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Biodegradation in water: screening tests

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Endpoint:
biodegradation in water: ready biodegradability
Type of information:
experimental study
Adequacy of study:
weight of evidence
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to guideline
Guideline:
OECD Guideline 301 B (Ready Biodegradability: CO2 Evolution Test)
Deviations:
no
GLP compliance:
no
Oxygen conditions:
aerobic
Inoculum or test system:
activated sludge, domestic (adaptation not specified)
Details on inoculum:
- Source of inoculum/activated sludge: homogenised activated sludge from waste-water treatment plant at Taunusstein-Bleiderstadt, Lot-No.: 09-May-2001
Duration of test (contact time):
28 d
Initial conc.:
ca. 16.3 mg/L
Based on:
test mat.
Remarks:
Test solution 1
Initial conc.:
ca. 37.3 mg/L
Based on:
ThCO2
Parameter followed for biodegradation estimation:
CO2 evolution
Reference substance:
benzoic acid, sodium salt
Remarks:
20mg/l
Test performance:
The test substance and the inoculum were incubated together in a mineral nutrient medium at a temperature range of 19-15 °C. The test solution are aerated with CO2-free compressed air and are stirred on a magnetic stirrer.The generated CO2 is trapped in a system of gas-washing bottles in to bariumhydroxide.
Key result
Parameter:
% degradation (CO2 evolution)
Value:
ca. 83
Sampling time:
28 d
Results with reference substance:
The reference substance sodium benzoate was degraded 89% ithiin 28 days. The threshold of ready biodegradability of >= 60% was passed within 8 days.
Validity criteria fulfilled:
yes
Interpretation of results:
readily biodegradable
Conclusions:
The threshold of ready biodegradabilty of >= 60% was met within both test solutions. The 10-day window is not regarded as the test substance is a mixture. The final mean degradation value was 83%.
Executive summary:

Decanol, ethoxylated (6 EO) was tested for ready biodegradation according to OECD 301B. The degradation of the test item was 83% within 28 days (after acidification). The biodegradation of the test item reached the criterion for ready biodegradation.

Endpoint:
biodegradation in water: ready biodegradability
Type of information:
experimental study
Adequacy of study:
weight of evidence
Study period:
2009-03-17 to 2009-04-15
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: The study was conducted according to an appropriate OECD test guideline. It was not compliant with GLP.
Qualifier:
according to guideline
Guideline:
OECD Guideline 301 B (Ready Biodegradability: CO2 Evolution Test)
GLP compliance:
no
Remarks:
The test was not conducted in compliance with GLP, nevertheless the study was found to be consistent with other available data, reliable and acceptable for environmental assessment.
Oxygen conditions:
aerobic
Inoculum or test system:
activated sludge (adaptation not specified)
Details on inoculum:
- Source of inoculum/activated sludge (e.g. location, sampling depth, contamination history, procedure): Fairfield Wastewater Treatment Plant, Fairfield, Ohio

- Preparation of media: The media was prepared one day prior to test initiation. The media consisted of the following reagents (1ml/l) in high quality deionised water: magnesium sulfate (2.25%), calcium chloride (2.75%), ferric chloride (0.025%) and phosphate buffer (10 ml/l). The phosphate buffer solution consisted of potassium dihydrogen phosphate (8.5 g/l), dipotassium hydrogen phosphate (21.75 g/l), disodium hydrogen phosphate dihydrate (33.4 g/l) and ammonium chloride (0.5 g/l).

- Preparation of inoculum for exposure: Activated sludge solids centrifuged for 20 minutes at 3000rpm and the supernatant decanted. Solids resuspended in media and homogenised in a blender for 1 minute. The solids were washed a second time as descripbed above and the TSS (total suspended solids) measured. Sufficient inoculum was added to the media to obtain a solids concentration of 15 mg/l. This mixture was adjusted to pH7 and aerated overnight with CO2-free air.

- Concentration of sludge: 15 mg solids/l.
Duration of test (contact time):
28 d
Initial conc.:
15.1 mg/L
Parameter followed for biodegradation estimation:
CO2 evolution
Details on study design:
TEST CONDITIONS
- Composition of medium: test material, sludge inoculum and phosphate buffered media
- Solubilising agent (type and concentration if used): Trichloromethane was used as a solubilising agent. The solvent was then evaporated under a gentle stream of N2 gas to deposit the test material as a film on the walls of the vessel.
- Test temperature: 22 C


TEST SYSTEM
- Culturing apparatus: 1 litre bottles
- Number of culture flasks/concentration: 15.1 mg/l. Two replicates.

SAMPLING
- Sampling frequency: 12h
- Sampling method: Conductivity probe immersed in 1% NaOH to measure production of CO2.

CONTROL AND BLANK SYSTEM
- Inoculum blank: Yes. Six replicates
- Reference substance: Sodium Benzoate. Three replicates
Key result
Parameter:
% degradation (CO2 evolution)
Value:
74.6
St. dev.:
0.4
Sampling time:
28 d
Details on results:
The final SOC levels ranged from 0.5 to 0.6 mg/l, and were <0.1 mg/L for reference substance.

Table 1: Degradation kinetics

Type of suspension

% degradation at sampling time (days)

0

1

2

3

6

8

10

14

16

20

22

24

27

28

 

 

 

 

 

 

 

 

 

 

Test sample (mean of 2 replicates)

0

0

5.64

17.07

49.22

60.61

64.81

70.02

71.79

73.92

73.54

74.45

74.60

74.59

 

 

 

 

 

 

 

 

 

 

 

Reference substance (mean of 3 replicates)

0

0

26.03

41.45

68.48

76.51

79.90

81.88

82.14

82.10

82.19

81.76

81.42

81.69

 

 

 

 

 

 

 

 

 

 

 

Validity criteria fulfilled:
yes
Interpretation of results:
readily biodegradable
Conclusions:
A reliable study conducted according to an appropriate test protocol (OECD 301B), but not conducted according to GLP, determined the substance to be readily biodegradable (74.6% CO2 evolution in 28 days), meeting the ten day window.
Executive summary:

P&G (2009) conducted ready biodegradation screening tests on even saturated single chain length alcohols (C6-C22) using an appropriate test method (OECD 301B). Although, the test was not conducted in compliance with GLP, the study was found to be consistent with other available data, reliable and acceptable for environmental assessment. All tests substances were found to behave in a similar way. The substances were found to be readily biodegradable meeting the ten day window after a brief lag period.

Description of key information

Based on a Weight of Evidence approach, decan-1-ol, ethoxylated (1-2.5 moles EO) (CAS 26183 -52-8) can be considered readily biodegradable.

Key value for chemical safety assessment

Biodegradation in water:
readily biodegradable
Type of water:
freshwater

Additional information

Since no data for decan-1-ol, ethoxylated (1-2.5 moles EO) (CAS 26183 -52-8) are available, ready biodegradability is assessed on the basis of data from the parent alcohol decan-1-ol and the alcohol ethoxlate decan-1-ol, ethoxylated (6 moles EO).

A ready biodegradation screening test was conducted for Decan-1-ol (CAS No.: 112-30-1; EC No.: 203-956-9) in water by P&G in 2009 according to OECD 301B. The test substance was found to be readily biodegradable with 74.6% CO2 evolution in 28 days and meeting the 10-day window after a brief lag period. The study was found to be reliable and consistent with other available data, and therefore, the study is acceptable for environmental assessment.

A ready biodegradation study was also conducted for Decan-1-ol, ethoxylated (6 EO) (CAS No.: 67254-71-1) by Weyand and Lebertz in 2001 according to OECD 301B. The degradation of the test substance (CO2 evolution) was 83% in 28 days. The threshold of readily biodegradability of ≥ 60% was met. Therefore, the biodegradation of the test substance met the criterion for ready biodegradation. The study was found to be reliable and consistent with other available data, and therefore, the study is acceptable for environmental assessment.

 

Justification for WoE for Decan-1-ol, ethoxylated (1-2.5 EO) biodegradability

Decan-1-ol, ethoxylated (1-2.5 EO) contains Decan-1-ol and various ethoxymers of Decan-1-ol ranging from 1 to 7 moles EO, with an average ethoxylation degree of 1-2.5 moles EO.

The data used in this WoE approach is derived from Decan-1-ol (CAS No.: 112-30-1), a single chain length alcohol, and Decan-1-ol, ethoxylated (6 EO), an ethoxylated alcohol with an average of 6 moles of EO. Decan-1-ol, ethoxylated (6 EO) is a mixture of decan-1-ol and decan-1-ol ethoxymers with variying ethoxylation degrees ranging from 1 to 15 moles EO. The difference between Decan-1-ol, ethoxylated (1-2.5 EO) and Decan-1-ol, ethoxylated (6 EO) is the average ethoxylation degree.

As both WoE substances are readily biodegradable the results can be interpolated to the registered substance.

REACH Annex XI recommends the grouping of substances and read-across approach for fulfilling data gaps if the following conditions are met:

•       Results are adequate for the purpose of classification and labeling and/or risk assessment;

•       Results have adequate and reliable coverage of the key parameters addressed in the corresponding test methods;

•       An exposure duration comparable to or longer than the corresponding test method is covered, if this parameter is relevant; and

•       Adequate and reliable documentation of the applied method is provided.

The biodegradation data for the WoE substances (Decan-1-ol and Decan-1-ol, ethoxylated (6 EO)) indicate that these conditions have been met.

Conclusion

Use of the data from the WoE substances (Decan-1- ol and Decan-1-ol, ethoxylated (6 EO)) provides robust data to conclude on the biodegradation potential of Decan-1 -ol, ethoxylated (1-2.5 EO). Given that both Decan-1-ol, ethoxylated (6 EO) and Decan-1-ol are readily biodegradable, Decan-1-ol, ethoxylated (1-2.5 EO) is also expected to be readily biodegradable.