Hydrocarbons, C11-C13 (odd numbered), n-alkanes, <2% aromatics

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:

key study

Study period:

28 Jul - 25 Aug 2010

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: GLP guideline study with acceptable restrictions: The substance is classified as readily biodegradable in the 10 day window although the 10 day window was not passed.

Qualifier:

according to guideline

Guideline:

OECD Guideline 310 (Ready Biodegradability - CO2 in Sealed Vessels (Headspace Test)

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Oxygen conditions:

aerobic

Inoculum or test system:

activated sludge, domestic, non-adapted

Details on inoculum:

- Source of inoculum/activated sludge: obtained from the sewage plant at Hildesheim (Germany), which predominantely treats municipal sewage
- Pretreatment: The activated sludge was washed twice with autoclaved tap water.After the second washing the settled sludge was resuspended in
mineral salts medium and was maintained in an aerobic condition by aeration for 3 hours. Thereafter the sludge was homogenized with a blender . The supernatant was decanted and was maintained in an aerobic condition by aeration with CO2-free air for 4 days. Then it was filtered through a fol ded filter and aeration continued for 1 day until test start. 10 mL/L were used to intiate inoculation.
- Initial cell/biomass concentration: 10E5 - 10E8 CFU/L
- Water filtered: yes
- Type and size of filter used, if any: folded filter

Duration of test (contact time):

28 d

Initial conc.:

20 mg/L

Based on:

TOC

Initial conc.:

23.5 mg/L

Based on:

test mat.

Parameter followed for biodegradation estimation:

CO2 evolution

Details on study design:

TEST CONDITIONS
- Composition of medium: mineral medium according to guideline
- Test temperature: 20 - 22 °C
- Continuous darkness: yes

TEST SYSTEM
- Culturing apparatus: 120 mL headspace flasks
- Number of culture flasks/concentration: 3 (test end 5 replicates)
- Method used to create aerobic conditions:
- Measuring equipment: Determination of CO2 was carried out by IC analysis with a carbon analyser according to DIN EN 1484
- Other: The test vessels were stirred throught the test (150 - 200 rpm) at low light conditions

SAMPLING
- Sampling frequency: at day 0, 1, 5, 7, 9, 14, 21 and 28
- Sampling method: Sodium hydroxide solution (0.74 mL 7 mol/L solution to 80 mLmedium) was injected to each vessel sampled. The vessels were shaken on an overhead shaker (100 rpm) for 1 h at test temperature. Suitable volumes of the liquid phase were analyzed.

CONTROL AND BLANK SYSTEM
- Abiotic sterile control: yes

Reference substance:

benzoic acid, sodium salt

Remarks:

17.5 mg TOC/L

Key result

Parameter:

% degradation (CO2 evolution)

Value:

78

Sampling time:

28 d

Remarks on result:

other: CI: 77 - 79%

Details on results:

7d: 52%
14d: 61%
21d: 68%

Results with reference substance:

The percentage degradation of the functional control reached the pass level of 60% after 4 days and came to 90% after 28 days. The 95% confidence interval on day 28 was 88 - 92%.

Validity criteria fulfilled:

yes

Interpretation of results:

readily biodegradable, but failing 10-day window

Conclusions:

The test substance reached a biodegradation of 78% in 28 days. The 10-day-window was not passed. However, for substances with different chain lengths the 10-day window should not be used for the interpretation of the results. Therefore, the test substance is judged to be readily biodegradable.

Executive summary:

The ready biodegradability of the test substance was tested according to OECD guideline 310 under GLP conditions. Non-adapted municipal activated sludge was used as inoculum. The test substance was tested at a concentration of 23.5 mg/L in triplicates.

The 10% level was reached after 2 days and the 60% pass level after 14 days. Thus, the 10-day-window was not achieved (according to biodegradation curve). According to “OECD Guidelines for the testing of chemicals – Revised introduction to the OECD guidelines for testing of chemicals, Section 3 – Part 1: Principles and strategies related to the testing of degradation of organic chemicals degradation” published by OECD (2006) the ready biodegradability data for mixtures should be evaluated carefully. For substances with different chain lengths the 10-day window should not be used for the interpretation of the results. It is possible that a sequential biodegradation took place which might have led to a prolonged lag-Phase and therefore a slower biodegradation period although the test substance was biodegraded in a large amount after the test duration. In this case the pass level can be applied at 28 days. The test substance was biodegraded 78% after 28 days. Therefore, the test substance is readily biodegradable.

Reference 2

Endpoint:

biodegradation in water: ready biodegradability

Type of information:

experimental study

Adequacy of study:

supporting study

Study period:

28 Jan - 04 Mar 2010

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: GLP guideline study

Qualifier:

according to guideline

Guideline:

other: ISO 10708 adopted in 1997

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Oxygen conditions:

aerobic

Inoculum or test system:

activated sludge, domestic, non-adapted

Details on inoculum:

- Source of inoculum/activated sludge: obtained from the sewage plant at Hildesheim (Germany), which predominantely treats municipal sewage
- Pretreatment: The activated sludge was washed twice with autoclaved tap water. After the second washing the settled sludge was filled up with
mineral salts medium, the sludge was homogenized with a blender for 2 min and filtered through a folded filter. 50 mL/L were used to intiate inoculation.
- Initial cell/biomass concentration: 6.9E8 CFU/L
- Water filtered: yes
- Type and size of filter used, if any: folded filter

Duration of test (contact time):

28 d

Initial conc.:

29 mg/L

Based on:

test mat.

Parameter followed for biodegradation estimation:

O2 consumption

Details on study design:

TEST CONDITIONS
- Composition of medium: mineral medium according to guideline
- Test temperature: 20 - 21 °C
- Continuous darkness: yes
- Other: agitation on rotary shaker (125 - 175 rpm)

TEST SYSTEM
- Culturing apparatus: 300 mL BOD bottles with stoppers
- Number of culture flasks/concentration: 3
- pH: 6.82 - 7.35
- pH adjusted: no
- Measuring equipment: Oximeter , HQ 40d multi

SAMPLING
- Sampling frequency: on day 0, 4, 7, 11, 14, 18, 21, 26 and 28
- Sampling method: Prior to the measurement, each bottle was shaken vigorously by hand for about 30 sec. The oxygen concentration of each incubation vessel was measured successively. Afterwards the BOD bottles were aerated for 15 min and the oxygen concentration was measured again.

CONTROL AND BLANK SYSTEM
- Inoculum blank: yes
- Abiotic sterile control: yes
- Toxicity control: yes

Reference substance:

benzoic acid, sodium salt

Remarks:

60 mg/L

Parameter:

% degradation (O2 consumption)

Value:

49

Sampling time:

28 d

Details on results:

7d: 34%
14d: 43%
21d: 49%

Parameter:

COD

Value:

3.477 g O2/g test mat.

Results with reference substance:

In the case of the functional control, the adaptation phase transformed to a degradation phase after 1 day (degradation > 10 %). The 60 % pass level was reached after 4 days and the biodegradation reached a maximum of 91 % after 28 days.

The biodegradation rate of the inhibitory control came to 56 % after 14 days and 62 % deqradation were reached after 28 days. The biodegradation of the reference item was not inhibited by the test substance in the toxicity control.

Validity criteria fulfilled:

yes

Interpretation of results:

inherently biodegradable

Conclusions:

The test substance reached the 10 % level after 1 day. The pass level of biodegradation of > 60 % was not reached until day 28. The mean degradation came to a maximum of 49 % after 28 days.

Executive summary:

The ultimate aerobic biodegradability of the test substance was determined in the Two-Phase Closed Bottle Test with a non adapted activated sludge over a period of 28 days. The study was conducted according to ISO 10708 under GLP conditions. The test substance concentration selected as appropriate was 29 mg/L, corresponding to 5.8 mg test substance per vessel. Accordingly the ThOD was 100.8 mg O2/L in the test vessel. The degradation was followed by measuring the decrease of the dissolved oxygen concen tration. It is expressed as the percentage ThOD and was calculated for each oxygen analysis. In order to check the activity ot the test system , sodium benzoate was used as functional control. The 60 % pass level was reached after 4 days and the biodegradation rea ched a maximum of 91 % after 28 days. In the inhibitory control containing both test and reference substance 56 % degradation occurred within 14 days and 62 % degradation were reached after 28 days. The biodegradation of the reference substance was not inhibited by the test substance. The test substance reached the 10 % level after 1 day. The pass level of biodegradation of > 60 % was not reached until day 28. The mean degradation came to a maximum of 49 % after 28 days.

Reference 3

Endpoint:

biodegradation in water: screening tests

Type of information:

(Q)SAR

Adequacy of study:

supporting study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: Validated QSAR model. Calculation for main component of Hydrocarbons, C11-C13 (odd numbered), n-alkanes

Justification for type of information:

QSAR prediction: see QMRF and QPRF in overall remarks and executive summary

Principles of method if other than guideline:

Calculation based on BIOWIN v4.10, Estimation Programs Interface Suite™ for Microsoft® Windows v 4.10. US EPA, United States Environmental Protection Agency, Washington, DC, USA.

GLP compliance:

no

Oxygen conditions:

aerobic

Inoculum or test system:

activated sludge (adaptation not specified)

Details on results:

For detailed description on the model and its applicability, see "Any other information on materials and methods incl. tables".

 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): 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	2	Linear C4 terminal chain [CCC-CH3]	0.1084	0.2169
MolWt	*	Molecular Weight Parameter		-0.0744
Const	*	Equation Constant		0.7475
RESULT		Biowin1 (Linear Biodeg Probability)		0.8900

 

TYPE	NUM	Biowin2 FRAGMENT DESCRIPTION	COEFF	VALUE
Frag	2	Linear C4 terminal chain [CCC-CH3]	1.8437	3.6874
MolWt	*	Molecular Weight Parameter		-2.2197
RESULT		Biowin2 (Non-Linear Biodeg Probability)		0.9888

 

TYPE	NUM	Biowin3 FRAGMENT DESCRIPTION	COEFF	VALUE
Frag	2	Linear C4 terminal chain [CCC-CH3]	0.2983	0.5967
MolWt	*	Molecular Weight Parameter		-0.3454
Const	*	Equation Constant		3.1992
RESULT		Biowin3 (Survey Model – Ultimate Biodeg)		3.4504

 

TYPE	NUM	Biowin4 FRAGMENT DESCRIPTION	COEFF	VALUE
Frag	2	Linear C4 terminal chain [CCC-CH3]	0.2691	0.5381
MolWt	*	Molecular Weight Parameter		-0.2255
Const	*	Equation Constant		3.8477
RESULT		Biowin4 (Survey Model - Primary Biodeg)		4.1604

 

TYPE	NUM	Biowin5 FRAGMENT DESCRIPTION	COEFF	VALUE
Frag	2	Methyl [-CH3]	0.0004	0.0008
Frag	9	-CH2- [linear]	0.0494	0.4447
MolWt	*	Molecular Weight Parameter		-0.4650
Const	*	Equation Constant		0.7121
RESULT		Biowin5 (MITI Linear Biodeg Probability)		0.6927

 

TYPE	NUM	Biowin6 FRAGMENT DESCRIPTION	COEFF	VALUE
Frag	2	Methyl [-CH3]	0.0194	0.0389
Frag	9	-CH2- [linear]	0.4295	3.8654
MolWt	*	Molecular Weight Parameter		-4.5126
RESULT		Biowin6 (MITI Non-Linear Biodeg Probability)		0.8718

 

Interpretation of results:

readily biodegradable

Executive summary:

QPRF: BIOWIN v4.10

1.	Substance	See “Test material identity”
2.	General information
2.1	Date of QPRF	See “Data Source (Reference)”
2.2	QPRF author and contact details	See “Data Source (Reference)”
3.	Prediction
3.1	Endpoint (OECD Principle 1)	Endpoint				Biodegradability
		Dependent variable				Biodegradability
3.2	Algorithm (OECD Principle 2)	Model or submodel name				BIOWIN
		Model version				v. 4.10
		Reference to QMRF				QMRF: Estimation of Aerobic Biodegradability using BIOWIN v4.10 (EPI Suite v4.11): BIOWIN1 to BIOWIN6 and Ready Biodegradability Prediction
		Predicted value (model result)				See “Results and discussion”
		Input for prediction				- Chemical structure via CAS number or SMILES
		Descriptor values				- Structure fragments - Molecular weight
3.3	Applicability domain (OECD principle 3)	Domains (Appendix D, On-Line BIOWIN User’s Guide):
		1) Molecular weight				See below (Assessment of estimation domain)
		2) Fragments:				See below (Assessment of estimation domain)
3.4	The uncertainty of the prediction (OECD principle 4)	Parameter	BIOWIN model
			1	2	3		4	5	6
		Total correct	264 / 295	275 / 295	167 / 200		165 / 200	485 / 589	488 / 589
		% correct, total	89.5	93.2	83.5		82.5	82.3	82.9
		% correct, fast	97.3 (181 / 186)	97.3 (181 / 186)	93.5 (101 / 108)		84.9 (101 / 119)	79.1 (201 / 254)	80.3 (204 / 254)
3.5	The chemical mechanisms according to the model underpinning the predicted result (OECD principle 5)	The chemical structure influences the biodegradability of the substance. Therefore, chemical fragments were selected having a potential effect on biodegradability. In order to be able to predict the biodegradability probability of substances without these specific fragments, the molecular weight was integrated into the models.

 

References

- US EPA (2012). On-Line BIOWIN User’s Guide.

 

 

Assessment of estimation domain (molecular weight, fragments):

Model:	BIOWIN v4.10
Substance:	Undecane
CAS-#:	1120-21-4
SMILES:	C(CCCCCCCCC)C
Molecular weight (g/mol):	156,31
AppendixD - Fragment Coefficients for Biodegradation Models
BIOWIN1 and BIOWIN2: Linear / Non-Linear Biodegradability
Fragment description	Coefficient			Training set fragment count					No. of instances of each bond found for the current substance
	Linear	Non-linear		Min		Max	No. of compounds in training set containing the fragment		.
Linear C4 terminal chain [CCC-CH3]	0,10843	1,8437		-		3	44		2
Molecular Weight	---	---		31,06		697,7			in range
.
BIOWIN3 and BIOWIN4: Ultimate / Primary biodegradability
Fragment description	Coefficient				Training set fragment count				No. of instances of each bond found for the current substance
	Ultimate	Primary			Min	Max		No. of compounds in training set containing the fragment	.
Linear C4 terminal chain [CCC-CH3]	0,29834	0,26907			-	3		26	2
Molecular Weight	---	---			53,06	697,65		-	in range
.
BIOWIN5 and BIOWIN6: MITI Biodegradability Coefficients (Linear / Non-Linear)
Fragment description	Coefficient				Training set fragment count				No. of instances of each bond found for the current substance
	Linear	Non-Linear			Min	Max		No. of compounds in training set containing the fragment	.
Methyl [-CH3]	0,000411	0,01942827			-	9		295	2
-CH2- [linear]	0,049416	0,42949426			-	51		214	9
Molecular Weight	---	---			30,02	959,2		-	in range
.
BIOWIN7: Anaerobic Biodegradation Coefficients
Fragment description	Coefficient		Training set fragment count						No. of instances of each bond found for the current substance
			Min			Max		No. of compounds in training set containing the fragment
Linear C4 terminal chain [CCC-CH3]	-0,317727891	---	-			3		41	2
Methyl [-CH3]	-0,079572183	---	-			4		86	2
-CH2- [linear]	0,025989832	---	-			44		67	9
Molecular Weight	---	---	46,07			885,46			in range

Reference 4

Endpoint:

biodegradation in water: screening tests

Type of information:

(Q)SAR

Adequacy of study:

supporting study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: Validated QSAR model. Calculation for main component of Hydrocarbons, C11-C13 (odd numbered), n-alkanes

Justification for type of information:

QSAR prediction: see QMRF and QPRF in overall remarks and executive summary

Principles of method if other than guideline:

Calculation based on BIOWIN v4.10, Estimation Programs Interface Suite™ for Microsoft® Windows v 4.10. US EPA, United States Environmental Protection Agency, Washington, DC, USA.

GLP compliance:

no

Oxygen conditions:

aerobic

Inoculum or test system:

activated sludge (adaptation not specified)

 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): 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	2	Linear C4 terminal chain [CCC-CH3]	0.1084	0.2169
MolWt	*	Molecular Weight Parameter		-0.0878
Const	*	Equation Constant		0.7475
RESULT		Biowin1 (Linear Biodeg Probability)		0.8766

 

TYPE	NUM	Biowin2 FRAGMENT DESCRIPTION	COEFF	VALUE
Frag	2	Linear C4 terminal chain [CCC-CH3]	1.8437	3.6874
MolWt	*	Molecular Weight Parameter		-2.6180
RESULT		Biowin2 (Non-Linear Biodeg Probability)		0.9833

 

TYPE	NUM	Biowin3 FRAGMENT DESCRIPTION	COEFF	VALUE
Frag	2	Linear C4 terminal chain [CCC-CH3]	0.2983	0.5967
MolWt	*	Molecular Weight Parameter		-0.4074
Const	*	Equation Constant		3.1992
RESULT		Biowin3 (Survey Model – Ultimate Biodeg)		3.3884

 

TYPE	NUM	Biowin4 FRAGMENT DESCRIPTION	COEFF	VALUE
Frag	2	Linear C4 terminal chain [CCC-CH3]	0.2691	0.5381
MolWt	*	Molecular Weight Parameter		-0.2660
Const	*	Equation Constant		3.8477
RESULT		Biowin4 (Survey Model - Primary Biodeg)		4.1199

 

TYPE	NUM	Biowin5 FRAGMENT DESCRIPTION	COEFF	VALUE
Frag	2	Methyl [-CH3]	0.0004	0.0008
Frag	9	-CH2- [linear]	0.0494	0.5436
MolWt	*	Molecular Weight Parameter		-0.5485
Const	*	Equation Constant		0.7121
RESULT		Biowin5 (MITI Linear Biodeg Probability)		0.7080

 

TYPE	NUM	Biowin6 FRAGMENT DESCRIPTION	COEFF	VALUE
Frag	2	Methyl [-CH3]	0.0194	0.0389
Frag	9	-CH2- [linear]	0.4295	4.7244
MolWt	*	Molecular Weight Parameter		-5.3225
RESULT		Biowin6 (MITI Non-Linear Biodeg Probability)		0.8772

 

Interpretation of results:

readily biodegradable

Executive summary:

QPRF: BIOWIN v4.10

1.	Substance	See “Test material identity”
2.	General information
2.1	Date of QPRF	See “Data Source (Reference)”
2.2	QPRF author and contact details	See “Data Source (Reference)”
3.	Prediction
3.1	Endpoint (OECD Principle 1)	Endpoint				Biodegradability
		Dependent variable				Biodegradability
3.2	Algorithm (OECD Principle 2)	Model or submodel name				BIOWIN
		Model version				v. 4.10
		Reference to QMRF				QMRF: Estimation of Aerobic Biodegradability using BIOWIN v4.10 (EPI Suite v4.11): BIOWIN1 to BIOWIN6 and Ready Biodegradability Prediction
		Predicted value (model result)				See “Results and discussion”
		Input for prediction				- Chemical structure via CAS number or SMILES
		Descriptor values				- Structure fragments - Molecular weight
3.3	Applicability domain (OECD principle 3)	Domains (Appendix D, On-Line BIOWIN User’s Guide):
		1) Molecular weight				See below (Assessment of estimation domain)
		2) Fragments:				See below (Assessment of estimation domain)
3.4	The uncertainty of the prediction (OECD principle 4)	Parameter	BIOWIN model
			1	2	3		4	5	6
		Total correct	264 / 295	275 / 295	167 / 200		165 / 200	485 / 589	488 / 589
		% correct, total	89.5	93.2	83.5		82.5	82.3	82.9
		% correct, fast	97.3 (181 / 186)	97.3 (181 / 186)	93.5 (101 / 108)		84.9 (101 / 119)	79.1 (201 / 254)	80.3 (204 / 254)
3.5	The chemical mechanisms according to the model underpinning the predicted result (OECD principle 5)	The chemical structure influences the biodegradability of the substance. Therefore, chemical fragments were selected having a potential effect on biodegradability. In order to be able to predict the biodegradability probability of substances without these specific fragments, the molecular weight was integrated into the models.

 

References

- US EPA (2012). On-Line BIOWIN User’s Guide.

 

 

Assessment of estimation domain (molecular weight, fragments):

Model:	BIOWIN v4.10
Substance:	Tridecane
CAS-#:	629-50-5
SMILES:	C(CCCCCCCCCCC)C
Molecular weight (g/mol):	184.37
AppendixD - Fragment Coefficients for Biodegradation Models
BIOWIN1 and BIOWIN2: Linear / Non-Linear Biodegradability
Fragment description	Coefficient			Training set fragment count					No. of instances of each bond found for the current substance
	Linear	Non-linear		Min		Max	No. of compounds in training set containing the fragment		.
Linear C4 terminal chain [CCC-CH3]	0,10843	1,8437		-		3	44		2
Molecular Weight	---	---		31,06		697,7			in range
.
BIOWIN3 and BIOWIN4: Ultimate / Primary biodegradability
Fragment description	Coefficient				Training set fragment count				No. of instances of each bond found for the current substance
	Ultimate	Primary			Min	Max		No. of compounds in training set containing the fragment	.
Linear C4 terminal chain [CCC-CH3]	0,29834	0,26907			-	3		26	2
Molecular Weight	---	---			53,06	697,65		-	in range
.
BIOWIN5 and BIOWIN6: MITI Biodegradability Coefficients (Linear / Non-Linear)
Fragment description	Coefficient				Training set fragment count				No. of instances of each bond found for the current substance
	Linear	Non-Linear			Min	Max		No. of compounds in training set containing the fragment	.
Methyl [-CH3]	0,000411	0,01942827			-	9		295	2
-CH2- [linear]	0,049416	0,42949426			-	51		214	11
Molecular Weight	---	---			30,02	959,2		-	in range
.
BIOWIN7: Anaerobic Biodegradation Coefficients
Fragment description	Coefficient		Training set fragment count						No. of instances of each bond found for the current substance
			Min			Max		No. of compounds in training set containing the fragment
Linear C4 terminal chain [CCC-CH3]	-0,317727891	---	-			3		41	2
Methyl [-CH3]	-0,079572183	---	-			4		86	2
-CH2- [linear]	0,025989832	---	-			44		67	11
Molecular Weight	---	---	46,07			885,46			in range

Description of key information

Readily biodegradable: 78% in 28 days (OECD 310)

Key value for chemical safety assessment

Biodegradation in water:

readily biodegradable

Type of water:

freshwater

Additional information

Two studies investigating the ready biodegradability of Hydrocarbons, C11-C13 (odd numbered), n-alkanes, <2% aromatics are available. The key study was performed according to OECD guideline 310 under GLP conditions (Fiebig 2010a). Non-adapted municipal activated sludge was used as inoculum. The test substance was applied at a concentration of 23.5 mg/L in triplicates. A biodegradation of 78% was observed after 28 days. The 10% degradation level was reached after 2 days and the 60% degradation level after 14 days. Thus, the 10-day-window was narrowly missed (based on the biodegradation curve). According to “OECD guidelines for the testing of chemicals – Revised introduction to the OECD guidelines for testing of chemicals, Section 3 – Part 1: Principles and strategies related to the testing of degradation of organic chemicals degradation” published by OECD (2006) the ready biodegradability data for mixtures should be evaluated carefully. For substances with different chain lengths the 10-day window should not be used for the interpretation of the results. It is possible that sequential biodegradation caused a prolonged lag-phase and therefore a slower biodegradation period, although the substance was substantially mineralized after the test duration of 28 days. Thus, the pass level at 28 days should be used. Due to a biodegradation of 78% after 28 days, the test substance can be considered as readily biodegradable.

This conclusion is supported by QSAR calculations for the main components tridecane and undecane using BIOWIN v4.10 (BASF 2014a,b). According to Annex XI of Regulation (EC) No 1907/2006 (Q)SAR results can be used if (1) the scientific validity of the (Q)SAR model has been established, (2) the substance falls within the applicability domain of the (Q)SAR model, (3) the results are adequate for the purpose of classification and labeling and/or risk assessment and (4) adequate and reliable documentation of the applied method is provided.

For both components the QSAR tool predicted ready biodegradability. In addition, several tests presented in the REACh dossiers of undecane and tridecane, published on the ECHA data base, confirm ready biodegradability of C10 to C14 paraffins. This also strongly supports the ready biodegradability assumption made for Hydrocarbons, C11-C13 (odd numbered), n-alkanes, <2% aromatics (table 1).

 

Table 1: Biodegradation test results listed in the REACh dossiers of undecane and tridecane

Result	Test	Test substance (as cited in RSS)
83.1% in 28 days, 10d- window passed	OECD 301F	normal C13 paraffin
76.6% in 28 days, 10d-window passed	OECD 301F	normal C11 and C12 paraffins
ca. 80% in 28 days, 10d-window passed	OECD 301F	normal C14 paraffin
ca. 79% in 28 days, 10d-window passed	OECD 301F	normal C13 and C14 paraffins

 

A second available study was performed according to ISO 10708 under GLP conditions (Fiebig 2010b). The test substance concentration selected as appropriate was 29 mg/L, corresponding to 5.8 mg test substance per vessel. Accordingly the ThOD was 100.8 mg O2/L in the test vessel. The degradation was followed by O2 consumption. The test substance reached the 10 % level after 1 day. The pass level of biodegradation of > 60 % was not reached until day 28. The mean degradation came to a maximum of 49 % after 28 days. It is assumed that adsorption of the substance to the sludge may have hindered the degradation process. Due to the stringent conditions of ready biodegradation tests positive degradation results overrule negative ones, and thus the result of this test is not considered to be relevant for the biodegradation assessment of Hydrocarbons, C11-C13 (odd numbered), n-alkanes, <2% aromatics.