41

(est.)

 0.037

(est.)

 0.0037

(est.)

 0.0004

(est.)

 0.0006

(est.)

 0.0009

(est.)

75

 (exp.)

Log Kow

4.6 (meas)#

 3.8

(est.)

 4.8

(est.)

 5.8

(est.)

 6.8

(est.)

 7.7

(est.)

 8.4

(est.)

 8.5

(est.)

 8.3

(est.)

3.65

(exp.)

Fate

 

 

 

 

 

 

 

 

 

Readily Biodegradability

Readily (Read across)

Readily (Read across)

Readily (Read across)

Readily (Read across)

Readily (Read across)

Readily (Read across)

Readily (Read across)

Readily (Read across)

Readily biodegradable (OECDTG 301F)

*The C’s are related to the chain length not the overall number of Cs (as would be presented in the Empirical formula); (est.) = estimated using EpiSuite; (exp.) = experimental;#In this column the values are for Oenanthic ether as such.

 

References

Dodecanedioc acid, SIDS dosser, Cas no. 693-23-2,http://www.inchem.org/documents/sids/sids/693232.pdf,

 

Fisk, P.R., Wildey, R.J., Girling, A.E., Sanderson, H., Belanger, S.E., Veenstra, G., Nielsen, A., Kasai, Y., Willing, A., Dyer, S.D., Stanton, K., 2009, Environmental properties of long chain alcohols. Part 1: Physicochemical, environmental fate and acute aquatic toxicity properties, Ecotoxicol Environ Saf., 72, 980-95.

 

Hexadecane, ECHA website:https://echa.europa.eu/nl/registration-dossier/-/registered-dossier/12643

 

Wheelock, C.E., Philips, B.M., Anderson, B.S., Miller, J.L., Miller, M.J., and Hammock, B.D., 2008, Application of carboxylesterase activity in environmental monitoring and toxicity identification evaluations, (TIEs), in Reviews of Environmental Contamination an Toxicology, ed. Whitacre, 117-178, D.M., Springer.