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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:
experimental study
Adequacy of study:
key study
Study period:
10 October - 7 November 2000
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
guideline study
Remarks:
No CoA, no clarity on meeting time window of 14 days for a CBT, only SOP numbers are given but no summary provided
Qualifier:
according to
Guideline:
OECD Guideline 301 D (Ready Biodegradability: Closed Bottle Test)
Deviations:
no
GLP compliance:
yes
Oxygen conditions:
aerobic
Inoculum or test system:
activated sludge, domestic, non-adapted
Details on inoculum:
Secondary effluent of a domestic sewage treatment plant, collected 6 Oct 2000, (Kläranlage Odenthal). The effluent was preconditioned by seperation of coarse particles by filtration and aeration of mineral medium plus inoculum (filtrate) for 4 days.
The effluent concentration in the reaction mixture was 5 ml/L
Duration of test (contact time):
28 d
Initial conc.:
2.3 mg/L
Based on:
test mat.
Parameter followed for biodegradation estimation:
O2 consumption
Details on study design:
Reference is made to SOPs, no summary description available.
Incubation temperature was 20 +/- 1 C
Reference substance:
benzoic acid, sodium salt
Remarks:
at 2.9 mg/L
Test performance:
Test was considered acceptable as all validity criteria were met.
Key result
Parameter:
% degradation (O2 consumption)
Value:
72
Sampling time:
28 d
Parameter:
% degradation (O2 consumption)
Value:
66
Sampling time:
21 d
Parameter:
% degradation (O2 consumption)
Value:
56
Sampling time:
14 d
Parameter:
% degradation (O2 consumption)
Value:
35
Sampling time:
7 d
Results with reference substance:
The reference substance showed 80% degradation after 14 days.

Name

Substance

% degradation

7 d

% degradation

14 d

% degradation

21 d

% degradation

28 d

Test substance

Tetrahydro-myrcenol (THM)

35

56

66

72

Reference substance

Sodium benzoate (SB)

67

80

82

84

Toxicity control

THM & SB

42

59

68

66

The following criteria were met: The reference substance was degradaed >60% (80%) in 14 days; No toxicity of the test substance was observed in the toxicity control; The difference of the extremes of the replicates at the end of the test is less than 20%; Oxygen depletion in the inoculum blank did not exceed 1.5 mg/L dissoved oxygen after 28 days and residual oxygen concentrations in the test bottles were > 0.5 mg/L at all times.

Validity criteria fulfilled:
yes
Remarks:
The reference substance, toxicity of the test substance, the difference of the replicates at 28d, O2 depletion (inoculum blank) and residual O2 conc in the test bottles met the validity criteria.
Interpretation of results:
readily biodegradable
Conclusions:
The substance showed 72% biodegradation in an OECD TG 301D test meeting the 14-day time window and is considered to be readily biodegradable.
Executive summary:

The ready biodegradability of Tetrahydromyrcenol was investigated in a study conducted in accordance with OECD TG 301D (closed bottle test) and GLP. The concentration tested was 2.3 mg/l test substance, with a secondary effluent concentration of 5 mg/l. There was 80% biodegradation of the reference substance sodium benzoate at 14 d. A toxicity control was included not showing toxicity of the test substance. The test substance biodegrades for 72% meeting the 14-day time window.

Description of key information

The ready biodegradability of Tetrahydromyrcenol was investigated in a study conducted in accordance with OECD TG 301D (closed bottle test) and GLP. The concentration tested was 2.3 mg/l test substance, with a secondary effluent concentration of 5 mg/l. There was 80% biodegradation of the reference substance sodium benzoate at 14 d. A toxicity control was included not showing toxicity of the test substance. The test substance biodegrades for 72% meeting the 14-day time window.

Key value for chemical safety assessment

Biodegradation in water:
readily biodegradable

Additional information