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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:
28 days
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to
Guideline:
OECD Guideline 301 F (Ready Biodegradability: Manometric Respirometry Test)
GLP compliance:
yes
Oxygen conditions:
aerobic
Inoculum or test system:
activated sludge, adapted
Details on inoculum:
- Source of inoculum/activated sludge: An aeration tank at Joint Abbotsford Mission Environmental System (JAMES) wastewater treatment plant, Abbotsford, BC.
- Pretreatment: sludge was centrifuged, supernatant discarded, and sludge pellet re-suspended in mineral medium twice; sludge was brought up to the original volume; aerated in the dark at test temperature until use.
Duration of test (contact time):
28 d
Initial conc.:
66.5 mg/L
Based on:
test mat.
Parameter followed for biodegradation estimation:
O2 consumption
Details on study design:
- Test temperature: 20-21°C
- Suspended solids concentration: 0.03g/L
Reference substance:
benzoic acid, sodium salt
Remarks:
Sodium benzoate(CAS NO. 532-32-1)
Remarks on result:
other: Test Item cannot be considered readily biodegradable under the test conditions as the Test Item did not enter the 10 day window and as a result did not surpass 60% biodegradation by the end of the 10-day window.
Results with reference substance:
At Test completion(Day 28), the biodegradation was 72%.

At the end of the test, the difference between replicates was 1%. At Day 14 during the study, the biodegradation of the Reference Item was 73% and the percent biodegradation in the Toxicity Control was 46%. The mean oxygen uptake of the blanks was 6.3mg O2/L. The pH values were 7.1-7.6 between test initiation and completion.

Table 1. Percent Degradation of the Test and Reference Items Over the 28 Day Exposure Period

Treatment

Biodegradation at Start of 10-day Window

Biodegradation at End of 10-day Window

Biodegradation at Day 14*

Biodegradation at Test Completion

Test 1

N/A

N/A

 

-1%

Test 2

N/A

N/A

 

-2%

Mean

N/A

N/A

 

-2%

Reference Item

 

 

73%

72%

Toxicity Control**

 

 

46%

45%

N/A-Not Applicable

*    Validity criteria for Reference Item and Toxicity Control are measured on Day14

**  Calculation of biodegradation in the Toxicity Control is based on the combined ThOD value for the Reference Item and Test Item

Validity criteria fulfilled:
yes
Interpretation of results:
not readily biodegradable
Conclusions:
According to OECD 301F test method, CJ301 was not be considered readily biodegradable.
Executive summary:

This test using the procedures outlined in the Maxxam Study Plan for TOX1603 which is based on the SOP for the OECD 301F (BBY2 SOP-00023) and OECD 301F (OECD, 1992).The results of this OECD 301F test for CJ301 show that all validity criteria were met. CJ301 can not be considered readily biodegradable under the test conditions as CJ301 did not enter the 10 day window and a result did not surpass 60% biodegradation by the end of the 10-day window. Due to the stringency of this test, test items which do not achieve pass levels may still be biodegradable in the environment.

Description of key information

Not readily biodegradable. (OECD TG 301F).

Key value for chemical safety assessment

Biodegradation in water:
inherently biodegradable, not fulfilling specific criteria

Additional information

At the end of the test, the difference between replicates was 1%. At Day 14 during the study, the biodegradation of the Reference Item was 73% and the percent biodegradation in the Toxicity Control was 46%. The mean oxygen uptake of the blanks was 6.3mg O2/L. The pH values were 7.1-7.6 between test initiation and completion. All test validity criteria were met. CJ301 can not be considered readily biodegradable under the test conditions as CJ301 did not enter the 10 day window and a result did not surpass 60% biodegradation by the end of the 10-day window. Due to the stringency of this test, test items which do not achieve pass levels may still be biodegradable in the environment.