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Environmental fate & pathways

Biodegradation in water: screening tests

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Reference
Endpoint:
biodegradation in water: ready biodegradability
Type of information:
read-across from supporting substance (structural analogue or surrogate)
Adequacy of study:
key study
Study period:
27 October - 25 November 2011
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Remarks:
Study meets Test Guideline 301D requirements
Justification for type of information:
Read-across from substance nerol (see the document provided in section 13 for the justification).
Reason / purpose:
read-across source
Reason / purpose:
reference to other study
Parameter:
% degradation (O2 consumption)
Value:
90
Sampling time:
28 d
Details on results:
Initial test material concentration: 2 mg/L
- Theoretical oxygen demand (ThOD) = 2.9 mg/mg
- % biodegradation on Day 2: > 10 %
- % biodegradation on Day 7: > 60 %
- % biodegradation on Day 28 = 90 %
Results with reference substance:
- Theoretical oxygen demand (ThOD) = 0.8 mg/mg
- % biodegradation on Day 7: > 60 %
- % biodegradation on Day 14 = 78 %

Table 5.2.1/1: Dissolved oxygen concentrations (mg/L) in the closed bottles

 

Time (days)

Oxygen concentration (mg/L)

Ocs

Ot

Oc

Oa

0

9.1

9.1

9.1

9.1

 

9.1

9.1

9.1

9.1

Mean (M)

9.1

9.1

9.1

9.1

7

8.4

4.6

8.6

5.0

 

8.6

4.3

8.6

5.0

Mean (M)

8.5

4.5

8.6

5.0

14

8.2

3.1

8.3

4.0

 

8.2

3.5

8.3

4.2

Mean (M)

8.2

3.3

8.3

4.1

21

8.0

3.2

 

 

 

8.0

2.8

 

 

Mean (M)

8.0

3.0

 

 

28

8.0

2.9

 

 

 

7.9

2.6

 

 

Mean (M)

8.0

2.8

 

 

Ocs: River water with nutrients and silica gel but without test material

Ot: River water with nutrients, test material (2.0 mg/L), and silica gel

Oc: River water with nutrients

Oa: River water with nutrients and sodium acetate (6.7 mg/L)

 

Table 5.2.1/2: Oxygen consumption (mg/L) and the percentages biodegradation of the test substance, nerol (BOD/ThOD) and sodium acetate (BOD/ThOD) in the Closed Bottle test

 

Time (days)

Oxygen consumption (mg/L)

Biodegradation (%)

Test substance

Sodium acetate

Test substance

Sodium acetate

0

0.0

0.0

0

0

7

4.0

3.6

69

67

14

4.9

4.2

84

78

21

5.0

 

86

 

28

5.2

 

90

 

Validity criteria fulfilled:
yes
Remarks:
endogenous respiration at Day 28 was 1.1 mg/L; differences of the replicate values at Day 28 were < 20%; degradation in reference material was 78 % at Day 14; O2 concentration during the test was > 0.5 mg/L
Interpretation of results:
readily biodegradable
Conclusions:
Under the test conditions, nerol was readily biodegradable.
Executive summary:

In a ready biodegradation study performed according to OECD Guideline 301 D and GLP, nerol was tested at concentrations of 2 mg/L and the inoculum was river water (near to a domestic wastewater treatment plant, 3 km upstream). The degradation of the test material was assessed by the determination of the oxygen consumption. The test treatments, inoculum blank, and reference (sodium acetate) were measured in duplicates.

At 2 mg/L, greater than 10% of degradation was reached by Day 2 and greater than 60% of biodegradation was reached by Day 7. Hence, the test material met the 14 day window requirement for ready biodegradability. On Day 28, the biodegradation was 90%.

 

The reference material, sodium acetate, reached greater than 60% of biodegradation on Day 7. Nerol was considered to be non-toxic to micro-organisms as inhibition of the endogenous respiration of the inoculum was not detected during the test. Hence, it met the validity criteria for reference material and toxicity control. The endogenous respiration at Day 28 was 1.1 mg/L and oxygen concentration during the test was greater than 0.5 mg/L.

 

Therefore, nerol was readily biodegradable.

Description of key information

Based on a read-across from a GLP study performed according to Guideline OECD 301D on nerol, substance neryl acetate can be considered as readily biodegradable.

For the justification, please see the document provided in section 13.

Key value for chemical safety assessment

Biodegradation in water:
readily biodegradable

Additional information

One reliable study was available for substance nerol. The biodegradability of the substance was studied according to OECD TG No. 301D and GLP. The biodegradation percentage of the substance reached 90% after 28 days (based on O2 consumption) and the substance met the time window requirement. Thus, the substance is considered as readily biodegradable.