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Environmental fate & pathways

Biodegradation in water: screening tests

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Reference
Endpoint:
biodegradation in water: screening tests
Type of information:
experimental study
Adequacy of study:
key study
Study period:
18/3/2009 to 16/4/2009
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to
Guideline:
other: OECD 306
GLP compliance:
yes
Oxygen conditions:
aerobic
Inoculum or test system:
natural water
Details on inoculum:
Natural seawater, collected at 3 m depth at Espegrend, Bergen-Norway. Salinity 31.4o/oo.
Duration of test (contact time):
28 d
Initial conc.:
1 mg/L
Based on:
COD
Parameter followed for biodegradation estimation:
O2 consumption
Details on study design:
TEST CONDITIONS
- Composition of medium: Seawater with added minerals according to OECD 306
- Test temperature: 15-20 C
- pH: 7.1-7.9
- pH adjusted: no
- Continuous darkness: yes

TEST SYSTEM
- Culturing apparatus: Wheaton bottles
- Number of culture flasks/concentration: 2 (4 on day 28)
- Method used to create aerobic conditions: gentle aeration prior to test
- Test performed in closed vessels

SAMPLING
- Sampling frequency: 0,7,14,21,28 days
- Sampling method: Oxygen meter and stirrer
- Sterility check if applicable: none
- Sample storage before analysis: none

CONTROL AND BLANK SYSTEM
- Inoculum blank: 10% O2 depletion in 28 days
- Abiotic sterile control: o o2 consumption in 28 days
- Toxicity control: No toxicity observed (68% biodegradation in 28 days)
Reference substance:
benzoic acid, sodium salt
Remarks:
Test concnetration not reported, but inferred as 1.0 mgO2/L COD based on inhibition control.
Preliminary study:
None
Test performance:
Microbial activity was satisfactory as demonstrated by >60% degradation of sodium benzoate within 14 days. The test temperature remained within the range 15-20 C and the oxygen consumption within the control media was below 30% of the original amount (day 0). The inhibitory test gave 68% degradability which demonstrated no inhibition. Also, no oxygen consumption took place in the aboitic test.
Key result
Parameter:
% degradation (O2 consumption)
Value:
43
Sampling time:
28 d
Details on results:
The test substance was degraded by 43% in 28 days.
Results with reference substance:
>60% degraded after 14 days

Percent biodegradation for reference chemical, the test substance, abiotic- and inhibitory test media

Time (day)

SPE0878

Sodium benzoate

Inhibitory

Abiotic test

0

0

0

 

7

21

76

14

43

67

21

19

80

28

14

77

68

-22

Validity criteria fulfilled:
yes
Remarks:
Microbial activity was satisfactory as demonstarted by >60% degradation of sodium benzoate within 14 days. The test temperature remained within the range 15-20 C and the oxygen consumption within the control media was below 30% of the original amount.
Interpretation of results:
inherently biodegradable
Conclusions:
The test substance was measured to be 43% degraded within 28 days, and is, according to this study, inherently biodegradable in natural seawater. The test substance had no inhibitory effect on the degradation, no abiotic oxygen consumption occurred and the reference chemical, sodium benzoate, was >60% degraded after 14 days.
Executive summary:

A sample of the test substance was assessed for biodegradation properties by exposing the substance to microorganisms in natural seawater. The test was carried out according to OECD Guideline: OECD 306 1992. OECD Guideline for testing of chemicals, Biodegradation in seawater. Chemical oxygen demand for the test substance was measured as 0.50 mgO2/mg. The test substance at 2mg/L (COD: 1.0 ngO2/L) was added to seawater in closed bottles and the oxygen content was measured once a week for four weeks. Biodegradation is given as the ratio of biological oxygen demand and chemical oxygen demand. In this study, under the test conditions, the test substance showed inherent biodegradability. Within 28 days, the test substance was 43% degraded.

Description of key information

A reliable (Klimisch 1) study with the test substance SPE1415 is available. The study was conducted according to GLP and following internationally accepted test guidelines.

The test substance was measured to be 43% degraded within 28 days, and is, according to this study, inherently biodegradable in natural seawater. The test substance had no inhibitory effect on the degradation, no abiotic oxygen consumption occurred and the reference chemical, sodium benzoate, was >60% degraded after 14 days.

Key value for chemical safety assessment

Biodegradation in water:
inherently biodegradable

Additional information